Final Report Summary - MICROMILK (Nutritional and shelf stable milk by novel microwave processing)
Executive summary:
The MICROMILK project involved the development of a novel microwave heating process to facilitate cost-effective, energy efficient, easy to clean and flexible processing of a wide range of different milk variants, including those with high viscosities with minimum start-up and shut-down and minimal surface fouling. Currently, most common technology is indirect heating by using plate heat exchangers. This requires a cleaning in place system to be used quite often because of milk layers burning at the surfaces of the heat exchangers and other equipment, leading to increased shut-down time. The milk industry aims at reducing the cleaning time of milk processing plants to increase the production time while saving water and energy.
Accordingly, the MICROMILK project aims were:
(a) to create an electro-thermal model of microwave cavity to enable controlled and uniform heating;
(b) to design, simulate, optimise and develop a demo-system;
(c) to enhance the microbiological, nutritional and organoleptic quality and the shelf life of milk;
(d) to reduce the cleaning time and minimise the contamination sources of milk via equipment;
(e) to comply with hazard analysis and critical control points (HACCP) and good manufacturing practice (GMP) regulations; and
(f) to decrease cost of overall milk treatment.
Within this project a 400 L / h novel microwave milk pasteurisation prototype was successfully developed and validated. Benchmark comparisons between thermal processing via conventional indirect heating and microwave heating were conducted using reference methods of analysis to evaluate key quality parameters. For this purpose, the cavity reactor was integrated to an existing pasteurisation system, including newly developed full process automation and control.
Within the prototype system, relationships between temperature rise (dT) and milk matrix composition were established. It was observed that at constant flow rate, dT increases linearly with dry matter content. Further, temperature rise was reached 3 times quicker with microwaves than with conventional indirect heating (under equivalent flow rates and retention time conditions). Non-significant differences between microwave pasteurisation and indirect pasteurisation of milk in terms of physicochemical (e.g. furosine and HMF formation), microbiological, nutritional (vitamin B1) and sensory properties (colour, taste) were observed.
Based on performance results and end-user requirements, the MICROMILK cavity reactor was further optimised and extended to an industrial concept at a scale of 1000 L / h. Optimisation was achieved in cooperation with MICROMILK partners by using the quality function deployment (QFD) approach, followed by computer-aided design (CAD) modelling, and field simulations to predict the propagation of the electric field inside the cavity. The developed system replaces the conventional heating unit (plate heat exchanger), and is integrated into a standard milk pasteurisation plant, including clean-in-place cleaning and full energy recovery.
Project context and objectives:
The MICROMILK project involves a consortium of the small and medium-sized enterprises (SMEs) across the European Union (EU) that has identified a low energy, time efficient and easy to clean microwave milk processing system that can improve nutritional value and taste of milk and milk products due to shorter heating times required to reach the holding temperatures during heating.
The system is based on the advanced application of microwaves
The heating time to reach the retention temperature can be significantly reduced and hence the nutritional quality of the milk can be maintained. Currently, the most used technology is heating by plate heat exchangers, which requires the cleaning in place system to be used quite often because of milk layers burning at the surfaces of the equipment, leading to increased shutdown time. This innovative advanced microwave processing system can rapidly achieve the retention temperature by direct interaction of milk with microwaves. The routing of microwave transparent piping ensures the homogeneous heating of the milk.
Accordingly, the overall objectives of the MICROMILK project were:
(1) to design, simulate, optimise and develop a system to process milk through microwave treatment with a throughput of 60 litres / hour;
(2) to design and develop a reactor with antenna and rotating channels for milk flow in continuous process and appropriate to food industry hygienic standards;
(3) to design and develop process control diagrams to couple the processing control parameters with microwave input circuitry;
(4) to reduce the cleaning time and minimise the contamination sources of milk via equipment;
(5) to validate the microbiological, organoleptic and nutritional quality of the milk processed with the microwave system as compared to the conventionally produced milks and in compliance with full HACCP and GMP;
(6) to validate and verify pilot scale prototype system with a throughput of at least 60litres/hour considering economical, energy consumption and shelf life quality aspects;
(7) to decrease the cost of milk heat treatment by use of microwave milk processing to be less than EUR 1 000 / tonne comparative to the cost of EUR 1 200 / tonne with state of the art systems.
The specific objectives and tasks within the project are described below:
Objectives within WP1:
(1) To provide a scientific framework for the understanding of the process, milk behaviours in terms of quality risks and the development parameters to enable a continuous milk pasteurisation process which is compatible with the European Commission (EC) standards and market.
(2) To define control system benchmarks and a process layout by process and instrumentation diagram (PID).
To achieve these objectives, the following tasks had to be conducted:
- Task 1.1: Scientific concept building for the novel process.
- Task 1.2: Scientific characterisation of parameters to define benchmark controls of milk (in terms of enzyme and microbial inactivation as well as physical, chemical, nutritional and organoleptic properties).
- Task 1.3: Setup of a lab scale microwave unit and specification of the microbiological and organoleptic properties and identification of the threshold limits for system automation.
- Task 1.4: Process flow and layout by basic PID.
Objectives within WP2:
(1) to design, simulate and develop the microwave cavity and feeding antenna;
(b) (2) to develop other reactor system components including milk flow channels.
To achieve these objectives, the following tasks had to be conducted:
- Task 2.1: To design and develop rotating milk channels.
Task 2.2: Simulation, design and development of microwave cavity system.
- Task 2.3: Simulation, design and development of antenna.
Objectives within WP3
(1) develop of a sensor system and an overall process control system to enable an efficient and product reliable process;
(2) develop an algorithm to interlock microwave generator with emergency stop and sensory thresholds.
To achieve this objective, the following tasks were defined:
- Task 3.1: Detailing the PID according to the process requirements defined in WP1 and specification of control algorithms, including control loops.
- Task 3.2: Specification and evaluation of available sensors to fulfil the control tasks.
- Task 3.3: Development of a control system interlocked with microwave generator, quality control and feeding system.
- Task 3.4: Evaluation by simulation tests (Verification of defined control loops and algorithms according to the detailed plan made in task 3.2).
Objectives within WP4
(1) To review the development work, design the mobile frame for system integration and integrate the system.
(2) Test the electromagnetic and mechanical safety aspects of the system.
(3) Conduct systematic test trials along with product relevant analytics to validate the system in dairy laboratory at Uni Hohenheim with milk.
To achieve these objectives, the following tasks had to be conducted:
- Task 4.1: Review developments made in WP 2 and WP3.
- Task 4.2: Design of a mobile demonstration unit in part scale, ensuring proper assembling strategy and also safety of components during mobility.
- Task 4.3: System integration and laboratory test trials.
Objectives within WP5
(1) to review the development work, design the mobile frame for system integration, integrate the system and test the system;
(2) To validate and verify the system performance by its suitability for use in milk processing and validate economic and environmental impact (effective reduction of time, energy and cleaning efforts) by comparison with State-of-the-art technologies using equivalent throughput.
(3) To ensure milk quality and subsequent regulatory approval, including HACCP and GMP compliance. This approach shall give the complete insight into the safety and the hygiene of the novel continuous MICROMILK process itself within the real time frame.
(4) To enable post project industrialisation of the developments to be commercially viable for dairies.
(5) To enable post project scale up to an industrial system capable of processing 5 000 litres / hr.
(6) To conduct validation trials at commercial dairies according to their milk processing practices;
(7) evaluate milk quality and shelf life via microbiological, chemical and organoleptic analyses, analogue to methods established in WP1, and compared to state of the art.
To achieve these objectives, the following tasks had to be conducted:
- Task 5.1: Review of laboratory test results and potentially modifications to adjust.
- Task 5.2: System validation by tests and analytics on site at various diaries.
- Task 5.3: Review of field test trials and fixing of principles and specifications for an industrial design.
Objectives within WP6:
(1) To raise the scientific understanding of the technology, its benefits and limitations by training to SME partners.
(2) To protect the design and results.
(3) To create a consortium agreement that handles all background intellectual property issues and ensures that all foreground intellectual property belongs to the SME participants.
(4) To broadcast and disseminate the benefits of the developed technology and knowledge beyond the consortium to other potential industrial communities and the public.(D6.1).
(5) To identify, assess and, where appropriate, protect all the project results.
(6) To develop an Exploitation Strategy which will become a firm Business Plan including routes to market for all project results (D6.2).
(7) To identify opportunities for financing of post-project development work; both of venture finance and through the EC 'Competitiveness and Innovation Framework Programme' (CIP) Eco-Innovation programme, to enable scale up to industrial first application and market replication system to a 1 tonne / hour scale;
(8) To develop a dissemination strategy that will enable widespread publication of the project results - after all protection activities have been concluded.
(9) To disseminate the project results internally between the RTD Performers and the SMEs, and to train the SMEs in the processes developed by the RTD performers.
To achieve these objectives, the following tasks had to be conducted:
- Task 6.1: Exploitation Agreement;
- Task 6.2: Identification, assessment and protection.
- Task 6.3: Exploitation strategy.
- Task 6.4: Post project opportunity.
- Task 6.5: Dissemination strategy.
- Task 6.6: Training and transfer of knowledge.
Objectives within WP7:
(1) To manage the consortium of RTD and SME partners for coordination, individual work packages and technical management.
(2) To ensure that that the knowledge management processes and innovation related activities are conceived and implemented in a coherent manner;
(3) To ensure that all aspects of the EC requirements for communication and reporting are met.
(4) To co-ordinate the overall legal, contractual, financial and administrative management of the consortium.
To achieve these objectives, the following tasks had to be conducted:
- Task 7.1: Overall management and risk contingency planning.
- Task 7.2: Formal consortium management.
- Task 7.3: Formal administration.
- Task 7.4: IPR management.
- Task 7.5: Obtaining audit certificates / if necessary) by each of the participants and coordinating payments and the distribution of money.
- Task 7.6: Communication between the consortium and the EC.
Project results:
In this report, main project achievements are presented:
WP1: Scientific concept building for novel process
Objectives within WP1:
(1) To provide a scientific framework for understanding of the process, milk behaviours in terms of quality risks and the development parameters to enable a continuous milk pasteurisation process which is compatible with EC standards and market.
(2) To define control system benchmarks and process layout by PID.
- Task 1.1: Within this task similarities and differences between conventional heating methods have been identified and pros and cons of conventional heating methods and microwave heating have been sketched. Furthermore, preliminary considerations for the MILCROMILK concept have been sketched.
- Task 1.2: Within this task, specifications and theoretical considerations for conventional milk pasteurisation methods (e.g. HTST, ESL and UHT) have been described and discussed. Furthermore, physical, chemical, nutritional and organoleptic quality indicators and its observed concentrations in different milks obtained by conventional heating were defined, explained and compared for process benchmark.
- Task 1.3: Within this task, a lab scale microwave unit should be setup and first microbiological and organoleptic properties of microwave heated milk should be collected. However, some deviations from the original plan concerning this task occurred. A lab setup was aimed at, but some fundamental background information, such as reliable dielectric constant values of milk at various fat levels were missing. These data were urgently needed to proceed with further calculations. Project partners considered that such equipment should be able to manage all commercial milk types and cream, with fat levels ranging from 0 to 40 %. For instance, pasteurisation of cream and further correction of the fat content is a common practice. On the other hand, distribution of microwaves within a standard cavity with and without the interference of the product needed to be evaluated to understand how flow channels should be placed to have maximum possible homogeneous exposure of electromagnetic fields to flowing milk. For this reason, the first lab setup was a batch system, where a first approach of the time-power profile for a standardised product was defined. No sensory or microbiological data were collected because at batch level, milk can be quickly heated but not cooled down and those analyses would not make sense. Nevertheless, this activity not only helped to obtain first temperature-power profiles but also to obtain background information for Task 2.1 (Design and development of rotating milk channels). On the basis of these first experiments, a continuous prototype system was planned and built. However, tests to complete required nutritional, microbial and organoleptic analysis as well as required temperature-power profiles at continuous conditions were conducted at the University of Hohenheim at a later stage (after conducting performance tests). A test plant available at the University of Hohenheim has been adapted for this purpose. The latter activities required the identification of the threshold limits for system automation, which fulfils one of the objectives of Task 1.3.
- Task 1.4: The first process flow and layout by basic P&ID for test plant has been completed. This first system will be tested and experiences will be extrapolated to setup the final prototype as stipulated in WP4. Deliverables D1.1 (Scientific details, parameters, tabulation and benchmarks of pasteurisation and process flow chart) and D1.2 (Report on lab scale tests about microbiological and organoleptic properties and threshold limits) summarise the fulfilment of these tasks.
WP2: Development of reactor system components
Objectives within WP2
(1) To design, simulate and develop the microwave cavity and feeding antenna.
(2) To develop other reactor system components including milk flow channels.
- Task 2.1: Identification and selection of suitable microwave transparent material for milk flow channels.
Within this task materials commonly used in microwave food processing have been sumarised. Report D2.1 includes the comparison of several different materials according to several parameters. Advantages and disadvantages for those materials are also described. It was concluded that transparent materials such as quartz, glass, Teflon, PTFE or PFA are suitable to be applied in the microwave process. However, no glass materials should be used in food processing due to high risk of breakage. Therefore PFA and PTFE have been recommended for this application.
- Task 2.2: Simulation, design and development of microwave cavity system
Within this task a first cavity approach was developed. At an early stage of the project, it was decided that the prototype would be designed for a flow rate of 400 L / h. This is due to the availability of peripheral units to test the cavity, and to the need to gather representative data. CAD modelling, field simulation and development of a single mode rectangular cavity system including milk flow channels and feeding was conducted. The single mode cavity has been simulated in an empty cavity (without pipe), with several types of pipe materials (PVDF, PTFE, and PFA), and with or without milk.
The project approach was to select most suitable cavity geometry and mode for a flash pasteurisation process. As electric field intensity in the centre of the cavity is higher than rest of the cavity space for single mode, it was decided to place the milk pipe in a cavity in which the electric field would have maximum potential intensity. An additional benefit of this approach is that wave guide serves a dual function as both an energy coupling medium from the magnetron and as a cavity, eliminating the need of any extra resonating chamber. In order to verify these theoretical assumptions, a single mode cavity was simulated in an empty cavity (without pipe) and with several types of pipes (with or without milk). Simulation of the empty cavity -The empty cavity with width a = 86 mm, height b = 43 mm and length l = 2 000 mm was simulated to show the propagation of electric field in the single mode cavity. The figure below shows the propagation of the electric field inside the cavity. It shows clearly that in the middle of the cavity the strength of the electric field is stronger, as indicated by red arrows. It was also s established that safety pipes will avoid any leakage beyond the standard limit of international electro-technical commission IEC. Beyond safety pipes, additional safety features e.g. automatic leakage sensor, milk flow switch have been proposed.
Simulation of cavity with pipe - dielectric properties of PVDF, PTFE and PFA materials were used to simulate the propagation of the electric field in the cavity. It was observed that PVDF absorbed most microwave power, and was therefore not suitable for this process. By contrast, PTFE and PFA revealed both high levels of microwave reflection (99 and 100 % respectively), indicating that microwaves are not absorbed to any significant level by these materials and enabling rather that it would be absorbed by the product.
Simulation of cavity with pipe and milk- these simulations revealed that 6 to 9 % of the microwave power is reflected back to the feeding port in the presence of product (milk). Therefore it can be assumed that the remainder is absorbed by the milk.
Deliverable D2.2 'CAD modelling, simulation and development of cavity system including milk flow channels and feeding' summarises the fulfilment of this task.
Task 2.3: Simulation, design and development of antenna
This activity was not necessary, since the selected cavity approach of a single-mode, single magnetron cavity does not require an antenna. Efforts where derived to optimise the proposed cavity reactor.
WP3: Sensor and Control System
Objectives within WP3
(1) To develop of a sensor system and an overall process control system to enable an efficient and product reliable process.
(2) To develop an algorithm to interlock microwave generator with emergency stop and sensory thresholds.
- Task 3.1: Within this task, the PID of the whole test system was outlined. This system included the integration of MICROMILK prototype (cavity reactor) to the peripheral units available at Uni Hohenheim's pilot pasteurisation system. Process requirements, as defined in WP1, control algorithms and control loops were specified accordingly.
- Task 3.2 within this task, sensors required to fulfil the control tasks previously defined were specified and selected after expert's advisory and market research, while considering hygienic design and GMP issues. Sensor selections were based on the PID generated in task 3.1.
- Task 3.3: Within this task the control system and algorithms were specifically developed for microwave pasteurisation and adapted for an initial test rig (including safety signals). As a standalone control system, it included all the features to completely cover all the functions of the existing the pasteurisation system available at the University of Hohenheim. New functions were implemented to satisfy the MICROMILK system requirements. For this purpose, new sensors and equipment, including all safety measures were implemented. The main control areas include: Milk cycle, heating cycle, microwave cooling cycle, system control, human-machine interface (HMI), and milk cooling cycle. A PLC control software program was included.
- Task 3.4: Within this task, the control system was tested at the laboratory in an initial test rig at Fraunhofer IGB built to verify performance of cavity reactor, determine temperature-power rise curves, and verify simulations on electric field and heat distribution within the cavity.
A microwave test rig unit was set-up, including a full safety and risk assessment. The microwave leakage limit was set at 5 mW / cm2. Accordingly, the pilot plant setup automatically shuts down when leakage exceeds this upper limit ensuring operator safety. Safety clothes and mobile microwave leakage detector were issued to plant operators. A user manual and a training program were established.
D3.1 'Details of PID, control loops and selection of suitable sensors and actuators', and D3.2 'Design and development of specified control system: Design and development of specified control system' summarise the fulfilment of these tasks.
WP4: System Integration and pilot run
Objectives within WP4
(1) To review the development work, design the mobile frame for system integration and integrate the system.
(2) Test the electromagnetic and mechanical safety aspects of the system.
(3) Conduct systematic test trials along with product relevant analytics to validate the system in dairy laboratory at Uni Hohenheim with milk.
Description of work and role of partners
Task 4.1: within this task, all previous developments were revised to ensure that MICROMILK prototype can be integrated to pasteurisation system, as outlined in previous work package. The consortium decided to focus on milk pasteurisation for the initial prototype, and then extend gained knowledge to design a UHT unit at a later stage.
Before system integration, system performance and operational studies of stand-alone microwave unit were conducted. These activities were carried out using water as fluid media.
The aim was to gather data of heating profile within cavity for further design improvements. According to performance results, flash pasteurisation was possible using a single mode cavity, with a microwave propagation limited to ca. 80 cm. Factors affecting power efficiency were identified. Stability test and auto-tuner optimisation were conducted for up to 3.5 hours. After 1 hour of operation at 394 L / h, a max. temperature increase of 6.8 Kelvin was obtained using a microwave power of 3.6 kW. This resulted in 87 % efficiency.
Adaptations of the algorithms were required during this test phase, before cavity reactor was able to be integrated to the full pasteurisation system.
Task 4.2: Within this task, the cavity reactor was modified according to the performance results carried out in task 4.1. The cavity was shortened from its original length of 2 m down to 1 m as the part of the cavity away from the MW source did not contribute to the heating. Temperature profile within the modified cavity was examined and regression curves describing the relationship between temperature rise and microwave power were established.
After required design modifications, a mobile demonstration unit in part scale was built. A proper assembling strategy was defined and all safety issues related to the operation of this unit and its transport were ensured. The task led to successful MICROMILK prototype integration into a pasteurisation unit which will be explain more detail in the next Task 4.3.
Task 4.3: Within this task, developed microwave cavity was then integrated with an existing pasteurisation unit located at the University of Hohenheim. The PID was updated in accordance with microwave pasteurisation requirements. Sensors, control system and safety issues were revised before validation tests. Validation test trials were conducted in Task 5.1.
D4.1 'MICROMILK system integration', and D4.2 'Report on processing and efficiency trials' summarise the fulfilment of these tasks.
WP5: System verification
Objectives within WP5
(1) To review the development work, design the mobile frame for system integration, integrate the system and test the system.
(2) To validate and verify the system performance by its suitability for use in milk processing and validate economic and environmental impact (effective reduction of time, energy and cleaning efforts) by comparison with State-of-the-art technologies using equivalent throughput.
(3) Ensure milk quality and subsequent regulatory approval, including HACCP and GMP compliance. This approach shall give the complete insight into the safety and the hygiene of the novel continuous MICROMILK process itself within the real time frame.
(4) Enable post project industrialisation of the developments to be commercially viable for dairies.
(5) Enable post project scale up to an industrial system capable of processing 5 000 litres / hr.
(6) Conduct validation trials at commercial dairies according to their milk processing practices.
(7) Evaluate milk quality and shelf life via microbiological, chemical and organoleptic analyses, analogue to methods established in WP1, and compared to state of the art.
- Task 5.1: Within this task, performance results of cavity reactor were reviewed and an experimental plan for further process validation with milk as fluid media was setup. Up to this point only data with water was available. During the project, it was agreed that this was the best way to optimise the operation of the system at Fraunhofer IGB installations. Trials with milk at an earlier stage were not possible, since the MICROMILK unit would have to be installed at the dairy processing plant at the University of Hohenheim, where strict hygienic conditions are required, limiting the entrance of technicians and the development team.
- Task 5.2 :Within this task, microbiological, organoleptic and nutritional quality of the milk processed with the microwave system was verified. However, the system could not be validated on site at various dairies. MICROMILK prototype was designed for milk pasteurisation at flow rate of 400 l / hr, sufficient to obtained significant, scalable data at pilot scale. Because the prototype is not yet robust enough to be installed at an industrial site and requires further adaptation, the consortium decided to run all experiments at the University of Hohenheim's dairy plant. This has all the characteristics of a small dairy, including hygienic and GMP standards, and is right next to the laboratory facilities, facilitating sampling and replication of trials as required.
The applicability of the continuous microwave processing of milk and milk products was determined by two interdependent factors: the efficiency of the energy transfer and the effect of microwave energy transfer on the quality of milk and milk products. The process validation consisted of:
(a) Microwave heating tests with dairy matrices of highly different composition regarding protein content, fat content, and dry matter content (0 to 27 %). The aim was to specify to which degree the prototype MICROMILK cavity approach was able to master industrially relevant milk processing operations, taking into account important process parameters such as flow rate, product composition etc. Microwave heating became more efficient with higher the dry matter contents, i.e. the lower the water content of the matrix. This reveals promising potential applications with high-viscosity products, which usually suffer from less flow turbulence which impedes heat transfer which also increases the likelihood of the build-up of surface fouling of process plant. With microwave heating of these products, fouling and formation of burning layers is avoided or diminished.
(b) Microwave heating of skim milk and whole milk (3.5 % fat) at different, industrially relevant time-temperature combinations at constant flow rates. The aim was to generate knowledge to determine if microwave heated milk products were of equal or superior quality compared to conventionally heated milk products. The results showed that both the indirect and microwave heating result in comparable reductions in total bacterial count and enterobacteriacae. Further, both treatments result in inactivation of the enzyme alkaline phosphatase, a legal prerequisite for the sale of drinking milk. This confirmed that microwave pasteurisation of milk is suited for the commercial production and distribution of drinking milk. These and the sensory properties (triangle test) of the resulting products were comparable to indirect pasteurised milk.
Further analysis regarding heat indicators and vitamin reduction were conducted while comparing microwave and indirect heating. According to results the following conclusions can be drawn:
(1) For furosine, acceptable levels in HTST-pasteurised milk are considered to be below 1 mg/kg protein, while for UHT-milk a concentration of 3 to 10 mg / kg is regarded acceptable. With regard to the deviation from the mean, it can be concluded that the microwave pasteurisation process gives acceptable results with regard to furosine formation, and is comparable to indirect pasteurisation.
(2) Regarding the formation of total and free hydroxymethyl-furfural (HMF), no differences between microwave and indirect pasteurisation were detected.
(3) The content of Vitamine B1 showed no differences in microwave and indirectly pasteurised milk. With regard to the nutritional value of microwave pasteurised milk, it can hence be concluded that there are no disadvantages as compared to conventional, indirect heated milk.
In general, it can be concluded that microwave heating is comparable to indirect heating in terms of product quality during pasteurisation. Different trends might be expected for UHT processes, where higher temperatures are required.
- Task 5.3: Within this task, test trials were reviewed and the design of an optimised MICROMILK unit in compliance with industrial pasteurisation was conducted. Inputs associated with industrial pasteurisation unit were obtained by conducting QFD assessment together with MICROMILK consortium, followed by CAD modelling, and field simulations to predict the propagation of the electric field inside the cavity.
According to MICROMILK partners, their pasteurisation unit has minimum flow rate of 1 000 l / hr. Accordingly, a final design of MICROMILK unit for 1 000 l / hr has been proposed.
Project partners actively participated providing their requirements with product quality and plant safety being the most important points to consider in further design optimisation. After discussion of several design options based on geometry mode and number of magnetrons the best suitable solutions were selected and further simulated. The proposed optimised system was scaled at 1 000 L / h and consists of single mode reactor split into more than one section, with each section being fed by only one magnetron. Based on number of magnetrons and sections of single mode cavity being more than one, the concept has been described as SMMM (Single Mode Multi Magnetron) design. The control system, required sensors and interfaces to integrate the optimised cavity design with peripheral pasteurisation components (as provided by van't Riet) has been specified.
The optimised microwave cavity was designed to be integrated with a standard pasteurisation peripheral system provided by van't Riet for further post-project demonstration.
Final design drawings and laboratory test results were reviewed together with MICROMILK consortium at the MICROMILK final meeting, 30 October 2012, in the Netherlands. Accordingly, it was identified that MICROMILK unit has the potential to be applied on other applications within the dairy sites. It was recognised that the MICROMILK system is highly efficient for heating up milk products with high solids content and low pH value or even containing large particles (e.g. fruit pieces). However, adjustment has to be made to fulfil the requirements of these products. These adjustments would be part of post-project activities.
D5.1 'Report on optimised MICROMILK process parameters and effects on milk quality and shelf life', and D5.2 'Industrial specifications to commercialise MICROMILK system summarise the fulfilment of these task'.
WP6: Dissemination and exploitation
Objectives within WP6:
(1) To raise the scientific understanding of the technology, its benefits and limitations by training to SME partners.
(2) To protect the design and results.
(3) To create a Consortium Agreement that handles all background intellectual property issues and ensures that all foreground intellectual property belongs to the SME participants.
(4) To broadcast and disseminate the benefits of the developed technology and knowledge beyond the consortium to other potential industrial communities and the public (D6.1)
(5) To identify, assess and, where appropriate, protect all the project results.
(6) To develop an Exploitation Strategy which will become a firm business plan including routes to market for all project results (D6.2).
(7) To identify opportunities for financing of post-project development work; both of venture finance and through the EC CIP Eco-Innovation programme, to enable scale up to industrial first application and market replication system to a 1 tonne / hour scale.
(8) To develop a dissemination strategy that will enable widespread publication of the project results after all protection activities have been concluded.
(9) To disseminate the project results internally between the RTD Performers and the SMEs, and to train the SMEs in the processes developed by the RTD performers.
Task 6.1: Exploitation agreement
An exploitation agreement has been drafted (D6.12) and discussed during the following management meetings. Piet Verburg provided market information and his experience on possible applications and markets.
- Task 6.2: Identification, assessment and protection
Results have been identified and discussed, but consortium decided to keep gained knowledge secret (no patent application within the duration of the project). Nevertheless all available patents were checked and consortium has freedom to operate with the MICROMILK system.
- Task 6.3: exploitation strategy
Workshop to develop a business plan and identify opportunities for this development was conducted during the 3rd management meeting, held in Stuttgart on 11 July 2012. The results of this workshop have been summarised in the Plan for Use and Dissemination (PUD) of the project results (D6.9).
Task 6.4: Post-project opportunity
Post-project opportunities have been identified. The consortium is applying for a DEMO project under the 'Research for the benefit of SMEs' Theme of the Seventh Framework Programme (FP7). Further opportunities have been identified under the knowledge-based bioeconomy (KBBE) programme 'Saving water and energy for resource efficient food processing'.
On the other hand, Schwarwaldmilch has expressed his interest on installing a prototype in his dairy plant, which would have a slightly different purpose, namely, tempering condensed milk before the spray-drying process. According to M. Rauber, there is a huge opportunity to introduce the MICROMILK system into the dairy market as a unit operation for intermediate products containing high solids contents.
Task 6.5: Dissemination strategy
Dissemination activities were intensified during the last 15 months. Participation in the Anuga FoodTech exhibition between 27 and 30 March 2012 provided a large exposition of the project, and several persons, companies and journalists contacted the project management team for further information. A detailed list of activities and publications is given in the corresponding deliverables.
Task 6.6: Training and transfer of knowledge
Internal dissemination occurred during technical meetings. An operation manual of the MICROMILK prototype has been created. Security trainings were a requirement before running trials at Uni Hohenheim. Final results were transferred during the last management meeting.
Potential Impact:
According to the MICROMILK consortium, the developed system should be modular, allowing its docking to current milk processing plants or its use as a stand-alone unit for pasteurisations systems. The latter will have the advantage of providing farmers the alternative to treat their milk on-site, especially in non-European markets, where logistics and cool chain are still hurdles to overcome.
A number of market opportunities have been identified for the MICROMILK system, which can be extended to further applications within the dairy and food and beverage industries. An analysis of the dairy industry has identified that 80% of energy consumption is used to generate steam and hot water primarily for heating, pasteurisation, and sterilisation, drying and cleaning. Significant potential for water and energy savings have been identified, especially due to the reduction of fouling, and consequently cleaning efforts and shutdown times. This is in line with current EU flagship initiatives on 'resource efficiency' and innovation for sustainable food production and manufacturing, to be coherent with Europe's 20:20:20 energy efficiency target for 20 % primary energy savings by 2020 compared to 1990 .Further demonstration and validation on identified products and processes are aimed at as part of post-project activities.
Contact details: Fraunhofer Institute for Interfacial Engineering and Biotechnology
Dr Ana Lucía Vásquez-Caicedo
analucia.vasquez@igb.fraunhofer.de
Nobelstr. 12
70569 Stuttgart
Phone +49-711-9703669
Fax +49-711-9703997
Mr Siegfried Egner
siegfried.egner@igb.fraunhofer.de
Nobelstr. 12
70569 Stuttgart
Phone +49-711-9703643
Fax +49-711-9704200
The MICROMILK project involved the development of a novel microwave heating process to facilitate cost-effective, energy efficient, easy to clean and flexible processing of a wide range of different milk variants, including those with high viscosities with minimum start-up and shut-down and minimal surface fouling. Currently, most common technology is indirect heating by using plate heat exchangers. This requires a cleaning in place system to be used quite often because of milk layers burning at the surfaces of the heat exchangers and other equipment, leading to increased shut-down time. The milk industry aims at reducing the cleaning time of milk processing plants to increase the production time while saving water and energy.
Accordingly, the MICROMILK project aims were:
(a) to create an electro-thermal model of microwave cavity to enable controlled and uniform heating;
(b) to design, simulate, optimise and develop a demo-system;
(c) to enhance the microbiological, nutritional and organoleptic quality and the shelf life of milk;
(d) to reduce the cleaning time and minimise the contamination sources of milk via equipment;
(e) to comply with hazard analysis and critical control points (HACCP) and good manufacturing practice (GMP) regulations; and
(f) to decrease cost of overall milk treatment.
Within this project a 400 L / h novel microwave milk pasteurisation prototype was successfully developed and validated. Benchmark comparisons between thermal processing via conventional indirect heating and microwave heating were conducted using reference methods of analysis to evaluate key quality parameters. For this purpose, the cavity reactor was integrated to an existing pasteurisation system, including newly developed full process automation and control.
Within the prototype system, relationships between temperature rise (dT) and milk matrix composition were established. It was observed that at constant flow rate, dT increases linearly with dry matter content. Further, temperature rise was reached 3 times quicker with microwaves than with conventional indirect heating (under equivalent flow rates and retention time conditions). Non-significant differences between microwave pasteurisation and indirect pasteurisation of milk in terms of physicochemical (e.g. furosine and HMF formation), microbiological, nutritional (vitamin B1) and sensory properties (colour, taste) were observed.
Based on performance results and end-user requirements, the MICROMILK cavity reactor was further optimised and extended to an industrial concept at a scale of 1000 L / h. Optimisation was achieved in cooperation with MICROMILK partners by using the quality function deployment (QFD) approach, followed by computer-aided design (CAD) modelling, and field simulations to predict the propagation of the electric field inside the cavity. The developed system replaces the conventional heating unit (plate heat exchanger), and is integrated into a standard milk pasteurisation plant, including clean-in-place cleaning and full energy recovery.
Project context and objectives:
The MICROMILK project involves a consortium of the small and medium-sized enterprises (SMEs) across the European Union (EU) that has identified a low energy, time efficient and easy to clean microwave milk processing system that can improve nutritional value and taste of milk and milk products due to shorter heating times required to reach the holding temperatures during heating.
The system is based on the advanced application of microwaves
The heating time to reach the retention temperature can be significantly reduced and hence the nutritional quality of the milk can be maintained. Currently, the most used technology is heating by plate heat exchangers, which requires the cleaning in place system to be used quite often because of milk layers burning at the surfaces of the equipment, leading to increased shutdown time. This innovative advanced microwave processing system can rapidly achieve the retention temperature by direct interaction of milk with microwaves. The routing of microwave transparent piping ensures the homogeneous heating of the milk.
Accordingly, the overall objectives of the MICROMILK project were:
(1) to design, simulate, optimise and develop a system to process milk through microwave treatment with a throughput of 60 litres / hour;
(2) to design and develop a reactor with antenna and rotating channels for milk flow in continuous process and appropriate to food industry hygienic standards;
(3) to design and develop process control diagrams to couple the processing control parameters with microwave input circuitry;
(4) to reduce the cleaning time and minimise the contamination sources of milk via equipment;
(5) to validate the microbiological, organoleptic and nutritional quality of the milk processed with the microwave system as compared to the conventionally produced milks and in compliance with full HACCP and GMP;
(6) to validate and verify pilot scale prototype system with a throughput of at least 60litres/hour considering economical, energy consumption and shelf life quality aspects;
(7) to decrease the cost of milk heat treatment by use of microwave milk processing to be less than EUR 1 000 / tonne comparative to the cost of EUR 1 200 / tonne with state of the art systems.
The specific objectives and tasks within the project are described below:
Objectives within WP1:
(1) To provide a scientific framework for the understanding of the process, milk behaviours in terms of quality risks and the development parameters to enable a continuous milk pasteurisation process which is compatible with the European Commission (EC) standards and market.
(2) To define control system benchmarks and a process layout by process and instrumentation diagram (PID).
To achieve these objectives, the following tasks had to be conducted:
- Task 1.1: Scientific concept building for the novel process.
- Task 1.2: Scientific characterisation of parameters to define benchmark controls of milk (in terms of enzyme and microbial inactivation as well as physical, chemical, nutritional and organoleptic properties).
- Task 1.3: Setup of a lab scale microwave unit and specification of the microbiological and organoleptic properties and identification of the threshold limits for system automation.
- Task 1.4: Process flow and layout by basic PID.
Objectives within WP2:
(1) to design, simulate and develop the microwave cavity and feeding antenna;
(b) (2) to develop other reactor system components including milk flow channels.
To achieve these objectives, the following tasks had to be conducted:
- Task 2.1: To design and develop rotating milk channels.
Task 2.2: Simulation, design and development of microwave cavity system.
- Task 2.3: Simulation, design and development of antenna.
Objectives within WP3
(1) develop of a sensor system and an overall process control system to enable an efficient and product reliable process;
(2) develop an algorithm to interlock microwave generator with emergency stop and sensory thresholds.
To achieve this objective, the following tasks were defined:
- Task 3.1: Detailing the PID according to the process requirements defined in WP1 and specification of control algorithms, including control loops.
- Task 3.2: Specification and evaluation of available sensors to fulfil the control tasks.
- Task 3.3: Development of a control system interlocked with microwave generator, quality control and feeding system.
- Task 3.4: Evaluation by simulation tests (Verification of defined control loops and algorithms according to the detailed plan made in task 3.2).
Objectives within WP4
(1) To review the development work, design the mobile frame for system integration and integrate the system.
(2) Test the electromagnetic and mechanical safety aspects of the system.
(3) Conduct systematic test trials along with product relevant analytics to validate the system in dairy laboratory at Uni Hohenheim with milk.
To achieve these objectives, the following tasks had to be conducted:
- Task 4.1: Review developments made in WP 2 and WP3.
- Task 4.2: Design of a mobile demonstration unit in part scale, ensuring proper assembling strategy and also safety of components during mobility.
- Task 4.3: System integration and laboratory test trials.
Objectives within WP5
(1) to review the development work, design the mobile frame for system integration, integrate the system and test the system;
(2) To validate and verify the system performance by its suitability for use in milk processing and validate economic and environmental impact (effective reduction of time, energy and cleaning efforts) by comparison with State-of-the-art technologies using equivalent throughput.
(3) To ensure milk quality and subsequent regulatory approval, including HACCP and GMP compliance. This approach shall give the complete insight into the safety and the hygiene of the novel continuous MICROMILK process itself within the real time frame.
(4) To enable post project industrialisation of the developments to be commercially viable for dairies.
(5) To enable post project scale up to an industrial system capable of processing 5 000 litres / hr.
(6) To conduct validation trials at commercial dairies according to their milk processing practices;
(7) evaluate milk quality and shelf life via microbiological, chemical and organoleptic analyses, analogue to methods established in WP1, and compared to state of the art.
To achieve these objectives, the following tasks had to be conducted:
- Task 5.1: Review of laboratory test results and potentially modifications to adjust.
- Task 5.2: System validation by tests and analytics on site at various diaries.
- Task 5.3: Review of field test trials and fixing of principles and specifications for an industrial design.
Objectives within WP6:
(1) To raise the scientific understanding of the technology, its benefits and limitations by training to SME partners.
(2) To protect the design and results.
(3) To create a consortium agreement that handles all background intellectual property issues and ensures that all foreground intellectual property belongs to the SME participants.
(4) To broadcast and disseminate the benefits of the developed technology and knowledge beyond the consortium to other potential industrial communities and the public.(D6.1).
(5) To identify, assess and, where appropriate, protect all the project results.
(6) To develop an Exploitation Strategy which will become a firm Business Plan including routes to market for all project results (D6.2).
(7) To identify opportunities for financing of post-project development work; both of venture finance and through the EC 'Competitiveness and Innovation Framework Programme' (CIP) Eco-Innovation programme, to enable scale up to industrial first application and market replication system to a 1 tonne / hour scale;
(8) To develop a dissemination strategy that will enable widespread publication of the project results - after all protection activities have been concluded.
(9) To disseminate the project results internally between the RTD Performers and the SMEs, and to train the SMEs in the processes developed by the RTD performers.
To achieve these objectives, the following tasks had to be conducted:
- Task 6.1: Exploitation Agreement;
- Task 6.2: Identification, assessment and protection.
- Task 6.3: Exploitation strategy.
- Task 6.4: Post project opportunity.
- Task 6.5: Dissemination strategy.
- Task 6.6: Training and transfer of knowledge.
Objectives within WP7:
(1) To manage the consortium of RTD and SME partners for coordination, individual work packages and technical management.
(2) To ensure that that the knowledge management processes and innovation related activities are conceived and implemented in a coherent manner;
(3) To ensure that all aspects of the EC requirements for communication and reporting are met.
(4) To co-ordinate the overall legal, contractual, financial and administrative management of the consortium.
To achieve these objectives, the following tasks had to be conducted:
- Task 7.1: Overall management and risk contingency planning.
- Task 7.2: Formal consortium management.
- Task 7.3: Formal administration.
- Task 7.4: IPR management.
- Task 7.5: Obtaining audit certificates / if necessary) by each of the participants and coordinating payments and the distribution of money.
- Task 7.6: Communication between the consortium and the EC.
Project results:
In this report, main project achievements are presented:
WP1: Scientific concept building for novel process
Objectives within WP1:
(1) To provide a scientific framework for understanding of the process, milk behaviours in terms of quality risks and the development parameters to enable a continuous milk pasteurisation process which is compatible with EC standards and market.
(2) To define control system benchmarks and process layout by PID.
- Task 1.1: Within this task similarities and differences between conventional heating methods have been identified and pros and cons of conventional heating methods and microwave heating have been sketched. Furthermore, preliminary considerations for the MILCROMILK concept have been sketched.
- Task 1.2: Within this task, specifications and theoretical considerations for conventional milk pasteurisation methods (e.g. HTST, ESL and UHT) have been described and discussed. Furthermore, physical, chemical, nutritional and organoleptic quality indicators and its observed concentrations in different milks obtained by conventional heating were defined, explained and compared for process benchmark.
- Task 1.3: Within this task, a lab scale microwave unit should be setup and first microbiological and organoleptic properties of microwave heated milk should be collected. However, some deviations from the original plan concerning this task occurred. A lab setup was aimed at, but some fundamental background information, such as reliable dielectric constant values of milk at various fat levels were missing. These data were urgently needed to proceed with further calculations. Project partners considered that such equipment should be able to manage all commercial milk types and cream, with fat levels ranging from 0 to 40 %. For instance, pasteurisation of cream and further correction of the fat content is a common practice. On the other hand, distribution of microwaves within a standard cavity with and without the interference of the product needed to be evaluated to understand how flow channels should be placed to have maximum possible homogeneous exposure of electromagnetic fields to flowing milk. For this reason, the first lab setup was a batch system, where a first approach of the time-power profile for a standardised product was defined. No sensory or microbiological data were collected because at batch level, milk can be quickly heated but not cooled down and those analyses would not make sense. Nevertheless, this activity not only helped to obtain first temperature-power profiles but also to obtain background information for Task 2.1 (Design and development of rotating milk channels). On the basis of these first experiments, a continuous prototype system was planned and built. However, tests to complete required nutritional, microbial and organoleptic analysis as well as required temperature-power profiles at continuous conditions were conducted at the University of Hohenheim at a later stage (after conducting performance tests). A test plant available at the University of Hohenheim has been adapted for this purpose. The latter activities required the identification of the threshold limits for system automation, which fulfils one of the objectives of Task 1.3.
- Task 1.4: The first process flow and layout by basic P&ID for test plant has been completed. This first system will be tested and experiences will be extrapolated to setup the final prototype as stipulated in WP4. Deliverables D1.1 (Scientific details, parameters, tabulation and benchmarks of pasteurisation and process flow chart) and D1.2 (Report on lab scale tests about microbiological and organoleptic properties and threshold limits) summarise the fulfilment of these tasks.
WP2: Development of reactor system components
Objectives within WP2
(1) To design, simulate and develop the microwave cavity and feeding antenna.
(2) To develop other reactor system components including milk flow channels.
- Task 2.1: Identification and selection of suitable microwave transparent material for milk flow channels.
Within this task materials commonly used in microwave food processing have been sumarised. Report D2.1 includes the comparison of several different materials according to several parameters. Advantages and disadvantages for those materials are also described. It was concluded that transparent materials such as quartz, glass, Teflon, PTFE or PFA are suitable to be applied in the microwave process. However, no glass materials should be used in food processing due to high risk of breakage. Therefore PFA and PTFE have been recommended for this application.
- Task 2.2: Simulation, design and development of microwave cavity system
Within this task a first cavity approach was developed. At an early stage of the project, it was decided that the prototype would be designed for a flow rate of 400 L / h. This is due to the availability of peripheral units to test the cavity, and to the need to gather representative data. CAD modelling, field simulation and development of a single mode rectangular cavity system including milk flow channels and feeding was conducted. The single mode cavity has been simulated in an empty cavity (without pipe), with several types of pipe materials (PVDF, PTFE, and PFA), and with or without milk.
The project approach was to select most suitable cavity geometry and mode for a flash pasteurisation process. As electric field intensity in the centre of the cavity is higher than rest of the cavity space for single mode, it was decided to place the milk pipe in a cavity in which the electric field would have maximum potential intensity. An additional benefit of this approach is that wave guide serves a dual function as both an energy coupling medium from the magnetron and as a cavity, eliminating the need of any extra resonating chamber. In order to verify these theoretical assumptions, a single mode cavity was simulated in an empty cavity (without pipe) and with several types of pipes (with or without milk). Simulation of the empty cavity -The empty cavity with width a = 86 mm, height b = 43 mm and length l = 2 000 mm was simulated to show the propagation of electric field in the single mode cavity. The figure below shows the propagation of the electric field inside the cavity. It shows clearly that in the middle of the cavity the strength of the electric field is stronger, as indicated by red arrows. It was also s established that safety pipes will avoid any leakage beyond the standard limit of international electro-technical commission IEC. Beyond safety pipes, additional safety features e.g. automatic leakage sensor, milk flow switch have been proposed.
Simulation of cavity with pipe - dielectric properties of PVDF, PTFE and PFA materials were used to simulate the propagation of the electric field in the cavity. It was observed that PVDF absorbed most microwave power, and was therefore not suitable for this process. By contrast, PTFE and PFA revealed both high levels of microwave reflection (99 and 100 % respectively), indicating that microwaves are not absorbed to any significant level by these materials and enabling rather that it would be absorbed by the product.
Simulation of cavity with pipe and milk- these simulations revealed that 6 to 9 % of the microwave power is reflected back to the feeding port in the presence of product (milk). Therefore it can be assumed that the remainder is absorbed by the milk.
Deliverable D2.2 'CAD modelling, simulation and development of cavity system including milk flow channels and feeding' summarises the fulfilment of this task.
Task 2.3: Simulation, design and development of antenna
This activity was not necessary, since the selected cavity approach of a single-mode, single magnetron cavity does not require an antenna. Efforts where derived to optimise the proposed cavity reactor.
WP3: Sensor and Control System
Objectives within WP3
(1) To develop of a sensor system and an overall process control system to enable an efficient and product reliable process.
(2) To develop an algorithm to interlock microwave generator with emergency stop and sensory thresholds.
- Task 3.1: Within this task, the PID of the whole test system was outlined. This system included the integration of MICROMILK prototype (cavity reactor) to the peripheral units available at Uni Hohenheim's pilot pasteurisation system. Process requirements, as defined in WP1, control algorithms and control loops were specified accordingly.
- Task 3.2 within this task, sensors required to fulfil the control tasks previously defined were specified and selected after expert's advisory and market research, while considering hygienic design and GMP issues. Sensor selections were based on the PID generated in task 3.1.
- Task 3.3: Within this task the control system and algorithms were specifically developed for microwave pasteurisation and adapted for an initial test rig (including safety signals). As a standalone control system, it included all the features to completely cover all the functions of the existing the pasteurisation system available at the University of Hohenheim. New functions were implemented to satisfy the MICROMILK system requirements. For this purpose, new sensors and equipment, including all safety measures were implemented. The main control areas include: Milk cycle, heating cycle, microwave cooling cycle, system control, human-machine interface (HMI), and milk cooling cycle. A PLC control software program was included.
- Task 3.4: Within this task, the control system was tested at the laboratory in an initial test rig at Fraunhofer IGB built to verify performance of cavity reactor, determine temperature-power rise curves, and verify simulations on electric field and heat distribution within the cavity.
A microwave test rig unit was set-up, including a full safety and risk assessment. The microwave leakage limit was set at 5 mW / cm2. Accordingly, the pilot plant setup automatically shuts down when leakage exceeds this upper limit ensuring operator safety. Safety clothes and mobile microwave leakage detector were issued to plant operators. A user manual and a training program were established.
D3.1 'Details of PID, control loops and selection of suitable sensors and actuators', and D3.2 'Design and development of specified control system: Design and development of specified control system' summarise the fulfilment of these tasks.
WP4: System Integration and pilot run
Objectives within WP4
(1) To review the development work, design the mobile frame for system integration and integrate the system.
(2) Test the electromagnetic and mechanical safety aspects of the system.
(3) Conduct systematic test trials along with product relevant analytics to validate the system in dairy laboratory at Uni Hohenheim with milk.
Description of work and role of partners
Task 4.1: within this task, all previous developments were revised to ensure that MICROMILK prototype can be integrated to pasteurisation system, as outlined in previous work package. The consortium decided to focus on milk pasteurisation for the initial prototype, and then extend gained knowledge to design a UHT unit at a later stage.
Before system integration, system performance and operational studies of stand-alone microwave unit were conducted. These activities were carried out using water as fluid media.
The aim was to gather data of heating profile within cavity for further design improvements. According to performance results, flash pasteurisation was possible using a single mode cavity, with a microwave propagation limited to ca. 80 cm. Factors affecting power efficiency were identified. Stability test and auto-tuner optimisation were conducted for up to 3.5 hours. After 1 hour of operation at 394 L / h, a max. temperature increase of 6.8 Kelvin was obtained using a microwave power of 3.6 kW. This resulted in 87 % efficiency.
Adaptations of the algorithms were required during this test phase, before cavity reactor was able to be integrated to the full pasteurisation system.
Task 4.2: Within this task, the cavity reactor was modified according to the performance results carried out in task 4.1. The cavity was shortened from its original length of 2 m down to 1 m as the part of the cavity away from the MW source did not contribute to the heating. Temperature profile within the modified cavity was examined and regression curves describing the relationship between temperature rise and microwave power were established.
After required design modifications, a mobile demonstration unit in part scale was built. A proper assembling strategy was defined and all safety issues related to the operation of this unit and its transport were ensured. The task led to successful MICROMILK prototype integration into a pasteurisation unit which will be explain more detail in the next Task 4.3.
Task 4.3: Within this task, developed microwave cavity was then integrated with an existing pasteurisation unit located at the University of Hohenheim. The PID was updated in accordance with microwave pasteurisation requirements. Sensors, control system and safety issues were revised before validation tests. Validation test trials were conducted in Task 5.1.
D4.1 'MICROMILK system integration', and D4.2 'Report on processing and efficiency trials' summarise the fulfilment of these tasks.
WP5: System verification
Objectives within WP5
(1) To review the development work, design the mobile frame for system integration, integrate the system and test the system.
(2) To validate and verify the system performance by its suitability for use in milk processing and validate economic and environmental impact (effective reduction of time, energy and cleaning efforts) by comparison with State-of-the-art technologies using equivalent throughput.
(3) Ensure milk quality and subsequent regulatory approval, including HACCP and GMP compliance. This approach shall give the complete insight into the safety and the hygiene of the novel continuous MICROMILK process itself within the real time frame.
(4) Enable post project industrialisation of the developments to be commercially viable for dairies.
(5) Enable post project scale up to an industrial system capable of processing 5 000 litres / hr.
(6) Conduct validation trials at commercial dairies according to their milk processing practices.
(7) Evaluate milk quality and shelf life via microbiological, chemical and organoleptic analyses, analogue to methods established in WP1, and compared to state of the art.
- Task 5.1: Within this task, performance results of cavity reactor were reviewed and an experimental plan for further process validation with milk as fluid media was setup. Up to this point only data with water was available. During the project, it was agreed that this was the best way to optimise the operation of the system at Fraunhofer IGB installations. Trials with milk at an earlier stage were not possible, since the MICROMILK unit would have to be installed at the dairy processing plant at the University of Hohenheim, where strict hygienic conditions are required, limiting the entrance of technicians and the development team.
- Task 5.2 :Within this task, microbiological, organoleptic and nutritional quality of the milk processed with the microwave system was verified. However, the system could not be validated on site at various dairies. MICROMILK prototype was designed for milk pasteurisation at flow rate of 400 l / hr, sufficient to obtained significant, scalable data at pilot scale. Because the prototype is not yet robust enough to be installed at an industrial site and requires further adaptation, the consortium decided to run all experiments at the University of Hohenheim's dairy plant. This has all the characteristics of a small dairy, including hygienic and GMP standards, and is right next to the laboratory facilities, facilitating sampling and replication of trials as required.
The applicability of the continuous microwave processing of milk and milk products was determined by two interdependent factors: the efficiency of the energy transfer and the effect of microwave energy transfer on the quality of milk and milk products. The process validation consisted of:
(a) Microwave heating tests with dairy matrices of highly different composition regarding protein content, fat content, and dry matter content (0 to 27 %). The aim was to specify to which degree the prototype MICROMILK cavity approach was able to master industrially relevant milk processing operations, taking into account important process parameters such as flow rate, product composition etc. Microwave heating became more efficient with higher the dry matter contents, i.e. the lower the water content of the matrix. This reveals promising potential applications with high-viscosity products, which usually suffer from less flow turbulence which impedes heat transfer which also increases the likelihood of the build-up of surface fouling of process plant. With microwave heating of these products, fouling and formation of burning layers is avoided or diminished.
(b) Microwave heating of skim milk and whole milk (3.5 % fat) at different, industrially relevant time-temperature combinations at constant flow rates. The aim was to generate knowledge to determine if microwave heated milk products were of equal or superior quality compared to conventionally heated milk products. The results showed that both the indirect and microwave heating result in comparable reductions in total bacterial count and enterobacteriacae. Further, both treatments result in inactivation of the enzyme alkaline phosphatase, a legal prerequisite for the sale of drinking milk. This confirmed that microwave pasteurisation of milk is suited for the commercial production and distribution of drinking milk. These and the sensory properties (triangle test) of the resulting products were comparable to indirect pasteurised milk.
Further analysis regarding heat indicators and vitamin reduction were conducted while comparing microwave and indirect heating. According to results the following conclusions can be drawn:
(1) For furosine, acceptable levels in HTST-pasteurised milk are considered to be below 1 mg/kg protein, while for UHT-milk a concentration of 3 to 10 mg / kg is regarded acceptable. With regard to the deviation from the mean, it can be concluded that the microwave pasteurisation process gives acceptable results with regard to furosine formation, and is comparable to indirect pasteurisation.
(2) Regarding the formation of total and free hydroxymethyl-furfural (HMF), no differences between microwave and indirect pasteurisation were detected.
(3) The content of Vitamine B1 showed no differences in microwave and indirectly pasteurised milk. With regard to the nutritional value of microwave pasteurised milk, it can hence be concluded that there are no disadvantages as compared to conventional, indirect heated milk.
In general, it can be concluded that microwave heating is comparable to indirect heating in terms of product quality during pasteurisation. Different trends might be expected for UHT processes, where higher temperatures are required.
- Task 5.3: Within this task, test trials were reviewed and the design of an optimised MICROMILK unit in compliance with industrial pasteurisation was conducted. Inputs associated with industrial pasteurisation unit were obtained by conducting QFD assessment together with MICROMILK consortium, followed by CAD modelling, and field simulations to predict the propagation of the electric field inside the cavity.
According to MICROMILK partners, their pasteurisation unit has minimum flow rate of 1 000 l / hr. Accordingly, a final design of MICROMILK unit for 1 000 l / hr has been proposed.
Project partners actively participated providing their requirements with product quality and plant safety being the most important points to consider in further design optimisation. After discussion of several design options based on geometry mode and number of magnetrons the best suitable solutions were selected and further simulated. The proposed optimised system was scaled at 1 000 L / h and consists of single mode reactor split into more than one section, with each section being fed by only one magnetron. Based on number of magnetrons and sections of single mode cavity being more than one, the concept has been described as SMMM (Single Mode Multi Magnetron) design. The control system, required sensors and interfaces to integrate the optimised cavity design with peripheral pasteurisation components (as provided by van't Riet) has been specified.
The optimised microwave cavity was designed to be integrated with a standard pasteurisation peripheral system provided by van't Riet for further post-project demonstration.
Final design drawings and laboratory test results were reviewed together with MICROMILK consortium at the MICROMILK final meeting, 30 October 2012, in the Netherlands. Accordingly, it was identified that MICROMILK unit has the potential to be applied on other applications within the dairy sites. It was recognised that the MICROMILK system is highly efficient for heating up milk products with high solids content and low pH value or even containing large particles (e.g. fruit pieces). However, adjustment has to be made to fulfil the requirements of these products. These adjustments would be part of post-project activities.
D5.1 'Report on optimised MICROMILK process parameters and effects on milk quality and shelf life', and D5.2 'Industrial specifications to commercialise MICROMILK system summarise the fulfilment of these task'.
WP6: Dissemination and exploitation
Objectives within WP6:
(1) To raise the scientific understanding of the technology, its benefits and limitations by training to SME partners.
(2) To protect the design and results.
(3) To create a Consortium Agreement that handles all background intellectual property issues and ensures that all foreground intellectual property belongs to the SME participants.
(4) To broadcast and disseminate the benefits of the developed technology and knowledge beyond the consortium to other potential industrial communities and the public (D6.1)
(5) To identify, assess and, where appropriate, protect all the project results.
(6) To develop an Exploitation Strategy which will become a firm business plan including routes to market for all project results (D6.2).
(7) To identify opportunities for financing of post-project development work; both of venture finance and through the EC CIP Eco-Innovation programme, to enable scale up to industrial first application and market replication system to a 1 tonne / hour scale.
(8) To develop a dissemination strategy that will enable widespread publication of the project results after all protection activities have been concluded.
(9) To disseminate the project results internally between the RTD Performers and the SMEs, and to train the SMEs in the processes developed by the RTD performers.
Task 6.1: Exploitation agreement
An exploitation agreement has been drafted (D6.12) and discussed during the following management meetings. Piet Verburg provided market information and his experience on possible applications and markets.
- Task 6.2: Identification, assessment and protection
Results have been identified and discussed, but consortium decided to keep gained knowledge secret (no patent application within the duration of the project). Nevertheless all available patents were checked and consortium has freedom to operate with the MICROMILK system.
- Task 6.3: exploitation strategy
Workshop to develop a business plan and identify opportunities for this development was conducted during the 3rd management meeting, held in Stuttgart on 11 July 2012. The results of this workshop have been summarised in the Plan for Use and Dissemination (PUD) of the project results (D6.9).
Task 6.4: Post-project opportunity
Post-project opportunities have been identified. The consortium is applying for a DEMO project under the 'Research for the benefit of SMEs' Theme of the Seventh Framework Programme (FP7). Further opportunities have been identified under the knowledge-based bioeconomy (KBBE) programme 'Saving water and energy for resource efficient food processing'.
On the other hand, Schwarwaldmilch has expressed his interest on installing a prototype in his dairy plant, which would have a slightly different purpose, namely, tempering condensed milk before the spray-drying process. According to M. Rauber, there is a huge opportunity to introduce the MICROMILK system into the dairy market as a unit operation for intermediate products containing high solids contents.
Task 6.5: Dissemination strategy
Dissemination activities were intensified during the last 15 months. Participation in the Anuga FoodTech exhibition between 27 and 30 March 2012 provided a large exposition of the project, and several persons, companies and journalists contacted the project management team for further information. A detailed list of activities and publications is given in the corresponding deliverables.
Task 6.6: Training and transfer of knowledge
Internal dissemination occurred during technical meetings. An operation manual of the MICROMILK prototype has been created. Security trainings were a requirement before running trials at Uni Hohenheim. Final results were transferred during the last management meeting.
Potential Impact:
According to the MICROMILK consortium, the developed system should be modular, allowing its docking to current milk processing plants or its use as a stand-alone unit for pasteurisations systems. The latter will have the advantage of providing farmers the alternative to treat their milk on-site, especially in non-European markets, where logistics and cool chain are still hurdles to overcome.
A number of market opportunities have been identified for the MICROMILK system, which can be extended to further applications within the dairy and food and beverage industries. An analysis of the dairy industry has identified that 80% of energy consumption is used to generate steam and hot water primarily for heating, pasteurisation, and sterilisation, drying and cleaning. Significant potential for water and energy savings have been identified, especially due to the reduction of fouling, and consequently cleaning efforts and shutdown times. This is in line with current EU flagship initiatives on 'resource efficiency' and innovation for sustainable food production and manufacturing, to be coherent with Europe's 20:20:20 energy efficiency target for 20 % primary energy savings by 2020 compared to 1990 .Further demonstration and validation on identified products and processes are aimed at as part of post-project activities.
Contact details: Fraunhofer Institute for Interfacial Engineering and Biotechnology
Dr Ana Lucía Vásquez-Caicedo
analucia.vasquez@igb.fraunhofer.de
Nobelstr. 12
70569 Stuttgart
Phone +49-711-9703669
Fax +49-711-9703997
Mr Siegfried Egner
siegfried.egner@igb.fraunhofer.de
Nobelstr. 12
70569 Stuttgart
Phone +49-711-9703643
Fax +49-711-9704200