Community Research and Development Information Service - CORDIS

Final Report Summary - UHPH (Development and optimisation of a continuous ultra high pressure homogeniser for application on milks and vegetable milks)

The objective of the UHPH project was to develop and optimise a continuous Ultra high pressure homogeniser (UHPH), for application on milks and vegetable milks. This machine would be capable of applying pressures of up to 400 MPa, using a special homogenising system which allows the elimination of microbes while maintaining the nutritional value, and combines this with the development of a system to control the treatment temperature (30 - 150 degrees Celsius). This system could substitute HTST pasteurisation and UHT sterilisation with less energy consumption and less contamination.

The work focused on the development of dairy products (pasteurised milk, sterilised milk, fresh and ripened cheese and yoghurt from UHPH treated milk, desserts and whey protein concentrates), and vegetable milks (lupine, soya and almond milks). Research was carried out to ensure the safety of the process (killing of pathogenic microorganisms, absence of toxic and carcinogenic substances). Five SME, three universities and two research centres participated in this project creating a multidisciplinary team.

The first part of the work was the design and development of the machine, and its adaptation to the food industry (connections, cleaning procedures, etc.). This machine will be connected to an aseptic tank, which is connected to an aseptic packaging machine (Tetra Pak), to fully simulate industrial production. The second part is the application of UHPH treatment to milks and vegetable milks for drinking (pasteurised and sterilised milks), or for making cheese, yoghurt and desserts, and also protein concentrates for additive applications.

During the first period, SFP have liaised with UAB, UCC and UMII to ensure equipment in the project maintained operation. Implementation of improved valve materials and design has been made to the systems at UMII and UCC (the pressure control of the homogeniser was reconditioned for an easier utilisation: the hydraulic actuator already in place on the equipment was changed to a pneumatic one) and inter-stage cooling system added to UCC system.

SFP worked on the design and building of the new 90 L/h - 400 MPa homogeniser system which was delivered and installed at the UAB by the end of the second period. Improvements to the opening and closing system have been implemented for this system, to provide more reliable operation. Improvements have been made to the overlap timing operation to provide more reliable synchronisation of intensifier handover by user of modified software. Ceramic rams have been developed and tested on the new 90 L/hr system. These are expected to provide improved wear resistance and seals life. Material changes and geometry changes have been made to the seal gland housings to improve the reliability of these components. A new valve seat has been developed and implemented for evaluation in tests. Initial reports are that the performance of this valve seat is an improvement. An external inter-stage heat exchanger has been introduced. Additional thermocouples have been introduced into the product flow path so that the systems can be more fully instrumented. Operation and maintenance manuals for both benchtop and 90 L/h machines have been drafted.

In order to achieve the machine optimisation for milk as well as to assess equivalence among devices, SFP, UAB, UCC and UM II have adapted the different UHPH equipments. They all comprehend heating / cooling devices, thermocouples and pressure probes located at key control points.

For preliminary research on food components, at FRCN facilities it was first installed a simple laboratory UHPH apparatus for producing own samples until partners were able to deliver UHPH treated samples. Starting material was commercial pasteurised and homogenised milk and untreated milk from a local farmer. As a second step, simple continuously working laboratory UHPH equipment was assembled for the production of larger samples that could be used for sensory testing. For this purpose, a new sensory panel according to DIN (German institute for standardisation) 10961 'Training of assessors for sensory analysis' was established and trained. The course included basic tests for training the sense of taste and smell. Overall, electrophoretic patterns of the UHPH samples were similar to that of the control ones. Peroxidase activity decreased mostly after 200-300 MPa treatments for bovine and almond milk samples, whereas it remain unaltered for soy milk. The number of free sulphydryl groups decreased with the pressure treatment applied; on the contrary the formation of di-sulphyde bonds was increased in the three kinds of samples as well as surface hydrophobicity. The formation of aggregates might explain these results. Antioxidant potential was slightly altered in soy milk samples but showed no changes in almond and bovine milk samples. Antimutagenic potential was reduced for soy milk samples; no changes were observed in mutagenicity and toxicity in Salmonella spp. tests due to UHPH treatments. Neither was observed positive reactions in the acute toxicity tests (except for some raw almond milk samples). Antigenicity values were reduced for soy bean and soy bean allergens. The study of possible undesirable compounds formed on milk and vegetable milks components by UHPH treatment found neither negative effects nor severe changes in the assays applied. Changes were mainly detected in macromolecular systems like e.g. particle sizes, surface hydrophobicity of proteins, free sulfhydryl groups, aggregations. The possible consequences of these changes, negative or positive, regarding human nutritional physiology will be subject of further research.

Overall, regarding sensory trials, most of the UHPH products (except for some cheese varieties) were more appreciated than the traditional products; in other occasions, it was not possible to tell the difference between the UHPH products and the traditional products (thermally processed products by high pasteurisation or ultra-high temperature treatments) by both trained panellists and consumers.

Taking into consideration all the results for the foods involved in this project with a potential successful development we can state that from sensory, physicochemical, safety and allergenicity points of view:
- UHPH bovine milk is as good as UHT or pasteurised milks.
- Yoghurt made from UHPH treated bovine milk is as good as industrial yoghurts prepared from pasteurised bovine milk. Both are prepared with the aid of traditional starter cultures (Streptococcus termophilus and Lactobacillus delbrueckii subsp. bulgaricus); in the case of UHPH yoghurts they are produced more efficiently (good texture and less syneresis without protein enrichment) with acceptable sensory quality.
- Cheese made from UHPH bovine or goat milk present high quality values (microbiologically, technological, and organoleptical attributes) once cheesemaking process is optimised.
- Almond milk is a Spanish product commercialised for more than 30 years. UHPH almond milk presents similar microbiological quality to pasteurised almond milk but increased stability during shelf life and improved consumer acceptance.
- Almond milk yoghurt is prepared from the same almond milk using traditional starters taken from the dairy industry (Streptococcus termophilus and Lactobacillus delbrueckii subsp. bulgaricus), and thus should not be considered as a novel food.
- UHPH treated lupine milk presents enhanced stability and rheological properties while it is completely similar to the traditional product for both consumer and trained panelists.
- Soy milk and soghurt products are currently being commercialised throughout the European Union. The main advantages regarding the use of UHPH rely on the improvements achieved in texture, taste and stability properties.

From the results described above, it can be concluded that UHPH products are in most aspects similar to traditional products processed by heating. This questions whether UHPH foods should demand authorisation to be commercialised as novel foods.

Nevertheless, for industrial development and commercialisation of the UHPH products involved in this project, it will be of every firm responsibility to prepare a report with the most relevant information supplied by RTD partners, comparing UHPH products with traditionally pasteurised treatments. This report should be delivered to the food safety agency of the country where commercialisation is intended. Consultation to local government food safety office is advisable from the beginning. The European Food Safety Agency (EFSA) could be asked for a definitive opinion in the case where arbitration is necessary or product exportation envisaged.

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