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Energy innovative food process for production of high quality frozen foods

Periodic Reporting for period 1 - COLDmicroWAVE (Energy innovative food process for production of high quality frozen foods)

Reporting period: 2015-05-01 to 2017-04-30

COLDμWAVE project carried out under the aegis of Marie Skłodowska-Curie actions which aim to support the career development and training of researchers with a focus on innovation skills in science through international and intersector mobility. COLDµWAVE project aimed to improve the research skills of Epameinondas Xanthakis through the development of an innovative environmentally sustainable process for blanching and freezing vegetables with improved textural and nutritional quality at SP Technical Research Institute of Sweden.
This study involved the use of MW electromagnetic irradiation (MW) for blanching and subsequently the innovative MW assisted freezing of vegetables. During the implementation of COLDµWAVE project a tailored equipment for MW blanching of vegetables that has high energy efficiency and no water consumption compared to the conventional blanching methods has been developed. Furthermore, this project also developed innovative pathways in freezing to improve the quality of frozen vegetables by exploring, in a new context, previous results acquired by the fellow. The starting point of “COLDµWAVE” was the need to develop and industrially implement sustainable and innovative processes for the production of attractive, tasty, and high-quality frozen fruit and vegetable products. Several technologies and treatments have been developed over the past centuries to extend the shelf-life and transform these perishable vegetables into safe, stable and tasty products. However, for many of these processes the maintenance of the quality characteristics remains a challenging aspect, as they can significantly influence the colour, texture, flavour, and nutritional value of the vegetables. From a sustainability point of view, technologies currently used for the processing of fruits and vegetables consume considerable amounts of energy and water, and produce organic waste due to the leaching of solids.
During the 2 years duration and with the support of the MSCA-IF grant the fellow had the opportunity to gain valuable multidisciplinary experience and new theoretical and practical skills in the areas of heat transfer modelling, food nutrition and quality measurements. The fellow further investigated innovative processes having industrial importance and finally became a real specialist in the MW assisted food blanching and freezing. Therefore, COLDμWAVE project offered the tools and contributed to the career development and integration of the fellow and fulfilled the aim of the MSCA-IF grant.
COLDµWAVE aimed to develop and evaluate an innovative sustainable concept for blanching and freezing of fruit and vegetables with improved quality and lower environmental impact.
The first part of the project was related to the exploration, investigation and evaluation in terms of efficiency, quality and sustainability of blanching of fruits performed with MW heating. In that stage a lab scale batch prototype MW blancher was developed and used for the evaluation of the blanching process.
MW blanching treatment was computer simulated and validated in terms of temperature distribution. The fruit samples (Mangoes) which were used for this study were evaluated in terms of enzymatic inactivation efficiency, remaining nutrients, weight losses and sensory characteristics of the products.
The main results related to this part of the study showed that although the temperature distribution generated by MW is less even than the hot water blanching is equally efficient in terms of ascorbic acid oxidase inactivation. Nutrients such as vitamin C and sugars contained in the fresh mango samples showed higher retention in the case of MW blanching compared to hot water blanching. Sensory evaluation of the MW and hot water blanched samples of mango showed that no significant differences were observed. The overall conclusion of this part of our study was that MW heating can be an alternative process for the efficient blanching of fruits with lower environmental impact since no water consumption is needed and there is no waste water production.
The second part of the project was related to the development of the innovative MW assisted freezing of vegetables. For this purpose a tailored prototype equipment was designed and constructed offering the flexibility to investigate this technology under different processing conditions. With the term MW assisted freezing we determined a process where the food matrix is getting frozen in cold environment under low power MW radiation.
The results acquired showed that MW assisted freezing showed that can improve the microstructure of the frozen vegetable compared to the conventional freezing. More specifically, three different conditions of MW radiation such as pulsed and constant power where tested during freezing. All the MW assisted cases showed that the ice crystal size and distribution was improved compared to the conventional freezing.
The application of MW to fruit and vegetable processing is a novel method which is explored the last years, and much remains to be learnt regarding the physics of the processes, optimal design of the equipment, and the physicochemical impacts on food matrices. MW blanching treatments are termed ‘dry blanching’ technologies, since no water or steam is needed. In addition, as heat is transferred directly to the product there is large potential for energy savings. Another aspect is that fruits and vegetables differ in terms of nutrients, enzymes, tissue structure and deteriorative mechanisms which raise the necessity to be investigated individually. Our MW blanching study focused on mango and the retention of vitamin C after blanching and frozen storage, since this is one of the most attractive and highly perishables fruits while around 30% of the production is wasted. To our knowledge there were not available information in literature regarding the thermal inactivation kinetics of ascorbic acid oxidase contained in mango. Moreover the inactivation of enzyme had not been correlated with ascorbic acid concentration on frozen products and changes during storage. Our study offered valuable knowledge and information in those areas while it was a full study giving valuable information regarding the temperature distribution, the nutrient retention and sensory attributes not only on MW blanched but also for the conventionally blanched mangoes. This study can promote food industry to involve alternative blanching methods such as MW heating in order to improve the quality as well as to decrease the operational costs. On the other hand by raising the advantages of MW blanching offers societal benefits since no water resources are required and no waste water is produced.
Freeze damage can be reduced by applying a high freezing rate using a low freezing temperature and high air velocity or a cryogenic refrigerant, which results in a high energy demand. Several studies have been proposed but still missing of industrial applicability. COLDμWAVE confirmed the positive impact of MW radiation to the microstructure of the frozen matrix. This study upgraded the previous findings of the fellow and strengthened the potentials to be more explored and industrially applicable. Technologies that improve the quality of the frozen food can certainly have positive impact on the society and the industrial profitability.
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