34 2013 CONVENIENCE FOOD Die Gemüsegerichte aus der Mikrowelle zeichnen sich durch eine gute mikrobiologische Haltbarkeit aus. The vegetable dishes cooked in the micro-wave oven is characterized by a good microbiological shelf life. mentioned doesn‘t multiply at fridge temperatures. Some types of germs can only be avoided by testing the raw.material prior to production. Apart from most commonly used thermal treat-ment methods (pasteurisation by cooking or in an autoclave), there are several further options that can be used in order to influence or prevent the growth of hazardous germs. These include – apart from obligatory cooling – factors that can be exter-nally influenced (extrinsic factors) such as pH-value, aw-value, redox potential or preservatives. The factors are selected and combined during the pro-cess of product design and creates synergy effects, which ensure the durability of a product. Against this background the question arises of whether these requirements can be fulfilled by other thermal treatment measures and how they influence the safety, quality and value of a product. The heating regime serves as the crucial evaluation criteria because – all other factors aside – an adequate thermal treatment is crucial in order to ensure that all present pathogens or toxic germs are eliminated. After in mid 2009 the findings of a publicly funded project on procedure tests and development of Cooked&Chilled products showed that the application of micro-wave technology was SECOND PROJECT PHASE Based on the findings of the first project phase, the second phase continued the research in Sep-tember 2012. Both project phases have been/ will be funded by the Future Initiative Economy of the Land Schleswig-Holstein, which is financed by the EU, the Federal Government of Germany, Schleswig-Holstein and own funds of the KIN food institute. Apart from continuing the research about product safety and quality (amongst others nutritional benefits), process control, process automation as well as determination and comparison of operational costs, the project also focuses on the topic of sustainability. a promising solution for the production of chilled ready-meals, the KIN food institute started testing this treatment method. Findings during the first project phase During a series of tests, different products were produced using the same recipe.Then they were heated either in a steam cooker, an autoclave or in a micro-wave. Meanwhile, the temperature curve in the products was measured and the corresponding pH-value determined. Apart from that, a sensory evaluation of the product samples was made. For products treated in a steam cooker, the results showed an optimum treatment time of approx. 50 minutes in order to achieve the equivalent values (90°C/10min). In an autoclave the equivalent was reached after approx. 55 minutes. Products heated in a micro-wave only required 10 minutes in order create equivalent conditions. A comparative sensory evaluation was used to check the sensory qualities. The results showed that – roughly said – the attributes associated to freshness, colour, and preferred texture of food prepared in a micro-wave has been received positively during the test. The other two processing methods had some advantages, if long treatment periods were received positively by the testers e.g. intensive roast aroma, denser texture of the gravy (if preferred in this way). The comparative analysis showed that a treatment in the micro-wave only needs 20% of the time required by conventional methods. The products treated in this way, achieved significantly better results with regard to sensory qualities and microbiological stability. The observation that shorter treatment periods would also have a positive effect on sensory qualities has been confirmed. It‘s also expected that there will be advantages considering germ reduction, vitamin preservation and further positive effects on nutritional values. The better microbiological characteristics of products heated in a micro-wave, result from the different principle of operation. Whereas traditional heat treat-ment methods are based on heat conduction into the product – the time required in order to reach the desired temperature in the core is decisive –, micro-wave treatment has an equal effect on the entire product. Dr. rer. nat. and Certified Food Engineer Bernhard Roth, Innovation Consultant and of the KIN-Lebensmittelinstitut, Neumünster/D F Table 1: Growth limits of pathogen micro-organisms1 micro-organisms and growth limits2 min.Temp. (°C) Min. pH Min. aw aerobic/anaerobic3 Listeria monocytogenes -0,41 4,3 0,92 facultative Bacillus cereus 44 4,55 0,931 facultative Campylobacter jejuni 32 4,9 0,99 microaerophilic Clostridium botulinum 10-121 4,6 0,93 anaerobic (mesophil/proteolytic Clostridium botulinum (psy-chotrophic/ non-proteolytic 3,3 5,0 0,97 (0,5%NaCl) anaerobic Clostridium perfingens 121 5,5-5,81 0,9351 anaerobic E.coli 0157:H7 6,5 4,5 0,95 facultative Salmonella 6 4,0 0,94 facultative Staphylococcus aureus6 5,27 4,5 0,86 facultative Vibrio cholera 10 5,0 0,97 facultative Vibrio parahaemolyticus 5 4,8 0,94 facultative Yersina entercolitica -1,31 4,2 0,96 facultative Yersina entercolitica 7-8 4,4 0,95 facultative 1 micro-organisms in foodstuff. Vol. 5 Microbiological Specifications of Food Pathogens (1995), ICMSF, Blackie Academic & Professional; ACMSF Report on Verocytoxin-Producing E.coli (1995), HMSO, London, ISBN 0-11-321909-1. 2 Growth limits under otherwise optimal conditions. Growth criteria depend on stem, temperature and acid type, soluble substances and further factors. Usually they occur in food in relatively high concentrations. However, a false variability must be considered and a certain error margin included. 3 Notification: It should be considered that anaerobic mikcro-organisms can grow even in anaerobic processed food as there may be an internal anaerobic environment. 4 No emetic toxin formation at a temperature below 10°C. 5 These marginal values have been verified by LL Prokopavo (1979) Multiplication and toxigenicity of Bacillus cereus contained in food products stored under different thermal conditions. Voprosy Pitanila, 29,56-61 and M. Reavuori and C. Gerigeorgis (1975). Effect of pH and sodium chloride on growth of Bacillus cereus in laboratory media and certain foods. Applied Microbiology, 29, 68-73 6 limiting values for enterotoxin formation, no growth 7 Most serotypes stop growing at a temperature of <7°C. CONCENIENCE-PRODUKTION
Ftec_01_2013
To see the actual publication please follow the link above