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Chilled and frozen foods

Pasteurization of products with different storage periods

 Pasteurization of products with short shelf life (1 and 2 classes)


The products with a short shelf life are being developed so that they are fit for 10-14 days. Heat treatment of such products during production should reduce the number of infectious pathogens (Salmonella и Listeria) at least 106 times, and handling of products after the heating and packaging must prevent recontamination. At neutral pH in non-antiseptic products with high activity of the combination of water temperature and durationи treatments equivalent to 70 ° C for 2 min are more than sufficient for the indicated reduction in the number of pathogens. Experience has shown that a longer exposure in this temperature range is required to effectively combat some spore-forming bacteria that cause spoilage (for example, lactic acid) Such a combination of time and temperature can be used by the consumer to destroy these infectious pathogens in products. 

Pasteurization of products with a long shelf life (3 and 4 classes)

Products with a long shelf life at refrigerated stored long enough so that we can grow any disputes psihrotrofnye survivors in them. toы to ensure the safety of such products and to eliminate spoilage during Unknowntion shelf life, to destroy any spores capable of growing need to use thermal processes. This means that technology developed to ensure food security, should lead to a decrease in the number of strains growing in the cold Clostridium botulinum at least 106 once commonly believed that safety is sufficient to use heating at 90 ° C for 10 minutes or an equivalent technology, but this repress It is not sufficient to destroy the equally dispute of all kinds psihrotrofnyh Bacillus. In some types of unpreserved products are able to growи и reach levels spoilage for about three weeks at temperatures 7-10 ° C, which are known to be used in the system sales of refrigerated products in many countries. These growing cold disputes often have znachеof D at 90 11 ° C and min.


Microwave processing


Cooking or warming up with microwave heating, especially at home, has become very common in recent years. At the same time, in response to consumer demand, the variety and volume of sales of products intended for subsequent microwave heating and stored at ambient temperature in a chilled or frozen form has increased. In addition, it is very likely that the use of microwave ovens for the preparation and pasteurization of food will continue to grow. The key issues here are the development and preparation of products with predicted absorption in the microwave range. It is known that heating is determined by the dielectric properties, location and thickness of the product in the furnace chamber. The problem in practice is a fairly accurate dosing on an industrial scale to ensure a homogeneous and predictable product heating taking into account absorption in the microwave range.

There is no fundamental difference in the effect on microorganisms of heating by means of microwaves or other forms of energy, although there is no reliable data on the additional bactericidal nonthermal effects of industrial or household microwave equipment. At the same time, the microbiological safety of products heated in household microwave ovens raises some concerns; So, the inconstancy of heating and its effect on the survival of microorganisms. Of particular concern are cases where the products are not completely cooked, can be contaminated after cooking or contain raw ingredients. Anxiety was mainly expressed after the presence in the retail Listeria monocytogenes In a wide range of products, including some suitable for microwave heating. For example, a survey in the UK showed that this microorganism can be detected in 25-gram samples in 18% of the tested refrigerated products manufactured commercially and commercially. The concern was that the UK Ministry of Agriculture conducted a thorough study of the problem with the involvement of furnace manufacturers, various food industries, retailers and consumers, and then disseminated recommendations on the proper use of microwave ovens to achieve effective pasteurization when the products were heated.

It has been suggested that the unexpected survival of microorganisms in foods heated by microwave radiation may be due to increased heat resistance of microorganisms (e.g. Listeria monocytogenes). It is now generally recognized that the survival of microorganisms occurs exclusively as a result of nonuniform heating, leading in certain parts of the product to the emergence of cold spots. This is a consequence of heating by microwave energy and that its absorption (and hence heating rate) depends on the composition and amount of the ingredients of the product and its packaging geometry to a greater extent than in the case of conventional heating means. Measuring the rate of inactivation Listeria monocytogenes in heating various food substrates revealed that a tenfold reduction of microorganisms is achieved by heating at 70 ° C for 0,14-0,27 min (D70 = 0,14- 0,27 minutes). Therefore, the recommendation that the products that can be developed Listeria, Should receive a minimum of microwave heating at 70 ° C for 2 min (as indicated in the UK Ministry of Health guidelines for prepared and cooled foods), aim to reduce the number of these microorganisms more than 10® times. If microwave treatment is used in the production of chilled products with a short shelf life, it must reliably ensure that the minimum allowable amount of heat is supplied to all parts of the product or its ingredient. This is necessary to ensure the necessary reduction in the number of Listeria and other less heat resistant vegetative bacteria causing food poisoning, that is, when processing 70 ° C for min 2 or other combinations of time and temperature, providing a similar lethality microorganisms, based on the values D at 70 ° C for 0,14-0,27 minutes and values z by 6 to 7,4 ° C.

 Products cooked in the primary original packaging (food "underempty"and REPFED)


Although the term "underempty"(Processing in the packaging), strictly speaking, refers to vacuum packaging, without any indication of the heat treatment, it is applied to pasteurized ingredients or products, which are hermetically packaged reд heat treatment, often in their primary packaging (risk class 4). Products treated in this way include ready meals and their components, soups g: sauces; they all have a long shelf life at refrigerated and designedы for use in the catering, and more recently, for retail sale. Processing products underempty usually carried out at relatively low temperatures (55 ° C and more). The heat treatment should be sufficient dA compliance with food safety and microbiological stability at storage temperatures below 3 ° C (minimum theoretical temperature growing growththeir cold species Clostridium botulinum). Depending on the hardness of the thermal regimeth process and flora foods ingredients can have a shelf life of about six weeks. HACCP methodology Plan published for these products в work [2].

The most comprehensive study of early treatment underempty was performed s hospital Nacka in Stockholm. Finished product was packed in vacuo quickly охlazhdali and then stored in a well-controlled cooling conditions for one or two months before reheating for consumption. Spheresа application of the method is then extended to a more or less centralized spherery catering a number of European countries, and recently (mainly in France ) It extended to the products to retailers.

Concerns about possible problems microbiological safety ofwillCatching no doubt about the principles that underlie the process of Obraботки underempty, but because of the complexity required to ensure reliable maintenance of a low temperature (max. 3 ° C) during transportation over long distances, and particularly in home seen process efficiency underempty about Listeria monocytogenes).  Рassmatrivaetsya efficiency of the process with respect to Bacillus Cereus and bacteria that cause spoilage of chicken breasts, and offered some rules and regulations.

 Others treatment options

Production process operations that are processed in multiples (underempty и REPFED) basically follow the original concept and the traditional procedure of canning, packaging, sealing and then heating. Another option is heating followed by filling and sealing - if these operations are not performed truly aseptically, there is a risk of introducing microorganisms after heating and before sealing, and therefore it is mainly used for products with a short shelf life. If the products are hot when filling the container (> 80 ° C), an increase in shelf life at 3 ° C can be achieved. For such processing, special designs of packaging, filling and sealing equipment are used.

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