Chilled and frozen foods

Heat treatment. Cooling and packaging the finished product.

Heat treatment. Insufficient heating temperature and insufficient exposure of the product at this temperature slightly reduce the initial number of microorganisms, especially if their initial high content. It should take into account the volumes to be treated, since large volumes require more exposure time to all layers of the product reached the desired temperature.
Effect of roasting change the number of bacteria in various samples pies with fillings of birds are shown in Table. 58.
Table 58 Changing the number of bacteria in cakes during roasting

Cake roasting time at 215 °, min.

Number of bacteria on 1 г product

Temperature in the center of the pie in 4 min. after removal from the oven, ° C


coli bacteria group



to obzharki

after roasting

to obzharki

after roasting

to obzharki

after roasting

to obzharki

after roasting


20 тыс.










2200 тыс.

1800 тыс.



160 тыс.

80 тыс.





280 тыс.

190 тыс.



320 790

14 тыс.




110 тыс.

910 10


810 0 7300



25 (at 232 °)

180 тыс.

530 тыс.



18 тыс. 15 тыс. 43 тыс.

110 тыс.


As can be seen from the table. 58, when the temperature in the center of the cake is low (41 — 49 °), the content of the residual microflora was a large amount. In the study of fish sticks at the Moskov Fish Plant, it was established that the effectiveness of their roasting (that is, the percentage ratio of the number of dead bacteria when roasting to the number of bacteria in the raw product) at a temperature of 199 — 204 ° for 2,5 minutes. is 99,07 — 99,99%.
Cooling and packaging of the finished product. This stage of the technological process is the greatest danger from the point of view of microbiological contamination of the product. With prolonged cooling of large quantities of the product, favorable conditions may develop for the development of both the residual microflora and the microflora falling on the product from the air and from contaminated equipment (for example, with stirring). The duration of cooling from heat treatment to freezing, even with low product contamination, should be no more than 2 hour. To avoid microbial contamination of the product
during cooling is recommended to freeze it immediately after cooking.
However, the product directly after cooking may not always be subjected to freezing. Most often the product must be pre-cooled. For example, in the production of pies with chicken filling, chicken carcasses for filling are cooked after cooking, then they are conveyed to a groove, where one worker removes the meat from the bones, another cuts it into pieces, etc. Each of these operations can significantly increase the contamination of chicken stuffing. In addition, during these operations, especially if they continue for 2 — 3 hours at room temperature, bacteria can multiply on the product. The important point is the rate of reproduction of bacteria. Under favorable conditions, cell division occurs every 20 min. Even with relatively low contamination of the product (1 thousand bacteria per 1 g), as a result of microorganism multiplication in 3 hours at a temperature 21 - 32 °, the number of bacteria per 1 g product may increase to 1 million; therefore, the cooling of culinary products after heat treatment should be brought as quickly as possible to temperatures at which bacterial multiplication will be slowed down or completely stopped.
Sometimes the process conditions required to add some components of the finished product is not subjected to heat treatment, which may also lead to an increase in the content of bacteria. So, add to mashed potatoes eggs, flour and other ingredients, significantly increased the content of this item coliform bacteria.
Adding to the second dishes sauces can significantly increase contamination of culinary products in general.
In the study in vnih potato and carrot sauce and meatballs with sauce without established that the first contamination is much higher than that of the latter. So, if the number of bacteria in 1 g potato meatballs without sauce equal to 1 thousand., Then when you add to the same sauce cutlets seeding them on the 1 602 g increased to thousands.
Bacterial contamination of the finished product can occur through contact with contaminated utensils and equipment, such as when used for the finished product trays in which before housed the crude product, or by passing the cooked sausage meat through a meat grinder, where the pre-milled raw beef, and so on. Etc. .
So, fried potato patties were placed on baking sheets, some of which were clean, while others had raw patties before. The total number of bacteria in meatballs placed on clean trays was 400 cells per 1 g and E. coli bacteria - 275, and in meatballs placed on trays that were used, the total number of bacteria per 1 g was 350 thousand and bacteria E. coli 50 thousand.
Secondary contamination of finished products, particularly undesirable bacteria Escherichia coli and staphylococcus may be the result of a manual cutting or portioning of products, such as boned meat toppings for cakes or in manual layout of finished products into molds for freezing. So, if the seeding for the preparation of mashed potato cutlets was 500 cells, the number of bacteria in the cutlets after manual cutting has increased to thousands 1200. 1 to Mr. [94].
Of great importance is the sanitary condition of the packaging material (molds, boxes, crates), which can also be further increased bacterial contamination of ready culinary products.
Since the defrosted culinary represent a favorable environment for bacteria, they must be stored prior to use in frozen form.
Since frozen culinary products reach the consumer in finished form, it is necessary to control their quality.
The microbiological quality control of food, in particular frozen food products can not be separated from the sanitary conditions and modes of their production process.
Microbiological monitoring is to determine the total number of bacteria and coliform bacteria is an indication of the sanitary state of production.
For microbiological analysis it is recommended to select from the five samples of all replaceable output.
For analysis, samples by weight are placed in cans with a certain amount of sterile water (100 or 200 ml, depending on the sample size). In the study of some products (for example, pies with stuffing), they should be cut with a sterile knife into pieces, before placing them in water. The sample is then shaken in water for 3 min. And flushing water or dilutions are sown to appropriate, commonly used media: for meat-peptone or fish agar to determine the total number of bacteria and to the Kesler environment for the detection of E. coli bacteria (with subsequent identification).
Some researchers recommend that determine the quality of frozen food products from meat and poultry on the recovery time resazurin, which depends on the number of bacteria in the product.
When monitoring sanitary conditions of production and ready-frozen food products to take into account a number of researchers recommends a group of faecal streptococci.
Since the production of frozen food products is a relatively new branch of the food industry, up to the present time for these products are not yet established standard. For the first time in 1947, it was proposed to establish a common standard for product contamination in thousand 100. 1 on g and the bacteria Escherichia coli cells 100 100, the
When studying bacterial contamination of meat and vegetable culinary products (Table 60 and 61), it was found that in the majority of samples (83,2% for meat dishes and 85,1% for vegetable dishes), the number of bacteria did not exceed 30 thousand for 1. However, Single samples, the dissemination of which was higher than 300 thousand for 1. It is indicated that this can take place in enterprises that produce a variety of types of culinary products. A similar deviation is allowed in one of the five samples under study, provided that the remaining populations are less than 100 thousand per 1. Standards are recommended: for general seeding of 100 thousand bacteria per 1 g and for coli bacteria less than 10 at 1
These standards may be acceptable for our enterprises producing frozen culinary products.
The question of establishing bacteriological standards for frozen culinary products requires further elaboration and refinement.

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