Selection of sterilization temperature
The choice of sterilization temperature is very important. All canned food products are a good breeding ground for the development of microorganisms. But not in every product, microbes can develop equally well, since they are very sensitive in the active acidity of the environment in which they are located, and most of them develop poorly in an acidic environment, but act well in low-acid products. In addition, the negative effect of the acidity of the product on the development of microorganisms increases with heating. Therefore, when heat sterilization of acidic products, microbes die quickly. In low-acid food products, microorganisms develop well and, moreover, are more resistant to heat. That is why it is concluded that in relation to acid products, in which microorganisms are non-thermally resistant during sterilization, it can be confined to moderate temperatures of about 80-100 ° C. Low acid products, in which microbes are resistant to heat, should be sterilized at higher temperatures, above 100 ° C, of the order of 110-120 ° C and even higher.So, the choice of sterilization temperature is dictated by the level of active acidity of this food product.
As is known, the active acidity is measured by the so-called hydrogen indicator, and a completely neutral medium (for example, double distilled distilled water) is equal to 7. All values above 7 characterize alkaline environments, and below 7 - acidic.
However, almost all canned food products are characterized by a value below 7. Even such low-acid canned foods, such as meat, have about 6.0-6.4, and natural vegetables (for example, such as "Green peas"). However, such foods cannot be considered acidic, especially when compared to taste, say, with fruit juices, which are in the range of 3.1-3.8. The first seem to taste fresh as well. the second - sour.
That is why, setting the goal to distribute food products into groups according to the level of their active acidity, one should focus not on the ionic product of water, which is equal with the subsequent gradation to lower and higher values, but to tastes and the reaction of microorganisms to one or another value. In this case, of course, it was decided to take into account primarily the “tastes” of the causative agent of botulism, which is the most dangerous for human health.It turned out that this causative agent of spoilage of canned food considers the food environment unsuitable for themselves, if it is 4.2 and below. In such an environment, clostridium botulinum does not develop.
From here, microbiologists have made a practical conclusion: food products, which are 4.2 or lower, should be considered acidic and should be sterilized at temperatures of 100 ° C or lower. Nevertheless, food products, of which higher than 4.2 are low-acid and sterilized at temperatures above 100 ° C.
Low-acid canned food, sterilized at temperatures above 100 ° C (110-120 ° C), includes all canned and meat-and-cereal, fish, vegetable, natural, vegetable juices, including tomato, vegetable snack and dinner, vegetable salads.
Acid canned foods that can be sterilized at more moderate temperatures of about 100 ° C and lower (80-100 ° C) include all canned fruit - compotes, juices, jams, marmalades, and vegetable marinades.