Theoretical Substantiation of the Practical Need for the Sanitation of Spore Forms of Microorganisms in Raw Milk before Its Processing

Abstract

In the production of sterilized dairy products, a relevant problem is the control of vegetative and spore forms of thermophilic bacteria, whose active growth by the end of the technological process in milk can reach a high number and form a biofilm on the equipment parts which have elevated temperatures. The results of the experiments showed the possibility of cleaning raw milk from spore forms of bacteria by provoking their germination by preliminary low-temperature heat treatment with their further destruction by pasteurization. Spores of Bacillus cereus, after primary heat treatment (65 or 72 °C), do not germinate both at low storage temperatures (at + 5 °C) and when stored in uncooled milk (51–65 °C), at least for six hours. To provoke the germination of spores of Bacillus cereus, it is necessary to lower the temperature to +37 °C and hold for 5-6 hours; at the end of the sixth hour, the proportion of spores germinated into the vegetative state is about 35%. Primary heat treatment of milk reduces the germination time of spores of Bacillus cereus by half: from 10-12 hours to six. With the help of further pasteurization at 75 °C, it is possible to reduce the concentration of spore forms of microorganisms in milk to 3.102 CFU/cm3. The technology of double heat treatment of milk with its intermediate exposure for an hour and a half prevents the accumulation of metabolic products of a large group of bacteria: spore and vegetative, psychrophilic and thermophilic ones.