Development of microbiological criteria for evaluating frozen fish based on the amount of psychrotrophic microflora

Abstract

Unrefrigerated fish and seafood are dominated by mesophilic microflora. At the same time, during their storage in the conditions of refrigerating chambers, a cold-loving – psychrotrophic microbiota dominates, which, according to many scientists, causes organoleptic and chemical changes in fish and affects sanitary and hygienic indicators. Therefore, the microbiological assessment of frozen fish by the content of psychrotrophic microbiota, which participates in its reduced safety and quality, will make it possible to propose preventive measures against spoilage. The aim of the work was to develop a microbiological criterion for the hygiene of the technological process of frozen fish based on the assessment of the content of psychrotrophic microbiota. In the work, standard methods were used, in particular, the microbial number was determined in the samples at a temperature of (30 ± 1) ºС incubation of crops for 72 hours and at a temperature of (6.5 ± 0.5) ºС incubation for 10 days (psychrotrophic microbiota). It was established that during the storage of frozen fish at a temperature of -18 °С, the mesophilic microflora is inactivated, as a result of which its number gradually decreases. However, the intensity of inactivation of mesophilic bacteria in samples with insignificant microbial insemination is, on average, 1.4 times faster, compared to samples with a larger number of microorganisms. In our opinion, this is due to the fact that the composition of mysophilous microflora is largely represented by genera of bacteria that show tolerance to cold. At the same time, the psychrotrophic microflora of frozen fish does not become inactivated during the 8-month storage period at a temperature of -18 °C, and is more stable compared to the mesophilic one. That is, no significant increase or decrease in the number of microorganisms was noted. As a result, by the amount of psychrotrophic microflora of frozen fish, determined at any stage of storage, it is possible to judge its amount at the time of freezing. The amount of psychrotrophic microflora more objectively characterizes the hygienic conditions of production, compliance with the freezing temperature. The microbiological hygiene criteria of the technological process of frozen fish production were substantiated and developed based on the estimation of the amount of psychrotrophic microflora (n = 5; c = 3; m = 10000 CFU/g; M = 50000 CFU/g). These criteria indicate compliance with a set of hygienic measures from freezing to circulation of fish. Therefore, the determined microbiological criterion for the quantity of psychrotrophic microflora in frozen fish complements the existing methods of evaluating the hygiene of the technological process and aims to broadly assess the microbiological safety of frozen fish.