Monitoring of frozen fish by histamine content and microbiological parameters

Abstract

As a result of microbiological decomposition of fish raw materials, especially during putrefactive spoilage or when storage parameters are violated, the muscle tissue of fish characterised by an elevated L-histidine content may accumulate the biogenic amine histamine. The purpose of the study was to investigate the safety indicators of frozen fish sold in supermarkets in Odesa (Ukraine) by histamine content and microbiological criteria (number of mesophilic aerobic and facultative anaerobic microorganisms, coliform bacteria, coagulase-positive staphylococci, Salmonella, Listeria monocytogenes, sulphite-reducing Clostridia, Vibrio parahaemolyticus). Histamine content in frozen fish samples was determined by photometric method according to DSTU 4894:2007. Microbiological parameters were studied using the culture method. According to the findings of the study, 55.3% of the samples showed histamine in the range from 11.0 ± 1.13 mg/kg to 216.0 ± 3.24 mg/kg with a total average value of 45.7 ± 13.2 mg/kg. The highest concentrations of histamine were found in samples of longtail southern cod (177.0 ± 2.15), sprat (188.0 ± 2.01), horse mackerel (192.0 ± 5.05), herring (202.0 ± 2.11), and mackerel (216.0 ± 3.24 mg/kg). Histamine content of more than 100.0 mg/kg was detected in 12.1% of positive samples, more than 200.0 mg/kg – in 1.9%, histamine content that was at the limit of an acceptable concentration of 200.0 mg/kg – in 1.9% of samples, respectively. Exceeding the maximum permissible levels of mesophilic aerobic and facultative anaerobic microorganisms (MAFAnM) was detected in samples of “Blakytna” mackerel (Spain) in 10.7 % of the total number of samples with a maximum level of 6.7 x 104 CFU in 1 g; herring – in 6.7% of samples with a maximum level of 6.6 x 104 CFU in 1 g. Coliform bacteria were found in samples of mackerel (Norway) – 9.4% of the total number of samples; “Blakytna” mackerel (Spain) – 7.1%, herring – 13.3%, longtail southern cod – 5.9%, tilapia – 14.3%, sprat – 5.3%, horse mackerel – 5% of the total number of samples, respectively. All the above-mentioned samples had the highest histamine levels, indicating an association between this indicator and the presence of sanitary-indicative microflora. The findings confirmed the danger of some samples of frozen fish sold in the retail network of Odesa, and pointed out the need to strengthen monitoring of fish for histamine content.