Change On Several Safety Indicators And Evaluation During Processing Of Low-Salinity Cured Fish

Cured fish product is a traditional fishery food in China. It is popular with consumers because of its unique flavor. As the effect of microorganisms and enzymes in raw fish, it leads to a series of biochemical changes, such as nitrate reduction, protein hydrolysis, amino acid decarboxylation and deamination, lipid hydrolysis and oxidation with acidity, volatile nitrogen compounds, nitrosamines, aldehydes and ketones increasing during processing, which make consumers worry about the safety of cured fish. To evaluate the safety indicators of cured fish, effects of salt dosage, curing temperature, curing time, and drying conditions on nitrite content, nitrate content, TVB-N content, acid value, peroxide value, TBA value and luminous intensity of cured silver carp by dry-cured method were studied. The changes of N-dimethylnitrosamine and N-diethylnitrosamines were analyzed in the processing of cured fish. The main results were as follows:1. Effects of curing and drying conditions on nitrite, nitrate and TVB-N content of cured fish and the changes of N-dimethylnitrosamine and N-diethylnitrosamine were analyzed. Curing conditions and drying methods significantly affected nitrite, nitrate and TVB-N content. The nitrite, nitrate and TVB-N content of cured fish were higher with low salt dosage and high curing temperature. The nitrite and TVB-N content were higher, while nitrate content decreased initially and then increased as curing time prolonged. Among the four drying methods, the nitrite, nitrate and TVB-N content of cured fish using vacuum freeze-drying were lower, while the nitrite content of cured fish using hot-air drying were the highest. Under the experimental conditions, the nitrite content was 0.26～2.55mg/kg, nitrate content was 0.13～1.05 mg/g, TVB-N content was 1.75～22.96 mg/100g, N-dimethylnitrosamine content≤0.52μg/kg and N-diethylnitrosamines was not detected.2. Effects of curing and drying conditions on acid value, peroxide value, TBA value of cured fish were studied. The acid value of cured fish were higher with low salt dosage. The acid value, peroxide value, TBA value of cured fish were higher with curing temperature increased and curing time prolonged. Among the four drying methods, acid value, peroxide value, especially TBA value of cured fish using microwave drying were higher, while acid value, peroxide value and TBA value of cured fish using vacuum freeze-drying were lower. Under the experimental conditions, the acid value was 0.073～0.63 mgKOH/g, peroxide value was 0.0052～0.018 g/100g, TBA value was 1.23～10.54 mgMDA/kg.3. Effects of curing and drying conditions on Luminous intensity of back and belly of cured fish were studied. Curing and the drying conditions did not affect the luminous intensity of cured fish. Under the experimental conditions, the luminous intensity was 705～751 counts/s, which was much lower than that of luminous cured fish. It is indicated that the cured fish is safe under normal production conditions.4. The cured fish were cured at 10℃for 4 days with salt dosage of 6%, the nitrite content, TVB-N content, N-dimethylnitrosamine content, N-diethylnitrosamine content, acid value, peroxide value, TBA value and luminous intensity of dry-cured fish were much smaller than that of the standard limit requirements (GB 2760-2007, DB 44/421-2007, GB 2762-2005, GB 10136-2005 and DB 43/344-2007). The cured fish products under the conditions above were safe for eating.