Optimization of the cold air drying conditions and prediction on shelf-life of half-dried Scomber japonicus fillets

In order to investigate the effect of cold air drying parameters on the quality and flavor of half-dried Scomber japonicus fillets, Scomber japonicus were used as materials and tested by uniform design experiments of U^*₉(9⁴).The three different drying conditions(temperature, relative humidity and cold-air speed)were used as the independent variables. The optimal parameters of cold drying were determined by regression equation models with comprehensive analysis, which were established by the determination of the contents of total volatile basic nitrogen(TVB-N), aerobic plate count(TVC), thiobarbituric acid(TBA)and sensory quality of half-dried Scomber japonicus fillets. The shelf-life prediction models were studied by combining with the first order kinetic model and Arrhenius equation. The results showed that drying temperature and cold-air speed had an effect on TVB-N value(p<0.05)and drying temperature significantly affected the contents of TBA(p<0.05). Based on the regression equation models, the optimal conditions of drying were determined as follows:cold-air speed 2.4 m/s, temperature 15℃, humidity 25%. Under the optimal condition, the measured values of TVB-N and TBA were in good agreement with the predicted values, and the errors of TVB-N and TBA value were 0.71% and 1.16%, respectively.Under this optimized conditions, the time of cold air drying were 21 h, TVB-N value 25.33 mg/100 g, TVC was 5.93×10³ CFU/g, TBA value was 1.11 mg/kg and sensory score was 94.38.The kinetic models between TVB-N、TVC、TBA value and storage time, built from-5 to 10℃, had a good fitting degree. TVB-N and TBA value were chosen to predict the remaining shelf-life of half-dried Scomber japonicus fillets.This research will provide a theoretical basis for production in industrial scale of half-dried Scomber japonicus fillets.