Effect of different drying methods on flavor components of Chinese shrimp

Abstract: In order to study the flavor components of Chinese Shrimps (Fenneropenaeus Chinensis) with different drying methods, dried products were prepared by different drying methods in this paper. The methods included hot air (temperature: (50±2)°C, wind speed: 1.5 m/s, time: 8 h), cold air (temperature: 18-20°C, wind speed: 1.5 m/s, time: 56 h), microwave vacuum (power: 500 W, vacuum: 70 kPa, time: 40 min) and microwave vacuum united with cold air (first the cold air drying with the temperature of 18-20°C, the wind speed of 1.5 m/s, and the time of 27 h, and then the microwave vacuum drying with the power of 500 W, the vacuum of 70 kPa and the time of 10 min). The total free amino acid compositions, flavor nucleotides, equivalent umami concentrations and volatile components were determined in this paper. The results showed that the total free amino acid content of Chinese Shrimps was 63.31 mg/g after hot air drying, which was lower than the fresh shrimp (72.04 mg/g) (P>0.05). The mass fraction of flavor nucleotides of the shrimps after hot air drying was 7.9 mg/g, which was a serious loss on mass fraction of flavor nucleotides compared to the control, and the value of the control was 9.05 mg/g (P<0.05). The equivalent umami concentration of shrimps after hot air drying was the lowest among 4 drying methods, and the value was 127 g/100 g, which was significantly different from the fresh shrimp (180 g/100 g) (P<0.05). The resulting products presented barbecue and seafood flavor due to their main volatile components after hot air drying. The losses on mass fraction of total free amino acids of Chinese Shrimps made by cold air drying were low, and the values were 63.70 (P<0.05), but the equivalent umami concentration after cold air drying was lower than the control, whose value was 155 g/100 g (P<0.05). The volatile constituents after cold air drying were mainly dominated by hydrocarbon compounds, which made dried shrimp flavor insipid. The loss on mass fraction of total free amino acids in dried Chinese Shrimps with microwave vacuum drying method was 55.81 mg/g, which was a serious loss (P<0.05), but the flavor nucleotides and equivalent umami concentrations changed little (P>0.05), the values of which were 9.17 mg/g and 176 g/100 g respectively. And the volatile components of microwave vacuum drying mainly provided meat and roast flavor. The shrimps dried by microwave vacuum united with cold air had the highest mass fraction of flavor nucleotides and the equivalent umami concentrations, the values of which were 9.90 mg/g and 189 g/100 g (P<0.05) respectively. Although the mass fraction of total free amino acids was decreased (62.84 mg/g) compared with the fresh shrimps, it changed little (P<0.05), and the main volatile components were barbecue and seafood flavor. Therefore, the microwave vacuum united with cold air drying method has a promising prospect in the future, which has fewer losses on nutritional value, including total free amino acid compositions, flavor nucleotides, equivalent umami concentrations and volatile components.