Optimization of Radio Frequency-assisted Hot Air Drying on Penaeus vannamei and Its Effects on the Quality

To study the effects of radio frequency-assisted hot air drying (RFHAD) on the quality of South American white shrimp (Penaeus vannamei), the RFHAD process based on the dielectric properties of the shrimp was optimized. The effects of radio frequency drying (RFD) and RFHAD on the flavor nucleotide contents and equivalent umami levels in dried shrimp were compared with those of hot-air drying (HAD). The results showed that as the temperature and moisture content increased, the dielectric constant and loss factor of the shrimp also increased, facilitating moisture migration and enhancing the drying rate. The penetration depth of the RFD was negatively correlated with moisture content, temperature, and frequency. Additionally, increasing the number of stacked layers and reducing the plate spacing significantly increased the drying rate of the shrimp (P<0.05). Considering all these factors, the optimal RFD conditions for shrimp were determined to be the stacking of four layers of shrimp with a plate spacing of 9 cm. Compared with HAD, RFHAD treatment significantly increased the flavor nucleotide contents and equivalent umami levels in dried shrimp (P<0.05), and the equivalent umami levels were 4.86-fold higher than those in the HAD group. In conclusion, RFHAD significantly improved the drying rate of shrimp while increasing the flavor nucleotide content, thereby enhancing the flavor and freshness of dried shrimp.