Quality Changes of Dehydrated Restructured Fish Product from Silver Carp (Hypophthalmichthys molitrix) as Affected by Drying Methods

Restructured fish slices from silver carp (Hypophthalmichthys molitrix) were dried using air drying (AD), freeze drying (FD), and vacuum drying (VD) (4 mm thickness) and microwave-vacuum drying (MVD) (2, 4, 6, and 8 mm thickness). Quality attributes of the dried products were compared in terms of their rehydrated characteristics, change in dimensions, color, texture, sensory values before and after rehydration, and change in volatile compounds. AD, FD, and VD resulted in the different levels of shrinkage while MVD caused some expansion in diameter and thickness in the 4-, 6-, and 8-mm-thickness samples. Rehydration caused significant swelling in AD, FD, and VD products (p < 0.05) but insignificant change in MVD products (p > 0.05). Drying methods significantly affected the color and texture of both dried and rehydrated products (p < 0.05), but slice thickness had no significant effect on the color in MVD products (p > 0.05). MVD products rehydrated faster and had higher rehydration ratio as well as lower water hold capacity, hardness, springiness, cohesiveness, and chewiness than others. In sensory evaluation, MVD products alone exhibited acceptable crispness and favorable odor. The rehydrated dried products were acceptable by the sensory panelists and were preferred in the order: FD, VD, AD, MVD. Gas chromatography-mass spectrometry revealed that drying significantly decreased the n-alkanals and 1-octen-3-ol content (p < 0.05) and produced new aldehydes including 2-methyl-propanal, 3-methyl-butanal, and furfural in MVD products. This study demonstrated that drying restructured fish meat can be potentially used to develop the new dried fish products using optimal drying conditions.