This study examined the effects of different processing, microbial transglutaminase treatments before Protamex-Neutrase hydrolysis (TGPN), glycoside-linkage hydrolysis (PNA) and yeast treatment after Protamex-Neutrase hydrolysis (PNY), on the nutritional properties of oyster hydrolysates compared to standard Protamex-Neutrase processing (PN). The 280 nm to 220 nm absorption ratio in the range of 100∼1,000 Da was highest in TGPN hydrolysate, and lowest in PNY hydrolysate. The major amino acids of the hydrolysates were aspartic acid, glutamic acid, leucine and lysine. The proline level of PN was high, whereas that of PNY was low compared to those of TGPN and PNA. In the free amino acid composition, TGPN and PNA had a high phenylalanine and taurine content, respectively, whereas PNY had a high hydroxyproline content. The Fe, Cu, and Zn levels of TGPN were approximately 6.2, 1.8, and 2.0 times those of PN. Above 20 mg hydrolysate/mL, the water solubility was high in the order of PNA> TGPN≒PNY> PN. An increase in NaCl concentration did not influence the solubility of the hydrolysates, whereas pH influenced the solubility of the hydrolysates slightly except for PN. These results suggest that slightly different processing is responsible for the peptide size, total and free amino acid composition, and mineral composition. As a result, different compositions of the hydrolysates might affect the bioactivity as healthy foods. Therefore, it is important to investigate the different functionalities derived from different processes through bioactive assays.

Keywords: oyster hydrolysate, processing condition, amino acid, mineral, solubility