Effect of Drying Process on the Physicochemical Properties and Biological Activities of Enzymatic Protein Hydrolysate from Shiitake Mushroom (Lentinula edodes)

Abstract

Protein hydrolysate has been used for many years as flavouring agents, food supplement, and several food applications. In this research, Lentinula edodes was hydrolysed by 15% (w/w mushroom powder) papain (4,600 NF/mg) at 65 °C, pH 7.0 for 18 hrs. Protein hydrolysate was dried with two different methods (spray drying and freeze drying). Physicochemical properties, antioxidant activity, angiotensin-I converting enzyme (ACE) inhibitory and sensory characteristics of mushroom protein hydrolysate dried with spray-drying (SD-MPH) and freeze-drying (FD-MPH) were evaluated. The results showed that SD-MPH had a higher dry weight of protein content and a* value than that of FD-MPH (p<0.05). In contrast, SD-MPH had a lower aw and moisture content than that of FD-MPH (p<0.05). SD-MPH exhibited higher water solubility and pH value than FD-MPH (p<0.05). Most of amino acids loss was affected by drying process, except aspartic acid. The most abundant amino acids found in both MPHs powder were Glu, Phe and Asp and ranged from 1.65 to 4.05 mg/g sample. According to 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays, it was shown that both MPHs have high antioxidant activity. Whereas SD-MPH showed~10-fold higher ACE inhibitory activity comparing to FD-MPH. This was concomitant with the high amino acid contents. Sensory characteristics were evaluated by an electronic tongue using the Principle Component Analysis (PCA) and the result showed two separated clusters between SD-MPH and FD-MPH. Based on these results, spray-drying might be a suitable method to produce quality hydrolysates for functional food applications.