Ultrasonication-assisted enzymatic hydrolysis of shrimp shell protein isolate: characterization, antioxidant, and functional properties

Protein isolate was prepared using demineralization and deproteinization of shrimp (Litopenaeus vannamei) shells (SSPI). SSPI was hydrolyzed via alcalase and papain at various concentrations (0.5-3%; w/v of protein) without and with ultrasonication pretreatment at 60 and 70% amplitude for 15 and 30 min. When SSPI was subjected to hydrolysis, the degree of hydrolysis (DH) was increased with increasing enzyme concentration, irrespective of the type of enzyme and ultrasonication pretreatment. DH of 43 and 31% was attained when 3% papain (UPH) and 2% alcalase (UAH), respectively, used along with pretreatment of ultrasonication at 60% amplitude for 15 min (p < 0.05). Higher protein solubility was noticed for UAH and UPH as compared to SSPI. UPH showed decreased foaming capacity (FC) and emulsifying properties than SSPI and UAH (p < 0.05), whereas 4% UAH had the highest FC than other samples (p < 0.05). Like UPH, UAH also showed lower emulsifying properties as compared to SSPI (p < 0.05). UAH had higher ABTS, and metal chelating activity as compared to UPH. On the other hand, UPH showed higher DPPH and FRAP activity than UAH. UPH and UAH were rich in hydrophilic amino acids and volatile compounds of different flavors. Both hydrolysates had peptides with a wide range of molecular weight. The bitterness increased when UAH and UPH levels increased higher than 6% (w/v). Thus, shrimp shell protein isolate could be exploited to produce protein hydrolysate of high DH with the help of ultrasonication pretreatment. Those protein isolates and hydrolysates could be implemented in several foods of several functional and antioxidant properties.