Comparative studies on autolysis and antioxidative properties of salted shrimp paste (Kapi) from acetes vulgaris and macrobrachium lanchesteri

Autolysis of Acetes vulgaris and Macrobrachium lanchesteri was comparatively studied. Maximal autolytic activities were found at pH 7, 55°C for A. vulgaris and pH 8, 60°C for M. lanchesteri. Both shrimps dominantly contained serine proteases as indicated by the marked inhibition by PMSF and SBTI. When both shrimps were used for Kapi production and characterized, differences in characteristics as well as antioxidant activities were obtained. Kapi produced from A. vulgaris (KA) showed the higher degree of hydrolysis (15.93±0.51%), peroxide values (0.20±0.23 mg cumene peroxide/ kg sample) and TBARS value (0.55±0.16 mg MDA/ kg sample), compared with Kapi produced from M. lanchesteri (KM), indicating the higher protein degradation and lipid oxidation in this sample. Moreover, KA also possessed the higher antioxidative activities including ferric reducing antioxidant power (FRAP) (14.12±1.34 µmol TE/ g sample), chelating activity (3.21±0.05 µmol EE/ g sample), hydrogen peroxide (30.05±0.49 µmol TE/ g sample) and singlet oxygen scavenging activities (48.46±0.32 µmol EE/ g sample) than KM, except for DPPH and ABTS radical scavenging activities, which showed lower activity (P<0.05) and had no difference (P>0.05), respectively. Therefore, different levels and types of endogenous proteases in both shrimps determined the autolysis, characteristics and antioxidative properties of resulting Kapi.