Effects of cooking methods and in-vitro digestion on the digestibility and antioxidant properties of ngari (a fermented fish product of India)

Abstract

Ngari is a popular ethnic fermented fish product from North-Eastern India. It is consumed after heat process either as a part of regular meal or as a condiment. However, there is no adequate knowledge on the digestion of ngari and the bioactive potential of the digest. The present study was aimed to evaluate the effect of different heat processes viz., air frying, roasting and sautéing on the chemical attributes and in-vitro digestion characteristics of ngari with reference to digestibility and antioxidant potential. The different heat processes significantly increased the dry matter content, thereby altering the proximate composition of the ngari. Nutritional analyses revealed that the highest value of protein is in air fried ngari (44.14%), while maximum fat in sautéed ngari (27.57%). Fatty acids analysis showed that palmitic, oleic and linoleic acid were the major fatty acids present in ngari irrespective of different heat processing. Antioxidant potential of ngari was significantly influenced by heating processes and digestion methods (pepsin or pepsin-cum-pancreatin). Heat processes significantly reduced DPPH (2,2-diphenyl-1-picrylhydrazyl) and metal chelating activity, while increasing the reducing power of the nagri. Study on peptide released during digestion by SDS-PAGE (Sodium lauryl sulphate-polyacrylamide gel electrophoresis) showed that pepsin digestion led to formation of low molecular weight peptides (14-66 kDa). Subsequently, the pepsin-cum-pancreatin digestion degraded the relatively larger peptides into further smaller ones. The different heat processes enhanced the sensory appeal of the product without exerting any negative influence on its digestibility and bioactive properties.