Chemical and microbial properties of shidal, a traditional fermented fish of Northeast India.

Like Southeast Asian countries fermented fish is a well known strategy of food preservation in the Northeast region of India. Shidals are mostly preferred salt-free fermented fish product amongst all. Chemical and microbial composition, antioxidative potential, fatty acid profile and proteins profile in gel electrophoresis of shidals were studied. pH and total titratable acidity (TTA) have been found as 5.86 ± 0.11, 0.115 ± 0.01 and 6.62 ± 0.07, 0.092 ± 0.01 in punti and phasa shidal respectively. DPPH (·) radical scavenging activity of punti and phasa shidal was determined as 80.15 ± 5.67 and 68.30 ± 3.22 respectively. Presence of eicosapentaenoic, docosahexaenoic, arachidonic, linolenic and linoleic acid indicate the nutritional significance of shidal. However, the result showed that punti shidal was rich in omega-3 but poor in omega-6 fatty acid, whereas, reverse was observed in respect of phasa shidal. Poly acrylamide gel electrophoretic study of protein revealed disappearance of myosin head chain (MHC) in the dry puntius fish (raw material of shidal). Proteins or peptides with low molecular weight between 45 and 29 kDa and between 45 and 66 kDa were noticed in both the shidals and indicative of intensive protein degradation during fermentation. Therefore, fermented fish product, shidal could be used as a potential source of nutrients and natural antioxidants.