Differentiating the nutrient composition, in-vitro starch digestibility, individual polyphenols and anti-oxidant properties of raw and popped makhana (Euryale ferox)

Fox nut or makhana ( Euryale ferox ) seeds were subjected to a popping process and evaluated for nutritional and phenolic composition. The phytic acid content was reduced from 281 mg/100 g (raw makhana) to 168 mg/100 g while protein content decreased significantly up to 9.05 g/100 g upon popping. A significant increase in total sugar content by 154.40%, available carbohydrates by 27.45% and degree of gelatinization by 1117%, was recorded upon makhana popping. The starch digestibility and resistant starch (RS) content increased significantly upon makhana popping. The estimated glycemic index (eGI) of raw and popped makhana was found to be 35.63 and 61.52, respectively. The scanning electron microscopy (SEM) revealed an average granule size (diameter) of 54 μm. Free phenolic fraction of raw makhana was found to be predominated with catechin (1.806 mg/100 g) and gallic acid (1.336 mg/100 g), which were reduced by 58 and 49%, respectively upon popping. However, gallic acid (0.290 mg/100 g) and ferulic acid (0.143 mg/100 g) were found the highest among polyphenols in the bound fraction of raw makhana kernels. The TPC of raw and popped makhana was found to be 2.65 and 1.81 mg GAE/g, respectively. The raw and popped makhana samples’ DPPH-, ABTS-free radical scavenging activity, metal chelating activity and FRAP were found to be 20.23 and 10.08%, 79.59 and 77.97%, 83.36 and 86.34%, 6.96 and 6.06 µg Fe 2+ /100 g, respectively. Overall, the popping of makhana significantly altered the nutrients depending upon their type, although the minerals and fatty acids were the least affected by the popping process.