Aging-Induced Changes in Popping, Structural, Functional, Thermal, and Crystalline Properties of Roasted Makhana Seeds

The effect of storage duration on changes in the popping behavior due to structural, physico-chemical, and crystalline property alterations of raw, roasted, and 6-month-stored roasted makhana seeds was studied. The roasted seeds were stored in under airtight polypropylene packets for 6 months. Popped makhana recovery did not change significantly up to 150 days of storage and decreased significantly thereafter. SEM analysis showed that the capillaries were formed in the roasted kernel after 6-month storage due to the slow release of water molecules as a result of starch retrogradation during storage. FTIR analysis showed similar peaks for the functional groups, and 16 volatile compounds were identified by GC-MS analysis. The hydrated particle size of the samples decreased after 6-month storage, which was less than popped makhana but higher than raw makhana seeds. The degree of crystallinity of raw, fresh roasted, and 6-month-stored roasted seeds was 31%, 22.5%, and 30%, respectively. The increase in crystallinity was found to be responsible for the significant reduction in popped makhana recovery after 6-month storage because the water molecules detached from the starch were trapped in the capillaries and changed the starch structure to the crystalline phase.