Nutritional composition and volatile compounds stability in dry‐heat and extruded stabilised rice bran during storage

Abstract

SummaryFresh rice bran (RB) is susceptible to rancidity during storage and transportation and needs a stabilisation process to inactivate enzymes and retain maximum nutrients. Two stabilisation methods, i.e., dry‐heat and extrusion, were applied to study the changes in nutritional composition, volatile compounds, and storage stability of rice bran under varied conditions. Both methods stabilised phytic acid content at 0.55–0.60 μmol L−1; the overall oryzanol content was reduced and found to be less in untreated rice bran. The increase in dry‐heat treatment time and temperature accelerated the oryzanol loss and the loss rate was lower than untreated RB while the oryzanol content was higher at end of storage. Similarly, the reduction rate in oryzanol content by extrusion treatment was positively correlated with storage temperature. Both methods significantly increased the total dietary and soluble dietary fibre but reduced vitamin E content. The extrusion treatment was better at stabilising different volatile compounds (such as aldehydes and ketones) than the dry‐heat treatment in the rice bran. The most volatile substances were hydrocarbons. Dry heat and extrusion increase aldehydes and ketones, oxidising RB and reducing its quality while aldehydes and ketones decreased during storage.