EFFECTS OF DRYING METHODS ON ANTIOXIDANT ACTIVITIES OF GERMINATED GRAINS UNDER SALINITY STRESS

Abstract

The purpose of this research was to study the effects of drying methods on the antioxidant activities of germinated cereal grains under salinity stress. Ten cereal grains, mung beans, red beans, black beans, soybeans, black sesame, RD43 rice, jasmine rice, black rice, riceberry and Leum Pua black sticky rice were germinated under both salinity stress (0.50% NaCl) and normal conditions. Following germination, the samples were subjected to two drying methods: whole grain drying and powder drying. Antioxidant content was determined by measuring total phenolic compounds, proline and ascorbic acid. Antioxidant activities were evaluated using 2,2’-Azinobis (3-ethylbenzothiazoline-6-sulfonic acid); ABTS and 1,1-Diphenyl-2-picrylhydrazyl; DPPH radical scavenging assays, as well as ferric reducing antioxidant power; FRAP assay. The results indicated that drying process had differential effects on the antioxidant activity of cereal grains, depending on the drying method and type of grain. Powder drying was found to increase the total phenolic compounds and ascorbic acid content in mung beans, increase the proline content in black beans, soybeans, black rice and riceberry, and enhance the ABTS radical scavenging activity in red beans. While, whole grain drying was found to increase the total phenolic compounds content in soybean and black sesame, increase the proline content in mung bean, black sesame and RD43 rice, and increase the ascorbic acid content in red bean, RD43 rice and black rice, and also increase the FRAP in black sesame, RD43 rice and black rice. The finding of this research can serve as foundational data for extending the shelf life of germinated cereal grains through whole grain drying and powder drying processes. These methods help retain nutritional value and antioxidant compounds beneficial to health and also enhancing the convenience in consumption and storage.