PARAMESWARAN, M.PATEL, K. V.2018-04-132018-04-131987http://krishikosh.egranth.ac.in/handle/1/5810043434Bajra is superior to wheat in protein quality with respect to essential amino acid composition and biological value. Higher oil content is another added advantage. In spite of its better nutritional qualities use of bajra at home and in industry has been limited due to poor keeping quality of bajra flour. Hydrolytic and oxidative degradation of the lipids in bajra flour'are known to be responsible for its poor keeping quality. An attempt was made to study the nature of the degradative changes occurring in bajra grain and flour during storage. In the first experiment bajra grain was stored in aluminium tin or gunny bag for one yeair and samples withdrawn at four months interval. The moisture content and lipase activity decreased during storage while level of free fatty acids (FFA), Peroxide Value (PV) and Malondialdehyde (MDA) increased in grain in both types of storage. The level of FFA was lower in grain when stored in aluminium tin. Peroxidative changes in grain wereearlier and of higher magnitude when stored in gunny bag. The Gas Liquid Chromatographic (GLC) profile of free fatty acids did not show significant changes in either types of storage. In the first of the series of experiments with bajra flour the lipid degradative changes were examined in bajra flour stored in monsoon season. The level of moisture and lipase activity fluctuated while FFA, PV and MDA increased during storage. Hydrolytic release of fatty acids was continuous while peroxidative changes were maximum after 14 days of storage. The GLC profile of free fatty acids indicated a fall in the proportions of linoleic, oleic and palmitic acids during storage while the levels of linolenic acid fluctuated. The influence of synthetic antioxidants (ascorbic acid, 3-carotene and Butylated hydroxy toluene (BHT) 0.1% (w/w) level)and natural antioxidants (maize flour and tomato seed powder at 5% (w/w) level) on lipid degradation was studied in bajra flour in monsoon season. Activity of lipase decreased in flour treated with some of the antioxidants especially tomato seed powder. The free fatty acid concentration was higher in the antioxidant treated flour at 21 days of storage. This was possibly due to the deterrent action of the antioxidants on lipid oxidation as was shown by the significantly low peroxide value in antioxidant treated flours. MDA levels in stored flour was lowered by ascorbic acid,3-carotene and maize flour but not by BHT and TSP. In another experiment bajra flour was stored under simulated conditions of monsoon, winter and summer and the influence of BHT (at 0.1% level) and TSP (at 5 and 10% levels) on lipid degradative changes were examined. Peroxidative changes were maximum in simulated conditions of monsoon. Hydrolytic release of free fatty acids was maximum in simulated summer season but peroxidation was lower than that in monsoon. In the winter season both hydrolytic and peroxidative changes in flour lipids were low. Although both the antioxidants arrested peroxidative degradation the natural antioxidant TSP used at 5% level was more effective. The deterrent action of the antioxidants was greater in summer than in other seasons. Heat treatment at 50°C and 100°C for 2 hours to inactivate lipase in bajra flour led to a reduction in the release of free fatty acids and consequent peroxidation reactions for a period of 30 days. Overall it may be stated that the flour deterioration due to lipid peroxidation can be arrested to increase shelf life of bajra flour by judicious use of antioxidants or by heat treatments.enBIOCHEMISTRYA STUDYThesis