SOME BIOCHEMICAL AND MICROBIOLOGICAL CHANGES IN PROSO MILLET FLOUR DURING STORAGE

Proso millet flour was stored at 10(DEGREES)C and 13% rh; 10(DEGREES)C and 43% rh; 10(DEGREES)C and 80% rh; 25 (+OR-) 3(DEGREES)C and 13% rh; 25 (+OR-) 3(DEGREES)C and 43% rh; 25 (+OR-) 3(DEGREES)C and 80% rh; 45(DEGREES)C and 13% rh; 45(DEGREES)C and 43% rh; and 45(DEGREES)C and 80% rh. The sorption isotherms of proso millet grain were established to insure an equilibrium between the flour samples and the surrounding environment inside desiccators containing saturated salt solutions needed to generate the confined environments. Samples of the flour packed in cotton bags were taken for microbiological and analytical tests after 2, 6 and 12 months. Free lipids decreased while bound lipids in the flour increased during storage. However, samples stored at 25 (+OR-) 3(DEGREES)C and 80% rh and 45(DEGREES)C had an increase in free lipids and a decrease in bound lipids during the last 6 months. The percentages of fatty acids but not the fatty acid profile differed. A higher decrease in C(,18:2) but an increase in C(,16:0), C(,18:0), C(,18:1), and C(,20:0) in free lipids were found in samples stored at 45(DEGREES)C than those at 10 and 25 (+OR-) 3(DEGREES)C. Fat acidity and peroxide value in samples stored at 25 (+OR-) 3(DEGREES)C and 45(DEGREES)C and their rh combinations increased during the first 6 months but declined afterward. However, the peroxide values of samples stored at 25 (+OR-) 3(DEGREES)C and 43% rh continued to increase throughout storage. The protein content measured by Kjeldahl method decreased with time, reaching a minimum in samples stored at 45(DEGREES)C and 80% rh. The total microbial counts and mold and yeast counts generally decreased during the storage. The decrease was more severe at 45(DEGREES)C at which temperature molds and yeast were mostly affected. The counts indicated that mold growth was not of significance, thus lipid breakdown and increases in fat acidity might have been due to the native flour lipases only