Loading...
Theses
Browse
1 results
Search Results
ThesisItem Open Access Biochemical studies on fatty acid esterase isolated from pearl millet and wheat flours(CCSHAU, Hisar, 2020) Nisha; Chugh, L. KThe present investigation was conducted on pearl millet cv. HC 20 and wheat cv. WH 1105. Pearl millet fatty acid esterase (PM-FAE) and wheat fatty acid esterase (WH-FAE) were partially purified from by ammonium sulphate fractionation (30-60 % saturation) followed by dialysis by 3.03 and 7.75 folds with specific activity of 15.35 and 22.5 units/mg protein and recovery of 57and 56 % of the activity, respectively. PM-FAE and WH-FAE, both exhibited optimum pH of 8.0. Optimum temperature for PM-FAE (40oC) was lower than WH-FAE (45oC). WH-FAE was comparatively more stable at high temperature (70OC). Km value of PM-FAE (0.129 μM p-NPB) was lower than that of WH-FAE (0.28 μM p-NPB). Km values of PM-FAE for p-NPB and NPO were about 50 % lower compared to that of WH-FAE. Affinity of PM-FAE and WH-FAE for NPD was approximately equal. Ascorbic acid and palmitoyl ascorbate inhibited both FAEs in a concentration dependent manner. After 5 days of storage, reduction of 73 % in total buildup of fat acidity (FA), 84% reduction in rate of increase in FA, 55 % inhibition of in vitro activity of FAE, 52 % inhibition in situ activity of FAE and 50 % inhibition of activity of lipoxygenase (LOX) in 0.58 % ascorbic acid-fortified flour compared to unfortified flour were observed. Inhibitory effect of ascorbic acid fortification on in vitro activity of FAE, in situ activity of FAE and LOX increased with fortified concentration of ascorbic acid whereas rate of increase in FA was almost unaffected. Inhibition of LOX (62-69 %) in 0.84 % ascorbic acid-fortified flour was comparable to that (68-74 %) of blanched grain flour (BGF) throughout storage period. It was concluded that comparatively higher activity of PM-FAE in flour, lower Km value for its substrates and lower optimum temperature might be responsible for faster in situ hydrolysis of lipids and hence poor shelf life of pearl millet flour than wheat flour. Indirect fortification of flour by ascorbic acid treatment of pearl millet grains was effective in negatively modulating activities of FAE and LOX in flour for arresting not only in situ hydrolysis but also enzymatic oxidation of lipids.