Different heating techniques for oat lipase stabilization: Grain quality and storability

Incorporation of oats in the human diet has received great attention for its role in the lowering of blood plasma cholesterol levels; however, problems associated with postprocessing storage continue to limit its use. The action of lipases is believed to be the main problem. When lipase comes in contact with a lipid substrate after milling, it results in deteriorative effects such as oxidation that cause the development of off flavors and odors. The current industrial heat treatment uses convective heat and live steam to inactivate oat lipases. Alternative heat applications, including microwave (MW) energy, infrared (IR) processing, conventional oven heating (COH) and a simulated industrial heat treatment (IHT) were administered to samples of commercial whole oat kernels. Results were analyzed using the repeated measures procedure of the Statistical Analysis System (SAS) program (v6.12). Analysis of variance (ANOVA) was performed by following the General Linear Model (GLM) procedure for SAS. Principle component factor analysis was also performed. Treatment differences were determined using the LSD test and were reported to be significant when P \u3c 0.05. Significantly greater P \u3c 0.05. lipase activity was shown during oat storage in the control (CTRL) oats (with no heat treatment) after 3 and 6 months than for heat treated oats. IR treatment contained the least amount of activity after 3 months, but was not significantly different than IHT treated oats. POV was significantly higher P \u3c 0.05. for IF, MW and IHT heat treatments initially than for the other treatments, but decreased more for the IR and MW treatments over time. The COH, CTRL and IHT treatments exhibited a sharper reduction in POV after 3 months storage than for the IR and MW samples. FA levels were significantly different P \u3c 0.05. for IR treatments than for other heat applications, where an increasing trend was observed for C14:0 and C16:0/16:1 saturated and monounsaturated fatty acids; and a decreasing trend for C18:2 and C18:3 unsaturated fatty acids. SPME headspace analysis found that hexanal, the major volatile formed, was observed initially for IR treated oats only. When detected, it was present only at trace levels in (W-O) samples of the CTRL, COH, MW and IHT treatments. Although not significant, (G-O) samples produced higher hexanal volatiles than (W-O) samples of the same heat treatment, and were highest for the CTRL and IR treatments. IR treated (W-O) samples were the exception, however, where hexanal in (W-O) was higher than for (G-O) during the first 2 months, before decreasing to much lower levels for the remaining storage period. (Abstract shortened by UMI.