Enhanced Lipid Stability in Whole Wheat Flour by Lipase Inactivation and Antioxidant Retention

Abstract

Cereal Chem. 85(2):218-223The purpose of this study was to determine the effectiveness of dry heat, steam, and microwave treatments in decreasing lipase activity, while retaining antioxidant activity, to stabilize whole wheat flour against lipid degradation during storage. Bran was heat-treated in 230-g batches using four levels (exposure times) for each of the three treatment methods. Lipase activity and antioxidant activity were quantified for all treatment combinations. None of the treatments significantly decreased antioxidant activity; the levels determined to be optimal, inasmuch as further heating did not significantly decrease lipase activity, were 25 min of dry heat, 60 sec of microwave (1000W), and 60 sec of steam. These treatments effectively decreased lipase activity by 74, 93, and 96%, respectively. Optimum treatments were evaluated for acceptance using a consumer sensory panel during a 12-month storage period. No significant differences in acceptance were found between the control and any of the samples either at baseline or after storage. This suggests that whole wheat flour can be stabilized against lipolysis by utilizing the treatments described in this study without decreasing antioxidant activity, and that manufacturers may utilize these treatments without risking decreased consumer acceptance.

Improved Storage Stability of Pearl Millet Flour Through Microwave Treatment

“…Bookwalter et al [5] reported complete inactivation of lipid enzymes in whole proso millets by heat processing with steam-jacketed paddle conveyor having temperatures up to 110°C. The higher reduction (96 %) of lipase activity in whole wheat flour during steam heating as compared to the microwave heating (93 % reduction) for similar duration (60 s) was also observed by Rose et al [26]. Keying et al [13] also observed lipase inactivation in naked oat kernels during microwave heating and correlated with temperature and exposure time.…”

Wheat germ stabilization by infrared radiation

“…A previous study on germ stabilization described the inactivation of wheat germ lipase at 175°C in a forced draft oven (Rose et al 2008). Taking into account this previous study along with the temperature profiles and the features of the IR equipment of the present investigation, the following ranges of independent variables were selected to reach the optimum processing conditions: IRRI from 3000 to 9000 W/m 2, GD from 0.2 to 0.1 m and TT from 1 to 3 min.…”

Key issues and challenges in whole wheat flour milling and storage

“…Since the lipase activity is concentrated in the bran, this fraction can be heated separately and then added to wheat flour in the proper proportions to make whole wheat flour (Rose et al, 2008). This allows for the inhibition of lipase without risking influencing the flour functional properties.…”

“…Therefore, if lipase is denatured, lipoxygenase is also denatured. Vetrimani and Haridas Rao (1990) reduced lipase activity in wheat bran by 40% by heating at 175 C for 40 min Rose et al (2008) reported 74, 93 and 96% reduction in lipase activity when wheat bran was dry heated at 175 C for 25 min, 60 s of microwave (1000 W), or 60 s of steam, respectively.…”