A simple method to measure lipase activity in wheat and wheat bran as an estimation of storage quality

Abstract

Abstract The purpose of this research was to develop a simple method for measuring lipase activity as an indicator of wheat and wheat bran storage quality. This simplified method does not require the separation or purification of lipase. Optimal conditions for lipase activity measurements were determined by varying the substrate (olive oil) and water concentrations, temperature, and incubation time. Following incubation, FFA were quantified spectrophtometrically using a copper soap assay, and lipase activity was expressed as units/gram (U/g), where 1 U was defined as the microequivalents of oleic acid liberated per hour. The method was tested on one commercial and four pure wheat cultivars. The lipase activity was also correlated with the development of FFA during actual storage of heat‐treated commercial bran. Lipase activity in wheat bran ranged from 2.17 to 9.42 U/g, and in whole kernel wheat from 1.05 to 3.54 U/g. Optimal olive oil and water concentrations were 0.4 to 0.8 mL and 0.15 to 0.20 mL per g of defatted sample, respectively. Optimal incubation temperature was 40°C, and incubation times of up to 8 h were linear. Lipase activity was highly correlated with the buildup of FFA in stored wheat bran ( R 2 =0.97).