Comparison of methods used to determine protease activities of insect (Eurygaster integriceps) damaged wheat and flour

Abstract

Different methods have been used by different researchers to determine the protease activity (PA) of insect-damaged wheat. The aim of this research work was to determine the level of PA of wheat varieties with different sunn pest-damaged kernel ratio using four different literatures and to study the compatibility among them. The objective was to determine which method is more suitable for reliable measurement of PA in insect-damaged wheat and its flour. The method proposed by Yakovenko et al. (1973) and Sivri's method (1998) were not accepted because the amount of water-soluble protein in sound samples increases with time. AACC Method 22–62.01 (AACC International, 2010) was also not suitable for the determination of sunn pest PA. It was concluded that Every's method (1991a, 1991b) showed the difference between the PA of the samples more clearly than the other methods, but that this method is relatively low accuracy because it determines PA based only on gel height without the use of instrumental equipment. In this context, the modified SDS-protein gel method of Sivri (1998), performed with a spectrophotometer, is a successful method for the determination of PA, but when the amount of water-soluble protein was not considered, more accurate data were obtained.