ACTA ALIMENTARIA VOL. 8 (A QUARTERLY OF THE COMMITTEE ON FOOD SCIENCE OF THE HUNGARIAN ACADEMY OF SCIENCES, 1979)
1979 / 1. sz. - KOLOSTORI, M.: Flour quality and proteolysis
Acta Alimentaria, Vol. 8 (1), pp. 1 -12 (1979) FLOUR QUALITY AND PROTEOLYSIS M. KOLOSTORI (Received September 7, 1977; revision received April 19, 1978; accepted April 27, 1978) The protease activity in flours of various wheat varieties was studied on a synthetic substrate, N-a-benzoyl-DL-arginine-4-nitroanilid (DL-BAPA). Protease activity was found to depend largely on the wheat variety and conditions of cultivation. The correlation between various methods of protease activity measurement was studied using bacto-haemoglobin or DL-BAPA as substrate. The correlation discovered was characteristic only within variety, which points to the presence of different proteases in wheat. The effect of protease upon the physical characteristics of dough and the volume of the test loaf was studied in model experiments with papain. Hereafter the protease activity of many wheat flours was measured on bacto-haemoglobin and DL-BAPA substrates and the baking properties of the flours were established. With some of the wheat varieties protease activity significantly affected the baking properties. However, no close correlation was found between flour quality and protease activity. The physical characteristics of doughs prepared from wheat flour are determined mostly by the gluten proteins. Changes in these proteins cause changes in the physical characteristics of doughs and the quality of the end product . By breaking the peptide bonds of the gluten proteins proteases have a softening effect on the dough. Data found in the literature show cereal proteases to be of the papain type (SH proteinases). Their activity may be increased with cysteine, glutathione or other reducing agents (BALLS & HALE, 1938). However, some conflicting views were also encountered (HITES et al., 1951). The analysis of proteases extracted from wheat flour by starcli-gel electroforesis (KAMINSKI & BUSHITK, 1969) and their fractionation by gel chromatography (WANG & GRANT, 1969) indicate that wheat flour contains several proteases. HANEORD (1967) differentiates between alfa- and beta-proteases in wheat flour. The alfa-protease is responsible for the softening of gluten, the betaprotease for the increase in acid-soluble nitrogen. The pH optimum of betaproteinase falls in the mildly acid region and that of the gluten softening alfaproteinase is at pH 7-8. In the aleurone fraction and in the endosperm BELITZ and LYNEN (1974) found two types of proteases, which differ in their pH optimum, in their behaviour to indicators and in their molecular weight. Acta Alimentaria 8,1979