Functional Properties of Protease Modified Wheat Flours

Abstract

The effect of enzymatic modification of wheat flour proteins on their functional properties was evaluated as a function of the degree of hydrolysis (DH). Soluble protein increased from 7.1 to 53% for 0% to 36.7% DH flour, and viscosity and yield values decreased concomitantly. Emulsion capacity slightly decreased up to 14% DH and then increased. Baummann water and oil absorption capacities and farinograph water absorption had similar trends; they showed a maximum increase at 3.8% DH where Baumann and farinograph absorption values increased by 30%. Limited degree of hydrolysis (3.8-14.1% DH) was sufficient to improve quality parameters of cakes such as volume, moisture and crumb colour. Added protease resulted in pronounced reduction in molecular mass distribution of wheat proteins, especially glutenins. The increase in water soluble protein as hydrolysis proceeded was related to proteins of molecular mass less than 25 kDa. The reduction in viscosity and foam stability was related to the extent of hydrolysis of high molecular mass glutenin protein. The increased Baumann and farinograph water absorption by limited hydrolysis up to 3.8-5.4% DH may be related to increased number of polar sites and flexibility of protein network, without extensive degradation of glutenins. © 1997 Academic Press Limited.