FUNCTIONAL-PROPERTIES OF LOW M(R) WHEAT PROTEINS .2. EFFECTS ON DOUGH PROPERTIES

The effects of non-gluten low M(r) wheat proteins on bread-making quality and dough properties were investigated. Low M, proteins retarded the re-polymerisation of SDS-unextractable glutenin (glutenin macropolymer-GMP; gel protein) during resting of doughs from the cultivars Obelisk, Camp Remy, Castan and Rektor. Polymerisation in the overly-strong cultivar, Fresco, was not affected substantially Additions of 0.2% to 0.4% by weight of low M(r) proteins to flour increased the relaxation half-times of doughs from cvs Camp Remy and Rektor as measured in a Bohlin VOR Rheometer. Furthermore, the phase angle, delta (ratio of loss modulus to storage modulus), decreased at these levels of low it, protein addition, indicating the formation of a dough with greater elastic character. At 0.8% (w/w) addition, the relaxation time decreased and the phase angle increased. The effects on the dough of cv. Obelisk were relatively slight. The complex dynamic moduli of doughs from cvs Camp Remy and Rektor were relatively unaffected by the addition of low M(r) proteins, but the moduli decreased when they were added to cv. Obelisk flour. The rate of GMP re-polymerisation during resting was related negatively to the phase angle, whereas the complex modulus increased to a plateau value as the rate of GMP reassembly increased. In micro-baking tests with 10-g and 100-g pan leaves, increases in loaf volume of 11% to 12% were observed with up to 0.8% (w/w) addition of low M(r) proteins to cv. Camp Remy dough. For the weaker cultivar, Obelisk, addition of low M(r) proteins caused either no increase in loaf volume or a decrease of 13%, depending on the level of addition. The results indicate that, although low M(r) wheat proteins have inconsistent effects on loaf volume, they have profound effects on both the biochemical and rheological properties of dough.