Foaming and rheological properties of the liquid phase extracted from wheat flour dough

Dough liquor (DL) is considered as a good model of bread dough liquid phase which plays an important role in alveolar structure creation. In this work, DL was extracted from dough pieces of various contents (g for 100 g flour) of water (55-70), sugar (0-15), rapeseed oil (0-10) and bran (0-20). The extraction yield of DL was 5.0 +/- 2.4% and its dry matter content varied between 10.8 and 27.2% of total DL mass. Its composition has been determined in terms of lipids content (<= 0.08 mg/mL), polysaccharides, mostly arabinoxylans (0.9-4.7 mg/mL), arabinogalactan-proteins (AGP) and soluble proteins (20.7-38.0 mg/mL). The rheological properties (bulk and surface) of fresh DL, and foaming properties of diluted DL (1/10), were determined using cone-plate rheometry, pendant drop method and Foamscan device, respectively. DL behaved like a macromolecular solution, displaying a slight shear-thinning behavior with an apparent viscosity varying between 0.03 and 0.6 Pa s(n), at shear rate 10 s(-1). Its surface tension varied between 35 and 45 mN/m. Its adsorption kinetics, governed by protein diffusion to the interface, followed two regimes, the first one depending on sugar content, and the second one on AGP content. Drainage and foam stability kinetics were influenced by neutral sugars, probably through the impact of glucose and mannose on DL viscosity. The understanding of the mechanisms of fermented dough stability could be improved by taking the results of DL surface tension into account. (C) 2014 Elsevier Ltd. All rights reserved.