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Glass Transition Behavior and Rheological Properties of Surfactants and Gluten-Surfactant Mixtures

¹Department of Nutrition and Food Science, American University of Beirut, Riad El-Solh 1107 2020, Beirut, Lebanon. ²Center for Advanced Food Technology, Department of Food Science, Rutgers, The State University of New Jersey, P.O. Box 231, New Brunswick, NJ 08903-0231. ³Corresponding author. Fax: 961-1-744460. E-mail: toufeili@aub.edu.lb

Diacetyltartaric acid esters of monoglycerides (DATEM) and sodium stearoyl lactylate (SSL) displayed thermal events corresponding to glass transition temperature (T_g) and melting of crystalline domains, while monoglycerides (MG) exhibited an endothermic peak corresponding to melting of crystalline structures when heated in a differential scanning calorimeter. The plasticizing effect of water on T_g of gluten exhibited little apparent change in the presence of DATEM, MG, or SSL (glutensurfactant 10:1), in the moisture range of 6.5–21.3% as shown by mechanical spectrometry and differential scanning calorimetry. Glutensurfactant mixtures showed higher G′ and apart from gluten-SSL, which displayed higher tan δ (G″/G′) at ≤2.51 rad/sec, lower tan δ values than gluten in the frequency range of 0.1–100 rad/sec. DATEM and SSL softened the gluten network before cross-linking reactions, while MG shifted the onset of cross-linking reactions to higher temperatures at moisture contents of 30–40%. Complete vitrification of the gluten network occurred at higher temperatures, at the indicated moisture contents, in the presence of surfactants. Softening of the matrix and the delay in cross-linking of gluten, in the presence of surfactants, might allow for greater expansion of doughs during baking with concomitant increase in loaf volumes.