Wheat gluten structure and (non–)covalent network formation during deep-fat frying

• Published in: Food research international 2024-07, Vol.188, p.114503, Article 114503
• Main Authors: Riley, I.M., Verma, U., Verboven, P., Nicolai, B.M., Delcour, J.A.
• Format: Article
• Language: English
• Subjects: Cooking - methods; Deep-frying; Glass transition; Gliadin - chemistry; Gluten protein network; Gluten-water interactions; Glutens - chemistry; Hot Temperature; Microstructure; Polymerization; Triticum - chemistry; Water - chemistry; Wheat gluten
• ISSN: 0963-9969; 1873-7145; 1873-7145
• DOI: 10.1016/j.foodres.2024.114503

[Display omitted] •Gluten proteins polymerize mainly by disulfide cross-linking during deep-frying.•Deep-frying results in a denser gluten protein network.•Molecular mobility and protein polymerization contribute to structure expansion.•The gluten network structure does not depend on the initial hydration level. The aim of this work was to investigate wheat gluten protein network structure throughout the deep-frying process and evaluate its contribution to frying-induced micro- and macrostructure development. Gluten polymerization, gluten-water interactions, and molecular mobility were assessed as a function of the deep-frying time (0 – 180 s) for gluten-water model systems of differing hydration levels (40 – 60 % moisture content). Results showed that gluten protein extractability decreased considerably upon deep frying (5 s) mainly due to glutenin polymerization by disulfide covalent cross-linking. Stronger gliadin and glutenin protein–protein interactions were attributed to the formation of covalent linkages and evaporation of water interacting with protein chains. Longer deep-frying (> 60 s) resulted in progressively lower protein extractabilities, mainly due to the loss in gliadin protein extractability, which was associated with gliadin co-polymerization with glutenin by thiol-disulfide exchange reactions. The mobility of gluten polymers was substantially reduced during deep-frying (based on the lower T2 relaxation time of the proton fraction representing the non-exchanging protons of gluten) and gluten proteins gradually transitioned from the rubbery to the glassy state (based on the increased area of said protons). The sample volume during deep-frying was strongly correlated to the reduced protein extractability (r = –0.792, p