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Solvent Retention Capacity (SRC) Testing of Wheat Flour: Principles and Value in Predicting Flour Functionality in Different Wheat-Based Food Processes and in Wheat Breeding—A Review

¹U.S. Department of Agriculture, Agricultural Research Service, Soft Wheat Quality Laboratory, Wooster, OH 44691. ²Current address: Campbell Soup Company/Pepperidge Farm, Camden, NJ 08103. ³Food Polymer Science Consultancy, Morris Plains, NJ 07950. ⁴Corresponding author. E-mail: LevineHarry@optonline.net

Solvent retention capacity (SRC) technology, its history, principles, and applications are reviewed. Originally, SRC testing was created and developed for evaluating soft wheat flour functionality, but it has also been shown to be applicable to evaluating flour functionality for hard wheat products. SRC is a solvation test for flours that is based on the exaggerated swelling behavior of component polymer networks in selected individual diagnostic solvents. SRC provides a measure of solvent compatibility for the three functional polymeric components of flour—gluten, damaged starch, and pentosans—which in turn enables prediction of the functional contribution of each of these flour components to overall flour functionality and resulting finished-product quality. The pattern of flour SRC values for the four diagnostic SRC solvents (water, dilute aqueous lactic acid, dilute aqueous sodium carbonate, and concentrated aqueous sucrose solutions), rather than any single individual SRC value, has been shown to be critical to various successful end-use applications. Moreover, a new predictive SRC parameter, the gluten performance index (GPI), defined as GPI = lactic acid/(sodium carbonate + sucrose) SRC values, has been found to be an even better predictor of the overall performance of flour glutenin in the environment of other modulating networks of flour polymers. SRC technology is a unique diagnostic tool for predicting flour functionality, and its applications in soft wheat breeding, milling, and baking are increasing markedly as a consequence of many successful, recently published demonstrations of its extraordinary power and scope.