Oxidative Gelation of Solvent-Accessible Arabinoxylans is the Predominant Consequence of Extensive Chlorination of Soft Wheat Flour

Arabinoxylans and glutenins are two critical network-forming polymeric components of wheat flours, functionally related to mixing and baking performance and baked goods quality. For soft wheat flour applications, solvent-accessible arabinoxylans (pentosans) play a dominant role in both sweet and savory products. Solvent retention capacity (SRC) testing (Approved Method 5611, AACC International 2000) is a solvation assay for flours based on the swelling behavior of polymer networks in biochemically selective diagnostic solvents (Slade and Levine 1994; Kweon et al 2009). SRC is used to predict the functional contribution of each flour component capable of forming transient entanglement networks or permanent gel networks. Water SRC is related to overall water-holding capacity by all network-forming flour components. Diagnostic solvent that exaggerates swelling of arabinoxylan networks is 50% w/w sucrose solution in water compared to water alone. The diagnostic solvent that exaggerates swelling of glutenin networks is 5% w/w lactic acid solution in water compared to water alone. Therefore, SRC measures the magnitude of exaggerated swelling to predict the extent of functional contribution. It is well documented that aqueous extracts of wheat flour arabinoxylans form permanent gels when treated with oxidizing agents at room temperature (Durham 1925; Baker et al 1943; Neukom and Kündig 1962; Moore et al 1990; Vinkx et al 1991; Bettge and Morris 2007). Oxidative gelation is affected by oxidant type and concentration, arabinoxylan concentration, pH, and presence of organic compounds (Neukom et al 1967; Painter and Neukom 1968; Crowe and Rasper 1988; Moore at al 1990). It appears to be an important contributor to soft wheat batter viscosity and also contributes to the quality attributes of dough systems (Bettge and Morris 2007). Chlorination is an essential soft wheat flour treatment for production of high-ratio cakes in the United States (Gough et al 1978; Yamazaki and Kissell 1978), and a postmilling treatment is often used to reduce flour particle size (Chaudhary et al 1981; Gaines and Donelson 1985). A critical feature of high-ratio cake baking is batter viscosity (Huang et al 1982), which can be measured by Bostwick flow. In the present study, effects of flour milling yield, extent of chlorination, and flour particle size on cake-flour functionality and potential batter viscosity were explored by SRC and Bostwick flow.