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Two Metal Ions Improve Brightness in Wheat-Dough Products and Affect Aqueous Dispersion of Gluten¹

¹Contribution No. 96-551-J from the Kansas Agricultural Experiment Station, Manhattan, KS 66506. ²Graduate research assistant and professor, respectively, Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506. ³Corresponding author. E-mail: pas@wheat.ksu.edu

Zinc and aluminum ions at 0.05% of wheat flour, dry basis (7.4 and 18.5 mmol/100 g, respectively), improved the brightness of raw and dried spaghetti and salt and alkaline noodles. They also retarded bacteria and yeast and mold growth in salt noodles held at 25°C for two days as determined by total plate counts. Neither metal ion caused a change in noodle cooking quality, but they imparted a slight aftertaste in cooked noodles. Wheat flour dough mixed with 0.05% zinc or 0.025% aluminum ion (fwb), when kneaded in aqueous 0.1% calcium chloride, gave gluten with increased brightness. Zinc and aluminum ions appear to complex with enzymic browning chromophores in wheat dough and gluten and change their spectral properties. Zinc and aluminum ions affected the dispersion of gluten in water at pH ~5.0 and facilitated its spray-drying, but they were not detrimental to baking quality. Citric and tartaric acids at 5 mmol/100 g of gluten (db) gave wet gluten with pH ~4.5, which improved its brightness and water dispersibility.