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Retardation of Discoloration in Barley Flour Gel and Dough

¹Graduate research assistant and associate professor, Department of Food Science and Human Nutrition, Washington State University, Pullman, WA 99164-6376. ²Assistant professor, Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164-6420. ³Corresponding author. Phone: 509-335-8230. E-mail: bbaik@wsu.edu

Dark discoloration negatively influences the aesthetic properties of barley-based food products. The effects of abrasion and heat treatment of grains, exclusion of oxygen, and the use of antibrowning agents on the retardation of darkening in barley flour gel or dough were determined in four types of barley, including hulled proanthocyanidin-containing and hulled proanthocyanidin-free, hulless regular, and hulless waxy barley. Abrasion by >30% in hulled barley and by >15% in hulless barley significantly increased the brightness (L*) of barley flour dough by 0.1–7.1. Steam heating of abraded grains also significantly increased the L* of barley flour gels by 1.8–3.4. Ascorbic acid at 1,500 ppm was most effective for retarding discoloration of barley flour dough, followed by 50 ppm of 4-hexylresorcinol, which is an enzyme competitive inhibitor. The discoloration of barley flour dough was also effectively reduced by storing the dough sheets at 4°C under nitrogen gas to exclude oxygen or under anaerobic conditions at 20°C. Discoloration of barley-based food products may be effectively controlled by selecting genotypes with low discoloration development such as proanthocyanidin-free genotypes, by lowering total polyphenol content or polyphenol oxidase (PPO) activity through abrasion, by heat treatment, by exclusion of oxygen, and by the use of enzyme inhibitors.