Meeting Abstract

248
Retardation of dark discoloration in barley-based food products. Z. QUINDE and B.-K. Baik. Department of Food Science & Human Nutrition, Washington State University, Pullman, WA.

Dark discoloration negatively influences the aesthetic properties of cereal-based food products. Discoloration in barley-based products occurs by autoxidation and enzymatic (i.e. polyphenol oxidase, PPO) or metal ions catalyzed oxidation of phenolic compounds. Oxidized phenolic compounds, quinones, polymerize or precipitate with protein and metal ions, forming dark pigments. We determined the effects of abrasion and heat treatment of grains, exclusion of oxygen, and use of anti-browning agents on the retardation of darkening in barley flour gel or dough of four types of barley. Barley types included hulled proanthocyanidin-containing and free, and hulless regular and waxy barley. Abrasion by more than 30% in hulled barley and more than 15% in hulless barley increased the L* value (brightness) of barley flour dough by 1–7. Steam heating of abraded grains also increased L* value of barley flour gels by 1.8–3.4. The discoloration of barley flour dough was effectively reduced by storing the dough under nitrogen gas to exclude oxygen at 4°C. Ascorbic acid at 1,500 ppm was most effective for retarding discoloration of barley flour dough, followed by 50 ppm of 4-hexyl resorcinol, which is an enzyme competitive inhibitor. Discoloration of barley-based food products may be effectively controlled by lowering total polyphenol content and/or PPO activity through abrasion, heat inactivation, exclusion of oxygen, and use of enzyme inhibitors.