Effect of Refined Milling on the Nutritional Value and Antioxidant Capacity of Wheat Types Common in Ethiopia and a Recovery Attempt with Bran Supplementation in Bread

Abstract

The effect of wheat flour refined milling on nutritional and antioxidant quality of of two types of wheat (hard and soft) grown in Ethiopia was first evaluated. Then a recovery was attempted on bread prepared with the supplementation of the white wheat flour with different levels (0%, 10%, 20% and 25%) of wheat bran. Whole wheat flour (100% extraction) and white wheat flour (68% extraction) were subjected to proximate, mineral and antioxidant analysis. Results indicated that at low extraction rate (68%) the value of protein, fat, fiber, ash, Iron, zinc and phosphorous and antioxidant content of the samples were significantly affected (decreased) (P<0.05) by milling. The Total Phenolic Content (TPC) of white wheat flours, which ranged from 3.34 to 3.49 mg GAE/g were significantly lower (p<0.005) than those of whole wheat flours (ranging 7.66 to 8.20 GAE/g). At the concentration of 50 mg/mL, the DPPH scavenging effect of wheat extracts decreased in the order of soft whole, hard whole, soft white and hard white wheat flour, which was 90.39, 89.89, 75.80, and 57.57%, respectively. Moreover, the protein, fat, ash, fiber, iron and zinc contents of the bran supplemented breads increased significantly (P<0.05) with the progressive increase in the bran level of the bread. The highest value for protein, fat, fiber, ash, iron and zinc was 12.04, 2.61, 2.48, 3.27 g/100 g and 4.84 and 2.33 mg/100 g respectively were found in 25% bran supplemented bread. The sensory evaluation of bread showed that all level of supplementation had mean score above 4 on a 7 point hedonic scale on over all acceptances. The results indicated that refined milling at 68% extraction significantly reduces the nutritional and antioxidant activity of wheat flour. Bread of good nutritional and sensory qualities could also be produced from 10% and 20% bran supplementation.