Application of wheat and rice composite flour in breadmaking

Experiments were conducted to determine the suitability of substituting portions of wheat flours with flours from three different Thai rice varieties for breadmaking. Experimental levels of replacement were 5, 10, 15 and 20 percent with flour from RD 21 variety which has a low amylose content, RD 23 or LPT 123 varieties, both with high amylose contents. Two kinds of enzymes, barley malt and fungal amylase, were added to the composite flours and their effect on the volume and quality of the rice-based bread was determined. Results showed that in the composite flours studied, the enzymes, levels of replacement, and the varieties of rice have significant effect on the weight, specific volume and over-all acceptability of the bread samples. However, the enzymes did not introduce a significant effect on the volume, protein and fat content as well as to the character and color of the crust in the sensory analysis. The different tests showed that the protein, fat and ash content decreased as much as 10 %, 26 % and 14.5 %, respectively, as the replacement levels of wheat flour with rice flours were increased. However, the weight of the bread samples increased by as much as 11 grams at the same conditions. The increase or decrease of these properties can be fitted to a linear curve at different slopes for the respective properties with RD 21, which has a low amylose content, low gelatinization temperature, high negative setback viscosity and a soft gel consistency performing the best followed by RD 23 and LPT 123, respectively. Comparison of the nutritional and sensory qualities of the bread made of 100 percent wheat flour and the sample which performed best, the bread with 5 percent RD 21 flour with barley malt, showed a non-significant difference. The over-all acceptability of the products showed that it is suitable to substitute wheat flour with flours generated from rice by up to 15 percent replacement level only.