Physical Properties of Butter Cake Made from Mixed Hom-Mali and Glutinous Rice Flours

Abstract

The amylose content and the pasting and gelatinization properties are the most important physicochemical properties of starch. The amylose content of starch in flour is considered to affect the texture of food products. Glutinous rice contains very limited amylose content (2–4%) whereas the amylose content of Hom-Mali rice is about 15%. The objectives of the study were to investigate: 1) the pasting properties of mixed flours of Hom-Mali rice and glutinous rice and 2) the physical properties of butter cakes prepared from the mixed flours. Two glutinous rice varieties, RD6 (2.8% amylose content) and Niew Ubon (4.6% amylose content) were used in the study. Glutinous rice flour was blended with Hom-Mali rice flour (HMRF) in ratios of 1:0, 3:1, 1:1, 1:3 and 0:1, respectively. The results of the study of the pasting properties of the mixed flours using a Rapid Visco-Analyzer demonstrated that pasting temperature, trough, final viscosity and setback were significantly (P < 0.05) increased as the content of Hom-Mali flour increased, whereas breakdown decreased. The data suggested that the flour with high amylose content was more resistant to shear during heating and the starch had high ability to retrograde compared with the low amylose content equivalent. Increasing the content of Hom-Mali
flour resulted in a significant (P < 0.05) increase in the specific volume of the butter cake. Texture profile analysis of butter cake samples showed that their hardness significantly (P < 0.05) increased as the amount of Hom-Mali flour increased, whereas there was a decrease in springiness, chewiness and adhesiveness. Thus, butter cake prepared with a low content of Hom-Mali flour was softer. The total variance of the principal component analysis (PCA) of the pasting and physical properties of butter cakes was 80% (PC1= 60% and PC2 = 20%). PC1 was the component for the hardness and pasting properties, whereas the texture component was represented by PC2. The PCA result enabled the cake samples to be classified into three groups according to the amylose content and the textural properties of the samples: 1) high amylose (12.5–16%) consisting of samples using 100% HMRF, HMRF:RD6 and HMRF:Niew Ubon = 75:25; 2) medium amylose (5.5–10%) consisting of samples using HMRF:RD6 = 50:50 and 25:75, and HMRF:Niew Ubon = 50:50 and 25:75; and 3) low amylose (2–4%) consisting of samples of 100% RD6 and 100% Niew Ubon. The study revealed that less expensive glutinous rice flour could be used to reduce the amount of high cost Hom-Mali flour in bakery products. Further study on consumer acceptability of the cakes made from mixed flours needs to be done to explore the market potential of the products.