Abstract
Using various rice flours prepared by different milling methods, the relationship between rice flour properties and specific loaf volumes of one-loaf bread made from rice flour with wheat vital gluten were studied. Damaged starch content of rice flour varied from 1.0% to 22.1%. A significant negative correlation was verified between damaged starch content and specific loaf volume of one-loaf bread. Rice flour with low damaged starch content mainly consisted of compound starch granules, aggregated polyhedral single starch granules and smooth surface cells surrounded by the cell wall. The structures of starch granules and cells were maintained in rice flour with low damaged starch content. Rice flour with high damaged starch content consisted of only fine irregular particles without the apparent rice starch structure, or contained fractured large and small cells with rough surface. Although there was not significant correlation between specific loaf volume and median particle size, rice flours which were successful at making bread with high specific loaf volume commonly showed a peak centered around 60 µm with a smaller amount of larger size particles in the particle distribution profile. Thus, the flour particle size distribution appears to affect the specific loaf volume of one-loaf bread. Both the damaged starch content and the profile of particle size distribution were important for high specific loaf volume of one-loaf bread. Less damage to starch and cell structures while lowering the particle size during milling process is critical in obtaining better flour for rice one-loaf bread making.
