Effect Of Fermentation On Physicochemical Microbiological Properties Of Brown Rice Flour And The Related Brown Rice Bread Properties

Abstract

Brown rice bread is one of the most popular non-gluten products suitable for celiac patients. Brown rice (BR) contains a variety of nutrients, but its high phytic acid content inhibits dietary mineral absorption. Fermentation is one of the most effective treatments for reducing the antinutrient phytic acid via the action of microorganisms and grain phytases. The objective of this study was to investigate effect of fermentation (fermentation method and temperature) on physicochemical (pH, pasting property, phytic acid, iron, and total phenolic content) and microbiological properties of BR flour and its related bread properties. BR flour was fermented at RT (25oC) for 15 hours, either naturally or with yeast, and the fermented flour was then used to make bread. The differences in properties between samples from the two fermentation methods and the control were used to determine which fermentation method is superior. Fermentation decreased the viscosity, increased the microbiological count as well as lowered the pH values of fermented samples, released more phenolic compounds, and reduced the amount of phytic acid to enhance mineral bioavailability in fermented BR flour and BR bread. Natural fermentation was the best fermentation method, with the highest amount of reduced phytic acid and iron combined with the reserved total phenolic compound and a high sensory evaluation score. Three levels of temperature 25oC, 30oC, and 35oC were then used to determine the best fermentation temperature using natural fermentation for 15h. With increasing fermentation temperature, the microbiological counts increased, the pH value decreased, and the total content of phenolic compounds in BR flour and BR bread products. Natural fermentation at 30°C was the most effective fermentation condition for reducing antinutrients, increasing mineral bioavailability, and preserving the total phenol content of BR, with the highest overall acceptability score.