Effect of cooking and storage on the amount and molecular weight of (1->3)(1->4)-beta-D-glucan extracted from oat products by an in vitro digestion system

The extractability and molecular weight of beta-glucan in oat bran, oat bran muffins, and oat porridge and the changes taking place during processing and storage were studied. The beta-glucan was extracted using hot water and a thermostable alpha-amylase and by an in vitro system that simulated human digestion. Molecular weight (MW) of the extracted beta-glucan was determined using high-performance size-exclusion chromatography. Hot-water treatment extracted 50-70% of total beta-glucan in oat bran samples and rolled oats. The chromatographic peak MW of extracted beta-glucan was in the 1.4-1.8 x 10(6) range. Using the in vitro digestion system, 12-33% of total beta-glucan in bran and rolled oats was solubilized, and peak MW was in the same range as beta-glucan extracted by hot-water treatment. In muffins, 30-85% of total beta-glucan was solubilized by in vitro digestion, with a major difference in extractability among muffins from different recipes. Peak MW of extracted beta-glucan was lower in all muffins when compared to original bran. During frozen storage, extractable beta-glucan decreased by >50% in all muffins, but no change in peak MW of extracted beta-glucan was detected.