Molecular weight distribution of β-glucan in oat-based foods

Oats, different oat fractions as well as experimental and commercial oat-based foods, were extracted with hot water containing thermostable a-amylase. Average molecular weight and molecular weight distributions of beta-glucan in extracts were analyzed with a calibrated high-performance size-exclusion chromatography system with Calcofluor detection, specific for the beta-glucan. Oats. rolled oats, oat bran, and oat bran concentrates all had high Calcofluor average molecular weights (206 x 10(4) to 230 x 10(4) g/mol) and essentially monomodal distributions. Of the oat-containing experimental foods, extruded flakes. macaroni, and muffins all had high average molecular weights. Pasteurized apple juice. fresh pasta, and teacake, on the other hand, contained degraded beta-glucan. Calcofluor average molecular weights varied from 24 x 10(4) to 167 x 10(4) g/mol in different types of oat bran-based breads baked with almost the same ingredients. Large particle size of the bran and short fermentation time limited the beta-glucan degradation during baking. The polymodal distributions of beta-glucan in these breads indicated that this degradation was enzymatic in nature. Commercial oat foods also showed large variation in Calcofluor average molecular weight (from 19 x 10(4) g/mol for pancake batter to 201 x 10(4) g/mol for porridge). Boiling porridge or frying pancakes did not result in any beta-glucan degradation. These large differences in molecular weight distribution for beta-glucan in different oat products are very likely to be of nutritional importance.