Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/1996
Publication Date: N/A
Interpretive Summary: Oats contain a soluble fiber, known as beta-glucan, that can cause the lowering of blood cholesterol if incorporated in the diet in sufficient quantities. Beta-glucans make the contents of the gut more viscous, thereby inhibiting the absorption of cholesterol into the body. Although this is a favorable property for human food, it is less favorable for animal food and oats may actually inhibit weight gain in some animals, in particular, chickens. We have found that steaming of oat grain optimizes viscosity potential for oat flours, whereas raw oat flour slurries will rapidly lose their viscosity. Steaming, which is a routine process for all oat products, apparently inactivates enzymes that will breakdown beta-glucans. It would appear that if raw oats are fed to animals instead of processed oats, many of the problems associated with beta-glucans in animal feed could be eliminated.
Technical Abstract: Heat-treatment of oat grain had significant effects on the viscosity of flour slurries. Steamed oats produced highly viscous flour slurries, whose viscosity increased with time, whereas viscosity of flour slurries produced from raw or roasted (104 deg C for 120 min) oats were much lower and degraded rapidly. Slurry viscosity was correlated with (1-3), (1-4)-beta-D-glucan concentration in the flours and treatment of slurries with lichenase largely eliminated the viscosity. Effects of steaming were reversed by roasting treatment and vice versa. Mixtures of equal amounts of raw and steamed flour resulted in slurries more viscous than either flour alone, but that viscosity degraded after three hours to less than the mean viscosity of the steamed and raw controls. Water-soluble extracts from steamed flour had about twice the viscosity of raw or roasted flour extracts, but contained only 80% of the (1-3), (1-4)-beta-D-glucan present in those extracts. Molecular weight analysis of soluble carbohydrates from raw, roasted and steamed soluble extracts indicated that extensive degradation had occurred with raw and roasted samples. It is likely that enzymic degradation of (1-3), (1-4)-beta-D-glucans is responsible for much of the decreased raw and roasted flour slurry viscosity, but different heat treatments may also affect (1-3), (1-4)-beta-D-glucan polymer interaction.