CHEMICAL STUDIES ON MIXED-LINKED BETA-GLUCANS IN HULL-LESS BARLEY CULTIVARS GIVING DIFFERENT HYPOCHOLESTEROLEMIC RESPONSES IN CHICKENS

The structure of mixed‐linked β‐glucans was studied in three hull‐less barley (Hordeum vulgare L) cultivars, Arizona, a waxy‐starch genotype with high mixed‐linked β‐glucan content giving hypocholesterolaemic responses in chickens, and two genotypes with normal mixed‐linked β‐glucan contents. One of these, Washonupana, also a waxy‐starch type, reduces blood cholesterol whereas the other, Franubet has no effect. When a ground sample was suspended in water, Arizona and Washonupana gave highly viscous slurries whereas Franubet gave low viscosity. This viscosity was greatly reduced by addition of endo‐β‐glucanase. Arizona gave the highest yield of water‐soluble mixed‐linked β‐glucans, while the ratio of 1.3 to 1.4 linkages (1:26) was very similar in this fraction for all barleys. 13C‐NMR indicated that these water‐soluble fractions from all three barleys had essentially the same repeating sequence patterns and that 1.3 linkages occurred singly. Gel filtration established that the water‐soluble mixed‐linked β‐glucans in Washonupana had the highest average molecular weight and Franubet the lowest. The hypocholesterolaemic responses observed in chickens were attributed to viscous conditions within the gastrointestinal tract, and this was a function of the content and molecular weight of the mixed‐linked β‐glucans and of endogenous β‐glucanase activity in the barleys. Copyright © 1990 John Wiley & Sons, Ltd