The Major Biochemical Constituents of an Acid Extract of Barley Flour as Used in Viscosity Determinations by the Falling Ball Method

The viscosity of an acid extract of barley flour, measured as its ‘falling time’, has been used as a guide to malting potential.22 One such extract, made from a sample of Maris Mink, was examined in detail to identify the principle biochemical constituents and to investigate their contribution to viscosity. The extract contained a high concentration of carbohydrate (3·30 mg/ml) divided into two discrete fractions of high and low molecular weight (in the weight ratio of 39:61) by gel filtration. The high molecular weight component was polydisperse and consisted principally of β-glucan with some starch and pentosan also present. The low molecular weight fraction contained mostly fructose, glucose and some pentose. Protein present in the extract (1·07 mg/ml) was derived almost exclusively from the albumin and globulin (salt soluble) fraction of barley protein. Studies on the viscosities of reconstituted preparations of these components indicated that β-glucan made the major contribution to the viscosity of the extract. This conclusion is supported by observed changes in viscosity after the extract was treated with β-glucanase, α-amylase and protease.