EXTRACT VISCOSITY AS AN INDIRECT ASSAY FOR WATER-SOLUBLE PENTOSAN CONTENT IN RYE

Viscosity of extracts from rye grain were tested to predict the water- soluble arabinoxylan content. The extracts tested were water extracts from raw or autoclaved rye and a low-pH extract from raw rye. Similar, but not identical, viscosity values were obtained from the three star ting materials at extraction times of at least 1 hr and an extraction temperature of < 50-degrees-C. In all cases, there was a linear relati onship between dry matter, crude pentosan or crude arabinoxylan conten t of the extract, and viscosity (r greater-than-or-equal-to 0.97). The addition of purified or crude enzyme preparations to either rye extra cts or pure substrates demonstrated that nearly all of the viscosity i n the rye extracts was attributable to the arabinoxylans. Thus starch, protein, and beta-glucans did not contribute to the viscosity of rye extracts. A high correlation existed between the viscosity of a rye ex tract and its water-soluble arabinoxylan content.