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 starting materials at extraction times of at least 1 hr and an extraction temperature of < 50-degrees-C. In all cases, there was a linear relationship between dry matter, crude pentosan or crude arabinoxylan content of the extract, and viscosity (r greater-than-or-equal-to 0.97). The addition of purified or crude enzyme preparations to either rye extracts or pure substrates demonstrated that nearly all of the viscosity in 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 extract and its water-soluble arabinoxylan content.