Milling of Whole Grain Rye to Obtain Fractions with Different Dietary Fibre Characteristics

Abstract

Rye was separated by dry-milling into three fractions enriched in different rye grain tissue (pericarp/testa, aleurone and endosperm). The fractions varied considerably in gross chemical composition; the starch content ranged from 3·0 g/100 g dm in the pericarp/testa to 78·2 g/100 g dm in the endosperm, and the content of dietary fibre (DF) from 6·5 g/100 g dm in the endosperm to 73·3 g/100 g dm in the pericarp/testa. Protein, fat, ash and phosphorous were concentrated in the aleurone fraction. DF characteristics also differed largely between the rye milling fractions. Arabinoxylans (AX) comprised the majority of DF components in all samples, but on DF basis the milling fractions had different concentrations of lignin, cellulose and β-glucans. Moreover, a wide range in arabinose to xylose ratio of the water-unextractable AX (0·35–1·02) and in the proportion of water-extractable AX (14–70% of total AX) implied that variation in AX structure was obtained. Rye breads intended for a nutritional study were made from the milling fractions. It is concluded that the breads can be used to study the influence of DF characteristics on the colonic fermentation processes in monogastrics.