Extraction and in vitro fermentation of rye bran fractions

Rye bran was fractionated on a pilot scale into water-extractable, alkali-extractable and unextractable fractions. The fractions were enzymatically digested to partially remove starch and protein. The enzyme treated substrates were fermented in vitro using a human faecal inoculum. The water- and alkali-extractable fractions were fermented faster than the unextractable fraction and rye bran itself. However, the extent of fermentation after 24 h was similar in each case. The production of gases and short-chain fatty acids correlated well with the consumption of neutral sugars. All the rye substrates enhanced the molar proportion of propionic and butyric acids, among the short chain fatty acids.