Isolation and chemical characterisation of water-extractable arabinoxylans from wheat and rye during breadmaking

Water-extractable arabinoxylans from wheat and rye flour, dough and bread were isolated and characterised by the determination of the carbohydrate composition and the ferulic acid and diferulic acid contents. For both wheat and rye, the yield of water-extractable arabinoxylans decreased during the breadmaking process, indicating that some of the water-extractable arabinoxylans had become water-insoluble, possibly by the formation of ferulic acid–protein cross-links. The determination of ferulic acid and diferulic acids showed a low degree of dimerisation (less than 1%), which did not increase during the breadmaking process. Separation of the water-extractable arabinoxylans by size-exclusion chromatography showed that the molecular mass distribution of the arabinoxylans changed during breadmaking for both wheat and rye. Dual detection by measurement of the refractive index and the UV absorbance at 310 nm enabled screening for ferulic acid in the molecular mass fractions. Water-extractable arabinoxylans from wheat contained a medium molecular mass fraction which was not UV-active. The determination of ferulic acid in this fraction showed that it was free of ferulic acid.