Physicochemical characteristics of wheat bran glucuronoarabinoxylans

Graded ethanol precipitation of a wheat bran extract resulted in four fract ions of glucuronoarabinoxylans, the physicochemical properties of which wer e investigated in relation to their structure and molecular weight. Two fra ctions; consisting of lowly-substituted arabinoxylans, appeared to be very sensitive to aggregation, and gave hardly any viscosity to solutions. Moreo ver, the viscosity of these arabinoxylans was not affected by addition of s alt, nor by changes in temperature. Interaction with other polysaccharides, such as xanthan and kappa-carrageenan, based on observations with quite si milar lowly-substituted galactomannans, was not observed. Additionally, the se arabinoxylans gave no stabilising effects to emulsions. The other two fr actions consisted of highly-substituted glucuronoarabinoxylans, which had i ntrinsic viscosities of approximately 2.5 dL/g in 0.1 M potassium chloride. The viscosities were affected by temperature and addition of salt; the lat ter observation is in agreement with their polyelectrolyte nature. These po lysaccharides appeared to be semi-flexible and not very sensitive to aggreg ation, although some aggregation was observed upon partial removal of arabi nose substituents. Again, no interaction with xanthan and ii-carrageenan wa s observed for these fractions. However, they were very effective in stabil ising emulsions. (C) 1999 Academic Press.