Study of the classical and ultrasound-assisted extraction of the corn cob xylan

Various two-step extraction procedures with and without application of ultr asound in the first extraction step were used to isolate the xylan componen t of corn cobs in polymeric form. The obtained immunogenic water-soluble (w s-X) and the biologically inactive water-insoluble (wis-X) xylan fractions were characterised by yield, composition, structural and molecular properti es. The yield of ws-X was strongly affected by the alkali concentration and extraction temperature, particularly in the ultrasound-assisted procedures . The results indicate a higher efficiency of the ultrasonic extraction pro cedures expressed in the shortening of extraction time, and lowering of the alkali concentration and extraction temperature. In contrast to the molecu lar properties, there were no significant differences between the sugar com position and main structural features of the ws-X fractions obtained by ext raction in 5% NaOH with and without application of ultrasound. At similar l evels of yield, the biological activity of the ultrasonically extracted ws- X preparations was higher. (C) 1999 Elsevier Science B.V. All rights reserv ed.