EXTRACTION OF OLIGOSACCHARIDES FROM PASSION FRUIT PEEL BY SUBCRITICAL WATER TREATMENT

Passion fruit peel, a major by-product of the fruit processing, was treated in subcritical water under nonisothermal conditions in batch-type reactor containing the dried peel and water in the ratio 1: 16 (w/w), with maximum temperatures in the range of 100-245C. The effects of the treatment temperature and time on the composition of the obtained hydrolysates were combined and expressed as the severity factor (ln R-o). Both mono- and oligosaccharides with high degree of polymerizations (DP > 7) were extracted from the peel under every treatment tested. The treatment at ln R-o of 3.4 and 5.1, corresponding to the heating to 150C within 4.5 min and to 175C within 5.5 min, respectively, yielded the highest amount of oligosaccharides (ca. 21%) with galacturonan as a main component (ca. 65%), indicating that pectin was predominantly hydrolyzed and extracted under these conditions. The study showed that subcritical water treatment is an effective method for producing the oligosaccharides which may be useful as dietary fiber.