Complex formation between starch and stearic acid: Effect of enzymatic debranching for starch.

Effect of debranching for a high-amylose starch (∼70% amylose) on its V-complex formation with stearic acid was examined. Gel-permeation chromatograms showed that amylopectin was degraded to smaller molecules as the debranching time increased from 6 to 24 h. Increased formation of debranched starch/stearic acid complexes (recovery yield of stearic acid from 45.17 to 89.31% and starch from 39.92 to 55.43%) was observed with increased debranching time (from 6 to 24 h) and complexation time (from 6 to 24 h). The X-ray diffraction patterns of the debranched starch/stearic acid complexes displayed a mixture of B-type and V-type patterns, with 2θ peaks at 7.6°, 13.1°, 17.2°, 20°, 21.6°, and 23.4°. The melting temperature and enthalpy changes of the debranched starch/stearic acid complexes were gradually enhanced with increasing debranching time. These results suggest that starch can be modified by debranching to produce a significant amount of debranched starch/stearic acid complexes.

Volatile composition and sensory characteristics of onion powders prepared by convective drying.

Volatile composition and sensory characteristics of onion powders prepared by convective drying at different temperatures (50, 70, and 90°C) were investigated. Dipropyl disulfide was the major volatile compound in fresh onion (77.70% of total volatile compounds). However it was considerably lost during drying, reaching 6.93-32.25µg/g solids. Dipropyl disulfide showed a positive correlation with green sensory attribute perceived by descriptive sensory analysis. Thiophenes, which were responsible for caramel and sweet attributes, were produced by drying especially when the drying temperature was high. Aldehydes, another type of volatile compound found in fresh onion, showed a positive correlation with humidity. The aldehyde content in dried onion was the highest at the lowest drying temperature, possibly because the aldehydes were produced by the residual enzymes in fresh onion. Using a low temperature for drying was ideal to retain the aroma of fresh onion.