Abstract:

The ultrasonic-assisted acid extraction of pectin from litchi residues was optimized using Box-Behnken design. The
yield of pectin was investigated as a function of ultrasonication time, ultrasonic power and solid-to-solvent ratio. Litchi pectin
was tested by a texture analyzer for hardness, viscosity and degree of esterification. The optimum conditions for extracting pectin
from litchi residues were found to be ultrasonic-assisted extraction for 14.8 min at a power of 300 W using pH 2 hydrochloric acid
solution with a solid-to-solvent ratio of 1:10.7, addition of ethanol as a precipitant with a ratio to extract of 1:1.5 by volume, and
90 min precipitation. The maximum predicted yield of pectin under the optimized conditions was 17.86%, which was close to
the experimentally observed value of 17.38%. The pectin showed a viscosity of 55.8×10-3 Pa·s and a degree of esterification of
40.7%, and texture analysis indicated that the average hardness, elasticity and cohesiveness were 40.400 g, 55.51% and 12.880 g,
respectively. In addition, good color and gel-forming properties were observed.

Key words: litchi residues, pectin, ultrasonic