Autoclaving and ultrasonication for reducing digestible starch in cassava pulp: modification of cell wall composition, sorption properties, and resistant starch content

Abstract

Autoclaving (15 min, 121 °C, 1 atm overpressure) and high-intensity ultrasound (3 pulses of 1 min, 750 W, 20 kHz, 80% amplitude) were evaluated individually or combined in cassava pulp to reduce the digestible starch and increase the fibre content. Ultrasound alone produced minimal modifications, and the subsequent autoclaving increased the oil-binding capacity and swelling. Autoclaving alone significantly increased total dietary fibre (TDF) from 14.7% to 21.4%, and the ratio of hemicellulose to lignocellulose. It also reduced the extractable starch from 42.7% to 7.5% and the resistant starch from 7.4% to 3.1%. Despite the higher digestibility, the starch digestion rate with pancreatic α-amylase was slower. Starch solubility increased at 25, 68, and 90 °C. Ultrasonication after autoclaving reduced the hemicellulose percentage, but the sorption properties remained unchanged. Resistant starch substantially increased to 39.9%, mainly composed of RS1 (inaccessible starch), and starch solubility decreased at the three temperatures assayed.