EFFECT OF ACETYLATION ON THE PHYSICOCHEMICAL PROPERTIES AND MICROBIAL LOAD OF Manihot palmata STARCH FROM MOKWA, NIGER STATE, NIGERIA

Abstract

Starch expediency in industrial applications is well-defined by its physicochemical properties and functionality. Starch in its native form constitutes certain limitations. Manihot palmata starch extracted from cassava tubers by wet extraction method was modified by acetylation to improve its properties, using maize starch British Pharmacopeia (BP) as control. The effect of acetic anhydride (CH3CO)2O concentrations on the physicochemical properties, as well as the microbial load of the native sweet cassava starch, were studied. The percentage yield of the native cassava starch was 41.56 %; however, the value increased with an increase in acetylation from 89.44 % to 89.92 % for acetylated cassava starch I (ACSI) and acetylated cassava starch II (ACSII) respectively. The acetylation of the cassava starch decreased the pH, moisture content, gelatinization temperature, browning and charring power, and increased amylose/amylopectin content, swelling power, solubility, iodine, acidity, and viscosity. The amylose/amylopectin content, pH, moisture content, viscosity, gelatinization temperature, browning and charring power, solubility in cold water, hot water and ethanol of the acetylated starches were significantly similar at p < 0.05 except for the percentage yield and swelling power. Also, the percentage yield, pH, moisture content, swelling power, viscosity, browning and charring power, solubility in cold water and hot water of the NCS and the acetylated starches (ACSI and ACSII) were significantly different at p<0.05. The amylose/amylopectin contents of the NCS and acetylated starches were significantly similar but differed from the maize starch. The gelatinization temperatures of the studied starches were significantly similar while the swelling powers differ significantly from each other at p ? 0.05. The moisture content, and browning and charring power of the maize starch and acetylated starches were significantly similar at p<0.05 but differ from that of the NCS. The microbial loads of the native cassava starch decreased; with acetylation and an increase in the concentration of the acetic anhydride and serial dilution. However, the microbial loads increased with incubation time and were within the standard specifications but with much load in the unmodified than the modified starch. The results of the sensory parameters for the modified starches had better properties compared to that of the unmodified starch. Thus, acetylation improved its quality as a valuable raw material in the pharmaceutical and other food Industries.