Evaluation of the physico-chemical properties of acid thinned cassava starch

Abstract

The effect of acid hydrolysis on the physico-chemical properties of cassava starch was investigated. The acid hydrolysed (acid thinned) starches were prepared from cassava starch with 0.1M solution of hydrochloric acid. The acid hydrolysis of starch samples were carried out at 60°C in a thermostatically controlled water bath for 30 min, 1hr, 2hr and 3hr.The reducing number which is a measure of the degree of hydrolysis (increased aldehydic end-group) increased from 2.96 (raw starch), 3.20 (30min), 6.96 (1hr), 8.76(2hr) and 14.37 (3hr). The pasting (gelatinisation) temperature was found to increase with increase in acid hydrolysis from 6873°C (raw starch), 6265 °C (30min), 5863°C (1hr), 5560°C (2hr) and 5357°C (3hr). The setting (gelling) temperature was found to decrease progressively from 54°C (30min), 50°C (1hr), and 35°C (2hr). The flow properties of the pastes which is a measure of the viscosity increased with increase acid treatment as shown by flow rate of 0.8ml/sec (30min); 1.0ml/sec (1hr); 1.9ml/sec (2hr) and 2.3ml/sec (3hr). From the investigation, the acid modification of cassava starch at 60°C with 0.1M hydrochloric acid solutions for 1hr and 2hr gave pastes that are stable, and have workable viscosities and can form gel in food processing. Therefore, the results suggest that they are suitable for the food industry as food emulsifiers/stabilizers.

Keywords: acid thinned starch, manihot esculenta, starch gelatinisation, cassava starch, and starch hydrolysis.

Nigerian Food Journal Vol. 23 2005: 85-90