Abstract:
The physicochemical properties of starch and konjac glucomannan (KGM) composites were studied in maize and quinoa starch. KGM is a non-ionic polysaccharide widely used in food products to improve gel capacity. Purified KGM was extracted from crude konjac powder and quantified using three methodologies to provide a comparison. Analysis showed that the purified KGM obtained using a modified method contained 87.22% glucomannan, 12.19% water content and 1.59% ash content. A blend of starch and KGM was found to be a safe and effective method for improving the rheology properties, swelling ability, water solubility and starch hydrolysis of starch samples. KGM addition efficiently raised PV, H P V, C P V, BD and SB in maize and quinoa starch, especially at more than 10% (w/w) KGM concentration. Gel texture properties showed no noticeable improvement at various concentrations of KGM in quinoa starch. But there had gradual improvement in gel texture of maize starch with adding KGM. The presence of KGM significantly affected starch hydrolysis, changing the proportions of starch fractions and increasing the resistant starch (RS) fraction. The effect of KGM on starch hydrolysis is greatly dependent on starch type and the physical forms of starch. Quinoa starch was suggested to show more ES than maize starch. In general, the addition of KGM suppressed starch hydrolysis in gels, and a concentration dependent suppressive effect was observed. The presence of KGM was found to effectively enhance the swelling and solubility properties of maize and quinoa starch and this effect was concentration dependent. The effects on quinoa starch were more beneficial than for maize starch. The different results for the starch samples were due to their structural differences. The starch samples each had a different temperature range at which the leaching of starch granules was enhanced.