12 January - 20 June 2016

Research studies the effect of pulsed electric fields assisted acetylation on morphological, structural and functional characteristics of potato starch

7 October 2015

Potato starch is a widely used ingredient within the food industry. Often, it is modified by acetylation of the hydroxy groups to improve its properties. The degree of substitution (DS) dictates the properties of these starch esters. Esters with DS values of 0.01-0.20 are used as binding, thickening and stabilising additives; while starch esters with DS > 0.5 are limited to non-food based applications such as tablet binders.

A group from China investigated a novel pulsed electric field (PEF) assisted acetylation reaction of potato starch. The aim of the research was to investigate the effect of altering the PEF strength, reaction time and starch concentration, on the resulting DS and structure of the acetylated product. Hong et al. established the optimum conditions - a PEF strength of 5kV/cm, a 60 minute reaction time and a 30% w/w starch concentration which gave the largest DS value of 0.130.

The team used Fourier transform infra-red spectroscopy (FTIR) to study the reaction. Characteristic C=O stretching bands were observed in the acetylated product at ~1735 cm-1, while the intensity of the hydroxy peaks (3000-3600 cm-1) decreased as these groups were converted into the acetyl groups thus confirming a successful reaction.

Scanning electron microscopy (SEM) was conducted for each product to study the effects of the PEF on the morphology of the starch. It was found that the electric field caused pores to appear on the surface of the starch thus promoting the acetylation reaction due to an increased surface area. As such, the PEF assisted reaction was faster than the conventional reaction.

Along with a faster reaction, it was found that the solubility, swelling power and retrogradation were lower in the PEF assisted reaction versus the conventional reaction. For these reasons, the novel use of the PEF could be used in the future to obtain acetylated potato starch more efficiently.

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