The effect of heat or high pressure treatment on the physico-chemical properties and in vitro digestibility of corn starches

Abstract

In food industry, starch gelatinisation is an important process to achieve starch functionality and sensorial attributes. Gelatinisation of starch dispersions can be induced by heat treatment or high pressure processing (HPP) treatment. The main objectives of this study were to compare the effects of heat treatment or HPP treatment on the physico-chemical and digestion properties of different corn starch dispersions. Three types of corn starch varying in amylose content, namely Novation 2300 (1.370±0.090% w/w amylose), Gelose 50 (50.80±0.980% w/w amylose) and Gelose 80 (89.78±0.960% w/w amylose) were investigated in the form of starchwater dispersions at a concentration of 10% (w/w). Heat treatment was carried out at temperature ranging from 50 to 95 °C. Pressure applied in HPP treatments ranged from 200 to 600 MPa (for up to 30 min). The physico-chemical properties of starch dispersions after heating or HPP treatment were characterised in terms of pasting behaviour, microscopic appearance and particle size. The digestibility of the starch dispersions was measured as the amount of D-glucose released as a function of time (0 to 480 min) using an in vitro starch digestion method. The results showed that both heating and HPP treatment caused starch gelatinisation when treatment conditions were suitable (i.e. temperature applied over Tonset or pressure applied over 400 MPa). The extent of gelatinisation was found to be highly dependent on the starch amylose content. Novation 2300 was the most responsive to heat or HPP treatment. Although heat treatment was found to be more effective in achieving complete gelatinisation than HPP, under the conditions applied in this study. Starch digestibility was greatly influenced by the amylose content of starch and the extent of starch gelatinisation. Novation 2300 dispersion was digested to the greatest extent, whereas Gelose 80 showed the lowest digestibility. This is mainly due to the fact that high-amylose starch granules retain their aggregated state to a greater extent, even after the application of heat or HPP treatment. The knowledge obtained from this study not only contributes to the understanding of correlation between the extent of gelatinisation and the digestion of starch granules, but also demonstrates the possibility of manipulating digestion of starch through tailoring the gelatinisation process conditions.