Effect of freeze‐thawing treatment on the microstructure and thermal properties of non‐waxy corn starch granule

Abstract

In the present study, non‐waxy corn starch was processed by different freeze‐thawing temperatures and cycles. The effects of freeze‐thawing treatment on the surface structure, granules particle size, Maltese crosses, crystalline, and thermal properties of non‐waxy corn starch were investigated. The number of pores on the surface of starch granules increased with freeze‐thawing cycles. The granule size, crystalline intensity and degree, gelatinization temperatures, and enthalpy values of corn starch decreased with freeze‐thawing cycles increased. The Maltese crosses indicated that loss of Maltese cross increased when freeze‐thawing cycles increased, but decreased with increase in temperature. Moreover, clear cracks and big pores were observed on the surface of starch granules, and smaller granule size and lower thermal parameters were obtained in the distorted corn granules caused by the changes in crystalline structure under appropriate treatment (−20°C freezing and 25°C thawing, 20 cycles). Freeze‐thawing treatment significantly increased the porosity of corn starch, which indicated that it can improve adsorptive capacity of starches. Therefore, freeze‐thawing method is potentially very useful to produce porous starch as carrier or absorbent for food and medicine. These findings could have important applications in starch modification industry.