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 freezethawing 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 (À20°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.

Effects of oligosaccharides on particle structure, pasting and thermal properties of wheat starch granules under different freezing temperatures

“…The internal and external molten ice crystals may result in pores on the surface of starch granules. The morphology and melting of ice crystals create a certain microscopic mechanical force on the starch granules, expanding the internal channel molecules of starch so that more soluble components are dissolved, water is redistributed, and more dents appear in the pores and starch granules (Yu, Zhang, Li, Yan, Gong, Liu, et al, 2015).…”

Effects of Liquid Nitrogen Deep Freezing Treatment on Rice Starch Properties

“…Cracks on the granule surfaces were also observed by Yu et al. [ 24 ] They suggested that the formation of small ice crystals caused the outer layers of the granules to peel. Tao et al.…”

Modification of structural and physicochemical properties of repeated freeze-thawed cycle maize starch

“…The X-ray pattern of native revealed A-type starch pattern with two singles at 15° and 23°, and a double at 17° and 18° (2θ), and the freeze-thawed starch still exhibited A-type ( Figure 2), which was consistent with the result of Yu et al, who found that the crystal type of non-waxy corn starch still appeared A-type after freezethaw treatment. [10] However, the crystallinity of the native maize starch (19.93%) was significantly (P < .05) higher than that of the freeze-thaw cycle treated maize starch (15.21%-18.56%), and the crystallinity decreased non-significantly at freezing −80 °C with the freeze-thawing cycle times increased ( Table 1). The result was similar to the studies of Yu et al, who found that the crystallinity of non-waxy corn starch decreased after freeze-thaw treatment, [10] while the crystallinity of freezethaw of moistened potato starch granules was found to increase after freeze-thaw treatment.…”

“…[10] However, the crystallinity of the native maize starch (19.93%) was significantly (P < .05) higher than that of the freeze-thaw cycle treated maize starch (15.21%-18.56%), and the crystallinity decreased non-significantly at freezing −80 °C with the freeze-thawing cycle times increased ( Table 1). The result was similar to the studies of Yu et al, who found that the crystallinity of non-waxy corn starch decreased after freeze-thaw treatment, [10] while the crystallinity of freezethaw of moistened potato starch granules was found to increase after freeze-thaw treatment. [7] That might be due to the different conditions in freezing and thawing treatment and the different types of samples.…”

“…[9] Yu et al (2015) found that the structurl and physicochemical properties changed with the number of pores on the surface of starch granules increased under −20°C freezing and 25 °Cthawing within 20 cycles. [10] Up to now, the existed researches have revealed the changes of structure, physicochemical properties and characteristics of gelation of some freeze-thawed starches such as potato, tapioca, soft wheat, hard wheat and waxy rice starch granules under a multiple refrigerated temperatures, [7,9,11] while the systematic researches on different freezing temperatures and different freeze-thaw cycles on structural and physicochemical modification of starch granules are quite limited. Nevertheless, maize starch is commonly used as an important raw material in frozen foods such as yogurt, dumpling wrapper, meat filling and sweet dumpling etc.…”