This study investigated the effects and mechanisms of ultrasound (UT), freeze-thaw cycles (FTT1, FTT4, and FTT8 representing 1, 4, and 8 cycles, respectively), and their sequential combination (UT-FTT and FTT-UT) on the pasting properties of pea starch. The results showed that all treatments except UT alone caused the surface of starch granules to become rough and form indentations, with the combined treatments leading to partial breakage of starch granules. All treatments did not change the C-type crystal structure of pea starch, but reduced its relative crystallinity, short-range molecular order, and crystalline lamella thickness. UT-FTT1 more significantly reduced the amylose content, molecular molar mass, and the proportion of long chains of amylopectin compared with the other treatments. This was attributed to the depolymerization and rearrangement of amylopectin chains induced by ultrasonic cavitation, which enhanced the ordered breakage of starch chains from the amorphous region to the crystalline region of the granules caused by the mechanical force of ice crystals during the subsequent freeze-thaw cycles. The breakdown and setback values of pea starch were 1300.0 and 3622.0 cP and decreased to 952.3 and 2913.7 cP after UT-FTT1, respectively (P < 0.05). This indicates that UT-FTT effectively improves the thermal paste stability and anti-retrogradation ability of pea starch. This study provides new insights for the efficient regulation of starch pasting properties.

In order to improve the utilization value of Agriophyllum squarrosum and the eating quality of rice noodles, the effects of adding different levels (0%, 5%, 15%, 25%, 35% and 45%) of A. squarrosum flour on the pasting, rheological and thermal properties of rice flour as well as the firmness, cooking quality and digestive properties of rice noodles were systematically investigated. The results showed that the supplementation of 25% or above of A. squarrosum flour significantly (P < 0.05) increased the contents of protein, fat, and fiber, and 35% or above of A. squarrosum flour significantly (P < 0.05) decreased the content of carbohydrate in mixed flours compared to pure rice flour. With increasing concentration of A. squarrosum flour equal to or greater than 15%, the peak viscosity of mixed flours decreased significantly (P < 0.05), and the viscoelasticity of gels increased continuously; the cooking loss and resistant starch content of noodles increased significantly (P < 0.05). The addition of more than 25% of A. squarrosum flour deteriorated the cross-sectional compactness and surface flatness of rice noodles. The sensory score of noodles containing less than 15% of A. squarrosum flour was higher than that of pure rice noodles. Therefore, A. squarrosum flour can be used as an ingredient in the production of new rice noodles.

In order to explore an effective method to improve the adsorption property of maize starch granules, ultrasonic pretreatment at different temperatures (0, 25, 45, and 65 ℃) below the gelatinization temperature combined with α-amylase was used to modify maize starch. The results showed that after ultrasonic pretreatment, the surface of starch granules became rough with grooves on it. The molecular mass, relative crystallinity and short-range molecular order of the starch samples were significantly decreased (P < 0.05). Compared with single enzymatic hydrolysis, the combinatorial treatment increased the specific surface area and pore capacity of starch consequently improving its adsorption performance. With an increase in the pretreatment temperature from 0 to 65 ℃, the water- and oil-adsorbing capacities of starch granules subjected to the combinatorial treatment increased from 114.71% and 142.16% to 144.77% and 189.70%, respectively. Therefore, ultrasonic treatment at high temperature below the gelatinization temperature combined with α-amylase could be an effective method to prepare a green and high efficiency starch-based adsorbent. This study will be helpful for better understanding of the mechanism by which ultrasonic treatment promotes the enzymatic hydrolysis of starch and will provide a theoretical basis for the development of high-efficiency starch-based adsorbents.

This study was carried out in order to explore the effect of ultrasonic treatment at different temperatures (0, 20, 40 and 60 ℃) on the ability of maize starch to form a complex with lipid. Scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray diffractometry (XRD), laser confocal micro-Raman spectroscopy and were used to characterize the changes in the multilevel structure of maize starch granules before and after treatment, and the mechanism for the change in its lauric acid complexing capacity was analyzed. The results showed that the lipid complexing capacity of maize starch was significantly (P < 0.05) reduced by ultrasonic treatment, and the complexing index decreased from 27.9% to 15.0% with increasing temperature from 0 to 60 ℃; the enthalpy change (ΔH), relative crystallinity, degree of short-range order and relative content of resistant starch declined. Through the multi-level structure analysis, it was found that the molecular chain of the starch was depolymerized by ultrasonic treatment, and ultrasonic treatment at 60 ℃ caused the leaching of amylose from starch granules, thereby damaging their integrity and making the surface rough. In conclusion, ultrasonic treatment at different temperatures can reduce the lipid complexing capacity of starch by changing its multilevel structure.