| With the change of dietary structure of Chinese residents,chronic diseases,mainly diabetes,have posed a great challenge to the health of Chinese residents,and the improvement of their nutritional value from the perspective of food processing can lead to the alleviation and regulation of chronic diseases.Therefore,the development of healthy green foods with specific nutritional functions has become one of the current research hotspots in the field of food science.coarse cerealss are considered as healthy food ingredients,and most of the current research is focused on the structural identification and functional evaluation of the aforementioned nutritional components.The research on the structural changes and digestive characteristics of different grains during the typical physical processing has yet to be further enriched.In this study,we used two typical physical processing methods:heat-moisture treatment and annealing,with four kinds of grains:buckwheat,quinoa,yellow rice and oat as raw materials,and controlled the treatment conditions to compare the effects of heat-moisture treatmenttreatment and annealing on the physical and chemical properties,structural properties and digestive characteristics of different kinds of grains starch at the same temperature and different temperatures.The study was carried out to provide a theoretical basis for broadening the application and health food development of coarse cereals starches.The main research contents and conclusions are as follows:(1)Effect of heat-moisture treatment and annealing on the physicochemical properties of coarse cereals starches.Freeze-thaw stability test,differential scanning calorimetry,rapid viscosity analysis and other methods were used to study the physicochemical properties of four starches before and after heat-moisture treatment and annealing.The results showed that buckwheat,oat,yellow rice and quinoa starches showed different freeze-thaw stability after heat-moisture treatmenttreatment and annealing,in which the freeze-thaw stability of the toughened starches was poorer than that of the heat-moisture treatmenttreated starches.Compared with the control group,the freeze-thaw stability of the starch treated with heat-moisture treatmentand toughening showed a substantial decrease,with buckwheat starch decreasing from 79.61±0.6%to 49.54±2.51%,oat starch from 64.7±0.11%to 49.61±3.00%,yellow rice starch from 98.03±0.33%to 55.58±2.78%,and quinoa starch from 69.81±0.22%to 57.08±0.22%.The enthalpy of starch pasting was significantly lower after treatment.Moisture and heating caused partial pasting of starch,rearrangement of the internal double helix structure of starch molecules and consequent decrease in peak viscosity,and the annealing caused a higher decrease in peak viscosity of starch than the heat-moisture treatmenttreatment.(2)Effect of heat-moisture treatment and annealing on the structural properties of coarse cereals starch.X-ray powder diffraction,Fourier infrared spectroscopy and scanning electron microscopy were used to characterize the structures of the four starches before and after the heat-moisture treatment and annealings.The results showed that the heat-moisture treatment and annealings did not change the original A-type crystalline structure of the four starch species,but the crystallinity showed a decreasing trend.Among them,buckwheat starch decreased from 37.19%to 16.85%,oat starch decreased from 23.66%to 16.99%,yellow rice starch decreased from 28.87%to 20.02%,and quinoa starch decreased from 31.93%to 15.25%.In addition,the microstructure showed cracks and depressions in the surface structure of the treated starch granules and agglomeration behavior at high temperature and high moisture content.The hydrogen bond composition and starch helical structure were disrupted by the action of water molecules and heat energy,resulting in the disruption of the short-range ordered structure of starch.(3)Effect of heat-moisture treatment and annealings on the digestive properties of coarse cereals starches.In vitro enzymatic digestion experiments were used to study the digestive properties of four starches before and after heat-moisture treatment and annealings.The results showed that the contents of slow digesting starch(SDS)and resistant starch(RS)in the four starch types treated with heat-moisture treatmentand toughening increased to different degrees,among which the SDS and RS of yellow rice starch increased most significantly from 19.09 ± 0.25 to 34.52±4.72,and RS increased from 23.01±1.45 to 46.75±1.42.The annealing increased the resistant starch more than the heat-moisture treatmenttreatment.Using the in vitro static simulation of gastrointestinal digestion,the starch was almost undigested before and after treatment in the simulated digestion in the stomach,while in the simulated small intestine digestion,the digestibility showed a gradual decrease with the increase of moisture content of the heat-moisture treatmentsystem and the increase of the toughening temperature after treatment with different conditions.In summary,toughening and heat-moisture treatmenttreatment effectively modulated the physicochemical properties and structural characteristics and enzymatic properties of four starchy grains,namely buckwheat,oat,yellow rice and quinoa.This has some significance in alleviating the rapid rise of postprandial blood glucose caused by starchy food intake,and the study was conducted to provide sufficient and strong support for the preparation of slowly digested foods. |
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