| The extruded rice is an extruded product similar to the shape of rice grains,the process of extruding uniformly mixed materials from the die hole under the action of high temperature and high pressure.According to the nutritional needs of different groups of people,the corresponding food raw material combination can be selected,which can not only make the extruded rice have similar appearance,taste and cooking characteristics as natural rice,but also have higher nutritional value and functional characteristics than natural rice.To solve chronic diseases which caused by unbalanced dietary structure and unscientific dietary structure.At present,the edible quality of extruded rice is still different from that of ordinary rice.For example,the taste is not good,and the rice swells excessively after absorbing water,causing the rice grains to not form or stick into blocks.Therefore,it is necessary to add a certain amount of quality improver in the process of producing extruded rice.In this study,konjac flour and resistant dextrin were added to rice flour,acid-modified starch and polyglycerin fatty acid esters were added to improve the cooking and eating quality of extruded rice.Developing a staple food product with good taste quality and low glycemic index(GI)through researching on the recipe technology,edible quality,digestion characteristics and physical and chemical characteristics of extruded rice,for meeting the needs of people with chronic diseases such as diabetes and obesity.The main research results of this paper are as follows:(1)The preparation of acid-modified starch.The commonly used quality modifiers for extruded rice include emulsifiers,binders,polysaccharides and other additives to improve the texture,elasticity and smoothness of the product,and make it difficult to stick after cooking.Acid-modified starch has good gel and adhesive properties,and the gel Q formed by it has good elasticity,which can improve the structure of the product and increase its elasticity.Corn starch was treated with hydrochloric acid and lactic acid respectively,and acid-modified starch with good gel and strong adhesion was selected for subsequent research.The effects of acid treatment on the morphology and structure of starch,gel texture,and physical and chemical properties were studied,and the digestible starch content of acid-treated starch was determined by in vitro digestion.Polarized light cross,scanning electron microscope(SEM),Fourier transform infrared spectroscopy and X-ray diffraction(XRD)measurement results showed that hydrochloric acid hydrolysis is stronger than lactic acid,and the chemical groups and crystal forms of starch after two acid treatments are unchanged.The degree of short-range order was enhanced,and the relative crystallinity was increased.The results of the physical and chemical properties test showed that the hydrochloric acid-treated starch paste had strong fluidity,and its transparency and solubility were higher than lactic acid-treated starch.The results of rapid viscometer(RVA)showed that hydrochloric acid-treated starch had stronger thermal stability than lactic acid-treated starch,and was easy to age.At a certain concentration,hydrochloric acid-treated starch gel had better gel strength,adhesion and elasticity than lactic acid-treated starch.The results of in vitro digestion showed that the anti-digestive properties of hydrochloric acid-treated starch were better than those of lactic acid-treated starch.In summary,select hydrochloric acid to treat starch for follow-up research.(2)The determination of the optimized formula ratio of extruded rice.Rice flour,acid-modified starch,resistant dextrin,konjac flour and polyglycerin fatty acid ester were mixed in different proportions,and extruded rice was prepared by using a twin-screw extruder.Using single-factor and orthogonal optimization experiments of the formula,the sensory score,texture characteristics,and cooking water absorption were used as indicators to calculate the comprehensive score.In the single factor test,the optimum ratio of each additive was determined to be 15?75% for acid-modified starch,5?13% for resistant dextrin,0.2?0.8% for konjac flour,and 0.2?0.6% for polyglycerol fatty acid ester.Using orthogonal optimization test and verification,under 60% rice flour,30% acidmodified starch,9% resistant dextrin,0.5% konjac flour,0.5% polyglycerol fatty acid ester,extruded rice had the highest comprehensive score.The influence of various factors of extruded rice was the addition amount of acid-modified starch > konjac flour > polyglycerol fatty acid ester > resistant dextrin,the effect of acid modified starch in the extruded rice was the greatest,indicating that the acid-modified starch had a certain improvement effect.(3)The digestibility of extruded rice.With commercial rice(japanese rice and indica rice)as a control,the digestible starch content and GI value of the extruded rice were studied by in vitro simulated digestion experiments.The digestion of in vitro results showed that the extruded rice had higher RS content,lower digestion rate and more good digestion resistance,and the digestion rate of extruded rice was the lowest,and the GI of commercial japonica rice and indica rice were72.62±0.32,70.14±0.85,extruded rice was 48.26±0.92<55,which is a low-GI food.(4)The edible quality and physical and chemical characteristics of extruded rice.The texture properties,cooking physicochemical properties and sensory scores of extruded rice and commercial rice were measured,and the paste and rheology of extruded rice and commercial rice were compared with rapid viscometer(RVA)and rheometer.The properties were different,and the morphology and structure of the extruded rice and commercial rice were characterized and analyzed by scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy.The texture results showed that the hardness of extruded rice was not significantly different from that of commercial rice(P>0.05),and the cohesion,elasticity,chewiness and resilience of extruded rice were significantly higher than commercial rice(P<0.05).The results of cooking properties showed that the water absorption,expansion rate and iodine blue value of the extruded rice were lower than the commercial rice,and the dry matter content of the rice soup was close to the commercial indica rice;compared to the commercial rice,the extruded rice was more yellow.The aroma of extruded rice was not as obvious as commercial rice,but the integrity of the extruded rice grains was good.RVA results found that the heat stability and anti-aging properties of extruded rice starch were better than commercial rice.SEM results showed that there were cracks and fine particles on the surface of the commercial rice,while on the surface of the extruded rice was smooth and compact and has no cracks.XRD results showed that the extruded rice starch is an A+V structure,and the commercial rice starch is an A type structure.The infrared spectroscopy results showed that the short-range order of the extruded rice starch is lower than that of the commercial rice. |
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