Effects Of Freezing Treatment On Physicochemical Properties And Digestibility Of Glutinous Rice Flour

Glutinous rice flour is loved by people because it contains high branched chain glutinous rice starch,which makes its taste more sticky and elastic.Glutinous rice flour can be prepared by dry method,semi-dry method and wet method,but the dry method is easy to cause the damage of glutinous rice starch and the coarse grain of glutinous rice flour,which makes the quality of glutinous rice flour decline.The wet process will produce a lot of waste water,and make soluble nutrients lost.In this study,freezing treatment was combined with semi-dry powder process,and the texture of glutinous rice was cracked by freezing treatment,so that the glutinous rice grains could be more easily milled into powder.In this thesis,indica glutinous rice was selected as raw material to study the effects of different freezing time on the physicochemical properties of glutinous rice flour,and the effects of different milling techniques on the structure of glutinous rice grain,physicochemical properties and digestibility of glutinous rice flour.The main results are as follows:1.Based on the trend of water content in glutinous rice grains during soaking and drying and food safety factors,the glutinous rice flour prepared with the optimal soaking time of 2hour,the optimal drying time of 2 hour and the freezing time of 10 hour has the smallest damaged starch value,small particle size,high brightness,large light transmittion and low water precipitation.Therefore,it is determined that freezing 10 hour is the best freezing time for preparing frozen semi-dry glutinous rice flour.The optimum technological parameters of frozen semi-dry glutinous rice flour are: soaking time 2 hour,drying time 2hour,freezing time 10 hour.2.By comparing the effects of dry method,semi-dry method and frozen semi-dry method on the surface,cross section,internal structure characteristics,spatial distribution of components,crushing force and damaged starch value during the preparation of glutinous rice flour,the research shows that: The surface cracks and cracks of glutinous rice grains were more and the microstructure of starch in cross section was most clear and loose.The area of red fluorescence in the cross section of glutinous rice grains without treatment was the largest,indicating the highest protein content,which was consistent with the result of protein in the basic composition.The breaking force of pre-treated glutinous rice grains before freezing and semi-drying was the smallest(2.15 kg),and the damaged starch value was the lowest.In conclusion,freezing treatment significantly improved the porosity of glutinous rice grains and reduced the mechanical damage of starch in glutinous rice grains.3.The properties of glutinous rice flour obtained by freezing and semi-dry method were compared with those obtained by wet,dry and semi-dry methods.The results showed that there were significant differences in the basic components of glutinous rice flour obtained by different flour processing methods.The protein and fat content of frozen and semi-dry glutinous rice flour was second only to that of dry glutinous rice flour,and the ash content was lower than that of semi-dry glutinous rice flour.The starch granule dispersion of frozen semi-dry glutinous rice flour was second only to that of wet glutinous rice flour,D(50)was 17.74 μm;Starch agglomeration and adhesion of dry glutinous rice flour were serious,D(50)was 50.46 μm.The crystal structure of glutinous rice flour under different milling processes is B-type,and the effect of freezing and semi-drying method on the crystal structure of glutinous rice flour is only greater than that of wet method.The swelling degree,transparency,peak temperature,disintegration value,recovery value and freezing resistance of frozen semi-dry glutinous rice flour are second only to wet glutinous rice flour,and the acceptability of starch foods is high.The digestibility of frozen semi-dry glutinous rice flour was similar to that of wet glutinous rice flour,and the SDS was lower.In summary,the nutrition content of frozen semi-dry glutinous rice flour is higher than that of wet glutinous rice flour,and the quality of wet glutinous rice flour is closer.