| At present,people are more and more concerned about the high fat and calorie problems of food,and the quality and flavor requirements of food are gradually increasing,and healthy and green food is more popular and loved by people,but excessive intake can pose a threat to human health.Fat substitution is able to replace part or completely replace the fat in food under the condition that there is no significant effect on the quality and flavor change of food,thus changing the quality of low-fat and fat-free food and reducing the incidence of obesity and cardiovascular diseases.Therefore,to investigate the application of rice bran protein-polysaccharide complex to scones for the purpose of oil reduction,it is important to study safe and healthy substitutes.In this paper,rice bran protein and polysaccharide were used as experimental raw materials to prepare rice bran protein-polysaccharide complexes under different influencing conditions,and response surface modeling and optimization were carried out on the basis of single factor,so as to determine the best preparation process conditions for the complexes,to study the effects of glycosylation reactions on the structural and functional properties of rice bran protein,and to investigate the possibility of replacing fat in scones by the complexes.The specific findings of the study are as follows:1.The complexes were prepared by glycosylation modification of rice bran protein,and the process conditions for their preparation were optimized.A response surface optimization test was conducted on the basis of single factor with grafting degree as the index,and the optimal parameters such as solution p H,reaction time,reaction temperature and rice bran protein-polysaccharide mass ratio were derived.The results showed that the grafting degree of rice bran protein was 29.07% under the following conditions: p H=10,time 60 min,temperature40 ℃,protein-sugar ratio 2:1.Under the conditions of p H=10,time 70 min,temperature 50 ℃and protein-sugar ratio 1:1,the grafting degree was 37.34%.Under the conditions of p H=9,time60 min,temperature 50 ℃,protein-sugar ratio 2:1,the grafting degree of rice bran protein was34.23%.The conditions of rice bran protein complex maltodextrin were p H=10,time 70 min,temperature 40 ℃,protein-sugar ratio 1:1,and grafting degree 27.15%.Rice bran protein,rice bran protein pentosan complex,rice bran protein glucan complex,rice bran protein chitosan complex and rice bran protein maltodextrin complex were named RBP,RDP-P,RDP-D,RDP-C,RDP-M,and the degree of glycoylation reaction could be known by the degree of grafting:RBP-D > RBP-C > RBP-P > RBP-M.2.A comparative study of the structural and functional properties of rice bran proteins before and after the glycosylation reaction was performed.The comparative analysis of four polysaccharide grafters,the investigation of microstructural changes of rice bran protein and complexes,and the determination of surface hydrophobicity showed that the glycosylation reaction introduced a large number of hydrophilic hydroxyl groups into the protein and changed the spatial structure.The Fourier infrared spectra,ultraviolet absorption spectra and fluorescence spectra all confirmed that the complexation of rice bran protein with polysaccharide led to the change of spatial structure,and the groups were accessed in the form of covalent bonds.The sensitivity of rice bran protein and complex solubility to different solution p H is different,the solubility is improved compared with rice bran protein,the solubility is lowest at p H=4,the absorbance is RBP-P>RBP-D>RBP-C>RBP-M>RBP,the absorbance is RBP-P,RBP-D,RBP-C,RBP-M and RBP.RBP were 86.06%,79.93%,78.61%,76.89%,74.33% for moisture absorption,54.80%,56.21%,52.57%,48.34%,34.41% for water retention,42.44%,48.37%,44.91%,41.08%,28.84% for oil retention,and 36.54%,36.54%,41.08%,28.84% for foaming.The water-holding and foaming properties of rice bran protein polysaccharide complexes were improved compared to rice bran protein,and the products were more stable,The emulsifying properties of RBP-P,RBP-D,RBP-C,RBP-M and RBP were 23.58%,20.45%,27.63%,26.35%and 17.28%,respectively,and the emulsifying stability was 81.42%,78.75%,86.66%,65.65%and 35.47%,respectively,which improved the emulsifying and emulsifying stability and made the glycosylated products more similar to fat.The improved emulsification and emulsification stability made the sugar-based products more similar to fat,which is convenient for application in scones to achieve oil reduction.3.Different additions of rice bran protein polysaccharide complexes were studied to replace the fat content in the scones and the physicochemical properties of the scones were analyzed.The addition of rice bran protein polysaccharide complex can increase the deep bound water content of the dough and change the textural properties such as hardness and viscosity,which provides the theoretical basis for the subsequent experiments.The analysis of the apparent properties of the scones showed that the addition of rice bran protein polysaccharide complex could better simulate the specific volume and color of unabated bread and reduce the baking loss rate;while the excessive water content would show an increase in surface viscosity and a decrease in specific volume;the addition of the complex could better simulate the properties of hardness,shape and color of unabated bread,and the results were consistent with the results of dough texture characteristics.The analysis of the quality indexes of the scones showed that the best replacement fat contents of the four rice bran protein polysaccharide complexes in scones were RBP-P,RBP-D and RBP-C at 50% fat addition and 7.5 ml 15 mg/m L complex solution(50-15)and RBP-M at 75% fat addition and 3.75 ml 10 mg/m L complex solution(75-10),the amount of oil reduction in scones was as follows: RBP-P= RBP-D= RBP-C>RBP-M;and the analysis of quality indexes of scones showed that the effect of four rice bran protein polysaccharide complexes addition on the quality of scones under the best oil reduction conditions was as follows: RBP-D>RBP-C>RBP-P>RBP-M. |
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