The Research On The Preparation And Functional Properties Of Rice Protein-maltodextrin Conjugates

Rice protein was widely favored for its high nutrition and low hypoallergenic character.It has been confirmed to have better composing of essential amino acids,high value of BV,and lower irritability as compared with other plant proteins.Unfortunately,over 80% of the protein contained in rice kernels is glutelin,and the solubility of rice protein is very low.So the functional properties of rice protein were poor.The purpose of this paper was to discuss the Maillard reaction between RP and sugar,and to improve the functional properties of the protein by the reaction.The reactionship between the improved functional properties and the factors that influence the Maillard reaction was also studied.Single factor test was did by using recovery and solubility as indexes.The influence of the ratio to protein and sugar,reaction time,reaction temperature and pH to the recovery and solubility of compound was also investigated. Better reaction conditions determined by single factor test using recovery as index were as follows:RP reacted with maltodextrin in weight ratios of 1:4,at pH 12,110℃for 15min. Better reaction conditions determined by single factor test using solubility as index were as follows:RP reacted with maltodextrin in weight ratios of 1:4,at pH 12,80℃for 25min.The degree of solubility optimized by the method above was 60.76%.The process conditions were optimized by recovery on the base of the results of single factor test above.The influence of the ratio to protein and sugar,reaction time,reaction temperature and pH to the recovery of compound was also investigated. The optimal microwave reaction conditions determined by RSM were as follows:RP reacted with maltodextrin in weight ratios of 1:4,at pH 12.00,100℃for 21.5min.The recovery optimized by the method above was 98.45%.Better reaction conditions determined by single factor test using recovery as index were as follows:the microwave power was 400 to 600 W,at pH 12,80℃for 20min. The process conditions were optimized by recovery on the base of the results of single factor test above. Optimum reaction conditions determined by RSM test using recovery as index were as follows:the microwave power was 400 to 600 W,at pH 12,82℃for 16.8min. The recovery optimized by the method above was 96.25%.The process conditions of microwave reaction were better than that of wet- heating reaction.The former was 8℃lower than the latter.And time of the former was shorter than the latter.Though the recoveries obtained by two methods were close,the reaction time and reaction temperature was better than that of wet-heating method.The graft solubility at pH 5 was minimum,but at 35℃or 10% of protein concentration was maximum. The graft emulsibility and emulsibility stability at pH 5 were minimum, but growing larger as the protein concentration growing larger. The graft foaming ability was growing greater as the protein concentration growing larger, and was maximizing when at 3% of protein concentration. Then it reduced following the protein concentration growing larger. The graft foaming stability was maximum at 5% of protein concentration.The degree of solubility of extracted rice protein and RP-maltodextrin conjugant at pH7,25℃and 10% of protein concentration was 5.71% and 56.28%;EA was 0.153 and 0.318; ES was 17.79mim and 15.44mim; FA was 52.2ml and 32.0ml; FS was 80.95% and 81.25% respectively.The solubility of conjugant was improved remarkably than the rice protein unmodified.The maximum solubility was 69.58% at 35℃.The EA of conjugant was improved remarkably,but the ES was reduced slightly.The EA and ES was improved remarkably as the conjugant concentration increasing.The maximum of FA was 120mL when the conjugant concentration was 3%.The FS was improved slightly.