Enzymatic Preparation Of Modified Maltodextrin And Its Application In Baked Goods

Maltodextrin is an intermediate product in the process of starch hydrolysis and has been widely used in food baking.The properties of maltodextrin,such as bond ratio,product branching degree and molecular weight distribution,could be changed after treatment by biological enzyme.In this paper,a method of the preparation of maltodextrin by enzyme was studied.Combining the properties of Cyanothece sp.ATCC 51142 branching enzyme CyBE,which specifically transfers malt oligosaccharides from DP6 to DP 10,with the properties of 4,6-?-glucosyltransferases(4,6-?-GTs),which transfer individual glucose to produce continuous ?-1,6-glycosidic bond-linked heteromalt polysaccharides,the dual enzyme The combination was used to prepare modified maltodextrins with high specificity of branching chain length and high and dense branching.The main contents of this paper are as follows:(1)Recombinant expression and enzymatic characterization of CyBE.CyBE was recombinantly expressed in E.coli BL21(DE3),and its enzymatic activity on amylose and amylopectin was 2342.93 U·mL-1 and 1079.89 U·mL-1,respectively.The optimum temperature was 30?,the half-life under 30? was 27 hours,and the optimum pH was 7.0.(2)Preparation of modified maltodextrin and analysis of its physical and chemical properties.4,6-?-GTs can catalyze the transglycoside reaction to increase the branching degree of the product.Two kinds of 4,6-?-GTs used in this study were Lactobacillus fermentum GTF13 and Bacillus sporothermodurans GTF5.The modified maltodextrin was prepared by compound reaction of CyBE and 4,6-?-GTs,and effects of different enzyme sequence on the physicochemical properties of modified maltodextrin were studied.The results showed the dietary fiber content of maltodextrin was up to 43.57%after treatment of GTF 13 for 24 h and CyBE for 24 h.In vitro digestive properties of the modified maltodextrin was analyzed,and the digestion resistance was found to increase from 12.01%to 59.44%.(3)Effect of modified maltodextrin on bread quality.The modified maltodextrin could significantly reduce the hardness of bread,when added to common wheat starch to make bread in the addition range of 3%to 10%.The hardness of bread could be reduced to 640.15 g,28.98%of the control group of 2208.53 g under addition of 5%.Meanwhile,after 4? of storage for 21 days,the bread hardness of the experimental group added with modified maltodextrin was 1254.48 g,29.46%of the control group of 4257.57 g.(4)Study on the mechanism of chain length transferring of CyBE.In order to further improve the application effects of modified maltodextrin,the chain length transferring mechanism of CyBE was explored.Five mutants of ?W285,?S283-G287,F323 A,E204W and S374W were designed.The length of transferred chain results showed that compared with wild CyBE,?W285 and ?S283-G287 mutants showed better ability to transfer chains above 8 sugars,F323A showed weaker ability to transfer chains above 7 sugars,and E204W and S374W showed weaker ability to transfer chains above 9 sugars.