| Starch has abundant sources and is widely used in practical production.However,natural starch has certain defects,such as easy retrogradation and crystallization,poor shearing and thermal stability,and insufficient water holding capacity.Polyphenols are often added into starch-based products as functional factors to improve the physicochemical properties and delay the digestion of starch.Proanthocyanidins are a kind of natural plant polyphenols,which have antioxidant,anticancer,antibacterial,blood pressure lowering,blood lipid lowering and other biological activities,and their activity is closely related to the degree of polymerization.Polymeric proanthocyanidin(PPC)has a wide range of potential health benefits,such as a greater reduction in α-amylase activity,better antitumor,and other effects compared to oligomeric proanthocyanidin.Therefore,this study selects different degrees of polymerization of polymeric proanthocyanidins and five kinds of starch(rice starch(RS),potato starch(Po S),pea starch(Pe S),high amylose maize starch(HAM),and waxy maize starch(WAM))as the research objects,research into the interaction mechanism of polymeric proanthocyanidins and starch,explore the effect of polymeric proanthocyanidins on the physicochemical and digestive properties of starch,and apply it to the preparation of rice cakes.This study provides theoretical basis and guidance for the application of polymeric proanthocyanidins with hygienical function in starch-based products.The main contents and results of the study are as follows:(1)Starch is composed of amylose and amylopectin molecules,so this paper selected maize starch with different amylose/amylopectin ratios as the research object to explore the mechanism of interaction between starch and PPC.The results showed that starch interacted with PPC,and PPC could promote starch gelatinization and change starch paste viscoelasticity.Compared with amylose,PPC had stronger inhibition on retrogradation of amylopectin.When the PPC supplemental level was1%-5%(w/w),the degree of interaction between amylose and PPC was positively correlated with the concentration of PPC,and excessive PPC(10%,w/w)could inhibit the interaction between PPC and amylose.The interaction between amylopectin and PPC was positively correlated with the concentration of PPC(1%-10%,w/w).PPC mainly bonded between starch chains through hydrogen bonds,changed the crystal structure of starch and increased starch particle size.When the dosage of PPC was 10%,the average grain diameter of WAM and HAM increased by 22.45% and 34.09%,respectively.Moreover,PPC had a slightly greater effect on short-chain amylopectin than other amylopectin and amylose.(2)For starch with different crystal types,the addition of PPC increased the storage modulus(G’)values of RS(A-type),Po S(B-type)and Pe S(C-type),and enhanced the gel network structure of them.The addition of PPC(5%,w/w)increased the peak,trough and final viscosity of RS and Pe S,but decreased the relative viscosity of Po S.After adding PPC,the setback of RS,Po S and Pe S decreased by 18.32%,16.00%and 3.10%,respectively,and the degree of retrogradation was reduced by 15.30%,9.84%and 5.65%,respectively.The result showed PPC could inhibit the aging of starch with different crystal types,and the order of effect was RS > Po S > Pe S.The addition of PPC made Po S surface a slender three-dimensional layered network structure,while RS and Pe S gel surface became rougher.In vitro digestion results showed that in different PPC addition sequence,the co-gelatinization of PPC and starch significantly reduced the digestibility of starch.When co-gelatinized,the content of resistant starch of RS,Po S and Pe S increased by 14.73%,8.83% and 14.71%,respectively,showing the increase value of resistant starch content of RS and Pe S was higher than that of Po S.(3)PPC can enhance the thermal stability and improve the relative stability and uniformity of Po S gel structure.Among the three PPCs with different degree of polymerization(the average polymerization degrees of PPC1,PPC2 and PPC3 were6.39±0.13,8.21±0.76 and 9.92±0.21,respectively),Po S setback value decreased by37.53%,28.72% and 16.88%,the degree of retrogradation decreased by 7.91%,11.45%and 14.79%,and the content of rapid digestion starch decreased by 6.06%,9.93% and13.68%,respectively.PPC1 can significantly reduce the breakdown value,the hysteresis ring area and consistency coefficient K of Po S starch paste.The result showed that PPC1 with the lower degree of polymerization could significantly improve the gelation properties(including paste stability and gel network structure)and inhibit the short-term retrogradation of starch,while PPC3 with the higher degree of polymerization could significantly delay the long-term retrogradation of starch and reduce the starch digestion rate.(4)Through the orthogonal experiment,the hardness,viscosity and chewiness parameters were choosen as the main evaluation indexes of rice cake quality.The basic formula of rice cake was determined as follows: sugar content(the mass ratio to rice starch)was 15%,water content was 75%,and yeast content was 3%.In addition,the optimal supplemental level of PPC was determined as 2% based on specific volume,water retention,hardness,sensory score and digestibility.After PPC was added,there were more kinds of flavor substances in rice cake,and the contents of alcohols and esters were significantly higher than those of original rice cake,increasing from 41.42%to 48.70% and from 16.17% to 23.53%,respectively.PPC mainly inhibited the digestion of rice cake by reducing the total amount of digestible starch during rice cake digestion. |
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