| Starch plays an active role in maintaining life and is the main source of energy for the human body.However,long-term consumption of foods with a high glycemic index was positively associated with obesity,hyperglycemia,type 2 diabetes,and other complications.Pea is one of the important food crops,with rich nutritional and medicinal value.Pea starch is a by-product of pea protein extraction,with relatively high amylose content,low glycemic index,good film forming,high gel elasticity and high resistant starch content.Phenolic compounds are the main bioactive substances in pea,and the peel of pea is rich in dietary fiber,polyphenols and other bioactive substances,which can affect the physicochemical,processing and nutritional properties of starch,and have antioxidant,anti-cancer,blood sugar regulation and other effects.However,there are few studies on the interaction between phenols in pea and pea starch.Therefore,in this study,quercetin,catechin and pea starch in pea peel were selected as research objects to study the effects of quercetin and catechin on the physicochemical properties,structural properties and digestive characteristics of pea starch,and to explore the interaction between pea starch and polyphenols.The main research results are as follows:（1）The polyphenols from four kinds of pea samples were extracted,and the pea peel with the highest content of total phenols was selected to optimize the process according to the results of single factor experiment.The optimal extraction process of total phenol from pea peel was obtained as follows:solid-liquid ratio of 1:60,ethanol concentration of 50%,extraction time of 4.25 h,extraction temperature of 70℃.Under this process condition,the total phenolic content of pea peel was 3.9913 mg·g-1,and the scavenging rate of DPPH radical and ABTS radical was 88.56%and 74.75%respectively.（2）Quercetin and catechin in pea peel were selected to study their effects on physicochemical properties of pea starch.Gelatinization and thermal characteristics showed that the two polyphenols reduced the overall viscosity,disintegration value,recovery value and gelatinization enthalpy value of starch,delayed the short-term aging of starch,and enhanced the stability of starch cold paste,and the influence of catechin was greater.Quercetin decreased the solubility and expansibility of the system,while catechin increased the solubility and expansibility of the system.Quercetin and catechin significantly reduced the syneresis rate of starch during freeze-thaw process and improved the freeze-thaw stability of starch.Starch transparency decreased significantly with the extension of refrigeration time,and gradually decreased with the increase of the concentration of two polyphenols.The texture and rheological results showed that the composite system was typical pseudoplastic fluid,and the two polyphenols reduced the hardness,adhesiveness,chewability and viscoelasticity of pea starch,and destroyed the gel network structure of starch.（3）The effects of quercetin and catechin on starch structure of pea were determined.Both kinds of polyphenols significantly reduced the p H value and the starch-iodine binding capacity of pea starch solution,and the effect of catechin on the starch-iodine binding capacity was much greater than that of quercetin.Scanning electron microscopy（SEM）showed that some quercetin and catechin attached to starch surface and increased with the increase of polyphenol concentration.X-ray diffraction（XRD）results showed that the two polyphenols did not form V-shaped complex with pea starch,but interacted with starch through non-covalent bond such as hydrogen bond.Infrared spectrum（FT-IR）results showed that no new peaks appeared in the starch-polyphenol complex system,and the interaction was through non-covalent bond.（4）The effects of quercetin and catechin on the digestive characteristics of pea starch were determined.Both polyphenols had inhibitory effects onα-amylase andα-glucosidase,and the inhibitory effect of catechin was higher than that of quercetin.The results of fluorescence quenching analysis showed that both polyphenols could statically quenchthe fluorescence spectra ofα-amylase andα-glucosidase,and formed non-fluorescent complexes with starch digestive enzymes through hydrogen bonding,van der Waals force and hydrophobic interaction.The results of in vitro digestion of starch showed that both kinds of polyphenols reduced the content of rapid digestible starch（RDS）and increased the content of resistant starch（RS）,and effectively delayed the digestion of starch.In general,quercetin and catechin interact with pea starch mainly through non-covalent bond based on hydrogen bond,and significantly affect the processing and digestion properties of starch.This study provides beneficial information for pea as a functional food component to improve human health and provides certain theoretical guidance for polyphenols in the development of new starch functional food. |
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