| Nowadays,with the great progress of human society,habits,diet patterns and food structure are all changing,chronic disease has become one of the most serious public health problems in today’s society.Tea polyphenols(TP)are natural strong antioxidants that can inhibit amylase activity to achieve slow digestion of starch,prevent and treat chronic diseases like diabetes,but the bioavailability of tea polyphenols is low.Modified starch has a high adsorption capacity and slow digestion,and it can be used as a carrier for tea polyphenols.Therefore,this article first modified the starch to prepare a high-absorption modified starch to adsorb tea polyphenols,then embedded them with sodium alginate,chitosan,and calcium chloride as wall materials.Developed a new tea polyphenol transport system starch-TP composite,which can not only protect tea polyphenols in the stomach and reduce its loss,but also enable tea polyphenols to be released rapidly in the upper part of the small intestine,effectively exerting its physiological effects.At the same time,its effect on postprandial blood glucose response in mice was studied.The specific contents are as follows:1.The raw corn starch was used to prepare lightly gelatinized corn starch and porous corn starch as raw material.The optimum condition for preparing lightly gelatinized corn starch was treating at 90°C for 1min.The optimum condition for preparing porous corn starch was: reaction temperature was 55°C,at p H value of 4.4,enzyme dosage was 3.3%,enzyme ratio(α-amylase: glucoamylase)was 2:3,starch concentration was 15%,reaction time was 20 h.2.After the tea polyphenols were adsorbed by the core carrier modified starch,sodium alginate and chitosan were used as wall materials to prepare the starch-TP composites.Optimize the concentration and proportion of wall materials so that they can form a thin membrane to encapsulate the core material carrier and core material without too thick to affect the rapid release of the core material in the small intestine.The best preparation conditions were 1.5 g modified starch,20 m L tea polyphenols of 25 mg/m L,10 m L sodium alginate of 0.25%,25 m L chitosan of 0.1%,25 m L calcium chloride of 1.0%,adjusted p H to 3.5 with Na HCO3.The ratio of tea polyphenols embedded in the lightly gelatinized corn starch-TP composites prepared under this condition reached 84.08%,and the average loading capacity was 207.60 mg/g;The ratio in the porous corn starch-TP composites was 67.81%,and the average loading capacity was 167.44 mg/g.3.Characterize the lightly gelatinized corn starch-TP composites and porous corn starchTP composites.The results showed that the size of starch-tea polyphenols composite obtained after adding tea polyphenols increased,presumably due to the entrapment of tea polyphenols.Fourier infrared spectroscopy showed that the characteristic absorption peaks of tea polyphenols in the combination were significantly reduced,and the FTIR spectrum of the combination was similar to that of the samples before the addition of tea polyphenols,indicating that the tea polyphenols entered the inner cavity of the combination and proved the formation of embedded material.The results of X-ray diffraction indicated that the crystallinity of the mildly gelatinized corn starch was still type A,the crystallinity decreased from 55.82% to 46.35%,and the proportion of crystalline areas damaged by destructive amorphous areas increased,which facilitates the entry of tea polyphenols.The TGA results showed that the lightly gelatinized corn starch-TP composites were directly lysed at 300°C instead of splitting step by step,indicating that the lightly gelatinized corn starch absorbs the tea polyphenols and the lightly gelatinized corn starch was embedded in the network structure which was formed by sodium alginate,chitosan and calcium chloride,formed a whole,that was light gelatinized corn starch-tea polyphenol composites.After 5 weeks of storage,the decrease in DPPH radical scavenging rate of the lightly gelatinized corn starch-TP combination was reduced by 69.23% compared to the non-encapsulated tea polyphenol powder,demonstrating that tea polyphenols were successfully embedded.A mildly gelatinized corn starch-tea polyphenol composite was formed and the composite protected tea polyphenols and enhanced their storage stability.The results of the characterization of the porous corn starch-TP composite show the same trend as the lightly gelatinized corn starch-TP composite.4.The release rate of lightly gelatinized corn starch-TP composites and porous corn starchTP composites in simulated gastric juice was 0.5 h: 10.09% ± 0.25%,12.19% ± 0.13%,and 2.0 h: 16.22% ± 0.84%,18.32% ± 0.75%,after staying for 0.5 h in the gastric fluid,the release rate in the simulated intestinal fluid for 0.5 h was 61.42% ± 1.13% and 63.01% ± 0.98% respectively,and after staying for 2.0 h in the gastric fluid,the release rates were 72.40%±1.32% and 74.70%±0.56% respectively,indicating that the prepared composites were relatively stable in the stomach and achieved rapid release of tea polyphenols in the intestine.Pasting and enzymatic hydrolysis of the composites with wheat flour showed that the content of fastdigesting starch in wheat flour decreased,at the same time the amount of resistant starch became larger,which proved that tea polyphenols in the composites played an effective role in promoting slow digestion of starch.5.The mice were given the starch-tea polyphenols composites by gavage and the postprandial blood glucose levels,intestinal adipose digestive enzyme activity and antioxidant capacity of mice were measured.The results indicated that compared with mice directly administrated with tea polyphenols,the overall trend of mice’s postprandial blood glucose fluctuations fed gavage with starch-tea polyphenols composites was relatively flat,and the peak blood glucose was significantly reduced and delayed.The activities of α-amylase and α-glucosidase in the small intestine were significantly reduced,the activities of T-AOC,SOD,GSH-Px were significantly increased,and the MDA level was significantly reduced,demonstrating that starch-tea polyphenols composites can better protect and carry tea polyphenols so that tea polyphenols can achieve slow digestion of starch and exert its antioxidant biological activity in the upper part of the small intestine. |
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