| Starch is cheap and widely available.However,there are strong intramolecular and intermolecular hydrogen bonds in native starch,resulting in poor solubility in water,which limits the practical application of native starch.Ionic liquids(ILs)stand out from traditional solvents due to their excellent properties.At present,it has been reported that ILs are used for starch dissolution.However,the effect of the different amylose content starch on the dissolution behavior of starch in ILs is still unclear.In addition,the structural changes of starch occur during dissolution and regeneration,which provides a new method for starch loading active substances.Therefore,three kinds of corn starch with different amylose content,namely high amylose corn starch(HACS),corn starch(CS)and waxy corn starch(WCS),and two ILs,including1-butyl-3-methylimidazolium chloride([BMIM]Cl)and 1-allyl-3-methylimidazolium chloride([AMIM]Cl),were selected to study the dissolution behavior in ILs.Tea polyphenols(TP)were selected as a typical alcohol-soluble active substance,and the regenerated starch dissolved by ILs was used to load it.The optimal loading process,the physicochemical properties and antibacterial activity of the regenerated starch-polyphenol complex were studied,and the practical application of the complex in food packaging was preliminarily explored.The main results are as follows:The dissolution behavior of starch in ILs was analyzed by polarizing microscope,differential scanning calorimeter,X-ray diffractometer,Fourier transform infrared spectroscopy and thermogravimetric analyzer.The results showed that the dissolution rate of crystalline region and HACS with smaller molecular weight was the slowest and the solubility was the highest for the three kinds of starch with different amylose content.Compared with the native starch,the crystal structure of the starch after dissolution-regeneration was completely destroyed,and the thermal stability was improved.Among the three regenerated starches,HACS formed a more ordered V-type structure.For the two ILs,[AMIM]Cl with smaller cation had faster dissolution rate,higher solubility,and less damage to the structure of starch.Starch/ILs were a pseudoplastic fluid in non-Newtonian fluid.Temperature,starch concentration,amylose content and ILs type did not affect the fluid type of the solution.Using TP as active substances,the effects of process conditions on the loading of polyphenols by regenerated starch were studied by single factor experiments,and the optimum process for loading was obtained as follows:WCS/B had better loading effect on TP,the concentration of TP was 8 mg/m L,the loading time was 120 min,the loading p H was 7,the loading rate was 67.15%,and the loading amount was53.72 mg/g.The morphological structure and activity of regenerated starch-polyphenol complex were analyzed.The results showed that starch and polyphenols were combined by hydrogen bond during the loading process.The number of hydrogen bonds in the loaded starch was more and the strength was greater,and the thermal stability of the complex was better than that of the regenerated starch.The stability,antioxidant and bacteriostatic properties of TP before and after loading were compared.It was found that the light and thermal stability of TP were improved after loading.At the same time,the complex showed antioxidant capacity on DPPH and ABTS~+free radicals.When the concentration of the complex reached 10 mg/m L,the antioxidant capacity of DPPH could reach 100%,which was consistent with the effect of pure TP,and the antioxidant capacity of ABTS~+free radicals could reach70%.It had antibacterial effect on Escherichia coli(EC)and Staphylococcus aureus(SA),and the antibacterial rate could reach 50%and 18%respectively.The starch composite film(WCS/B-TP)was prepared by using regenerated starch-polyphenol complex as the base material,and it was used for the preservation of fresh pork.The juice loss rate,p H value,volatile base nitrogen content and total bacterial count were used as indicators to explore its application in pork preservation.The results showed that compared with the blank group of native starch film and native refrigeration,the fresh pork placed on the regenerated starch-polyphenol composite film could play a better preservation effect to a certain extent.With the prolongation of storage time,the juice loss rate,p H,total volatile basic nitrogen and total bacterial count of fresh meat on WCS/B-TP composite film were lower than those of the control group. |
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