| Starch is the main carbohydrate found in plants,and it is widely utilized in food,pharmaceuticals,cosmetics and textile industries due to its non-toxic,harmless,abundant,and renewable.The multi-layer structure of starch includes granule,shell,corpuscle,and molecular structure.The outer shell of starch granules has a dense structure,resulting in high hardness and making it difficult for the reagent to penetrate into the starch granules.This characteristic affects the solubility,in vitro digestion,viscosity,crystallization,and chain length distribution of starch.Starch granules primarily consist of amylose and amylopectin.Amylose not only inhibits reagent migration within starch granules,but also hinders reagent modification,and has a significant effect on the digestion and viscosity properties of starch.In order to investigate the starch modification efficiency of amylose and shell treatment,red bean,potato,and sorghum starch were removed by warm water extraction,and different degrees of amylose granule models were obtained.These models were then subjected to hydrochloric acid acidolysis,citric acid esterification,and microwave treatment,respectively.Additionally the surface gelatinization method was employed to remove the shell of red powder,lotus root,and wheat A-starch,the granule model of gelatinized shelled starch was obtained and combined with acetic anhydride esterification,toughening,and wet-heat modification,respectively.The effects of starch shell and amylose content on multi-scale structure,physicochemical properties,and digestion properties before and after modification were analyzed systematically.The main results are as follows:After different degrees of gelatinization and shelling treatment of sweet potato,lotus root and wheat A starch,it was found that the gelatinization pattern was the same,and the transparent gelatinization layer was formed from outside to inside,and the granule integrity was maintained after gelatinization treatment.With the increase of gelatinization time,the crystallinity and peak viscosity of different crystal starches decreased,while the rapidly digested starch,gelatinization temperature and solubility increased.With the increase of toughening time,the amylose content and crystallinity of wheat A starch granules with the same degree of shelling decreased gradually,while the A-chain ratio,molecular weight of amylose and gelatinization temperature initially decreased and then increased.Gelatinization time and resistant starch content gradually increased.After toughening treatment,it was found that the amylose content,molecular weight,A-chain ratio and peak viscosity decreased with the increase of shelling time,while the gelatinization temperature increased,but the resistant starch decreased gradually.The results showed that the exfoliation changed the permeation rate and modification efficiency of water molecules.After gelatinization and shelling of lotus root starch,with the increase of wet-heat treatment time,contrary to the digestive characteristics of damaged wheat A-starch toughening treatment,the content of resistant starch gradually decreased and the content of amylose increased gradually;while the crystallization characteristics,chain length distribution and molecular weight distribution were the same,the crystallinity and A-chain ratio decreased gradually,in addition,the peak viscosity and expansibility of the samples gradually decreased,but the solubility increased gradually.Under the same wet-heat treatment,with the increase of gelatinization time,the chain length distribution,digestion,viscosity and crystallization properties of lotus root modified samples were similar to those of wheat A-starch samples,while A-chain ratio,peak viscosity,resistant starch content,amylose content and crystallinity decreased gradually.The difference is that the gelatinization temperature of lotus root starch samples decreases gradually,which may be related to the hygrothermal treatment temperature,and the migration rate of water molecules is proportional to the treatment temperature.Therefore,the shell structure of lotus root starch can inhibit water permeability and maintain the structure of starch granules.After esterification of gelatinized sweet potato starch with acetic anhydride,it was found that the crystallization properties,amylose content,chain length distribution,viscosity,solubility and expansion of sweet potato modified samples were similar to those of lotus root and wheat A-starch.the difference is that the content of resistant starch increased at first and then decreased after esterification of damaged sweet potato starch.This may be because acetyl groups affect the binding sites of digestive enzymes.The transparency and degree of substitution increased significantly with the increase of treatment time.Therefore,the starch shell not only affects the permeation rate of water molecules,but also has a significant effect on the reagent.It may be because the gelatinization treatment destroys the integrity of sweet potato starch and the reagent is easy to enter into the granules.With an increase in water bath treatment time,the amylose content decreased gradually in red bean,sorghum,and potato starch.It had similar effects on chain length distribution,viscosity,expansibility,and digestibility of starch.The ratio of A-chain,decay value,peak viscosity,expansibility and resistant starch decreased significantly,while gelatinization temperature,gelatinization time and B3-chain ratio increased.With the increase of hydrochloric acid concentration,the amylose content,crystallinity,Achain ratio,peak viscosity,valley viscosity,disintegration value,retrogradation value,and swelling power of red bean starch with the same water bath treatment time decreased gradually,while the solubility,gelatinization temperature and gelatinization time increased gradually.The amylose content,crystallinity,A-chain ratio,peak viscosity,retrogradation value,and solubility of red bean starch modified with the same concentration of hydrochloric acid decreased with the increase of water bath time.The solubility and gelatinization temperature increased significantly.Therefore,the effects of water bath treatment and acid hydrolysis treatment on the solubility,crystallization,chain length distribution,and viscosity of red bean starch were similar.The results showed that the effect of amylose was similar to that of starch shell,and both inhibited the penetration of reagents.For sorghum starch with the same amylose content,with the increase of microwave treatment time,the effects of amylose content,chain length distribution,crystallization,viscosity and expansion were the same,and the A-chain ratio and peak viscosity decreased gradually;the difference is that the gelatinization temperature and solubility of sorghum samples increased at first and then decreased.With the increase of water bath and microwave treatment time,the resistant starch increased at first and then decreased.At the same microwave treatment time,the amylose content of the sample decreased gradually with the increase of water bath time.The characteristics of chain length distribution,crystallization and viscosity were similar to those of red bean samples,and decreased gradually.The difference is that the solubility of the sample decreases gradually,and the crystallinity decreases at first and then increases.The results showed that amylose had a certain effect on microwave modification.The substitution degree and solubility of potato starch with the same amylose content increased with the increase of citric acid content,while the amylose content,Achain ratio,crystallinity and enthalpy decreased.With the decrease of amylose content,the crystallization,dissolution and chain length distribution of potato samples were consistent with those of red bean and sorghum starch.On the contrary,the degree of substitution increased with the decrease of amylose content.Therefore,both amylose and starch shell structure can inhibit the penetration of water molecules and chemicals,maintain the stability of starch granule structure,and have significant effects on the structure and physicochemical properties of all kinds of modified starch. |
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