| In the long-term production practice,it was found that the fabric sizing with corn starch size has worse desizing property by α-amylase,compared with cassava starch size and potato starch size,which affects the printing and dyeing process and the quality of finished products.The worse desizing property of corn starch is an unresolved problem in the textile printing and dyeing industry,and the reason for this result is also unclear.In order to explore the reasons for the worse desizing property of corn starch size and reveal the influence of starch chain structure and non-starch components,the corn starch,cassava starch,potato starch commonly used in warp sizing and waxy corn starch were used as research objects,comparing the differences in the hydrolysis of these starches from two aspects: hydrolysis of starch in solution and desizing of warp sizing,based on the starch-iodine colorimetric method,and preliminarily analyze the factors that inhibit hydrolysis of starch;The amylose and amylopectin from pure starch was separate,and compared the chain structure of different varieties of starch,analyzing the influence of starch chain structure on the hydrolysis;Removed lipids from corn starch or add exogenous oils to confirm the relationship between the existence or not of lipids and the hydrolysis property,and determining the effect of lipids on the hydrolysis of corn starch;The interference of proteins on hydrolysis of corn starch was analyze and revealed the mechanism of inhibiting the hydrolysis.Finally,it explored the effect of synergistic with trypsin,lipase,isoamylase,and α-amylase on the hydrolysis property of native corn starch.It provided the method to overcome the impact of non-starch components and starch chain structure on the hydrolysis.The main research content and conclusions are as follows:Firstly,it compared the starch chain structure,lipid content,and protein content among varieties of native starch to explore the possible reasons for the worse enzymatic desizing property of corn starch.The gelatinized corn starch,cassava starch,potato starch,and waxy corn starch were hydrolyzed by α-amylase to investigate the differences in hydrolysis property and the structure of the hydrolyzed product.And it analyzes the diversity in starch chain structure,lipid content,and protein content to reveal the possible reasons for the worse hydrolysis properties of corn starch.Based on the starch-iodine colorimetric method,it was compared the differences in the desizing properties of starches.It explored the correlation between the swelling property of the starch film,lipid content,protein content,and desizing efficiency.The results showed that corn starch had the worst hydrolysis property compared with cassava starch,potato starch,and waxy corn starch.At the end of the reaction,9.7% of the corn starch could not be completely hydrolyzed,and the amount was much higher than cassava starch,potato starch,and waxy corn starch(1.1%,2.0%,and 3.7%).After increasing the amount of α-amylase,corn starch still has lots of starch that could not be hydrolysed entirely(4.8%).The desizing efficiency of warp yarns sizing with corn starch is 91.1%,which is lower than that of warp yarns sizing with cassava starch,potato starch,and waxy corn starch(93.9%,93.6%,and 93.1%).And the starch in the residue of corn starch size has a higher maximum absorption wavelength(λmax)of starch-iodine complex,weight average molecular weight(MW),and the proportion medium-chain-length and long chain(DP ≥ 13)than that of the other three types of starch residues.The higher molecular density,short-chain of branched ratio,and a higher content of lipids and proteins may impact the desizing properties of starch sizes.Secondly,pure starch was obtained by completely removing non-starch components from the starch,and the amylose and amylopectin in the pure starch were separated.It was further studied the influence of starch chain structure on the hydrolysis property of starch measured based on starch-iodine colorimetry method.The amylose and amylopectin were separated and used as the research objects,analyzed the differences in the structure of starch chains,and explored the relationship between starch chain structure and hydrolysis property.The results showed that corn amylose,cassava amylose,and potato amylose could rapidly hydrolysis by α-amylase,with hydrolysis rates of 99.4%,99.3%,and 99.6% at the end of the reaction,respectively,and no significant difference of them.Compared to amylose,amylopectin has worse hydrolysis property due to its branching structure.At the end of the reaction,the hydrolysis rates of corn amylopectin,cassava amylopectin,potato amylopectin,and waxy corn amylopectin were 97.5%,98.3%,98.2%,and 98.0%,respectively.Among them,corn amylopectin has the highest molecular density and more short-chain branches,resulting in a lower hydrolysis rate than the other amylopectin.The structure of starch chain can affect the hydrolysis of starch,but the less incomplete hydrolyzed starch in the amylose hydrolysate and amylopectin hydrolysate shows that the difference in the chain structure of starches is not the main reason for the worse hydrolysis property of corn starch.Thirdly,the effect of lipids on the hydrolysis property and desizing property of corn starch was studied.Removing lipids or adding exogenous oils(emulsified oil or saponified oil)to starch to analyze the effects of lipids on the hydrolysis rate and λmax of hydrolyzed productsiodine complexes;Based on the changes in the hydrolysis property in solution,investigate the desizing property of starch sizes after removing lipids or adding exogenous oils,as well as the changes in the starch chain structure in the desizing residues,and analyze the inhibitory mechanism of lipids on the desizing.The results showed that after removing endogenous lipids,the hydrolysis rate of corn starch slightly increased(0.7%).After adding emulsified oil or saponified oil,the hydrolysis rate of starch decreased by 1.1% and 2.6%,respectively.After hydrolysis,the λmax of starch-iodine complex also reduces and increases by removing lipid or adding oils.After removing lipids,the desizing efficiency of corn starch size slightly increased(0.9%),while the desizing efficiency of starch sizes decreased(1.1% and 2.9%)after adding emulsified oil or saponified oil.The combination of lipids and starch to form a V-type complex can inhibit the hydrolysis of corn starch,resulting in the λmax of starch-iodine complexes in the desizing residue,MW,z-average radius of gyration(RZ),and long chain branching ratio slightly increased.Still,the changes in desizing property after removing lipid or adding oils showed that lipids were not the main reason for the relatively weak desizing property of corn starch sizes.Fourthly,the influence of protein on the hydrolysis properties of corn starch was explored,revealing the differences in binding force between proteins and starch and the inhibitory mechanism on the hydrolysis of starch.By removing granule surface proteins and granule channel proteins from corn starch,the effect of endogenous proteins on the hydrolysis property of starch in solution was investigated using the starch-iodine colorimetric method.The impact of protein on the hydrolysis of starch was further verified by adding exogenous proteins(corn protein and gelatin).In addition,it analyzed the effects of different proteins on the desizing efficiency,the composition of desizing residue,and the chain structure of starch residue;Furthermore,exploring the changes in the rheological properties of starch colloids after the addition of urea,sodium dodecyl sulfate,and Na Cl,the difference in binding force between protein and starch was clarified,and the inhibitory mechanism of protein on the hydrolysis was revealed.The results showed that after removing granule surface proteins,granule channel proteins,and completely removing endogenous proteins,the hydrolysis rates of corn starch increased by 3.2%,5.2%,and 7.0%,respectively,and λmax decreased with the removal of endogenous proteins.Removing granule channel proteins is more conducive to improving the hydrolysis properties of corn starch in solution than granule surface proteins.In addition,removing either of these endogenous proteins can promote the desizing property of starch size.Desizing efficiency increases by 2.4% after the complete removal of endogenous proteins.The decrease in the desizing efficiencies of starch size after adding exogenous proteins further proves that the proteins negatively impact the hydrolysis of corn starch.The primary binding forces between granule surface proteins and starch are hydrogen bonds,while hydrophobic interactions and hydrogen bonds are the main combined forces between granule channel proteins and starch.These differences in binding forces are the reasons why endogenous proteins play different inhibitory roles in the hydrolysis.Compared to pure cassava starch,pure potato starch,and pure waxy corn starch,it is found that the hydrolysis properties of pure corn starch are slightly poor,and 2.0% corn starch is difficult to be completely hydrolyzed by α-amylase,higher than pure cassava starch(0.4%),pure potato starch(0.7%),and slightly higher than pure waxy corn starch(1.4%).The difficulty of complete hydrolysis of corn amylopectin may be the reason for this phenomenon.There was no significant difference in the desizing efficiencies of the four pure starch sizes,which further confirms that the presence of endogenous proteins is the fundamental reason for the worse hydrolysis property of corn starch.Finally,in response to the effects of protein,lipid,and starch chain structure on the hydrolysis of native corn starch,the changes in hydrolysis property of corn starch under the synergy of multiple enzymes were explored by hydrolyzing non-starch components and breaking the starch chain structure.The trypsin,lipase,and isoamylase were used alone or in combination to compare the changes in the hydrolysis of native corn starch by α-amylase.The hydrolysis property and structure of hydrolyzed product were analyzed after adding these enzymes.In addition,the alone or combination use of trypsin and isoamylase was explored to improve the desizing property of the native corn starch size.The results showed that after adding trypsin or isoamylase,the hydrolysis property of native corn starch by α-amylase was improved,and the hydrolysis rate increased by 3.5% and 3.3%,respectively,at the end of the reaction;After protein hydrolysis by protease,adding the isoamylase and α-amylase could further increase the hydrolysis rate of corn starch(4.2%)and reduce the λmax of the hydrolyzed product-iodine complex.In addition,the addition of trypsin or isoamylase could promote enzymatic desizing of corn starch sizes,the desizing efficiency increase of 1.7% and 1.0%,respectively;Trypsin,isoamylase,and α-amylase were used together could further improve the desizing efficiency of starch size(2.8%),promote the reduction of weight MW and branch chain length in the starch residue.The lipase has no significant impact on the hydrolysis of corn starch by α-amylase,which is related to the small effect of lipids on hydrolysis of starch,and the lipase cannot rapidly hydrolyze lipids in solution. |
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