| Starch is a kind of polysaccharide,which can be used as the auxiliary material of the food,such as thickening agent,adhesive,moisture preserving agent,emulsifier,etc,to beautify food or change the structure of the food.But the starch food at low temperature for a period of time will appear aging phenomenon which may lead to short shelf life,poor quality and impaired earnings of starch food.?-PGA is a kind of high molecular polymer,which has a lot of free carboxyl groups in the main chain.It has been widely used in the food industry like delaying the aging of bread,noodles,cakes,etc.Some studies had pointed out that starch was an important component of the flour product,and it was directly related to the aging of the products.In this study,?-PGA was added into the starch and the effect of ?-PGA on the pasting and aging properties of starch were analysed to lay a firm theoretical foundation for the application of ?-PGA in starch industy.The main contents and results of this research are as follows:The gelatinized mixture was obtained by adding ?-PGA into starch,to study the effect of ?-PGA on the properties of starch.The results of this study showed that the solubility,swelling power,pasting properties,freeze-thaw stability and retrogradation of starch could be changed in different degrees.Effect of ?-PGA on the properties of sweet potato starch,corn starch and wheat starch:With the increased of the concentration of ?-PGA,the solubility and swelling power of the sweet potato starch,corn starch and wheat starch showed the trend of increasing first and then decreasing.Both these two parameters reached the highest values when the concentration of ?-PGA was 0.08%,and the swelling power and solubility of starch were still greater than the control when the concentration of?-PGA was 0.12%.Compared with the parameters of the control,when the concentration of ?-PGA was 0.08%,the swelling power increased by 11.11%,13.04%,14.06% and the solubility increased by 50%,44.44%,40% respectively,resulting in the swelling power of the starch granules.The results showed that ?-PGA could promote the water absorption capacity of sweet potato starch,corn starch and wheat starch.After adding ?-PGA into these three starch,compared with the parameters of thecontrol,their pasting viscosity were increased while their retrogradation were reduced.Measured by RVA,TPA and NMR analysis,the addition of ?-PGA was able to reduce the freeze-thaw stability,hardness,setback and the attenuation values of those starch gel,and extend the water holding capacity of starch gel.When the concentration of?-PGA was 0.08%,compared with the control,the retrogradation values of starch were respectively reduced by 52.26%,86.78%,53.07%.By X-ray diffraction analyzing the starch granules,compared with the parameters of the control,the crystallinity of starch granules decreased from 18.13%,19%,19.84% to 17.67%,16.81% and 18.11% respectively.The results showed that the stability of these three kinds of starch could be enhanced by ?-PGA,the crystallinity of the particles was decreased and the aging rate of starch was inhibited at the same time.These three kinds of starch were also analysed by FT-IR spectrogram,which had similar peak patterns.After adding the ?-PGA whose concentration was 0.08% into starch,the O-H and C-H?unsaturated?of the starch were respectively transferred from3434 cm-1and 2939 cm-1 to 3236 cm-1and 2917 cm-1.However,the peak of-COOH was not observed.The pattern showed that the-COOH of ?-PGA bonded with the-OH of starch as a substituent so that the molecular structure of starch was changed.Effect of ?-PGA on the properties of potato starch:?-PGA could reduce the swelling power of the potato starch and increase the solubility,retrogradation and freeze-thaw stability of the starch.Compared with the parameters of the control,the swelling power of potato starch decreased by 16.25%,the solubility increased by 93% and the setback value increased by 58.84% when the concentration of ?-PGA was 0.08%.Measured by RVA,TPA and NMR analysis,?-PGA could reduce the pasting viscosity and the water holding capacity of starch gel,and could increase the gel hardness,setback and attenuation values of potato starch.In addition,by X-ray diffraction analyzing,the crystallinity of starch was changed from 13.89% to 14.08% after adding the ?-PGA whose concentration was 0.08%.The results illustrated that ?-PGA could increase the crystallinity of starch granules and inhibit the aging of potato starch.By the FT-IR spectrogram analyzing,the-COOH of?-PGA were disappeared after mixing with potato starch,and the-OH of potato starch in 3498 cm-1 transferred to 3454 cm-1.The results showed that the-COOH of ?-PGA were mainly related to the-OH of starch.Seen from the overall results,?-PGA could inhibit the aging of sweet potato starch,corn starch and wheat starch,but the aging of potato starch was presented as afacilitating role. |
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