Effect of different starch source properties on crystal leather textural quality

High transparency and delicate taste are the most important quality indices of the crystal starch products.In order to clarify the effect of starch characteristics on the crystal products' textural quality, 5 kinds of starch originated from wheat, corn, potato, cassava and mung bean were selected as research material to determine the starch granule property, damaged starch content, gelatinization property, as well as their correlation with crystal skin transparency and texture quality.The brightness, transparency and texture properties were chosen as indices for evaluating the quality of crystal starch product, which could not only reflect the product palatability, but also avoid the difference of artificial factors.The indices were determined by the colorimeter, the ultraviolet-visible spectrophotometer and the texture analyzer, respectively.The experiment was carried out in Henan Agricultural University from March to June in 2015.The results showed that different starch skin showed significant difference in the quality.By evaluating the starch skin brightness, transparency and texture qualities, the wheat starch skin showed the best quality, followed by potato, cassava and corn.The worst quality was found in mung bean starch product.The brightness of wheat starch skin was 77.81, which was the highest brightness in research.The wheat starch skin had the light transmittance of 22.83%, and it also had better chewiness, more moderate hardness, springiness and firmness under the same condition.Therefore, wheat starch skin demonstrated the best palatability to make crystal skin, because it had more excellent quality characteristics.The average particle size of starch was significantly and positively correlated with crystal skin brightness and light transmittance, which should be attributed to the reason that starch molecules with larger size were easier to swell and be fully extended.The average particle size of starch was significantly and negatively correlated with crystal skin springiness and chewiness.The results suggested that excess starch inflation would lead to a water-based starch, which was adverse to the springiness and chewiness of the starch skin.The expansion of the starch granules at 95 ℃ was significantly(P<0.05) related to the light transmittance of crystal skin, but not significantly related to other quality characteristics.The damaged starch content of the starch had significantly positive correlations (P<0.05) with crystal skin brightness and light transmittance.Whereas, the damaged starch content had negative correlations with springiness and chewiness.Therefore, the best overall crystal skin texture quality would be obtained only when the damaged starch content was moderate.In this study, the crystal skin quality was good when iodine absorption rate was 93.94%.Moreover, the crystal starch product quality also showed a close relationship with starch gelatinization, which was evident by the results that starch peak viscosity and breakdown had significantly(P<0.01) positive correlation with the light transmittance of crystal starch products.The results suggested that the starch with greater swelling was easier to form better thermal paste stability, and as a result the transparency of the starch skin was higher.Setback and final viscosity had negative correlation with the light transmittance.Setback reflected the aging trend of starch.Starch aging would lead to the reorganization of molecules, which reduced crystal skin transparency.The positive correlation was also observed between the trough viscosity, final viscosity, setback and the crystal starch product hardness, springiness, chewiness, firmness.However, there was no significant correlation between the gelatinization temperature and the crystal starch products quality.To sum up, the present results suggest that when one kind of raw material is selected for crystal starch products, the viscosity is capable of being used as an important evaluation index.Meanwhile, the particle size, swelling, peak viscosity and breakdown can be well used for predicting the crystal starch product's brightness and light transmittance.The damaged starch content, trough viscosity, final viscosity and setback are the crucial factors that affect the palatability of the crystal starch products.The present result has a great application potential in crystal starch product processing industry, and especially offers a basic theoretical support for raw material selection and quality improvement.