Research On The Preparation Of Corn Amylose Starch By Enzymolysis Method And Its Application In Soft Candy

Corn amylose starch has rapid gel speed, good gel-strength and hardness as well as high structural stability for its high amylose content. In China, the application of high-amylose corn starch are restricted for the lack of high-amylose maize breed. In this study, corn amylose starch were made by enzymolysis method in the laboratory. The preparation process of corn amylose starch were studied and optimized, the morphological, physicochemical and rheological properties of corn amylose starch and its application in soft candy were researched as well. This article can be used as the theory basis for its use in food industry.The main conclusions of this study are as follows:1. Corn amylose starch was made from commercially available ordinary corn starch by enzymolysis method. Amylose content was measured according to the method in GB7648-87, and the optimum process condition was determined by the level of amylose content. Judging by range analysis, the factors that effect amylose content are pullulanase dosage>enzymolysis temperature> concentration of starch suspension> enzymolysis time in order. The optimal combination of processes of preparing corn amylose starch are concentration of starch suspension15%, pullulanase dosage lU/g (dry starch), enzymolysis temperature40℃, enzymolysis time2hour.2. From the optical microscope figures, we can see that the shape of ordinary corn starch granules are round or ellipse and the particle size is uniform, nearly every granule has a umbilical point in its center. While the particles of corn amylose starch are of different size, the shapes are polygonal or prismatic, the surface is not smooth, and no umbilical point or no obvious umbilical point.The results of infrared spectra analysis show that the peak shape of corn amylose starch made by enzymolysis method and normal corn starch are nearly the same, which proved that no functional groups were introduced in corn amylose starch that we made. The analysis results illustrated that the degree of crystallization increased as the increase of amylose content.To study the physicochemical properties of corn amylose starch, transparency, solubility, swelling power and freeze-thaw stability were determined, the results are as follows:The transparency of high-amylose corn starch is lower than that of ordinary corn starch, and its transparency is reduced as the apparent amylose content increased. The solubility of high-amylose corn starch is higher than that of ordinary corn starch, and its solubility rises as the apparent amylose content increased. On the contrary, The swelling power of high-amylose corn starch is lower than that of ordinary corn starch, and its swelling power is reduced as the apparent amylose content increased.Apparent amylose content has much to do with freeze-thaw stability, with the increase of apparent amylose content, the rate of water released also increased, so the freeze-thaw stability drops. As a result, corn starch which has a high amylose content is suitable to used in low temperature or frozen foods.3. The rheological behavior of corn amylose starch at different conditions were measured by rheometer.The dynamical rheological test results show that during the heating process from40℃to90℃, G’ or (G ") of corn amylose starch first increased then decreased and50℃is the critical point. The higher the amylose content is, the greater the G’or (G ") is, and the range of the rise and fall of G’or (G ") is wider. From90℃to130℃, as the temperature rises, G’or (G ") is sharply increased, and the lower the amylose content is, the more G’or (G ") rises.The Static rheological test results show that Corn amylose starch paste(CASP) was a typical non-Newtonian, shear-thinning and thixotropic fluid. As the increase of the shear rate, the apparent viscosity of CASP gradually decreased. Instead, when shear rate decreased, the apparent viscosity of CASP gradually increased. Because the destruction rate and recovery rate of the internal structure of CASP are different, the flow curves exhibit unclosed hysteresis loops with different areas and yield stress. Besides, under a fixed shear rate (10s-1and100s-1), the results of the continuous heating scan from30℃to100℃proved that CASP is not sensitive to temperature.4.The optimum formula of amylose candy are OCS:CAS=10:6, white sugar41g, maltose syrup41g, citric acid0.5g. The results of texture testing show that the hardness and chewiness of soft candy are gradually increased as the amylose content in the formula increases, while the Springiness, Cohesiveness and Resilience of soft candy are nearly of no change. So in practical application, we can choose corn starch with proper content to make the candy that we need.