Glucoamylase P (H. resinae)

Effects of adding resistant starch (RS), inulin (IN) and xylo-oligosaccharide (XOS) on the cooking properties, texture properties, ordered structure of starch, water mobility and in vitro digestion of Yiyang rice cake were investigated. The cooking loss of rice cake was reduced to 2.8-4.6% with the addition of XOS. Addition of these fermentable carbohydrates increased the hardness, viscosity, chewiness and order of starch. As the content of carbohydrates increased, the rice cakes gradually became smoother. RS and XOS promoted the starch retrogradation and the free movement of water in the rice cakes, and increased the ordered structure formed by the association between starch chains; IN had no obvious effect on the retrogradation. Compared with the control group, digestion rate and final digestibility level of the starch digestion model in RS and XOS groups decreased, especially the total amount of available starch of XOS120 decreased to 73.8%, indicating that they had a certain inhibitory effect on starch digestion. The crystallinity formation theories for high-moisture starch gels are not applicable to rice cakes.

Background and objectives: Cycloamylose (CA), a promising encapsulating agent, was efficiently produced from high amylose corn starch (HACS, HYLON ® VII) by sequentially‐combined enzyme treatment of isoamylase and Thermus aquaticus 4‐α-glucanotransferase (TAαGT). The CA production performance of HACS was compared with that of rice starch, especially from the viewpoint of differences in their molecular characteristics. Findings: The maximum conversion yield of CA from HACS reached 76.35%, which was 2.4‐times higher than that from rice starch (31.36%). The degree of polymerization (DP) of CA produced from HACS ranged from 7 to 41, where a major portion lied in DP 23-41, with DP 26 showing the highest yield. In contrast, CA produced from rice starch showed a relatively larger amount of smaller cyclic glucans (DP 6-16). Conclusion: The significantly high production yield and DP profile of CA were attributed to high apparent amylose content and long average amylopectin branch chain length of HACS compared to those rice starch. Significance and novelty: This study can provide a better understanding of CA production depending on starch molecular characteristics, and attract industrial consideration in utilizing HACS for CA production.