Effects Of Microwave Irradiation On Lotus Seed Starch

Lotus seed starch was a kind of high amylose which easily led to quality deteriation of products due to the impact of starch aging. Microwave heating had vast applications in the field of food processing such as drying and cooking of food materials due to its ability to achieve high heating rates, significant reduction in cooking time, and more uniform heating. Moreover, microwave heating might reduce the starch recrystallization and change the digestibility of lotus seed starch, which suggests that the effect of microwave irradiation on lotus seed starch was significant. In this paper, effects of microwave irradiation on structure and digestibility of lotus seed starch were evaluated. The results offered a theoretical basis for the application of microwave radiation to the nutrition and safety of lotus seed.With water bath heating as the control, the effects of microwave irradiation on starch components were elaborately discussed. The results showed the total starch, amylose and soluble amylose decreased and soluble carbohydrates increased with increasing power, and there is no significant change in total carbohydrates in microwave irradiation. The granule morphology revealed that the cell wall disappeared and smaller lipid was scattered across the paste which was led to the purple image in the light microscopeThe MLS was prepared by alkali.Particle shape and crystalline structure of MLS was studied with scanning electron microscopy (SEM), infrared spectroscopy scanner, Multi-angle laser light scattering (MALLAS), nuclear magnetic resonance scanner (NMR). The results showed that microwave irradiation was evidenced to cause the fragmentation of lamellar structure and a drop in crystallinity which was compared to WLS. The analysis of NMR scanning also showed that single-peak structure was presented in the position of Cl. It was concluded that the extent and the type of these changed depend on the inhibition of the recrystallization. In addition, the analysis of molecular weight showed that the molecular weight (MW and Mn) increased with the increasing power and it was higher than that of WLS. The protein and lipid of lotus seed interacted with starch in complicated system that hindered the starch gelatinization process or cause the incomplete swelling of starch granule.Lotus seed starch-water was subjected to microwave heated by Microwave station. The physicochemical properties and structure of lotus seed starch affected by microwave irradiation was investigated. The result shows that Microwave heating was evidenced to cause a drop in swelling power, amylose leaching, molecular weight with the increase in microwave power, the swelling power and leaching of amylose were 5.75 and 68.58 mg/g when microwave power is 8.0W/g,35.17% and 48.35% decline as compare as control. The change of infrared spectrum crystal area analysis and molecular weight also decreased with the increasing power, which caused no difference in the group structure of starch granules.1H NMR in low field showed that microwave can change the water distribution and improve the constraints of water molecules, resulting in the formation of strong gel due to vibrational motion and the rapid increase in temperature.First-order hydrolysis kinetics equation was applied to describe the digestive behavior of lotus-seed starch which was treated in microwave irradiation. It was concluded that the digestibility and GI decreased significantly and slowly digestible starch increased, but GI can not meet the requirement of low glycemic index. The absence of a continuous of network of amylose chains and the transformation between RDS and SDS contributed to the change of digestive characters in microwave irradiation, meanwhile, a layer of non-starchy barrier material such as polysaccharides on the surface of starch granules might result in less susceptible to digestion enzymes.