Effect of Peeling on Physicochemical Properties and Biological Activity of the Yam Powders

In order to study the effect of peeling procedure on the physicochemical properties and biological activity of yam powder,yam powder was prepared by hot air drying method;The total starch content and in vitro digestibility were determined by enzymatic hydrolysis. Scanning electron microscopy,X-ray diffraction and Fourier transform infrared spectroscopy were used to investigate the morphology and crystal structure of different yam powders. The total flavonoids,total soluble polyphenols content,reducing power and DPPH free radical scavenging ability were determined by spectrophotometry. The results showed that the total starch content and resistant starch content of the yam powder prepared with the peeling procedure were higher,and were 45.39% and 31.11% respectively. The yam powder prepared without the peeling procedure had larger water binding capacity(194.53 g/100 g),and its swelling power and solubility at different temperatures were also larger with the maximum increase rates 43% and 18%,respectively. The morphological characteristics and crystal structure of the two kinds of yam powder were similar. The total flavonoids and total soluble polyphenols content of yam powder prepared without peeling process were larger,and were 0.059 mg RE/g and 0.028 mg GA/g,respectively. Also,its DPPH free radical scavenging ability(EC₅₀ value 43.86 mg/mL)and reducing power(0.223 mg V_C/g)were higher. Therefore,the peeling procedure has obvious effect on the physicochemical properties and biological activity of the yam powder. According to the characteristics of the two kinds of yam powder,the appropriate yam powder can be selected for use in different foods.