Effects of Different Heating Methods on the Dietary Fiber Content and Physical Properties of Sweet Potatoes

Abstract

  We compared the effects of different methods of heating sweet potatoes on the soluble dietary fiber (SDF) content, insoluble dietary fiber (IDF) content and resistant starch (RS) content, as well as the water holding capacity and adsorption ability of dietary fiber, through steaming and microwave heating. There was no difference in SDF content of sweet potatoes before and after heating for both steaming and microwave heating methods. The IDF content of raw sweet potatoes was 1.09%. After steaming, the IDF content increased significantly (p < 0.01) to 2.10%, but it was 1.29% after microwave heating, with no significant difference from that of raw sweet potatoes. The RS content of raw sweet potatoes was 0.93%, while it increased significantly (p < 0.05) to 1.89% and 1.34% after steaming and microwave heating, respectively. As the increase in IDF and RS after steaming was almost the same, the IDF that increased after steaming was thought to be RS. The water holding capacity and amaranth adsorption per gram of IDF in steamed sweet potatoes were significantly (p < 0.01) lower than those in raw and microwave heated sweet potatoes.