Root samples were directly sliced w

Root samples were directly sliced with a food processor into approximately 4-mm chips. To measure the root dry matter content, a freshly mixed 20-g sample of root slices was oven-dried to a constant weight at 80°C for 48 h. The dried root was ground to a powder, and the starch content was determined as previously described (Li et al. 2011). The amylose and amylopectin contents were determined using the dual wavelength method (620/480 nm) described by Hovenkamp-Hermelink et al. (1988). RVA measurements were conducted using RVASuper4 (Newport Scientific Pty., Ltd., Australia) as reported by Noda et al. (1996). Each sample was measured three times.