Preparation, physico-chemical characterization and biological activities of two modified starches from yam (Dioscorea Opposita Thunb.)

Physicochemical and bio-functional properties of three starches including native starch (NS), the dual enzyme-treated starch (DES) and the cross-linked carboxymethyl starch (CCS) were investigated in the current study. The resistant starch (RS) contents ranged from 33.91 to 43.71%, which were decreased by modification. For the first time, the anti-constipation and hypolipidemic effect of yam starches are demonstrated. Three starches were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and FT-IR spectroscopy. DES's crystalline structure collapsed and lost its granular shape during modification, indicating that DES had a high water binding capacity and high solubility. However, only minor changes of CCS's granular surface and crystallinity were observed. Furthermore, anti-constipation effect of the three yam starches was evaluated by intestine propulsion and defecation in constipated mice. There was more short chain fatty acids (SCFAs) produced in colon with DES and CCS, than that with native starches. Therefore, the modified starches were proved to be better for improving the small intestine propulsion function by generating more SCFAs. Hypolipidemic effect was also evaluated by monitoring the triglyceride (TG) and total cholesterol (TC) levels in mice. This study reports new bioactive starches, with potential applications in the pharmaceutical and food industries. (C) 2015 Elsevier Ltd. All rights reserved.