Synthesis,characterisation and in vitro digestibility of carboxymethyl potato starch rapidly prepared with microwave-assistance |
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Authors: | Jia Liu Jian Ming Weijin Li Guohua Zhao |
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Affiliation: | 1. College of Food Science, Southwest University, Tiansheng Road 1, Chongqing 400715, PR China;2. Key Laboratory of Food Processing and Technology of Chongqing, Chongqing 400715, PR China;3. Chongqing Sweet Potato Engineering and Technology Centre, Chongqing 400715, PR China;4. College of Food Science, Sichuan Agriculture University, Yaan 625000, PR China |
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Abstract: | Carboxymethyl potato starch was synthesised with the aid of microwave. Optimal degree of substitution (DS) of 0.32 was obtained at 45 °C in 25 min using aqueous ethanol media with water/solvent of 0.15 at 200 W. The molar ratio of sodium hydroxide and monochloroacetic acid to anhydroglucose unit for optimal DS were 2.5 and 1.0, respectively. FT-IR spectrometry revealed the carboxymethyl starch to show new bands at ν = 1614 cm−1 and ν = 1429 cm−1. Wide angle X-ray diffractometry and DSC revealed a remarkable reduction in starch crystallinity after carboxymethylation, which was consistent with destroyed surface observed in SEM. The digestibility of carboxymethyl starch (CMS) was lower than that of native starch. With similar DS, there was no difference in digestibility of carboxymethyl starch prepared with and without microwave. As DS increased from 0.05 to 0.32, the amount of resistant starch in microwave-assisted carboxymethyl starch was elevated from 14.6% to 20.0%, which was much higher than that of native starch (10.8%). |
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Keywords: | AUC area under the hydrolysis curve CT conventional modification method CMS carboxymethyl starch DS degree of substitution DSC differential scanning calorimetry FG free glucose FT-IR Fourier transform infrared GI estimated glycemic index H-CMS carboxymethyl starch in hydrogen form HI hydrolysis index MAT microwave-assisted MCA monochloroacetic acid NPS native potato starch RDS rapidly digestible starch RS resistant starch SDS slowly digestible starch SEM scanning electron micrographs TS total starch XRD X-ray diffractometry |
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