Methodologies for the extraction and analysis of konjac glucomannan from corms of Amorphophallus konjac K. Koch |
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Authors: | Melinda ChuaKelvin Chan Trevor J HockingPeter A Williams Christopher J PerryTimothy C Baldwin |
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Institution: | a School of Applied Sciences, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1SB, United Kingdom b HMREC, Faculty of Pharmacy, University of Sydney, NSW2006, Sydney, Australia c CompleMED, College of Health and Science, University of Western Sydney, NSW2560, Sydney, Australia d Glyndwr University, Plas Coch, Mold Road, Wrexham LL11 2AW, United Kingdom |
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Abstract: | Here we present a comparison of commonly used methodologies for the extraction and quantification of konjac glucomannan (KGM). Compositional analysis showed that the purified konjac flour (PKF) produced using a modified extraction procedure contained 92% glucomannan, with a weight average molecular weight (Mw), polydispersity index (PDI) and degree of acetylation (DA) of 9.5 ± 0.6 × 105 g mol−1, 1.2 and 2.8 wt.%. These data, plus Fourier-transform infrared spectral (FTIR) and zero shear viscosity analyses of the extract (PKF) were all consistent with the literature. Comparison of three existing methodologies for the quantitative analysis of the KGM content of the PKF, namely 3,5-dinitrosalicylic acid (3,5-DNS), phenol-sulphuric acid and enzymatic colorimetric assays; indicated that the 3,5-DNS colorimetric assay was the most reproducible and accurate method, with a linear correlation coefficient of 0.997 for samples ranging from 0.5 to 12.5 mg/ml, and recoveries between 97% and 103% across three spiking levels (250, 500 and 750 μg/g) of starch. These data provide the basis of improved good laboratory practice (GLP) for the commercial extraction and analysis of this multifunctional natural polymer. |
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Keywords: | CKF crude konjac flour CMA Chinese Ministry of Agriculture DA degree of acetylation 3 5-DNS 3 5-dinitrosalicylic acid FCC Food Chemicals Codex FTIR Fourier-transform infrared spectra GLP good laboratory practice GPC-MALLS gel permeation chromatography coupled to multiangle light scattering detectors KGM konjac glucomannan LVKF low-viscosity konjac flour NKF nutraceutical-grade konjac flour PDI polydispersity index PHP potassium hydrogen phthalate PKF purified konjac flour RI refractive index RSD relative standard deviation DI deionised water |
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