Pertanika Journal of Tropical Agricultural Science, 2014
The antioxidant properties of whole fruits and fruits without seeds and pith of two varieties of ... more The antioxidant properties of whole fruits and fruits without seeds and pith of two varieties of Momordica charantia (commonly known as bitter gourd), var. minima and var. maxima were investigated. The antioxidant content was investigated using ascorbic acid and total phenolic contents whereas the antioxidant activity was investigated using 2,2-diphenyl-1-picryl hydrazyl radical scavenging activity and ferrous ion chelating activity. The results showed that the fruits without seeds and pith and whole fruits of the two varieties of Momordica charantia exhibited different antioxidant content and activities. The ascorbic acid content ranged from 8.12 mg/100g to 24.46 mg/100g whereas the total phenolic content ranged from 1.47 mg GAE/100g – 27.23 mg GAE/100g. The antiradical power ranged from 4.67 to 5.94 and the ferrous ion chelating activity using the fruit extract concentration of 0.34 g/mL ranged from 10.6% to 89.3%. The effect of blanching and boiling on the antioxidant properties of fruits without seeds and pith of Momordica charantia var. maxima and minima was also investigated. Blanching and boiling of fruits without seeds and pith of M. charantia var. maxima and var. minima induced changes in the antioxidant content differently. The radical scavenging activity of the fruits without the seeds and pith of M. charantia var. maxima and var. minima increased as a result of blanching and boiling but their ferrous ion chelating activity became undetectable. There was no clear correlation between the antioxidant content and the antioxidant activities.
Pectins are a diverse family of biopolymers with an anionic polysaccharide backbone of-1,4-linked... more Pectins are a diverse family of biopolymers with an anionic polysaccharide backbone of-1,4-linked d-galacturonic acids in common. They have been widely used as emulsifiers, gelling agents, glazing agents, stabilizers, and/or thickeners in food, pharmaceutical, personal care and polymer products. Commercial pectin is classified as high methoxy pectin (HMP) with a degree of methylation (DM) >50% and low methoxy pectin (LMP) with a DM <50%. Amidated low methoxy pectins (ALMP) can be obtained through aminolysis of HMP. Gelation of HMP occurs by cross-linking through hydrogen bonds and hydrophobic forces between the methyl groups, assisted by a high co-solute concentration and low pH. In contrast, gelation of LMP occurs by the formation of ionic linkages via calcium bridges between two carboxyl groups from two different chains in close proximity, known as the 'egg-box' model. Pectin gels exhibit Newtonian behaviour at low shear rates and shear-thinning behaviour when the shear rate is increased. An overview of pectin from its origin to its physicochemical properties is presented in this review.
Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked α-D... more Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked α-D-galacturonic acid units. This naturally occurring, renewable and biodegradable polymer is underutilized in polymer science due to its insolubility in organic solvents, which renders conventional polymerization methods impractical. To circumvent this problem, cerium-initiated radical polymerization was utilized to graft methoxy-poly(ethylene glycol) methacrylate (mPEGMA) onto pectin in water. The copolymers were characterized by 1 H nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), and used in the formation of supramolecular hydrogels through the addition of α-cyclodextrin (α-CD) to induce crosslinking. These hydrogels possessed thixotropic properties; shear-thinning to liquid upon agitation but settling into gels at rest. In contrast to most of the other hydrogels produced through the use of poly(ethylene glycol) (PEG)-grafted polymers, the pectin-PEGMA/α-CD hydrogels were unaffected by temperature changes.
Pertanika Journal of Tropical Agricultural Science, 2014
The antioxidant properties of whole fruits and fruits without seeds and pith of two varieties of ... more The antioxidant properties of whole fruits and fruits without seeds and pith of two varieties of Momordica charantia (commonly known as bitter gourd), var. minima and var. maxima were investigated. The antioxidant content was investigated using ascorbic acid and total phenolic contents whereas the antioxidant activity was investigated using 2,2-diphenyl-1-picryl hydrazyl radical scavenging activity and ferrous ion chelating activity. The results showed that the fruits without seeds and pith and whole fruits of the two varieties of Momordica charantia exhibited different antioxidant content and activities. The ascorbic acid content ranged from 8.12 mg/100g to 24.46 mg/100g whereas the total phenolic content ranged from 1.47 mg GAE/100g – 27.23 mg GAE/100g. The antiradical power ranged from 4.67 to 5.94 and the ferrous ion chelating activity using the fruit extract concentration of 0.34 g/mL ranged from 10.6% to 89.3%. The effect of blanching and boiling on the antioxidant properties of fruits without seeds and pith of Momordica charantia var. maxima and minima was also investigated. Blanching and boiling of fruits without seeds and pith of M. charantia var. maxima and var. minima induced changes in the antioxidant content differently. The radical scavenging activity of the fruits without the seeds and pith of M. charantia var. maxima and var. minima increased as a result of blanching and boiling but their ferrous ion chelating activity became undetectable. There was no clear correlation between the antioxidant content and the antioxidant activities.
Pectins are a diverse family of biopolymers with an anionic polysaccharide backbone of-1,4-linked... more Pectins are a diverse family of biopolymers with an anionic polysaccharide backbone of-1,4-linked d-galacturonic acids in common. They have been widely used as emulsifiers, gelling agents, glazing agents, stabilizers, and/or thickeners in food, pharmaceutical, personal care and polymer products. Commercial pectin is classified as high methoxy pectin (HMP) with a degree of methylation (DM) >50% and low methoxy pectin (LMP) with a DM <50%. Amidated low methoxy pectins (ALMP) can be obtained through aminolysis of HMP. Gelation of HMP occurs by cross-linking through hydrogen bonds and hydrophobic forces between the methyl groups, assisted by a high co-solute concentration and low pH. In contrast, gelation of LMP occurs by the formation of ionic linkages via calcium bridges between two carboxyl groups from two different chains in close proximity, known as the 'egg-box' model. Pectin gels exhibit Newtonian behaviour at low shear rates and shear-thinning behaviour when the shear rate is increased. An overview of pectin from its origin to its physicochemical properties is presented in this review.
Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked α-D... more Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked α-D-galacturonic acid units. This naturally occurring, renewable and biodegradable polymer is underutilized in polymer science due to its insolubility in organic solvents, which renders conventional polymerization methods impractical. To circumvent this problem, cerium-initiated radical polymerization was utilized to graft methoxy-poly(ethylene glycol) methacrylate (mPEGMA) onto pectin in water. The copolymers were characterized by 1 H nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), and used in the formation of supramolecular hydrogels through the addition of α-cyclodextrin (α-CD) to induce crosslinking. These hydrogels possessed thixotropic properties; shear-thinning to liquid upon agitation but settling into gels at rest. In contrast to most of the other hydrogels produced through the use of poly(ethylene glycol) (PEG)-grafted polymers, the pectin-PEGMA/α-CD hydrogels were unaffected by temperature changes.
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Papers by Siew Yin Chan