Charge modification of citrus and sugar beet pectins and physicochemical properties of pectin-whey protein complexes
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The hypothesis was that pectinmethylesterase (PME) fractions with different peptides will have different deesterifcation action pattern. Also physicochemical and rheological properties of pectin-whey protein isolate (WPI) complexes will be affected by and intrinsic factor, such as degree of esterification (DE), as well as extrinsic factors, such as heat-treatment and pH. Based on this hypothesis, the objectives of this research were to deesterify citrus and sugar beet pectin by PME fractions with different peptides, to determine DE and distribution of deesterified groups of modified pectin, and to characterize gelling property of original/modified pectin in the presence of calcium. Also, the physicochemical properties of original/modified pectin-WPI were investigated with/without heat-treatment (at 75ºC for 20 min) at two different pHs (4.5 and 7). Finally, the effect of different DE of pectin on rheological property of pectin-WPI complexes was investigated, as well as effects of heat-treatment and pH. PME with 36 kDa peptide showed highest specific activity followed by 27/36 kDa peptides, 13/27/36 kDa peptides, and 27 kDa peptide. All PMEs showed block wise deesterification pattern in citrus and sugar beet pectin, which increased sequential structure of deesterfied groups and decreased sequential structure of methyl-esterified groups. Elastic property (G’) of citrus and sugar beet pectin in the presence of calcium increased from 10.35 up to 1354.60 Pa and from 0.05 to 201.02 Pa by PME modification. The following physicochemical properties of WPI were affected by the presence of pectin: surface hydrophobicity, zeta potential, and particle sizes. The presence of citrus and sugar beet pectin decreased surface hydrophobicity, zeta potential, and particle size of WPI at pH 4.5. Heat-treatment at 75ºC for 20 min increased surface hydrophobicity of pectin-WPI complex. Zeta potential of WPI only at pH 7.0 was more negative than at pH 4.5. The presence of citrus or sugar beet pectin made zeta potential more negative at pH 4.5. The particle size of WPI only was increased with heat-treatment and at pH 4.5. The added citrus or sugar beet pectin decreased particle sizes of WPI at pH 4.5. Regardless of pH and heat-treatment, elastic property (G’) of modified citrus pectin-WPI were significantly (p”0.05) higher than those of original citrus- or original/modified sugar beet pectin-WPI. Heat-treatment at 75ºC for 20 min increased G’ of modified citrus pectin-WPI complex. At the combination of pH 4.5 and heat-treatment, G’ of modified sugar beet pectin-WPI mixture was significantly higher than that at pH 7 or without heat-treatment.
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Rivner, Joshua Scott (uga, 2008-12)Pectin methylesterase (PME), extracted from Valencia pulp, was fractionated into 36 kDa, 27 kDa, and 13 kDa isozymes and isozyme combinations using a series of ion exchange columns. The 36 and 27 kDa isozymes were salt ...
Hunter, Janice Lee (uga, 2002-12)Pectin can be used as a stabilizer in foods such as drinkable yogurts, protein fortified sports drinks, flavored milks, and liquid diet drinks. The structure of pectin influences its functional properties. Commercial pectin ...
Valencia pectinmethylesterase isozymes result in pectins of unique charge domain and functionality Kim, Yookyung (uga, 2004-05)Based on the hypothesis that PME fraction containing 36/27 kDa peptides (U-PME) will yield differently modified pectin than PME fraction containing 36/13 kDa peptides (B-PME), the objective of this study was to isolate the ...