152
Modification of Pectin with Chemical Treatment
A number of chemical methods are available in literature that has been utilized for
the extraction of pectin. On such method which has been used widely includes
alkylation. This method is broadly divided into two domains methoxylation and
long chain. In the former, minimum carbon chains are introduced while the latter
involves the introduction of more carbons to the carboxyl groups of pectin. When
the pectin is treated with an alkali, it results in the generation of the demethyesterfied residues which are randomly distributed along the polymer backbones that are
methylesterfied. These additions can change the structural, functional and physicochemical properties of the pectic polysaccharides. It has been reported by various
workers that alkylation enhances the water solubility, gel strength, antibacterial
activity and emulsifying cababilty. The synergistic interaction of some factors such
as DM, pH, ionic strength Amidation and demethoxylation influences the overall
properties of the modified pectins including water binding, emulsifying and interfacial properties. The reason for this can be attributed to the hydrophilic groups at the
galacturonic acid which are increased during the alkaline treatment. Similarly upon
acidic modification, there occurs the degradation of pectin which modifies its
molecular weight and composition subsequently. Fracasso et al. (2018) reported the
modification of citrus peels using alkaline and acidic treatment. The modified pectins displayed good water dissolving properties but poor strength gels, pseudoplastic rheological behaviour with less viscous behaviour and good stability.
Miscellaneous Modifications of Pectin by Blending with Proteins
Blending with Proteins
When pectin is blended with whey proteins, the resulting pectin-protein complex
forms a gel which can be employed for the production of gel controlled low-fat
mayonnaise (Sun et al. 2018). This treatment employs the interaction between the
positively charged proteins and negatively charged proteins polysaccharides. Guo
et al. (2018) reported an increase in the emulsifying properties of whey protein after
they were treated with sugar beet pectin for modification. Similar results were
obtained from citrus pectin (Koch et al. 2018). The mechanism can be understood
on the basis that higher degree of glycosylation in the protein-pectin conjugates
increases the emulsifying properties. Also it has been observed that the neutral
region of pectin is more readily conjugated with whey protein isolate in comparison
with the galacturonic region of pectin. The film incorporating the protein-pectin
blends is usually prepared in presence of transglutaminase. These films are often
employed for fresh-cut fruits and vegetables in order to prevent weight loss and
microbial growth.
N. Noor et al.
Modification of Pectin with Chemical Treatment
A number of chemical methods are available in literature that has been utilized for
the extraction of pectin. On such method which has been used widely includes
alkylation. This method is broadly divided into two domains methoxylation and
long chain. In the former, minimum carbon chains are introduced while the latter
involves the introduction of more carbons to the carboxyl groups of pectin. When
the pectin is treated with an alkali, it results in the generation of the demethyesterfied residues which are randomly distributed along the polymer backbones that are
methylesterfied. These additions can change the structural, functional and physicochemical properties of the pectic polysaccharides. It has been reported by various
workers that alkylation enhances the water solubility, gel strength, antibacterial
activity and emulsifying cababilty. The synergistic interaction of some factors such
as DM, pH, ionic strength Amidation and demethoxylation influences the overall
properties of the modified pectins including water binding, emulsifying and interfacial properties. The reason for this can be attributed to the hydrophilic groups at the
galacturonic acid which are increased during the alkaline treatment. Similarly upon
acidic modification, there occurs the degradation of pectin which modifies its
molecular weight and composition subsequently. Fracasso et al. (2018) reported the
modification of citrus peels using alkaline and acidic treatment. The modified pectins displayed good water dissolving properties but poor strength gels, pseudoplastic rheological behaviour with less viscous behaviour and good stability.
Miscellaneous Modifications of Pectin by Blending with Proteins
Blending with Proteins
When pectin is blended with whey proteins, the resulting pectin-protein complex
forms a gel which can be employed for the production of gel controlled low-fat
mayonnaise (Sun et al. 2018). This treatment employs the interaction between the
positively charged proteins and negatively charged proteins polysaccharides. Guo
et al. (2018) reported an increase in the emulsifying properties of whey protein after
they were treated with sugar beet pectin for modification. Similar results were
obtained from citrus pectin (Koch et al. 2018). The mechanism can be understood
on the basis that higher degree of glycosylation in the protein-pectin conjugates
increases the emulsifying properties. Also it has been observed that the neutral
region of pectin is more readily conjugated with whey protein isolate in comparison
with the galacturonic region of pectin. The film incorporating the protein-pectin
blends is usually prepared in presence of transglutaminase. These films are often
employed for fresh-cut fruits and vegetables in order to prevent weight loss and
microbial growth.
N. Noor et al.