147
Amidated Low Methoxy Pectin (ALMP)
Löfgren et al. (2006) reported that ALMP S generally have less sensitivity towards
calcium whereas (Capel et al. 2006) reported that the process of amidation may
slight influence the sensitivity towards calcium. Also the gels formed by ALMP and
LMP at a pH of 3 and 7 appear to be similar in kinetic behaviour and gel microstructure. ALMP gels are formed as a result of hydrogen bonding between amide groups
at low pH. These gels are thermally reversible and sensitive. With or without 30%
sucrose, these gels show a rapid formation when G’ > G”. When heated, they can be
solidified again whereas in case of pectin gel, the liquid state remains unaltered
(Chen et al. 2014a, b).
Factors Affecting the Gelation Process
Overall the process of gelation is affected by both extrinsic and intrinsic factors.
Extrinsic factors include concentration of calcium, concentration of pectin, pH,
ionic strength and temperature whereas the molecular weight, number and the pattern of free carboxyl groups and the types of pectin form the intrinsic factors (Gigli
et al. 2009). The underlying effect of molecular weight is well understood in terms
of rigidity of the gel as the lower the molecular weight, less will be the junction
zones per molecules and less will be the extent of cross linking and accordingly
weaker will be the gel. This parameter is mainly dependent upon the origin of pectin
but handling procedures like extraction can also have a significant effect on the
molecular weight of the pectin. In a study carried out by Seshadri et al. (2003) the
workers reported an increase in the yield of pectin when the extraction was carried
out by ultrasound although the rheological properties of pectin were inferior.
Further, by increasing the intensity and time of sonication, reduction in the gel
strength was reported. The underlying mechanism of this result was attributed to
chain degradation that was promoted by cavitation that brought the reduction in the
molecular weight of pectin. Another important factor, that is the presence of sugar
monomers such as rhamnose. This sugar monomer is not compatible with the configuration of the junction zones that are formed by the GalA monomers. As a result
it hinders the molecular orientation that is required for the formation of the junction
zones (Axelos and Thibault 1991a). As a consequence, the geling properties of the
polymer in solution are affected. Thus rhamnose, which is the abundant sugar in
rhamnogalactouranan forms the hairy region by dismantling the backbone of galactouranan and this hairy region further limits the inter-chain association. However,
these rhamnose interruptions vary within the same plant species or in different pectins from different plant species. This phenomenon of rhamnose displaying poor
gelling properties can be observed in sugar beet pectin, which is mostly composed
Pectin
Amidated Low Methoxy Pectin (ALMP)
Löfgren et al. (2006) reported that ALMP S generally have less sensitivity towards
calcium whereas (Capel et al. 2006) reported that the process of amidation may
slight influence the sensitivity towards calcium. Also the gels formed by ALMP and
LMP at a pH of 3 and 7 appear to be similar in kinetic behaviour and gel microstructure. ALMP gels are formed as a result of hydrogen bonding between amide groups
at low pH. These gels are thermally reversible and sensitive. With or without 30%
sucrose, these gels show a rapid formation when G’ > G”. When heated, they can be
solidified again whereas in case of pectin gel, the liquid state remains unaltered
(Chen et al. 2014a, b).
Factors Affecting the Gelation Process
Overall the process of gelation is affected by both extrinsic and intrinsic factors.
Extrinsic factors include concentration of calcium, concentration of pectin, pH,
ionic strength and temperature whereas the molecular weight, number and the pattern of free carboxyl groups and the types of pectin form the intrinsic factors (Gigli
et al. 2009). The underlying effect of molecular weight is well understood in terms
of rigidity of the gel as the lower the molecular weight, less will be the junction
zones per molecules and less will be the extent of cross linking and accordingly
weaker will be the gel. This parameter is mainly dependent upon the origin of pectin
but handling procedures like extraction can also have a significant effect on the
molecular weight of the pectin. In a study carried out by Seshadri et al. (2003) the
workers reported an increase in the yield of pectin when the extraction was carried
out by ultrasound although the rheological properties of pectin were inferior.
Further, by increasing the intensity and time of sonication, reduction in the gel
strength was reported. The underlying mechanism of this result was attributed to
chain degradation that was promoted by cavitation that brought the reduction in the
molecular weight of pectin. Another important factor, that is the presence of sugar
monomers such as rhamnose. This sugar monomer is not compatible with the configuration of the junction zones that are formed by the GalA monomers. As a result
it hinders the molecular orientation that is required for the formation of the junction
zones (Axelos and Thibault 1991a). As a consequence, the geling properties of the
polymer in solution are affected. Thus rhamnose, which is the abundant sugar in
rhamnogalactouranan forms the hairy region by dismantling the backbone of galactouranan and this hairy region further limits the inter-chain association. However,
these rhamnose interruptions vary within the same plant species or in different pectins from different plant species. This phenomenon of rhamnose displaying poor
gelling properties can be observed in sugar beet pectin, which is mostly composed
Pectin