158
with layered double hydroxide and antimicrobial molecules improved thermal resistance, mechanical, and barrier properties. Pectin composite films produced by
incorporating silver nanoparticles resulted in improved thermal stability, mechanical strength, water vapour, and UV-light barrier properties (Shankar et al. 2016).
Nutraceutical Potential
Metabolism of Cholesterol
Cholesterol synthesis begins with acetyl CoA and acetoacetyl-CoA and is converted
into two primary bile acids: cholic acid and chenodeoxycholic acid. Excessive cholesterol in the body is removed by the excretion of bile acids and free cholesterol but
bile acids get reabsorbed in the small intestine and are transported to liver. Dietary
fibers like pectin, psyllium and β–glucan enhance the excretion of bile acids thus
reducing the serum cholesterol levels (Theuwissen and Mensink 2008). Dietary
fibers lower the cholesterol levels by following possible mechanisms: (1) hindrance
of bile salt reabsorption, (2) reduction in the rate of glucose absorption leading to
decreased insulin production. Reduced insulin causes a reduction in HMG-CoA
activity, thus reducing cholesterol synthesis, and (3) production of short chain fatty
acids by colonic fermentation, hindering cholesterol synthesis in the liver (Gunness
and Gidley 2010). Cholesterol lowering ability of pectin is due to its viscosity,
molecular weight, degree of methoxylation, acetylation and degree of esterification.
Another factor responsible for cholesterol-lowering effect of pectin is that it forms
a viscous gel and binds cholesterol and bile acids, that promotes their excretion and
reduces reabsorption. Also, absorption of cholesterol is hindered by disruption of
micelle formation constituted by bile salts, phospholipids and fatty acids. Molecular
weight of pectin contributes towards lowering of cholesterol by inhibiting lipid
digestion, through viscosity effect. High molecular weight pectin form complex
gels that trap water and lipids inside, thus increasing the viscosity of the gastrointestinal phases. Increase in gel viscosity limits the diffusion and the resulting interaction of lipids and lipases. Further, the entrapment of lipids inside the pectin gels
make them inaccesible to be acted upon by lipases. This results in reduced lipolytic
activity overall (Espinal-Ruiz et al. 2016).The degree of methoxylation alters lipid
digestion through its interactive role in cation binding, thus helping in lowering of
cholesterol. Calcium ions play a crucial role in lipid digestion. Calcium ions form
insoluble soaps with long chain FFAs, thus making them inaccessible for lipases to
act upon. High methoxylated pectin (HMP) and medium methoxylatedpectin
(MMP) (Degree of Methoxylation = 52%) efficiently enclose the lipid droplets, thus
hinder the adsorption of lipases. On the other hand, low methoxylated pectin (LMP)
possesses an open structure due to repulsion with negative charge carrying lipid
droplets, thus making lipids easily availability for lipases to act upon. Acetylation of
pectins have been reported to decrease the interaction of pectin with bile acids
N. Noor et al.
with layered double hydroxide and antimicrobial molecules improved thermal resistance, mechanical, and barrier properties. Pectin composite films produced by
incorporating silver nanoparticles resulted in improved thermal stability, mechanical strength, water vapour, and UV-light barrier properties (Shankar et al. 2016).
Nutraceutical Potential
Metabolism of Cholesterol
Cholesterol synthesis begins with acetyl CoA and acetoacetyl-CoA and is converted
into two primary bile acids: cholic acid and chenodeoxycholic acid. Excessive cholesterol in the body is removed by the excretion of bile acids and free cholesterol but
bile acids get reabsorbed in the small intestine and are transported to liver. Dietary
fibers like pectin, psyllium and β–glucan enhance the excretion of bile acids thus
reducing the serum cholesterol levels (Theuwissen and Mensink 2008). Dietary
fibers lower the cholesterol levels by following possible mechanisms: (1) hindrance
of bile salt reabsorption, (2) reduction in the rate of glucose absorption leading to
decreased insulin production. Reduced insulin causes a reduction in HMG-CoA
activity, thus reducing cholesterol synthesis, and (3) production of short chain fatty
acids by colonic fermentation, hindering cholesterol synthesis in the liver (Gunness
and Gidley 2010). Cholesterol lowering ability of pectin is due to its viscosity,
molecular weight, degree of methoxylation, acetylation and degree of esterification.
Another factor responsible for cholesterol-lowering effect of pectin is that it forms
a viscous gel and binds cholesterol and bile acids, that promotes their excretion and
reduces reabsorption. Also, absorption of cholesterol is hindered by disruption of
micelle formation constituted by bile salts, phospholipids and fatty acids. Molecular
weight of pectin contributes towards lowering of cholesterol by inhibiting lipid
digestion, through viscosity effect. High molecular weight pectin form complex
gels that trap water and lipids inside, thus increasing the viscosity of the gastrointestinal phases. Increase in gel viscosity limits the diffusion and the resulting interaction of lipids and lipases. Further, the entrapment of lipids inside the pectin gels
make them inaccesible to be acted upon by lipases. This results in reduced lipolytic
activity overall (Espinal-Ruiz et al. 2016).The degree of methoxylation alters lipid
digestion through its interactive role in cation binding, thus helping in lowering of
cholesterol. Calcium ions play a crucial role in lipid digestion. Calcium ions form
insoluble soaps with long chain FFAs, thus making them inaccessible for lipases to
act upon. High methoxylated pectin (HMP) and medium methoxylatedpectin
(MMP) (Degree of Methoxylation = 52%) efficiently enclose the lipid droplets, thus
hinder the adsorption of lipases. On the other hand, low methoxylated pectin (LMP)
possesses an open structure due to repulsion with negative charge carrying lipid
droplets, thus making lipids easily availability for lipases to act upon. Acetylation of
pectins have been reported to decrease the interaction of pectin with bile acids
N. Noor et al.