Structure and Gelation of the Heteropolysacchairde: Pectin Flashcards
What is pectin, and where is it found?
Pectin is a complex polysaccharide found in the cell walls of plants, commonly used to gel jams, jellies, and gummy candies.
What is the primary source of commercially available pectin?
Most commercial pectin is valorized from the peels of fruits, particularly citrus fruits like oranges, lemons, and limes.
Why is blanching important in the extraction of pectin?
Blanching is crucial to eliminate pectinesterase (PE) or pectin methylesterase (PME), enzymes that hydrolyze pectin, leading to a drastic decrease in viscosity.
What are the two main structural components of pectin?
Pectin consists of smooth regions (homogalacturonan) and hairy regions (rhamnogalacturonan).
What characterizes the smooth region of pectin?
The smooth region contains homogalacturonan, a linear polymer of galacturonic acid linked via alpha (1→4) glycosidic bonds, with carboxylic acid groups introduced through oxidation.
What defines the hairy region of pectin?
The hairy region has numerous branch points with side chains of sugars like galactose and arabinose, linked via alpha (1→4) and alpha (1→2) glycosidic bonds
What is the typical size range of pectin molecules?
Pectin molecules typically range in size from 50 to 150 kDa.
How are low-methoxy and high-methoxy pectins classified?
Low-methoxy pectin has less than 50% methoxylation of galacturonic acid groups, while high-methoxy pectin has more than 50% methoxylation.
What are the gel formation conditions for low-methoxy pectin?
Low-methoxy pectin requires deprotonation of carboxylic acids at pH above 3.2 and the presence of divalent ions (like Ca²⁺ or Mg²⁺) to form gel structures.
What conditions are necessary for high-methoxy pectin gel formation?
High-methoxy pectin requires acidic pH (2.8 < pH < 3.2) and typically needs 65-70% sugar to prevent electrostatic repulsion and support gel formation.
