Which statement about pectin is false?

Which statement about pectin is false?

• A. Young/unripe fruits contain protopectin
• B. Old/over-ripe fruits contain pectinic acid
• C. The swelling of pectin is due to mannuronic acid
• D. Pectin is used as an antidiarrheal agent

Answer: (C)

Swelling behavior in pectin comes from its hydrophilic galacturonic acid backbone. Pectin is made of repeating galacturonic acid units; when many of these units are demethylated, the carboxyl groups lose protons and become negatively charged. Those negative charges repel each other and attract water, causing the polymer to swell and, with the right conditions, form a gel. Mannuronic acid, on the other hand, is a component of alginates, not pectin, so tying pectin’s swelling to mannuronic acid mixes up different biopolymers. Protopectin is the insoluble form in unripe fruit, which ripens into soluble pectin; with further aging, some pectin can be hydrolyzed to pectic acid in overripe fruit. Pectin’s water-absorption and gel-forming ability also explains its use as a mild antidiarrheal, by helping bulk and slow transit in the gut. So, the claim that swelling is due to mannuronic acid is not correct.

Swelling behavior in pectin comes from its hydrophilic galacturonic acid backbone. Pectin is made of repeating galacturonic acid units; when many of these units are demethylated, the carboxyl groups lose protons and become negatively charged. Those negative charges repel each other and attract water, causing the polymer to swell and, with the right conditions, form a gel. Mannuronic acid, on the other hand, is a component of alginates, not pectin, so tying pectin’s swelling to mannuronic acid mixes up different biopolymers. Protopectin is the insoluble form in unripe fruit, which ripens into soluble pectin; with further aging, some pectin can be hydrolyzed to pectic acid in overripe fruit. Pectin’s water-absorption and gel-forming ability also explains its use as a mild antidiarrheal, by helping bulk and slow transit in the gut. So, the claim that swelling is due to mannuronic acid is not correct.