Pectins and Gums
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What is dietary fiber?
Dietary fiber is the edible parts of plants or carbs that are resistant to digestion and absorption.
What are the important polysaccharides in foods?
Pectins and gums
Why are pectins and gums important polysaccharides in foods?
Pectins and gums are important because of their functional properties.
What are uses for pectins and gums?
Thickeners, stabilizers and gelling agents.
What are pectic substances?
Important constituents of plant tissue
What are different types of pectic substances?
Protopectin, pectinic acids, pectins and pectic acid.
What is considered as a linear polymer of D-galacturonic acid joined by α-1,4 glycosidic linkages?
Pectic substances
Each glycosidic linkage is a _________ bond.
Cross-planar
How are pectic substances classified?
Based on the number of methyl ester groups attached to the polymer.
Which derivative of pectic substances does not have a methyl group?
Pectic acid
Where is protopectin formed?
Protopectin forms in immature fruits
Where is pectinic acid formed?
Pectinic acid forms in ripened fruits
Where is pectic acid formed?
Over-ripe fruits
Which pectic substance forms a gel?
Pectinic Acid
Which pectic substnace is insoluble in water?
Protopectin
True or False. The degree of esterification varies for pectins.
True
What compound needs to be present for low-methoxyl pectins to form a gel?
Calcium
What needs to be added to high-methoxyl pectins for a gel to form?
Sugar and acid
What is commonly used to form pectin jellies?
High-methoxyl pectins
Why is pectin hydrophillic?
Due to the large number of polar hydroxyl groups and charged carboxyl groups
True or False. The positive charge on the pectin molecule, coupled with their attraction to water, keeps them apart, so they form a sol.
False. The negative charge does this.
How does pectin gel formation occur?
Decrease the forces that attract the pectin molecules for water or increase the forces that attract the pectin molecules to each other.
How does sugar help with gel formation?
Sugar competes with water, making water less available to bond with pectin molecules
How doe acid help with gel formatin?
Acid reduces the pH and the charge on the pectin molecules. Making the pectin molecules no longer repel each other.