CHEM215 Lecture 10: Lec 10 - Carbohydrates 3
Structural polysaccharides:
• Seaweed: consists of structural polysaccharides including alginates and agar.
-Alginates: linear polymers of 2 different monosaccharide units which are joined
by 1,4-links. These alginates join together to form alginic acid.
Calcium alginate gels do not melt below the boiling point of water and they have
therefore found anumebr of applications in food products. Eg. Fake fruit alginates.
The CHOs need to be made into their gel form then treated with calcium to
solidify them.
-Agars and carageenans: this are more complex than alginates. Most are linear
chains of galactose derivatives of B-D-galactose.
-carageenans: a family of linear sulphated polysaccharides that are extracted from red
edible seaweeds. They consist of repeating galactose units, with some having an
ester sulphate group. They are widely used in the food industry for their gelling,
thickening and stabilising properties. Used in products such as toothpaste, icecreams,
sherbets and whipped creams.
• Gums: extracted from plants or other non-cereal seeds. Xanthn gum and gallons
are secreted by bacteria. They have. High affinity for water and high viscosity
in aqueous solutions. Often used in low concentrations for stabbing emulsions and
to smoothen texture.
• Guar gums: affects the digestion and absorption of carbohydrates- flattens the peak
of glucose flow in the bloodstream. The sugars and starch get caught up in the 3-D
network of fibre molecules which makes them less accessible to digestive to
enzymes, which slows down their absorption in the small intestine. Commonly
used as a thickening agent for people with dysphagia (swallowing difficulties).
Don’t need to know alot about these CHOs —> mainly need to know about
glucose and fructose and the polymers they perform.
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Physical and chemical properties of sugars:
• Functional groups: two important functional groups are OH, which is important
for the level of sweetness we detect and solubility, and C=O group which
is important for reducing activity and browning.
1. Oxidation of sugars: sugars act as reducing agents by becoming oxidised (losing an
electron) —> hence why they are called reducing sugars. Reducing sugars have a
free anomeric OH group, as this opens up to form a double bond to the oxygen —>
loses an electron.
In order to test for reducing sugars, blue Cu2+ will be reduced to Cu which forms a red
precipitate.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Structural polysaccharides: seaweed: consists of structural polysaccharides including alginates and agar. Alginates: linear polymers of 2 different monosaccharide units which are joined by 1,4-links. These alginates join together to form alginic acid. Calcium alginate gels do not melt below the boiling point of water and they have therefore found anumebr of applications in food products. The chos need to be made into their gel form then treated with calcium to solidify them. Agars and carageenans: this are more complex than alginates. Most are linear chains of galactose derivatives of b-d-galactose. Carageenans: a family of linear sulphated polysaccharides that are extracted from red edible seaweeds. They consist of repeating galactose units, with some having an ester sulphate group. They are widely used in the food industry for their gelling, thickening and stabilising properties. Used in products such as toothpaste, icecreams, sherbets and whipped creams: gums: extracted from plants or other non-cereal seeds. Xanthn gum and gallons are secreted by bacteria.
