Don't feel like reading all 41 pages of the reader Food Ingredient Functionality?
This summary describes all theory of the Polysaccharides part (reader, knowledgde clips, lectures) in just 10 pages!
The content of the summary is:
- Physicochemical properties of polysaccharides
- Analytical techni...
Questions to practice exam Food Ingredient Functionality (Polysaccharides)
Flashcards108 Flashcards
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Flashcards108 Flashcards
$3.204 sales
Some examples from this set of practice questions
1.
Which type of carrageenan contains 2 SO3- groups?
Answer: iota carrageenan
2.
What are the two monomers in the backbone of carrageenan
Answer: galactosyl and anhydrogalactosyl
3.
Which type of carrageenan contains no anhydrogalactosyl?
Answer: Lambda carrageenan
4.
Which types of carrageenan can form a gel?
Answer: Kappa and iota
5.
Why is lambda carrageenan not able to make a gel?
Answer: Because it contains no anhydrogalactosyl which is needed for helix formation
6.
What kind of gel gives kappa carrageenan?
Answer: A brittle gel that gives syneresis
7.
What kind of gel gives iota carrageenan?
Answer: An elastic gel that is stable upon freezing and thawing.
8.
How is a gel formed with kappa carrageenan?
Answer: Helix is formed by carrageenan molecules (galactosyl and anhydrogalactosyl). Different helices are connected by potassium (K) moleculess that form a salt bridge. The potassium reduces the charge so the helixes can come together and the radius of potassium stabilizes the molecules
9.
How is a gel with iota-carrageenan formed?
Answer: Helixes are formed because of the interaction between galactosyl and anhydrogalactosyl in the carrageenan molecules. These helixes can aggregate because of calcium ions (divalent)
10.
How can kappa carrageenan stabilize a chocolate milk drink?
Answer: It forms complexes with milk proteins when milk proteins are positive and carrageenan is negative. If milk proteins are positive because of the pH, there will be salt bridges formed between the milk protein and carrageenan helix.
Besides that, there are also salt bridges between the different carrageenan molecules to form a network.
Polysaccharides
Physicochemical properties of polysaccharides
Polysaccharide building blocks
• Homoglycans: polysaccharides that consists out of the same monosaccharide
• Heteroglycan: polysaccharides that consist out of different monosaccharides
• The type of linkage between the monosaccharides (for instance alpha or beta) determines the
flexibility and stability of the polysaccharide.
Molecular weight
• High molecular weight → high viscosity
• Poly dispersed: there is a difference is the size of the polysaccharide molecules
• Mono dispersed: all polysaccharide molecules have the same size
• Hydrodynamic volume: the volume occupied by the molecule in solution
o Linear molecule → high hydrodynamic volume
o Dense, branched polysaccharide → lower hydrodynamic volume (because if 10 units
are branched, the radius is smaller than were they are linear next to each other)
Solubility and molecular interactions
• Branched molecules are more soluble than linear molecules because they have a lower
hydrodynamic volume
• Branched molecules have side chains so they cannot form junction zones with their selves. This
would decrease solubility.
• Repulsion in a molecule makes in hard for the molecule to form junction zones with itself →
better solubility
Charge
• Polysaccharides can contain uronic acid.
o Galacturonic acid in pectin
o Glucuronic acid in xanthan gum
o Mannuronic acid and guluronic acid in alginate
• These have a carboxylic acid group that can have a negative charge!
o pH = pKa → 50% neutral, 50% negative
o pH < pKa → neutral
o pH > pKa → negative
• Charge can also come from sulphate, phosphate or pyruvate (CH3-C-COOH)
Esterification and amidation
• Carboxyl group of uronic acids can be esterified
o Pectin can be esterified with methyl
o More esterified → less charge is possible
o Distribution of methyl esters over the pectin backbone determines the charge density
of the pectin molecule and its ability to interact with bi-valent ions like calcium.
• Carboxyl groups can be amidated
o A part of the carboxylic group is converted to an amide group
o Amidated pectin has different calcium binding and gelling properties.
, Analytical techniques
Molecular weight distribution
What?
Study the molecular weight distribution (hydrodynamic volume / size) of polysaccharides and
monitor the effect of modification.
How?
High Performance Size Exclusion Chromatography (HPSEC) where larger molecules are less
retained by the column compared to smaller molecules. Early peak = large molecule!
Monosaccharide composition
What?
Determine the carbohydrate composition.
How?
Hydrolysing polymer into its monomers (glucose, galactose etc.) and analysis of these monomers
by
• High Performance Liquid Chromatography (HPLC) or Gas Chromatography (GC) → for neutral
sugars
• High Performance Ion Exchange Chromatography → for both neutral and uronic acids
Degree of methylation, acetylation and amidation
What?
Determining the ester level of polysaccharide
How?
Saponification under alkaline conditions. Ester groups are released.
• Methanol can be quantified by GC or spectrophotometric colour essay (mole methanol/100
moles galacturonic acid)
• Acetic acid can be quantified by enzymatic colour assay, HPLC or GC (mole acetic acid/100
moles of sugar residues)
Level of amidation: presence and level of nitrogen is taken as measure for level of amide groups.
Anionic hydrocolloids
What?
Anionic = can become negatively charged
So the presence of negatively charged polysaccharides
How?
• Complex formation with methylene blue to determine if negative/ neutral
• Distinction between different anionic polysaccharides → sugar composition analysis
• Quick gel formation upon addition of calcium → pectin or alginate
• Presence of pectins → presence of esterified methanol by GC
• Rhodizonate colour assay → carrageenan (sulphate group binds with rhodizonate)
Degradation of polysaccharides using specific enzymes
What?
Distinguish between different types of polysaccharides
How?
Using enzymes that have a high specificity for specific carbohydrate building blocks or specific
linkage types. After that measuring molecular weight by HPSEC or HPAEC-PAD.
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