Food hydrocolloid diversity

Question 1

Properties may differ within 1 class of polysaccharides, in what? IMPORTANT

Answer 1

• Level and distribution of methyl esters over pectin.
• Acetylation and pyruvylation levels in xanthan.
• Galactose : Mannose ratio in galactomannans.
• GulA : ManA ratio in alginates.

Question 2

Types of distribution of methyl esters over a pectin molecule with DM 50 and also the enzymatic finger printing of pectines

Answer 2

1. Random: some activity of the enzyme.
2. Sequential: any activity of the enzyme.
3. Blockwise: long sequence of galacturonic acid non methylesterified are the ideal substrate for the enzyme.
4. Combi.

Question 3

How can you measure the degraded pectin after treatment with polygalacturonase (enzyme)?

Answer 3

1. By a size exclusion chromatography. All the pectins stars with a high molecular weight, and after digestion you may end up with oligomer released maybe different sets of different quantities of oligomers.
   For example for pectin 2, you do not have too much oligomers.
2. HPLC: you can easily recognize the presence of monomers, dimers, trimers, tetramers of uronic acid oligomers release. For pectin 2, the enzyme is hardly able to release any oligomers. You can explain this, assuming that in pectin 1 and 3 you have some blocks, but in pectin two is more random distributed, no chance ti split the molecule

Question 4

Distribution of methyl esters over the backbone of pectins. How to quantify it ?

Answer 4

Descriptive parameter : Degree of Blockiness= (monogalA+digalA+trigalA) /( unesterified galA in sample ) x 100%.
You can plotted in a dendogram.

Question 5

Methyl ester distribution of pectins

Answer 5

• Pectins are non homogenous mixtures of molecules differing in DM.
• Different DM pectins may exhibit different calcium sensitivity and viscous behaviour
• Different methyl ester distributions within the pectin molecule will affect calcium sensitivity and viscosity
• Even a DM 70 pectin may behave (partly) as a low DM pectin

Question 6

Diversity in xanthan

Answer 6

*Six different repeating units (RU)
* Acetylation also present on outer mannose
* Ratio of RUs varies for different xanthan preparations
* Distribution of RUs affects ratio ordered/disordered structure.
NO ENTIENDO LO DE RELEASE: Acetyl groups on the outer mannose stabilize the ordered xanthan conformation

Question 7

Can you explain why different DM pectins exhibit different viscosities in solution?

Answer 7

Not only the degree of esterification is of importance for pectin’s functionality, but also the distribution of methyl esters.
Even a high DM pectin molecules might have some calcium sensitive blocks within their structure. Maybe not enough to make a calcium pectate gel, but certainly enough to increase the viscosity in solution when calcium is present.