Lipids - E. Refining of fats and oils
20 important questions on Lipids - E. Refining of fats and oils
What are the different ways you can do refining in a product?
- Degumming
- Deacidification --> Neutralization (Alkali refining)
- Bleaching
- Deodorization
- (winterization: removal of wax)
What is the goal of degumming and why is it done?
Why: phospholipids can
- cause oil discoloration (decompose at high T)
- serve as a precursor of off-flavours
- cause problems in other refining processes (emulsifiers)
What are the different types of degumming?
- Water-degumming: only hydratable phospholipids
- Acid-degumming: also non-hydratable phospholipids
- Enzymatic degumming
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Why will acid degumming dissolve phospholipids that are not dissolving in water?
Why don't they use enzymes for degumming?
What is the goal of neutralization and why is it done?
This is done because the free fatty acids can:
- Cause acid tast
- are more sensitive to oxidation
How does the neutralization process go?
- Add caustic solution (often NaOH)
- Reaction between base and ffa (=neutralization) --> soap
- Removal of soap-stock (centrifugation)
How many free fatty acids are left after the neutralization process?
What is a possible disadvantage of neutralization?
What is the goal of bleaching and why is this doen?
Why:
1. pigments can be unwanted in end product
2. residues give problems in next step (deodorization)
How does the bleaching process go?
- Add adsorbent (bleaching earth / activated carbon / silicagel)
- Reaction time 20-30 min at 80-100°C (reduced pressure)
- Removal of adsorbent (filters)
Why is bleaching so expensive?
You have disposal costs
and you have oil losses
What is the goal of deodorization and why is this done?
Why: volatile components are possible unwanted odors
What are the different steps in the deodorization process?
- Deaeration
- Heating (180-240 °C)
- Deodorization: stripping with live steam (high temperature, low pressure)
- Cooling
Why is deaeration done in the deodorization process?
What are the processing conditions during deodorization in terms of:
- Stripping agent
- Amount of stripping agent
- Temperature
- Time
- Stripping agent: any inert gas Steam: cheap, most frequently used
- Amount of Stripping Steam:
not the mass but the volume higher T and low p: increasing the steam volume - Temperature: Above 180°C, below 240°C
- Time: 0.5 – 6 hours
time as short as possible to avoid side reactions
What is removed during deodorization?
- Free fatty acids
- Sterols
- Tocopherols
- Pesticides
- Hydrocarbons
- Carotenoids
What is an important disadvantage of deodorization?
So they try to put it back.
What happens if you have a prolonged deodorization at temperatures above 240 degrees?
- formation of primary and secondary oxidation products: volatile and non-volatile compounds
- geometric (cis/trans) and positional isomerizations (conjugation)
- ‘randomization’ resulting in an undesired change in melting and solidification characteristics
- pyrolysis of triglycerides (thermolysis)
What is the goal of winterization and why is it done?
Why: The components form a cloud when the oil is kept at a low temperature
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