10 Questions
What is the primary reason why it is impossible to select a single organic solvent to extract all types of lipids?
Different lipids have different polarities
What is a desirable property of a solvent for lipid extraction?
Low boiling point and non-toxicity
What is an advantage of using CO2 in supercritical fluid extraction?
It has a mild critical temperature and is recyclable
What is an advantage of Soxhlet extraction?
It allows for solvent reuse and is suitable for foods with small amounts of lipids
What is a characteristic of ethyl ether and petroleum ether?
They are among the most commonly used solvents
What percentage of fatty acids found in plants and animals are esterified to glycerol?
Over 99%
Which of the following types of lipids are considered to be polar lipids?
Glycolipids and Phospholipids
Why is it often necessary to dry samples prior to solvent extraction?
Because many organic solvents cannot easily penetrate into foods containing water
What is the purpose of acid hydrolysis in sample preparation?
To break the bonds which hold the lipid and non-lipid components together
What is the ideal characteristic of a solvent for lipid extraction?
It should completely extract all the lipid components from a food
Study Notes
Classes of Lipids
- Over 99% of fatty acids in plants and animals are esterified to glycerol, forming simple lipids
- Derived lipids include compounds such as phospholipids and glycolipids
- Phospholipids and glycolipids are considered polar lipids, while simple and derived lipids are non-polar
Sample Preparation
- Drying samples is necessary prior to solvent extraction, as many organic solvents cannot penetrate foods containing water
- Particle size reduction is performed to produce a homogeneous sample and increase the surface area of lipid exposed to the solvent
- Acid hydrolysis is used to break bonds holding lipids and non-lipid components together, releasing bound lipids into extractable forms
Solvent Selection
- The ideal solvent for lipid extraction would completely extract all lipid components while leaving other components behind
- Solvent selection depends on the polarity of the lipids present compared to the polarity of the solvent
- Polar lipids (e.g. glycolipids, phospholipids) are more soluble in polar solvents (e.g. alcohols), while non-polar lipids (e.g. triacylglycerols) are more soluble in non-polar solvents (e.g. hexane)
- It is impossible to select a single organic solvent to extract all lipids, and mixtures of solvents may be used
- Desirable solvent properties include being inexpensive, having a low boiling point, and being non-toxic and non-flammable
Solvent Extraction Methods
- Soxhlet extraction is advantageous for foods containing small amounts of lipids, and allows for solvent reuse
- Supercritical fluid extraction using CO2 has the advantages of mild temperature, easy recyclability, and environmental friendliness
Explore the different types of lipids, including simple and derived lipids, and learn about the importance of sample preparation in solvent extraction.
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