crude fat analysis

The term "Lipid" can be used for both

oil and fat

lipids

in general, are soluble in ether, chloroform, or other organic solvents, but are sparingly soluble in water. lipids are not defined based on their structures.

exceptions to lipids definition

1. Short chain fatty acids (soluble in water)

2. Trans-fatty acids (are not natural)

3. Synthetic fat substitutes (formed during frying or hydrogenation)

FDA's regulatory definition of total fat

oils = liquid triacylglycerols at room temperature

fats = solids triacylglycerols at room temperature

simple lipids

ester of fatty acids with alcohol (glycerol)

compound lipids

ester of fatty acid with alcohol + additional group ( phospholipids, lipoprotein, glycolipids, cerebrosides )

derived lipids

derivatives from simple or compound lipids, free fatty acids, long-chain alcohols, and hydrocarbons, fat soluble vitamins

why is it important to analyze fat content

1. nutritional labeling

2. regulatory requirements ( meet standard of identity )

3. manufacturing specification

4. stability

solvent extraction methods

continuous, semicontinuous, discontinuous, elevated pressure temp, gc method

nonsolvent wet extraction methods

nonorganic solvents used ( babcock and gerbere )

instrumental analysis methods

IR, foss-let method, nmr

Pre-drying sample:

water removal to make sample easier to grind,breaking fat-water emulsions to help fat dissolves more easily fats inorganic solvents

Particle size reduction

higher extraction efficiency

acid hydrolysis

breaking bonds between lipids and proteins/carbohydrates; Use ~ 3 N HC

ideal solvent for solvent selection extraction methods

-high solvent power for lipids

• low solvent power for other components (e.g., proteins and carbohydrates)

• easy to evaporate

• low boiling point

• nonflammable

• nontoxic

• good penetration into sample

• single component

• inexpensive

• non-hygroscopic

solvent selection for extraction methods

ethyl ether ( di-ethyl ether) and petroleum ether

soxtec

continuous method, automated version of goldfish ( more rapid than goldfish )

soxhlet method

semi continuous, solvent building up in extraction chamber for 5-10 min before siphoning back to boiling flask, time consuming