Chapter 8. Determination of lipids
Chapter 8. Determination of lipids
Section 1. General
Section 1. General
1. Lipids in foods • Lipids are usually defined as food components that are insoluble in water and that are soluble in organic fat solvents. lipids fats Fatlike substances
1. Lipids in foods • Lipids are usually defined as food components that are insoluble in water and that are soluble in organic fat solvents. lipids fats Fatlike substances
Lipids amounts in foods • Corn foods • Dairy foods • Plant or animal lipid • Vegetables and fruits • legume • Meat, fish, egg
Lipids amounts in foods • Corn foods • Dairy foods • Plant or animal lipid • Vegetables and fruits • legume • Meat, fish, egg
2. Significance of determining lipids • Lipids have at least three important functions in foods: culinary, physiological, and nutritional. ➢ Carrying odors and flavors and their contribution to the palatability of meats, to the tenderness of baked products, and to the richness and texture of ice cream. ➢ Affording energy. ➢ Providing essential fatty acids, and fatsoluble vitamins
2. Significance of determining lipids • Lipids have at least three important functions in foods: culinary, physiological, and nutritional. ➢ Carrying odors and flavors and their contribution to the palatability of meats, to the tenderness of baked products, and to the richness and texture of ice cream. ➢ Affording energy. ➢ Providing essential fatty acids, and fatsoluble vitamins
3. Determination of lipids • Lipids forms in foods: free and componds • Sparing solubility in water and considerable solubility in organic solvents • Organic solvents: ➢ Ethyl ether ➢ petroleum ether ➢ chloroform-methanol
3. Determination of lipids • Lipids forms in foods: free and componds • Sparing solubility in water and considerable solubility in organic solvents • Organic solvents: ➢ Ethyl ether ➢ petroleum ether ➢ chloroform-methanol
Pretreatment of samples • Grinding: The extraction of dry materials depends on particle size. • Drying: Only part of the lipids can be extracted with ether from moist material, as the solvent cannot penetrate the tissues and the extractant becomes saturated with water and inefficient for lipid extraction
Pretreatment of samples • Grinding: The extraction of dry materials depends on particle size. • Drying: Only part of the lipids can be extracted with ether from moist material, as the solvent cannot penetrate the tissues and the extractant becomes saturated with water and inefficient for lipid extraction
Determination methods • Soxhlet extraction method • Chloroform-methanol method • Acid hydrolyzed method • Rose-Gottlieb method, Babcock method, Gerber method
Determination methods • Soxhlet extraction method • Chloroform-methanol method • Acid hydrolyzed method • Rose-Gottlieb method, Babcock method, Gerber method
Section 2. Determination methods of lipids
Section 2. Determination methods of lipids
1. Soxhlet extraction method • Direct extraction of lipids is often carried out in a Soxhlet. • The sample in an extraction thimble from filter paper), covered with defatted cotton wool to prevent small particles from finding their way into the flask, is placed in the middle part of the apparatus. • The flask is filled with solvent; the condenser attached to a tap; and heating of solvent in the flask started
1. Soxhlet extraction method • Direct extraction of lipids is often carried out in a Soxhlet. • The sample in an extraction thimble from filter paper), covered with defatted cotton wool to prevent small particles from finding their way into the flask, is placed in the middle part of the apparatus. • The flask is filled with solvent; the condenser attached to a tap; and heating of solvent in the flask started