LAB 5 : LIPID ANALYSIS

LAB 5 : LIPID ANALYSIS

Objectives:

l To determine the total concentration of lipids in solid food samples.

Introduction :

Lipids are usually defined as those components that are soluble in organic solvents (such as ether, hexane or chloroform), but are insoluble in water. This group of substances includes triacylglycercols, diacylglycercols, monoacylglycercols, free fatty acids, phospholipids, sterols, caretonoids and vitamins A and D. The lipid fraction of a fatty food therefore contains a complex mixture of different types of molecule. Even so, triacylglycercols are the major component of most foods, typically making up more than 95 to 99% of the total lipids present. Triacylglycerols are esters of three fatty acids and a glycerol molecule.

The fatty acids normally found in foods vary in chain length, degree of unsaturation and position on the glycerol molecule. Consequently, the triacylglycerol fraction itself consists of a complex mixture of different types of molecules. Each type of fat has a different profile of lipids present which determines the precise nature of its nutritional and physiochemical properties. The terms fat, oil and lipid are often used interchangeably by food scientists. Although sometimes the term fat is used to describe those lipids that are solid at the specified temperature, whereas the term oil is used to describe those lipids that are liquid at the specified temperature.

Material and apparatus :

l Food samples ( potato chips, biscuit, sunflower seed and soybean )

l Petroleum ether

l Ethanol

l Deionised water

l Test tubes (smal land large) ans stand

l Pipette

l Measuring cylinder

l Dropper and spatula

l Erlenmeyer flask

l Beaker

l Weighing scale

l Hot plate

Methodology :

Result :

Foods	Weight of empty beaker (with glass rod) /g	Weight of beaker with crushed raw food (with glass rod) /g	Weight of crushed raw food /g	Weight of beaker with dried food (with glass rod) /g	Weight lost from food (weight of lipid extracted) /g	% Lipid extraction /%
Potato chip	58.20 g	60.18 g	1.94 g	59.61 g	0.57 g	29.30 %
Sunflower seed	51.21 g	53.16 g	1.95 g	52.24 g	0.92 g	47.18 %
Oreo biscuit	43.71 g	44.88 g	1.67 g	44.57 g	0.33 g	19.80 %
Cream cracker	45.19 g	46.71 g	1.52 g	46.28 g	0.43 g	28.3 %
Corntoz Hotz & Spicy	52.13 g	53.97 g	1.84 g	53.24 g	0.73 g	39.67 %

Discussion :

1. What are Lipids?

Lipids are a class of organic compounds consisting of Carbon, Hydrogen and Oxygen; their Hydrogen: Oxygen ratio is greater than 2:1. Lipids are non - polar compounds, meaning they are soluble in organic solvents (e.g. ethanol) and insoluble in aqueous solvents (e.g. water).

2. What is the reason for crushing the soild food sample and leaving it to stand in ethanol for a few minutes?

Breaking the cells exposes the lipids stored inside so that they can be extracted by the ethanol solvent.

3. Why is a fat-free diet unadvisable?

Persons who have a fat-deficient diet are also deficient in fat-soluble vitamins. ( A, D,E and K). Symptoms include blurred vision, weak bones – movement of calcium into soft tissues, digestive tract problems and numerous skin, hair and nail problems. A deficiency of Omega 3 essential fatty acids increases the risk for certain cancers – breast, prostate and colon, and also for diabetes.

Conclusion :

The conclusion is we can find the % lipid extraction in each food sample that we use through this example. For an example for the sunflower seed, the % lipid extraction is 47.18 %. Almost all types of food have a lipid.

References :