FAT DETERMINATION THEORY

Lipids are a family of naturally occurring compounds grouped together on the basis of their relative insolubility in water and solubility in nonpolar solvents. These are naturally occurring molecules that can be isolated from cells and tissues by extraction using nonpolar organic solvents.There are two classes of

i) those with ester linkages that can be hydrolysed, for example, fats and waxes

ii) those without ester linkages and so cannot be hydrolysed, for example, cholesterol and steroids.

Fats and oils are triacylglycerols. They are triesters of glycerol (propane-1,2,3-triol) with three long chain carboxylic acids. Reaction with aqueous sodium hydroxide yields glycerol and the three fatty acids. Fatty acids are usually unbranched and contain an even number of carbon atoms, usually from 12 to 20. If there are any double bonds, they tend to have cis geometry. Fats containing one double bond are monounsaturated and those with more than one double bond are polyunsaturated.Saturated fats have a uniform shape that allows them to pack together in a crystal lattice. Unsaturated fats have double bonds that introduces kinks into the hydrocarbon chain making crystal formation more difficult. This is why saturated fats have higher melting points and are solids at room temperature compared to unsaturated fats that tend to be liquids (oils).The most abundant lipid in olive oil is glyceryl trioleate, a triester formed from glycerol and oleic acid, a mono-unsaturated fatty acid with a cis double bond in the middle of the C18 chain

Saturated fatty acids have a chain of carbon atoms joined by single bonds, allowing for rotation about the bonds. In unsaturated fatty acids the double bond (or bonds) restricts rotation. Therefore an unsaturated acid with one double bond can exist in two forms. The cis or z form (z for zusammen-German for together) has the two parts of the carbon chain bent towards each other and the trans or e form (e from entgegen opposed) has the two parts of the chain almost linear. The trans fatty acids are therefore rather similar in conformation and behaviour to the saturated acids. The unsaturated fatty acids of vegetable oils are normally in the cis form. When an oil is partially hydrogenated some TFA are formed. Furthermore, some double bonds move along the fatty acid chain, so that a family of cis and trans isomers are formed. Some of the unsaturated fats ingested by ruminants are partially hydrogenated by bacteria in the rumen. In consequence, milk fat, diary products and beef and mutton fat also contain cis and trans fatty acid isomers, although the proportions are somewhat different. The levels found are about 2-9%. Small amounts of TFA are also present in poultry and pork fat, derived from the feed.

QUESTIONS

1-Determination of food products is important. The World Health Organization recommends a diet that contains 15-30% of the dietary calories as fat. Those consuming in excess of this level should reduce their fat intake in general, and saturated fat and cholesterol in particular. This is largely achieved by reducing the intake of animal products, including butter. In addition, many should cut down their intake of all fats, including trans fat and polyunsaturated fat. A tablespoon of vegetable oil provides 14 grams of fat and 125 calories (525 kJ). A tablespoon of either butter or regular margarine has about 10-11 grams of fat and 90-100 calories (375-420 kJ) due to the water content. Diet margarines contain a higher percentage of water, hence have they have less fat and fewer calories.Also fat contents of food products are defined to be legal by TSE in our country.Every food product should contain standard food contents as they defined.

2-fat is extracted from a dry sample with petroleum ether using a special soxhlet apparatus setup.the ether extract is collected in a flask then percent fat is determined by using weight difference.

3-petroleum ether is highly flammable and volatile.in order to extinguish dry chemical or foam we can use CO2. We should avoid strong oxidizing agents. Amild eye and mucous membrane irritant,primary skin irritant,and central nervous system depressant. Acute exposure irritates eye,nose,and skin. Narcosis may occur at elevated concentrations.

…