Determination

of Fat content

-By

Dr Savita Bhosale

Determination of Fat contents

Definition of fat:• Oil or fat are esters of long-chain fatty acids.

• Oils and fats have saturated, monounsaturated (MUFA), polyunsaturated (PUFA) and essential fatty acids (EFA).

• The amount of fat content in vegetable oils, any kind of fat or ghee can be calculated by just selecting the type of oil or fat.

A few interesting facts

• Lipids at room temperature that are solid are called fats while those that are liquid are called oils.

•Food items such as sunflower oil, gingley oil, soybean oil, fish etc. containing Poly Unsaturated (PUFA) should be preferred, yet consumed in moderation.

• Substitute unsaturated fat - either Poly Unsaturated (PUFA) or Mono Unsaturated (MUFA). Keep your fat calories to about 15-20% of your total calories.

• Trans fats are artificially hydrogenated oils used primarily to extend the shelf life of food. Extra hydrogen is pumped into polyunsaturated vegetable oils to saturate the carbon molecules in them.

Instruments for the determination of fat contents

• The soxhlet method described here is recognized by the association of official analytical chemists(AOAC).as the standard method for crude fat analysis. In addition some rapid instrumental methods are also approved by the AOAC

• As an example, FOSS has launched several types of "Soxtec Systems" including automated or semi-automated analyzers, which extract lipids rapidly and accurately.

• These instruments perform boiling, rinsing and solvent recovery. Similarly, Soxtherm extractors from Gerhardt GmbH was developed to reduce extraction times. 

The Büchi Extraction System B-811 is an automated system which can be used to perform an extraction according to the original Soxhlet principle. Four different extraction methods are possible without making any changes to the unit : Soxhlet standard, Soxhlet warm, hot extraction and continuous extraction.

A schematic representation of a Soxhlet extractor

1: Stirrer bar 2: Still pot3: Distillation path 4: Thimble5: Solid 6: Siphon top 7: Siphon exit 8: Expansion adapter 9: Condensor 10: Cooling water in 11: Cooling water out

Soxhlet

Apparatus

Application

• The soxhlet method for determining crude fat content is a lengthy process requiring up to a day for a single analysis. The solvent extraction step alone takes six hours the method is therefore not favoured for routine testing purposes rather it is used as a standard reference method.

Out line of Method• Crude fat content is determined by extracting the fat

from the sample using a solvent then determining the weight of the fat recovered the sample is contained in a porous thimble that allows the solvent to completely cover the sample the thimble is contained in an extraction apparatus that enables the solvent to be recycled over and over again .

• This extends the contact time between the solvent and the sample & allows it time to dissolve all of the fat contained the sample.

MethodEquipments

Round bottom flask 150ml Soxhlet extractor with condeser 60mlHeat source electrical heating mantle & steam bath.Cleaned beaker 100ml

ReagentsPetroleum ether b.p 40-60oC or anhydrous etherEther

Procedure:5gm of sample in thimble 90ml of petroleum ether extraction Evaporation of steam bath

Disadvantage• Despite disadvantages of this procedure poor

extraction of polar lipids,

• long time involved,

• large volumes of solvents,

• hazards of boiling solvents,

• several methods involving automatic solvent extraction were described.

• Different automated or semi-automated extraction instruments may be found on the market.

Determination of Solid Fat Content (SFC) in Oils and Fats by Spin Track NMR Analyzer

• Solid Fat Content (SFC) is the generally accepted analysis of fats and oils in the food industry.

• The traditional methods for SFC determination are slow, irreproducible and require additional chemicals.

• Direct measurements of SFC by NMR can be performed quickly and accurately.

• The Spin Track Portable NMR spectrometer is an ideal instrument for SFC measurements because of it's fine technical characteristics which make measurements very reproducible and accurate.