Determination Of Fat (food Analysis) 3o323o

PRACTICAL 2: DETERMINATION OF FAT

INTRODUCTION Lipids are one of the major constituents of foods, and are important in our diet for a number of reasons. They are a major source of energy and provide essential lipid nutrients. Nevertheless, over-consumption of certain lipid components can be detrimental to our health, e.g. cholesterol and saturated fats. In many foods the lipid component plays a major role in determining the overall physical characteristics, such as flavour, texture, mouth feel and appearance. For this reason, it is difficult to develop low-fat alternatives of many foods, because once the fat is removed some of the most important physical characteristics are lost. 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 triacylglycerols, 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. It is important to be able to accurately determine the total fat content in foodsfor a number of reasons such as economic which avoid to give away expensive ingredients in the food products. Besides that, the quality and food properties of the product depend on the lipid content on it. It is also important for legal conformation to standards of identity and nutritional labelling laws and health. A variety of techniques are available to perform quantitative analysis. The sample material, the time frame and the level of accuracy are the deciding factors to select the suitable technique. Among of the techniques are Goldfisch Fat Extractor (Continnuous), Soxhlet method (Semi-continuous) and Mojonnier method (Discontinuous). In this experiment, we will only do Soxhlet method and Mojonnier Method. Soxhlet Extraction method is a continuous solvent method that is usually used to remove fats from the food sample. Soxhlet also can be used to determine crude fat content. Crude fat content is determined by extracting the fat from the sample using a solvent, and then weigh the fat extracted. Mojonnier Method is a discontinuous solvent extraction method and does not require removal of moisture from the sample.

SOXHLET EXTRACTION METHOD OBJECTIVE To determine the fat content of selected food samples using Soxhlet method.

PRINCIPLE Fat is extracted semi continuously with an organic solvent. Solvent is heated and volatilized, then is condensed above the sample. Solvent drips onto the sample and soaks it to extract the fat. At 15-20 minutes intervals, the solvent is siphoned to the heating flask, to start the process again. Fat content is measured by weight of fat removed.

APPARATUS            

Analytical balance Dessicator Soxhlet apparatus Thimbles Round bottom flask 250 mL Heating mantle Water bath Graduated cylinder 500 mL Beaker 250 mL Mortar and pestle Spatula Oven

CHEMICAL Pet ether (boiling point: 40-60 ℃ )

PROCEDURE 1. About 1 g of dried sample was weighed accurately into an extraction thimble or a piece of filter paper. 2. The opening of the thimble was loosely plugged with cotton or fold the filter and plug with cotton.

3. The thimble or paper and content was placed into a Soxhlet extractor. 4. A dried round bottom flask was weighed accurately and 150 mL petroleum ether was added. 5. The apparatus was connected to the condenser. The water was turned on and extracted for 2 hours on an electrothermal extraction unit. 6. After the extraction has completed, the flask containing the petroleum ether extract was removed. 7. The petroleum ether was evaporated on a boiling water bath. 8. The flask was transferred into an oven at 105 ℃

for one hour to dry the

extract. 9. The flask was immediately transferred into a dessicator to cool and weigh.

MOJONNIER METHOD OBJECTIVE To determine the fat content of selected food samples using Mojonnier method.

PRINCIPLE Fat is extracted with a mixture of ethyl ether and petroleum ether, and the extracted fat is dried to constant weight and expressed as percent fat by weight. The assay uses not only diethyl ether and petroleum ether, but also ammonia and ethanol.

APPARATUS      

Mojonnier extraction flask with stopper Evaporating dish Analytical balance Oven Dessicator Graduated cylinder 25mL

CHEMICALS   

Ammonium hydroxide Ethanol Diethyl ether



Petroleum ether (boiling point: 40 – 60

℃ )

PROCEDURE FIRST EXTRACTION 1. 2. 3. 4. 5. 6.

10 g milk was weighed to the nearest 0.1 mg into a Mojonnier fat extraction flask. 1.5 mL NH4OH was added and was shake vigorously. 10 mL of 95% ethanol was added and was shake for 90 seconds. 25 mL of diethyl ether was added and was shake for 90 seconds. 25 mL of petroleum ether was added and was shake for 90 seconds. Ether solution was decanted fromthe Mojonnier flaskinto the previously weighed evaporating dish.

SECOND EXTRACTION 1. 2. 3. 4.

5 mL of 95% ethanol was added and shake vigorously for 15 seconds. 15 mL of diethyl ether was added and shake for 60 seconds. 15 mL petroleum ether was added shake for 60 seconds. Solution was decanted into the same evaporating dish.

THIRD EXTRACTION 1. 15 mL of diethyl ether was added and shake for 60 seconds. 2. 15 mL of petroleum ether was added and shake 60 seconds. 3. Solution was decanted into the same evaporating dish.

4. The solvent was distilled from the flask, the fat was dried at 105 ℃ hour, then it was cooled and weighed.

CALCULATION Trial 1: Weight of fat in sample = 124.1217 g – 123.7954 g = 0.3263 g % Fat in Sample =

0.3263 1.0131

g × 100

= 32.21%

Trial 2: Weight of fat in sample = 124.8453 g – 124.4432 g

for 1

= 0.4021 g % Fat in sample =

0.4021 1.0004

g × 100

= 40.19%

Trial 3: Weight of fat in sample = 124. 5480 g – 124.1451 g = 0.4029 g % Fat in sample =

0.4029 1.0057

g × 100

= 40.06%

Mean of weight of sample = 1.0131 g + 1.0004 g + 1.0057 g 3 = 1.0064 g Mean of weight of round bottom flask (g) = 123.7954 + 124.4432 + 124.1451 3 = 124.1279 g Mean of weight of round bottom flask + fat (g) = 124.1217 + 124.8453 + 124.5480 3 = 124.505 g Mean of % Fat = 32.21 + 40.19 + 40.06 3 = 37.49%

DISCUSSION In Soxhlet method, the fat is extracted semi continuously with an organic solvent. The solvent will be heated and volatilized, then condensed above the sample. Solvent drips onto the sample and soaks it to extract the fat. Fat content is measured by weighed of fat removed. The errors that occur during this experiment is the extraction take too much time than the actual time stated. This is because the preparation of sample is influenced which is the solvent is poured too much. The temperature also must be different and the sample does not have

accurate temperature during the water bath and drying. The weight may also be the cause by not weighing accurately. To overcome this, the temperature of water bath and oven must be set up first with the correct temperature. While doing the weighing, weigh it correctly with 3 times to get constant reading. The petroleum ether also need to be measure correctly. The Mojonnier method, the fat is extracted with a mixture of ethyl ether and petroleum ether, and the extracted fat is dried to constant weight. Ammonium hydroxide and ethanol was also use as the reagent. The errors that occur during the experiment are the time taken to shake the Mojonnier flask was not constant which is more time or less time. The volume of the reagent that has been put in the coconut milk also does not measured correctly. During the drying process, the fat content cannot be weighed because the reagent does not react or extracted correctly. To prevent this from happening, time taken and shaken must be set first and the temperature need to be the same. So the weight of fat content can be calculated.

CONCLUSION The objective of this experiment is to determine the fat content of selected food samples using Soxhlet method and to determine the fat content of selected food sample using Mojonnier method. In conclusion, we know how to determine fat content of selected food samples using Soxhlet method and Mojonnier method. As a result, biscuits contain 37.49% of fat. So the objective was achieved.

QUESTIONS 1. Draw and label the main components of Soxhlet apparatus.

2. Describe the function of the various reagents used in each method.  Petroleum ether: Removes moisture from the ethyl ether extract anddissolve non-polar lipid (reduce proportion of water and non-fatty solublesubstances)  Ethanol: Precipitates protein and prevents possible gel formation.  Diethyl ether: Dissolved the lipids  Ammonia: To neutralizes acidic samples and dissolve protein 3. Which is the best extraction procedure: a) One extraction with a large volume of solvent OR b) Several extractions with smaller volumes but the same total volume? Explain  The best extraction method is several extractions with smaller volumes but the same total volume because the steps are simple and reading is more accurate compared with large volume of solvent.

REFERENCES   

https://www.idoub.com/doc/203587765/Lab-Food-Analaysis-fat https://en.wikipedia.org/wiki/Fat http://pearl1.lanl.gov/external/ccde/scf/pubs/king/102_determination_of_fat_content.pdf