Lab Food Analaysis-fat

TITLE OF EXPERIMENT  Determination of Fat INTRODUCTION Fats are the substances that are soluble in organic solvents such as ether, hexane and chloroform but are insoluble in water. Fats consist of triacylglycerols, diacylglycerols, monoacylglycerols and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure and composition. Fats play a crucial role in determining the overall physical characteristics of foods. Lipids have at least three important functions in foods; culinary, physiological and nutritional. Lipids have the ability to carry odours and flavours and contribute to the palatability of meats, to the tenderness of baked products and to the richness and texture of ice cream. Dietary lipids represent the most compact chemical energy to man. They contain twice the caloric value of an equivalent of sugar. There are several methods for use for determination fat. That is organic solvent extraction methods (common method). The example of these methods has three. That is Continuous Solvent Extraction - Goldfisch Extraction, Semi-Continuous Solvent Extraction - Soxhlet Extraction, and Discontinuous solvent extraction – Mojonnier Method. Secondly, Non-solvent wet extraction methods. The examples for this method are Babcock Method for Milk Fat, Gerber Method for Milk Fat, and Detergent Method. Lastly, are Instrumental Methods. 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.

A. SOXHLET EXTRACTION METHOD OBJECTIVE  To determine the fat content of selected food samples using Soxhlet method. PRINCIPLE Fat is extracted semi continuosly with an organic solvent. Solvent is heated and volatilized,then is condensed above the sample. Solvent dripps onto the samle and soaks it to extract the fat. At 15-20min intervals,the solvent is siphoned to the heating flask,to start the process again. Fat content is measured by weight of fat removed. PROCEDURE 1. About 2 g of dried sample was weighed accurately into an extraction thimble or a piece of filter paper. 2. The opening thimble was plugged loosely with cotton or folded the filter and it was plugged with cotton. 3. The thimble or paper content was placed into soxhlet extractor. 4. A dried round bottom flask was weighed accurately and 150 mL petroleum ether was added. 5. All apparatus was connected to condenser and the water was turned on to extract for minimum 8 hours on an electro thermal extraction unit. 6. The flask containing the petroleum extract was removed after extraction complete. 7. The petroleum ether was evaporated off on a boiling water bath. 8. The flask was transferred into an oven at 105°C for one hour to dry the extract. 9. The flask was transferred immediately into a desiccator to cool and weigh.

CALCULATION % fat in sample = Weight of fat in the sample (g) Weight of sample taken (g)

Example: % Fat of Super Ring First Trial (129.0110 – 128.0920) x 100 = 45.66 % 2.0126 (129.0110 – 128.0900) x 100 = 45.76% 2.0126 (129.0110 – 128.0910) x 100 = 45.64% 2.0158

Mean % Fat of Super Ring : 45.66 + 45.76 + 45.64 3

=

45.69%

% Fat of Twisties (103.4020– 102.7680) x 100 = 31.45% 2.0162 (103.4000– 102.7700) x 100 = 31.24% 2.0164 (103.3980– 102.7700) x 100 = 31.15% 2.0160

Mean % fat of Twisties : 31.45 + 31.24 + 31.15 3

=

31.28%

x 100

DISCUSSION In this experiment, we have learned how to determine the fat content of selected food samples using Soxhlet method. We used Soxhlet method in this experiment in order to determine the fat content of sample. This method removes mainly non-polar lipids from sample. It is commonly used to increase the efficiency of lipid extraction from food. However, this method requires a dried sample for the hydroscopic ethyl ether extraction. In this experiment, Super Ring and Twisties were used as a sample. It was weighed accurately into an extraction thimble or a piece of filter paper. The thimble or paper content was placed into soxhlet extractor. All apparatus was connected to condenser and the water was turned on to extract for minimum 8 hours on an electro thermal extraction unit. Then, the flask containing the petroleum extract was removed after extraction complete. The flask was transferred into an oven at 105°C for one hour to dry the extract. After that, the flask was transferred immediately into a desiccator to cool and weigh. The weight was recorded in Table 2 .1 on Data Sheet. The result shows Super Ring has 45.69% of fat while Twisties has 31.28% of fat. If we compared both of them, Super Ring has a higher fat than Twisties.

B. MOJONNIER METHOD OBJECTIVE  To determine the fat content of selected food sample using Mojonnier method.

METHOD 

First Extraction

1.

10g milk was weighed into a Mojonnier fat extraction flask.

2.

1.5mL NH4OH was added and shakes vigorously.

3.

10ml of 95% ethanol was added and shakes for 90 seconds.

4.

25ml diethyl ether was added and shakes for 90 seconds.

5.

25ml of petroleum ether was added and shakes for 90 seconds after cooled down.

6.

The ether solution from the mojonnier flask was decanted into the previously weighed

evaporating dish.



Second Extraction

1.

5mL of 95% of ethanol was added and shakes vigorously for 15 seconds.

2.

15mL diethyl ether was added and shakes for 60 seconds.

3.

15mL petroleum ether was added and shakes for 60 seconds.

4.

The solution was decanted into the same evaporating dish.



Third Extraction

1.

15ml of diethyl ether was added and shakes for 60 seconds.

2.

15ml of petroleum ether was added and shakes for 60 seconds.

3.

The solution was decanted into the same evaporating dish.

4.

The solvent from the flask was distilled, and the fat was dried for 30 minutes at 105˚C,

cooled and weighted. 5.

It was washed out the fat from the flask with light petroleum ether, and then dried, and

re-weight and correct the result.

CALCULATION % Fat in Sample

= Weight of Fat in Sample (g) x 100 Weight of Sample Taken (g)

Weight of Fat in Sample = (weight of flask + fat) – weight of flask

Example: % Fat of milk (102.1894 – 101.8794) x 100 = 3.92 % 10.4496 (102.1894 – 101.8819) x 100 = 3.03% 10.1342 (102.0894 – 101.8796) x 100 = 2.24% 9.9860

Mean % Fat of Super Ring : 3.92 + 3.03 + 2.24 3

=

3.06%

DISCUSSION In this experiment, we have learned how to determine the fat content of selected food sample using Mojonnier method. The Mojonnier method is generally applicable to determination of the fat content for moist or liquid foods such as milk. This method also suitable to determine fat in cream, sweetened condensed milk products, ice-cream, frozen desserts and other dairy based products as well as liquid and solid sample. In this experiment, milk was used as a sample. It was extracted three times by using Mojonnier method. The weight was recorded in Table 2.2 on Data Sheet. The results shows milk has 3.06% of fat. Meanwhile, for theoretical value of fat in milk are ranges between 3.7% to 4.9%. If we compare the result value that we get from experiment and the theoretical value, there have no significant change.

CONCLUSION The objective this experiment are 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, Super Ring contains 45.69 % of fat, while Twisties has 31.28% by using Soxhlet method. While by Mojonnier method, milk has 3.06% of fat. 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 and dissolve non-polar lipid (reduce proportion of water and non-fatty soluble substances)  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 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.

REFERENCE 

http://www.scribd.com/doc/25575993/Determination-of-Fat



http://www.vconnection.nl/?p=49



http://www.ianrpubs.unl.edu/pages/publicationD.jsp?publicationId=703



http://web2.slc.qc.ca/jmc/www/Chemweb/oldchemweb/milk.htm