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 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 avour, texture, mouth feel and appearance. or this reason, it is di!cult to develop lo"-fat alternatives of many foods, because once the fat is removed some of the most important physical characteristics are lost. Lipids are usually de#ned as those components that are soluble in organic solvents $such as ether, hexane or chloroform%, but are insoluble in "ater. This group of substances includes triacylglycerols, triacylglycerols, diacylglycercols, monoacylglycercols, free fatty acids, phospholipids, sterols, caretonoids and vitamins & and '. The lipid fraction of a fatty food therefore contains a complex mixture of di(erent types of molecule. It is important to be able to accurately determine determine the total fat content in foodsfor a number of reasons such as economic "hich avoid to give a"ay expensive ingredients in the food products. )esides that, the *uality and food properties of the product depend on the lipid content on it. It is also important for legal conformation conformation to standards of identity and nutritional labelling la"s and health. & variety of techni*ues are are available to perform *uantitative analysis. The sample material, the time frame frame and the level of accuracy accuracy are are the deciding factors to select the suitable techni*ue. &mong of the techni*ues are +old#sch at xtractor $ontinnuous%, oxhlet oxhlet method $emi-continuous% $emi-con tinuous% and /ojonnier method $'iscontinuous%. $'iscontinuous%. In this experiment, "e "ill only do oxhlet method and /ojonnier /ethod. oxhlet xtraction xtraction method is a continuous solvent method that is usually used to remove fats from the food sample. oxhlet also can be used to determine crude fat content. rude fat content is determined by extracting the fat from the sample using a solvent, and then "eigh the fat extracted. /ojonnier /ethod is a discontinuous solvent extraction method and does not re*uire removal of moisture from the sample.
SOXHLET EXTRACTION METHOD OBJECTIVE To determine the fat content of selected food samples using oxhlet method.
PRINCIPLE at is extracted semi continuously "ith an organic solvent. olvent is heated and volatili0ed, then is condensed above the sample. olvent drips onto the sample and soa1s it to extract the fat. &t 23-45 minutes intervals, the solvent is siphoned to the heating as1, to start the process again. at content is measured by "eight of fat removed.
APPARATUS • • • • • • • • • • • •
&nalytical balance 'essicator oxhlet apparatus Thimbles 6ound bottom as1 435 mL 7eating mantle 8ater bath +raduated cylinder 355 mL )ea1er 435 mL /ortar and pestle patula 9ven
CHEMICAL :et ether $boiling point; <5-=5 ℃ %
PROCEDURE 2. &bout 2 g of dried sample "as "eighed accurately into an extraction thimble or a piece of #lter paper. 4. The opening of the thimble "as loosely plugged "ith cotton or fold the #lter and plug "ith cotton.
>. The thimble or paper and content "as placed into a oxhlet extractor. <. & dried round bottom as1 "as "eighed accurately and 235 mL petroleum ether "as added. 3. The apparatus "as connected to the condenser. The "ater "as turned on and extracted for 4 hours on an electrothermal extraction unit. =. &fter the extraction has completed, the as1 containing the petroleum ether extract "as removed. ?. The petroleum ether "as evaporated on a boiling "ater bath. @. The as1 "as transferred into an oven at 253 ℃ for one hour to dry the extract. A. The as1 "as immediately transferred into a dessicator to cool and "eigh.
MOJONNIER METHOD OBJECTIVE To determine the fat content of selected food samples using /ojonnier method.
PRINCIPLE at is extracted "ith a mixture of ethyl ether and petroleum ether, and the extracted fat is dried to constant "eight and expressed as percent fat by "eight. The assay uses not only diethyl ether and petroleum ether, but also ammonia and ethanol.
APPARATUS • • • • • •
/ojonnier extraction as1 "ith stopper vaporating dish &nalytical balance 9ven 'essicator +raduated cylinder 43mL
CHEMICALS
•
&mmonium hydroxide thanol 'iethyl ether
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:etroleum ether $boiling point; <5 B =5
• •
℃
%
PROCEDURE FIRST EXTRACTION 2. 25 g mil1 "as "eighed to the nearest 5.2 mg into a /ojonnier fat extraction as1. 4. 2.3 mL N7<97 "as added and "as sha1e vigorously. >. 25 mL of A3C ethanol "as added and "as sha1e for A5 seconds. <. 43 mL of diethyl ether "as added and "as sha1e for A5 seconds. 3. 43 mL of petroleum ether "as added and "as sha1e for A5 seconds. =. ther solution "as decanted fromthe /ojonnier as1into the previously "eighed evaporating dish.
SECOND EXTRACTION 2. 4. >. <.
3 mL of A3C ethanol "as added and sha1e vigorously for 23 seconds. 23 mL of diethyl ether "as added and sha1e for =5 seconds. 23 mL petroleum ether "as added sha1e for =5 seconds. olution "as decanted into the same evaporating dish.
THIRD EXTRACTION 2. 23 mL of diethyl ether "as added and sha1e for =5 seconds. 4. 23 mL of petroleum ether "as added and sha1e =5 seconds. >. olution "as decanted into the same evaporating dish. <. The solvent "as distilled from the as1, the fat "as dried at 253 ℃ for 2 hour, then it "as cooled and "eighed.
CALCULATION Trial 2; 8eight of fat in sample D 24<.242? g B 24>.?A3< g D 5.>4=> g 0.3263
C at in ample D
1.0131
g E 255
D >4.42C
Trial 4; 8eight of fat in sample D 24<.@<3> g B 24<.<<>4 g
D 5.<542 g 0.4021
C at in sample D
1.0004
g E 255
D <5.2AC
Trial >; 8eight of fat in sample D 24<. 3<@5 g B 24<.2<32 g D 5.<54A g 0.4029
C at in sample D
1.0057
g E 255
D <5.5=C
/ean of "eight of sample D 2.52>2 g F 2.555< g F 2.553? g > D 2.55=< g /ean of "eight of round bottom as1 $g% D 24>.?A3< F 24<.<<>4 F 24<.2<32 > D 24<.24?A g /ean of "eight of round bottom as1 F fat $g% D 24<.242? F 24<.@<3> F 24<.3<@5 > D 24<.353 g /ean of C at D >4.42 F <5.2A F <5.5= > D >?.
DISCUSSION In oxhlet method, the fat is extracted semi continuously "ith an organic solvent. The solvent "ill be heated and volatili0ed, then condensed above the sample. olvent drips onto the sample and soa1s it to extract the fat. at content is measured by "eighed of fat removed. The errors that occur during this experiment is the extraction ta1e too much time than the actual time stated. This is because the preparation of sample is inuenced "hich is the solvent is poured too much. The temperature also must be di(erent and the sample does not have
accurate temperature during the "ater bath and drying. The "eight may also be the cause by not "eighing accurately. To overcome this, the temperature of "ater bath and oven must be set up #rst "ith the correct temperature. 8hile doing the "eighing, "eigh it correctly "ith > times to get constant reading. The petroleum ether also need to be measure correctly. The /ojonnier method, the fat is extracted "ith a mixture of ethyl ether and petroleum ether, and the extracted fat is dried to constant "eight. &mmonium hydroxide and ethanol "as also use as the reagent. The errors that occur during the experiment are the time ta1en to sha1e the /ojonnier as1 "as not constant "hich is more time or less time. The volume of the reagent that has been put in the coconut mil1 also does not measured correctly. 'uring the drying process, the fat content cannot be "eighed because the reagent does not react or extracted correctly. To prevent this from happening, time ta1en and sha1en must be set #rst and the temperature need to be the same. o the "eight of fat content can be calculated.
CONCLUSION The objective of this experiment is to determine the fat content of selected food samples using oxhlet method and to determine the fat content of selected food sample using /ojonnier method. In conclusion, "e 1no" ho" to determine fat content of selected food samples using oxhlet method and /ojonnier method. &s a result, biscuits contain >?.
QUESTIONS 2. 'ra" and label the main components of oxhlet apparatus.
4. 'escribe the function of the various reagents used in each method. :etroleum ether; 6emoves moisture from the ethyl ether extract anddissolve non-polar lipid $reduce proportion of "ater and non-fatty solublesubstances% thanol; :recipitates protein and prevents possible gel formation. 'iethyl ether; 'issolved the lipids &mmonia; To neutrali0es acidic samples and dissolve protein •
• • •
>. 8hich is the best extraction procedure; a% 9ne extraction "ith a large volume of solvent 96 b% everal extractions "ith smaller volumes but the same total volumeG xplain The best extraction method is several extractions "ith smaller volumes but the same total volume because the steps are simple and reading is more accurate compared "ith large volume of solvent. •
REFERENCES • • •
https;HH""".scribd.comHdocH45>3@??=3HLab-ood-&nalaysis-fat https;HHen."i1ipedia.orgH"i1iHat http;HHpearl2.lanl.govHexternalHccdeHscfHpubsH1ingH254determinationoffatcontent.pdf
