Fat Lab - lab work PDF

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Andy Zheng Vicky Zhang (Partner) Abstract This experiment calculated the % of fat and fat-free meat in commercial meat products. We determined the percentage in hamburger meat and in hotdog meat. The Wiley extractor used acetone to wash out the fat and water. Then, we used an oven to dry out the acetone. We determined the fat by weighing the meat before washing it with acetone and after drying the meat. The franks ended up containing 30.1%, 37.8%, and 40.1% fat and the hamburgers ended up containing 36.9%, 38.7%, and 40.0% fat. Definitions Wiley extractor_ A system that uses a separation process to extract fat from a substance. Thimble_ A paper extraction tool used to carry the substance Acetone_ a colorless volatile liquid ketone made by oxidizing isopropanol, used as an organic solvent and synthetic reagent. Erlenmeyer flask_ a conical, flat-bottomed laboratory flask with a narrow neck. Siphon cup_ an oil cup in which oil is carried over the edge of a tube Calculations Weight of fresh meat + thimble + aluminum dish: 19 g Weight of thimble + aluminum dish: 2.85 g Weight of defatted meat + thimble + aluminum dish: 17.05 g Weight of fresh meat: 16.15 g Weight of defatted meat: 14.2 g Weight of extracted fat: 1.95 g % fat: 1.95g / 16.15g = .1207  12.07% % fat-free: 100-12.07%  87.93% Limitations Triple Beam Balance: +/- 0.05g 50ml graduate cylinder: +/- 0.25g Ruler: +/- 0.05 cm Hot Plate: +/- 0.5 heat (can only set for 1/2/3/4/5/6/7/8/9/10 of heat)

Assay of the Fat Content of Commercial Meat Products By Walter Scharf and Charles Malerich Natural Sciences/Chemistry Baruch College New York, NY 10010 Introduction Recent publicity by consumer-protection agencies, has focused attention on the unexpectedly high fat content of many commercially-ground meat products e.g. frankfurters and hamburger meats. Meat processors often disguise fatty bulk to look like red meat, with blood and coloring agents. This practice not only deceives the consumer, but also exposes him to the possible health hazard of incorporating too many cholesterol-generating fats into his diet. In the following experiment, the fatty components of hamburgers, bologna salami and frankfurters will be measured by weighing a sample of the meat product, extracting the fats with a suitable solvent, and finally weighing the defatted, dried meat residue. Extraction is the process of washing a mixture of two substances with a solvent, where one substance dissolves readily and the other does not. When the solvent is removed, the insoluble substance remains. Extraction is thus a purification or separation process. In this case with acetone as the solvent, the meat protein is the insoluble substance and the fat is soluble the soluble substance extracted from the meat by the acetone. Procedure Obtain a Whiley extractor unit (see Figure next page) from the stockroom and a sample of bologna, salami hamburger or frankfurter meat from your instructor. Note the brand name and the price per pound of your meat sample. Weigh a fresh paper extraction thimble in an aluminum dish, in the analytical balance. Record this weight on you report sheet. Weigh and record the aluminum dish alone. Shred a thumb-size piece of meat by means of a knife or spatula, and introduce the pieces into the extraction thimble. Reweigh thimble + contents in the aluminum dish. Fill the extraction thimble to within ¼” of the top. Now pour 50 ml of acetone into the ehrlenmeyer flask (which forms part of the Whiley extractor). Put the filled thimble into the glass siphon-cup and hang it, by means of the attached wire, from the cooling coil of the extractor (see diagram on the next page) over the flask with the cooling unit with siphon-cup so that the projecting siphon-tube hangs above the surface of the acetone. Attach one of the connecting rubber hoses to a cold-water tap, and have the other empty into the drain trough. (It is advisable to extend the exit hose with a piece of glass tubing). Now, stand the assembled extractor on a hot plate, topped with a wire mesh, and set the dial for MEDIUM before heating. Be careful that none of the rubber hoses touch the hot plate, and that there are no open flames in the vicinity of the apparatus. Let the contents of the extractor percolate for at least 15 minutes after the first drop of the condensed acetone drips from the cooling coil (A thirty-minute extraction period is recommended. Turn off the hot plate and remove the apparatus to the desktop. When the flask is comfortably cool to the touch, turn off the circulating water, detach the siphon cup, and remove the extraction thimble by means of a tweezers. Transfer the thimble and contents to the previously-used aluminum dish.

Place the dish + contents into a drying oven at 60oC and allow to dry for 20 minutes. After this time, check to see if any moisture is visible on the inside or outside of the dish. If dry, remove to the open air and carefully smell it. Should a pronounced odor of acetone persist, continue the drying for a longer period. Then, allow the dish to cool, and reweigh it with its contents on the analytical balance.

Report Sheet for Assay of Fat in Meat Name___________________ Lab Section ________________ Date______________ Data Brand and type of meat__________________________________________ Cost (in cents) per pound: ________________cents Weight of fresh meat ( + thimble + aluminum dish):

___________________g

Weight of thimble + aluminum dish:

___________________g

Weight of defatted meat (+ thimble + aluminum dish):

___________________g

Calculations Weight of fresh meat Weight of defatted meat: Weight of extracted fat:

____________________g ____________________g ____________________g

% fat in meat sample =weight of extracted fat/weight of fresh meat X 100 = _______% % fat-free meat sample = 100 – % fat in meat sample = _________% Cost (in dollars) per pound of fat-free meat = Cost(in cents per lb)/% fat free meat = $ ________________ Comparison of brands and types of meat Brand Name percent fat $cost/pound of fat-free meat 1._______________ 2._______________ 3._______________ 4._______________ 5._______________

_________ _________ _________ _________ _________

______________________ ______________________ ______________________ ______________________ ______________________

Questions 1. This experiment separates meat into an acetone-soluble part and an acetone-insoluble part. The calculations are based on the principal components of meat being fat (acetone soluble) and protein (acetone insoluble or fat-free meat in report sheet). More realistically, the principal components of meat are fat, protein, and water. Water is acetone soluble. Based on this information, the calculations correctly calculate what quantity, % fat or % fat-free meat? Is the incorrectly calculated quantity over or under estimated? The principal components of meat are fat, protein, and water. In our experiment, we did not calculate for water, thus part of our experiment is incorrectly calculated. The acetone pulls both the fat and water from the meat because they are acetone-soluble. The remaining % fat-free meat is the correctly calculated part because the dried protein is not affected by the water variable. The % of fat extracted is incorrectly calculated because not only fat, but also water was extracted. Thus, the % of fat is made of % of fat and % of water. 2. This experiment separates the fat from the protein by dissolving the fat in acetone. What advantage does using the Wiley extractor have over simply pouring acetone over the meat again and again? There are two advantages for using a Wiley extractor. The purposes of using a Wiley extractor are to save labor and material. It saves labor because the cycling process is automatic. Once the extractor is set up, you can do other things and just check it occasionally. The extractor cycles the fat from the meat into the glass flask. This system saves material because the acetone is recycled continuously instead of having to pour many portions of warm acetone. The boiling acetone condenses into the meat, touches glass, becomes liquid, then boils again from the Wiley extractor and rewashes through the meat. 3. Why was hot plate necessary to boil the acetone? Why not use a Bunsen burner? It's a safety issue: An open flame could cause the acetone to ignite because it is very flammable. Boiling acetone will convert it from its liquid state into a gaseous state, thus making it even more flammable. With a hot plate, there is no flame to ignite vapors. 4. What effect would each of the following changes in procedure have had on the calculated percentage of fat found for your meat product? a) The acetone-washed meat in the thimble was not completely dried before weighing. Protein + acetone would understate the fat because the undried acetone would make the ending fat-free mass higher. The fat would be understated. For example if the beginning weight was 100g for the meat and the acetone-washed meat that wasn’t completely dried weighed 50g, then the fat weighs 50g. But if the meat was completely dried and weighed 48g, then the true weight of the fat would be 52g. Thus, the % of fat found is understated.

b) The amount of acetone in the flask was increased from 50ml to 75ml, at the start of the extraction process. No change because the acetone-washed meat is completely dried in the end. The amount of acetone used does not effect the end result. c) The fresh meat was thoroughly dried, before starting the experiment. There might be a better result because the water is throughly dried. The % of fat and fat-free meat would be more accurate because there are fewer variables to mislead the calculations. Since the water is initially gotten rid of, we just need to dry all of the acetone in the end....