32 chapter 4 determination of fat content method b

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Chapter 4 Determination of Fat Content METHOD B: GOLDFISH METHOD Principle Fat is extracted, continuously, with an organic solvent. Solvent is heated and volatilized, then is condensed above the sample. Solvent continuously drips through the sample to extract the fat. Fat con- tent is measured by weight loss of sample or weight of fat removed. Chemicals Same as for Method A, Soxhlet. Hazards, Precautions and Waste Disposal Same as for Method A, Soxhlet. Supplies Same as for Method A, Soxhlet. Equipment Goldfish extraction apparatus Analytical balance Vacuum oven Procedure (Instructions are given for analysis in triplicate.) Note: Analyze samples in triplicate. 1. Follow Steps 1–4 in Soxhlet procedure. 2. Place the thimble in the Goldfish condenser bracket. Push the thimble up so that only about 1 cm. is below the bracket. Fill the reclaiming beaker with petroleum ether (50 ml) and trans- fer to beaker. Seal beaker to apparatus using gasket and metal ring. Start the water flow through the condenser. Raise the hotplate up to the beaker, turn on, and start the ether boiling. Extract for 4 h at a condensation rate of 5–6 drops per second. 3. Follow Steps 6 and 7 in Soxhlet procedure. Data and Calculations Using the weights recorded in the tables below, calculate the percent fat (wt/wt) on a wet weight basis as deter- mined by the Soxhlet extraction method. If the fat content of the food you analyzed was given on the label, report this theoretical value. Name of Snack Food: Label g fat/serving: Label serving size (g): Label g fat/100 g product: Data from Goldfish extraction: Rep Thimble (g) Wet sample + Thimble (g) Wet sample + Thimble + Glass wool (g) Wet sample (g) Dry sample + Thimble + Glass wool (g) 1 2 3 Data from moisture analysis: Rep Pan (g) Pan+Wet sample (g) Pan + Dried sample (g) % Moisture 1 2 3 X ¯ = SD = Calculation of % moisture: ( ) ( ) ( ) ( ) Wt of wet sample Pan Wt of dried sample Pan 100 Wt of wet sample Pan Wt of pan + - + ´ + - Rep % Fat + % Moisture Calc. % fat 1 2 3 Calculation of % fat: ( ) ( ) ( ) ( ) % fat moisture Initial wt of sample Thimble Glass wool 100 Final wt of sample Thimble Glass wool Wt of wet sample Thimble Wt Thimble + = é ù + + ´ ê ú - + + ê ú ë û é ù + - ë û % Fat (wt/wt) = ( % Fat + %Moisture) – (% Moisture) ( Note: Use average % moisture in this calculation) Questions 1. What would be the advantages of using ethyl ether rather than petroleum ether in a solvent extraction method, such as the Goldfish method? 2. What were the advantages of using the Goldfish extraction method rather than the Soxhlet extraction method? 3. If the fat content measured here differed from that reported on the nutrition label, how might this be explained? 33
Chapter 4 Determination of Fat Content METHOD C: MOJONNIER METHOD Principle Fat is extracted with a mixture of ethyl ether and petro- leum ether. The extract containing the fat is dried and expressed as percent fat by weight.

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