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Chapter 4 ●Determination of Fat ContentMETHOD B: GOLDFISH METHODPrincipleFat 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.ChemicalsSame as for Method A, Soxhlet.Hazards, Precautions and Waste DisposalSame as for Method A, Soxhlet.SuppliesSame as for Method A, Soxhlet.EquipmentGoldfish 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 CalculationsUsing 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:RepThimble (g)Wet sample+Thimble (g)Wet sample+ Thimble+ Glass wool (g)Wetsample (g)Dry sample+Thimble+ Glass wool (g)123Data from moisture analysis:RepPan (g)Pan+Wetsample (g)Pan+ Driedsample (g)% Moisture123X ¯=SD =Calculation of % moisture:() ()() ()Wt of wet samplePanWt of dried samplePan100Wt of wet samplePanWt of pan+-+´+-Rep% Fat + % MoistureCalc. % fat123Calculation of % fat:()()()()% fatmoistureInitial wt of sampleThimbleGlass wool100Final wt of sampleThimbleGlass woolWt of wet sampleThimbleWt Thimble+=éù++´êú-++êúëûéù+-ëû% Fat (wt/wt) = ( % Fat + %Moisture) – (% Moisture)(Note:Use average % moisture in this calculation)Questions1. 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 ContentMETHOD C: MOJONNIER METHODPrincipleFat 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.