Determination of Total Fat Content in Foods | Solid & Liquid Samples | GB 5009.6 Method

[00:00:00]Hello everyone. In this video, [music] you'll learn the standard laboratory procedure for determining the total fat percentage in food samples. This method can be used for [music] a wide variety of solid and liquid food products.

[00:00:12]Welcome to Microchem's experiments.

[00:00:15]Let's get started.

[00:00:17]This analytical method consists of four main steps: sample preparation, sample digestion, fat extraction, calculation, and reporting. To perform this analysis, you'll need the following equipment and reagents: laboratory [music] balance, water bath, hot air oven, hot plate, measuring cylinders with and without stoppers, glass rod, beaker, pipette with pipette filler, heat-resistant gloves, ethanol, distilled water, concentrated hydrochloric acid, and diethyl ether.

[00:00:46]Let's begin with sample preparation.

[00:00:52]We will prepare solid sample first.

[00:01:07]Weigh about 5 g of solid test sample.

[00:02:07]>> Transfer the sample in a 50 ml screw cap test tube.

[00:02:29]Add 8 ml of water in the tube.

[00:02:50]Mix the content well.

[00:03:11]If you want to test a liquid sample, follow the following preparation.

[00:03:52]Weigh about 10 g of liquid test sample [music] in a 50 ml test tube.

[00:04:07]That's all.

[00:04:08]No need to add distilled water here.

[00:04:15]Once the sample [music] is prepared, we can move on to the digestion step.

[00:04:29]Add 10 ml of concentrated hydrochloric acid in the test tube [music] containing the prepared sample.

[00:05:24]Place the test tube in a water bath maintained at 80° C and allow the sample to digest in acidic environment for 10 minutes.

[00:05:39]After 10 minutes of digestion, remove the tube carefully and stir the contents using a glass rod.

[00:06:26]>> Return the tube to [music] the water bath and continue the digestion.

[00:06:44]After digestion [music] of another 10 minutes, stir the sample using a glass rod again.

[00:07:05]In this way, continue [music] digesting the sample for approximately 50 minutes or until the sample is completely digested.

[00:07:13]Repeat this stirring process every 10 minutes.

[00:07:27]In this step three, we will extract the fat from the digested sample.

[00:07:57]>> Add 10 ml of ethanol to the digested sample.

[00:08:15]Mix the content thoroughly.

[00:08:22]Allow the mixture to cool to room temperature.

[00:08:34]Take a clean and [music] dry measuring cylinder with stopper.

[00:08:51]Next, transfer the entire contents into the clean, dry 100 ml stoppered [music] measuring cylinder.

[00:09:27]Rinse the test tube with 25 ml of diethyl ether.

[00:09:49]>> Transfer the rinse into the measuring cylinder.

[00:10:08]Repeat the washing once more with another 25 ml of diethyl ether.

[00:10:26]Transfer the rinse into the same measuring cylinder to combine both ether washes in the cylinder.

[00:10:35]Secure the stopper tightly and shake vigorously for 1 minute.

[00:10:51]Carefully loosen the stopper to release any fat adhering to the stopper Rinse any fat adhering to the stopper and the mouth of the measuring cylinder with a small amount of diethyl ether.

[00:11:03]Replace the stopper securely.

[00:11:07]Allow the cylinder to stand undisturbed for 20 minutes so that the layers separate completely.

[00:11:13]While waiting, prepare a clean 20 ml beaker that has already been dried to constant weight.

[00:11:26]Record its weight as it will be required during the final calculation.

[00:11:42]Once the layers have separated, carefully pipette the upper ether layer into the pre-weighed beaker.

[00:12:52]Now add another 25 ml of diethyl ether to the measuring cylinder and repeat the extraction process. [music] If a clear phase separation is not observed, add approximately [music] 5 ml of ethanol.

[00:13:27]Mix the content gently.

[00:13:37]Let the cylinder stand for another 10 minutes.

[00:13:47]Then transfer the upper ether layer into the same beaker to combine both extracts.

[00:14:24]If necessary, repeat the extraction until complete recovery of the fat is achieved.

[00:15:29]>> The extracted ether solution now contains the fat.

[00:15:32]To obtain the actual fat content, the solvent must be completely evaporated.

[00:15:36][music] The preferred method is to place the beaker in a hot air oven at 110° C.

[00:15:44]Since diethyl ether is highly volatile and harmful to inhale, ensure that the laboratory is well [music] ventilated and follow all laboratory safety procedures.

[00:15:53]Alternatively, the solvent may be evaporated on a hot plate.

[00:16:09]However, extreme caution is required because diethyl ether is highly flammable and can ignite if overheated.

[00:16:15][music] After the ether has completely evaporated, dry the extracted fat in the hot air oven at 110° C for 1 hour.

[00:16:32]Always wear heat-resistant gloves when handling hot equipment.

[00:16:42]After drying, place the beaker in a desiccator.

[00:16:53]Allow the beaker to cool for approximately 30 minutes before weighing. Repeat the drying, cooling, and weighing cycle until a constant weight is obtained.

[00:17:03]A constant weight is achieved when the difference between two consecutive weighings does not exceed 2 mg.

[00:17:17]You can now [music] clearly observe the extracted fat at the bottom of the beaker.

[00:17:34]Record the final weight of the beaker containing the extracted fat.

[00:17:42]Now it's time to calculate the total fat percentage.

[00:17:48]We know that sample weight equals 5.0193 g, empty beaker weight equals [music] 115.43 g, final beaker weight with extracted fat equals 116.4344 [music] g.

[00:18:03]Using the equation shown on the screen, substitute these values and calculate the fat percentage.

[00:18:09]In this example, the calculated total fat content is 20.01%.

[00:18:14]And that's how the total fat percentage of a food sample is determined using this laboratory method.

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