Determination of fat in soybeans

Operation steps

(1) Preparation of filter paper cylinder, take 15cm × Roll an 8cm qualitative filter paper into a 2cm diameter cylinder, tie it with a degreased white thread, fold one end of the filter paper cylinder into the cylinder, press it tightly into the bottom of the cylinder, take a small amount of degreased cotton and place it at the bottom of the cylinder. Accurately weigh the filter paper cylinder.

(2) Preparation of Sample: The soybean sample is crushed through a 40 mesh sieve using a grinder, and 2.000-5.000g is precisely weighed in a filter paper cylinder. A layer of degreased cotton (mixed with sea sand if necessary) is placed on the sample, and the top edge of the cylinder is folded into the cylinder to make the entire filter paper cylinder about 4cm high.

(3) Extract and install the filter paper cylinder into the fat extraction tube of the Soxhlet extractor. Connect the receiving bottle that has been washed with anhydrous ether and dried for weighing. Install the condenser and place a funnel at the top of the condenser. Pour anhydrous ether into the extractor through the funnel to two-thirds of the volume of the receiving bottle. Heat on a water bath at approximately 45 ℃, and it is advisable to control the reflux rate of ether at a water bath temperature of 8-12 times/h. Generally, extract for 6-12 hours (if ether is insufficient, it can be supplemented from the upper end of the condenser). After extraction, when the ether has just undergone siphoning, stop heating, remove the condenser, clip out the filter paper cylinder, and then install the condenser to continue circulating distillation once to clean the fat extraction tube. Continue distillation until the ether in the liposuction tube is about to return to the receiving bottle. Stop distillation immediately and quickly remove the receiving bottle and liposuction tube. Place another ether recovery bottle under the ground joint at the bottom of the liposuction tube, tilt the liposuction tube slightly, and the ether can flow into the recovery bottle through the siphon tube.

If there is still ether in the receiving bottle, repeat several times until about 2mL of ether is left in the receiving bottle. Remove the receiving bottle and let the ether completely evaporate on a water bath.

(4) Dry the water droplets attached to the outer wall of the evaporating receiving bottle with a dry cloth, dry them in an oven at 100-105 ℃ for about 1 hour, cool them in a dryer for 30 minutes, weigh them, and repeat the drying process to a constant weight. In the repeated operation of drying to constant weight, the weight should have been reduced, but due to the oxidation of the extracted fat, it will gain weight again. Therefore, the weighing value before the weight increases again can be used as the constant weight value.

6. Result calculation

In the formula - the content of fat in the sample,%

M - Mass of the sample (should be calculated based on the mass of the sample before drying), g

M1- Mass of receiving bottle and fat, g

M0- Mass of receiving bottle, g