Determination of Fat in Potato Chips Recently, there has been a lot discussion of calories and fats in our
foods in the news media.
Most food labels list recommended serving sizes, sometimes with
unrealistic quantities, of the food product and then lists the
nutritional information based on that serving, assuming a 2,000 calorie
per day diet. Nutritional information usually includes calories, total
fat, saturated fat, cholesterol, sodium, total carbohydrate (with
separate listing of dietary fiber and sugars), and protein. The label
information may also include vitamins and minerals.
Nutritionists recommend that no more than 30% of our daily 2000
calories come from fat. (~ 66 g per day)
However, in our snack food and
fast food world, we often eat a diet that contains a larger percentage
of fat. So, the question arises, how much fat is in a snack bag of a
food such as potato chips, or a standard serving of French fries? Hash
In this experiment, you will
determine the fat content of several different fat laden foods that you
probably each by the handful. You will be performing an extraction of
the fats by putting the sample in a non polar solvent, petroleum ether.
Fats are not water soluble, unlike carbohydrates and proteins. By using
a non polar solvent, only the fats will dissolve in the liquid. This
liquid will then be separated from the solid and the mass of fat
‘extracted’ will be measured. You can then compare this to the mass of
the original sample and determine the % of fat in the in original
Procedure in brief:
~0.5 g of crushed up chips into a 13x100 mm test tube. Add ~3mL of
petroleum ether, stopper, and shake the solution. Use the centrifuge to
settle the solid to the bottom. Pour off the liquid into a pre-weighed
25 mL flask. Add another 3 mL of petroleum ether and stir/centrifuge.
Again, pour of the liquid into the flask. Carefully heat the flask to
remove the petroleum ether.
Calculate the % fat in the sample, g of fat per serving (experimental) and determine the % error between your experimental g fat per serving to the label.
Lab report: You will be submitting only the complete data sheet and your graded pre-lab questions.
Prelab Questions: (to be graded by your instructor at beginning of lab)
Print a copy of the data sheet.
As you can see, you are given a set of data for McD’s French fries on
the data sheet. (first column) Complete the calculations for that
column of data. Show your calculations on a separate piece of recycled