in chemistry lab, we removed the fat from chips (corn chips) and then compared the percent of fat?

Question

we got and compared it to the percent fat that was on the servings. why would i get a less percent of fat than what the servings say? i used 2 g of chips and then 100 mL of petroleum ether. i got 23.2 percent fat for a total, but the servings label produced 35.7 percent fat. how is this possible? i can't seem to figure it out and it is getting on my nerves.

Answer 1

All of the preveious answers have valid points. Another possibility is that the technique used by the corn chip manufacturer might not be the same as yours.

Instrumental analysis is usually more accurate than a wet chemical test method.

Answer 2

Well,
I am a chemist. There could be a few things to consider. The first thing could be human error. During a step or steps taken, you could have lost product during the experiment meaning that somewhere during the experiment you may not have rinced a beaker or glassware good enough so that you get everything you are looking for. Also, a lot of the time, companies will put more on the label so that it is a worse case scenerio. Not all bags of chips are going to be identical in fat amounts. Some bags may have 30 if they say 40, meanwhile, another bag may be 35, sometimes it could even be more, there are laws on this allowing companies to go within a certain amount of what they say. Also, the bag of chips could say, per 10g of chips or something like that, you would have to mathamatically calculate what the difference is. You may not have used enough solution to extract the fat either, you need enough solvent to take out what you want, only so much will catch or grab onto the fat. for example, 100mL may only catch 23.2 percent were as maybe 200mL will catch onto double that or something. There are a number of things that could have gone wrong during the experiment, see what the bag of chips says they did for a weight. Hope this helps.

Wee Man

Answer 3

For some reason you didn't get all of the fat out.

I presume that you crushed into powder to expose as much of the fat as possible. Then used water AND petroleum ether mix. Water will keep the soluble non fat components. And added some table salt to the water to encourage the water/fat emulsion to break up.

Then you might get some more fat.

Answer 4

number 1: science isnt an exact science. the 35.7 listed might not necessarily be true in all cases.

number 2: human error

number 3: you may not have used the complete serving size

Answer 5

1)You could have a low result because you didn't extract it all or lost some of the extracted fat (if you're not an experienced wet chemist.)

2)Your sample size was pretty small so you might not have gotten a good representation, or average, of the product overall.

But if that was your first time doing something like that I would say that was pretty good.

Answer 6

May be you lost some during the experiment, what was the steps of the experiment?

Answer 7

You should have used a bigger sample size. Maybe 30 grams would do.