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If you look at the nutrition facts on a bag of popcorn, they sometimes list "popped" and "unpopped" separately:

Example labels (images above shamelessly stolen from the current answers :)

Unfortunately, when you calculate the total calories in the entire bag, the two don't match. I've seen a number of dubious claims online for why this is:

Personally, I believe it's because there's usually so much butter left at the bottom of the bag, but this doesn't explain why there would be a difference for non-buttered popcorn (which I think there is...).

So, which one of these claims, if any, are correct?

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Cooking definitely can decrease the energy a food can give. Compare a meatball vs coal brick achieved by cooking the meatball for ages. –  Boris Feb 16 '13 at 22:30
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Please cite an example label so we can see what it says. Is it by weight? By volume? etc. –  Oddthinking Feb 17 '13 at 4:12
    
Well, butter - because of the calorie density of fat - would explain it, but popcorn doesn't even imply butter where I come from. Perhaps add that not just in a subordinate clause? –  0xC0000022L Feb 18 '13 at 11:59
    
I think it is important to specify if you are talking about microwave popcorn bags or bags of popcorn. There is a distinct different in the two, and said difference is quantitative in regards to your question. –  The Real Bill Feb 18 '13 at 15:10
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a better question though is why do they bother to list the calories of unpopped corns?!?! Who eats them unpopped? :/ –  netrox Feb 18 '13 at 15:36

2 Answers 2

up vote 11 down vote accepted
+100

Popcorns expand when they pop, because of the moist inner of the pop corn, depending on the corn, the number of unpopped kernels varies.

P225 exhibited the highest (47%) number of unpopped kernels, whereas AP416 (27%) was higher than P615, P612, P415, and EXP92233 (around 16%). AP414 was the best hybrid as it had the least number (4%), whereas the remaining hybrids had 9-12% unpopped kernels.

Taken from the paper "Role of the Pericarp Cellulose Matrix as a Moisture Barrier in Microwaveable Popcorn" by "Agung S. Tandjung".

Number is usually around 10-20% was how I took it from that paper.

http://pubs.acs.org/doi/abs/10.1021/bm049220l

There is not any crazy reasons why the numbers doesn't match. On popcorn packages they estimate how much popped popcorns the end result will turn into. I thus assume they take in consideration that not all kernels pop. In the estimation on the amount of popped popcorns you will get they the number thus is lower than if all kernels popped, and if you multiply estimation with their energy value you will fall short of the unpopped's energy value.

This is simply math, not some magical phenomena or butter being stuck inside the bag. 15% of kernels doesn't pop in their estimation, most probably, which is why if you multiply estimation with popped energy value only get to 85% of the energy value of the unpopped kernels.

popcorns label

Popped Vs. Unpopped: Calorie Comparison

Many people wonder why unpopped popcorn has more calories in comparison to popped ones. The answer lies in popcorn kernels, popped popcorn has less kernels, therefore less calories. What I mean to say is, a cup of unpopped popcorn will have more calories because of the large number of kernels that are present. On the other hand, popped popcorn of the same measure will have less calories because of the absence of kernels. Moreover, a cup of unpopped popcorn will give you around four cups of popped popcorn. Therefore, the former has more calories.

The popped popcorns have less kernels. Why? Because not all kernels pops.

http://www.buzzle.com/articles/popcorn-calories-popped-vs-unpopped.html

I asked "Garret Popcorn Shop" if my assumption was correct.

From: C193181 Daniel Hambraeus Sent: Wednesday, February 20, 2013 07:26 am CST (GMT-06:00) Subject: Nutrition

Hello. On popcorn packages it's listed that X amount of unpopped popcorns turns into Y amount of popped popcorns. In the energy listings there is values for popped popcorns and unpopped popcorns. If you multiply the popped popcorn value with the estimated amount of popped popcorns you'll get, the energy value is lower than for the unpopped ones. Does this mean in the estimation that you take in consideration not all pop corn kernels pop?

This is my original mail.

Dear Mr. Hambraeus, Thank you for contacting Garrett Popcorn Shops. We appreciate your inquiry. You are correct, we do take into consideration the ratio of unpoped popcorn kernels and it is for this reason the energry value is lower. Please let us know if you have any further questions or concerns!

Best Wishes,

Lauren Wilk, Garrett Popcorn Shops

This is the answer I got from Garrett Popcorn Shops. They gave an answer directly. The reason the values doesn't add up is because they take in consideration the ratio of unpoped popcorn kernels.

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"On popcorn packages they estimate how much popped popcorns the endresult will turn into. They of course take in consideration that not all kernels pop." - Do you have any credible source for this (other than the dubious unsourced article that I already posted)? You say "of course," but in fact it is not at all obvious or intuitive that this would be the case. The calorie listing for popped popcorn is per-cup, not per-bag; and there's no reason to assume that the "servings per bag" are the unpopped servings, while the popped servings remain unlisted. –  BlueRaja - Danny Pflughoeft Feb 20 '13 at 13:09
    
It's logical deduction. If not all popcorns pop, if their estimate said 3tbs of unpopped turned into 5⅓cups, they would lie. First link says not all popcorns pop, if they make estimate on how much size the popped ones take, they of course calculate that not all pop. It's logical, because otherwise they would lie in their estimate. If they made an estimate that said 100% of kernels would pop when only 80% does, they would be sued. Their estimate is an average, probably gotten through testing. If you want I can ask a popcorn company about this, but I think it's going too far. –  Wertilq Feb 20 '13 at 13:13
    
That is not logical deduction, that's an educated guess. I mentioned this and other educated guesses in the question; I'm looking for a credible source which states which one is correct. –  BlueRaja - Danny Pflughoeft Feb 20 '13 at 13:16
    
Fair enough. I don't have a source on that, I'll find a source that says so, since I can't see why they would give a 100% kernels pop estimate. I mean why would they, if it's common knowledge not all popcorns pop? –  Wertilq Feb 20 '13 at 13:18
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I now asked a popcorn company support about this, hopefully you'll find the answer I will get then satisfying. –  Wertilq Feb 20 '13 at 13:27

Popcorn Nutrition Label

(2*130) = Unpopped 260 Calories
(13*15) = Popped 195 Calories

So it is at least true that popcorn nutrition labels show a difference between popped and unpopped (here: 25% difference).

If we're to take Micah's article, the average percentage of unpopped kernels after microwaving is between 4% and 47%, or 25.5%.

So it fits very well with the data available. I'd say it's perfectly reasonable to think that the difference is due to the average number of unpopped kernels after cooking.

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Fat-free butter sounds like some gross concoction only modern food industry could come up with. +1 for the answer. –  0xC0000022L Feb 18 '13 at 17:58
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So you're assuming that the "makes about 6.5 cups popped" figure is taking into account that 25% of the kernels won't be popped, even though it's not stated anywhere on the package or even in that article, and it only loosely fits one single data point? So now we have another explanation, which IMHO seems even more dubious than the other claims. –  BlueRaja - Danny Pflughoeft Feb 18 '13 at 19:50
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@BlueRaja-DannyPflughoeft - There's a lot of legislation governing the nutrition labels. One of the more infamous fillers for "low cal" carb products (like bread/muffins) is methylcellulose, which is basically wood pulp. They don't include the calories for the cellulose because humans can't digest it, even though it's entirely possible for other animals to harvest the energy. It's also why many boxed meals have the calories "as prepared" and "as boxed" denotations - there's a lot of variance. –  MCM Feb 18 '13 at 20:05
    
Interesting, but that has nothing to do with your answer (or, likely, the question)... –  BlueRaja - Danny Pflughoeft Feb 18 '13 at 20:52
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@BlueRaja-DannyPflughoeft - Sure it does. It's Occam's Razor. Either the label omits the portions of the food which you cannot digest, or there's another source of the missing calories. The oil can't explain the difference, as not all varieties are buttered. Salt has no calories. What else would you suggest it is? –  MCM Feb 19 '13 at 13:25

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