General Question

robmandu's avatar

Why is the chocolate at the bottom of a Reese's Peanut Butter Cup often melty?

Asked by robmandu (21331points) May 13th, 2008

Stored at room temperature, 70 degrees F. The rest of the chocolate is firm, the crinkly edge around the top is crisp even. So why is the chocolate on the bottom of the cup noticeably softer and stick to the wax paper, to the point of being pulled off? This is a consistently reproducible phenomenon.

And no, I don’t want to refrigerate/freeze ‘em. ;-)

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14 Answers

Fallstand's avatar

My guess is that the oils in the peanut butter sink down into the bottom of the chocolate and cause it to seem melted

But I DO freeze mine so i never have this problem :)

glial's avatar

I would suspect the peanut oil breaking down the chocolate.

Response moderated
robmandu's avatar

Compelling theory… but then, based on the organic peanut butters I’ve enjoyed, doesn’t peanut butter oil rise to the top, not sink to the bottom?

Bub's avatar

We should send a link to this question to the company that makes them!

wildflower's avatar

I’m gonna guess a combination of exposure to peanut butter and being covered by the wrapping. Less air getting to it might be part if it…..?

soundedfury's avatar

Yeah, I’m not certain about the peanut oil theory. Peanut oil is less dense than the peanut butter mass, so within the center the oil should rise over time.

My guess is that the thickness/density of the chocolate over most of the peanut butter cup raises it’s melting point, but that the relative thinness at the bottom means it melts easier (and at room temp).

robmandu's avatar

@fury, interesting theory re: the thinness affecting the melting temp.

It does appear that, where the chocolate is thickest, it’s also firmest. But then, the thickest points are the farthest from the center. So maybe it’s distance from the core of peanut buttery goodness?

What a tasty conundrum! I think I need to get some more experimental test subjects going here.

sccrowell's avatar

First; is a person holding this candy and if so I think their body temp will cause the chocolate to melt quicker

sccrowell's avatar

They are holding it in their hands, correct?

robmandu's avatar

@sccrowell, nope… room temp, sitting on a table. Only held long enough to unwrap. And it’s too dang tasty to dawdle with the wrap.

Seesul's avatar

I have made these at home and if it is anything like the factory process, you first coat the waxed paper cup with chocolate, let it harden (can be in the fridge) and then fill it with the peanut butter mixture, which is white chocolate coating and pb. You then top it off and seal it with another coat of chocolate. My it could be something to do with the waxed paper and not as much air getting to the bottom as to the top.

When I make these for gifts for pb/choco lovers, I use the Tupperware biggie funnel, (which turned upside-down is in the shape of a kiss) plug the hole with foil and make a huge peanut butter kiss out of it. The reaction is priceless.

sccrowell's avatar

@Seesul, Ohhhhh Myyy gosh!!! That sounds soo yummy!!!! This coming from a Full Fledge Chocoholic! My mouth is salivating as I write this… :)~ yummy!

rickf71's avatar

Two Factors contribute to this.

1. The specific heat of the peanut butter is higher than the surrounding chocolate. This means that the peanut butter changes temperature more rapidly than the surrounding chocolate. This, coupled with the fact that the peanut butter rests closest to the wrapping (at the “bottom”), it changes the temperature in that very thin layer the quickest, resulting in faster melting.

2. The other factor is that the wax paper used to line the peanut butter cup adheres to the candy somewhat, to keep the wax paper from separating during shipping/handling. Again since the chocolate layer is thinnest at the bottom it will cause the chocolate “pull-away” when removing the candy from the wax paper.

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