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I use a no-corn syrup, eggless marshmallow recipe and have had terrible results using them to make Rice Krispies Treats.

Marshmallow Recipe

  • 1/2 cup water, divided
  • 2 tablespoons gelatin powder
  • 1/2 cup water
  • 2 cups (400g) granulated sugar
  • 1/2 teaspoon table salt

Half the water is used to bloom the gelatin, the other half is used to make a sugar syrup. Bring the sugar syrup to the soft ball stage. Let it cool to 212F before adding it to the gelatin and whip to soft peaks. Pour into a pan dusted with a combination of icing sugar and corn starch. Allow the finished marshmallow cure overnight. Slice and coat with more icing sugar and/or cornstarch to prevent sticking.

The marshmallows are great in hot chocolate, but terrible for Rice Krispies Treats.

Rice Krispies Treats Recipe

Kellogg's Recipe:

  • 3 tablespoons butter
  • 1 package (10 oz., about 40) JET-PUFFED Marshmallows OR 4 cups JET-PUFFED Miniature Marshmallows
  • 6 cups Kellogg's® Rice Krispies® cereal

Melt the butter and marshmallows together. Stir in the cereal to coat. Press into a greased pan and let it set (30 minutes).

Result

I've tried different ratios of marshmallow to cereal with the same result. As soon as I add the cereal to the melted marshmallow and butter, it starts snap-crackle-popping so you know it's come in contact with water. They completely lose their crunch, making a very sad treat.

My most recent attempt, I brought the sugar syrup to the hard ball stage, hoping that less water would do the trick. After letting the treats set for 30 minutes, they were crunchier than my previous attempts, but had definitely lost the crunch of plain cereal. However, the next morning, they were completely soft and had a white, chalky film on top.

Recipe Comparisons

I've seen multiple recipes that call for using homemade marshmallows, and none of them mention that soggy cereal is even a problem. Gluten Free on a Shoestring uses an identical recipe to mine and doesn't even let the marshmallows set: dump melted butter and cereal straight into the mixing bowl where the marshmallow was whipped.

This recipe uses corn syrup and includes a warning that not letting the marshmallows cure first will make soggy treats.

  • 1/2 cup water
  • 2 1/2 tablespoons unflavored gelatin (about 3 packets)
  • 1/2 cup water
  • 1 1/2 cups granulated sugar
  • 1 cup light corn syrup
  • pinch salt

I started collecting recipes from other sites to see how they compare in terms of water content.

enter image description here

  • base_hydration = (weight of the water used to bloom the gelatin) / (weight of all ingredients excluding water content (including the water in corn syrup))
  • softball_hydration = base_hydration + (weight of water that should be in a sugar syrup brought to the softball stage)
  • hardball_hydration = base_hydration + (weight of water that should be in a sugar syrup brought to the hardball stage)

Bigger Bolder Baking and Joy of Baking had the lowest water content of all of the recipes I looked at. The recipe I followed has the highest water content, but bringing it to the hardball stage would have brought the water content inline with the Serious Eats recipe (intended for use in a sweet potato casserole).

This leaves me with 2 questions:

  • How low can I go in terms of water content and still get a functioning marshmallow?
  • Will this even solve my soggy cereal problem or is there some other magic going on at the Jet-Puffed marshmallow factory?
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  • Related: cooking.stackexchange.com/questions/77744/…
    – cimmanon
    Nov 13 '21 at 19:09
  • Possibly relevant: ccmr.cornell.edu/faqs/how-are-marshmallows-made
    – nick012000
    Nov 17 '21 at 3:07
  • According to the link, the setting process for marshmallows is thermoreversable, so have you tried adding the butter and puffed rice directly into the hot marshmallow mixture rather than allowing it to set? It sounds like the industrial marshmallow machines skip the multi hour setting stage somehow.
    – nick012000
    Nov 17 '21 at 3:37
  • 2
    Another point from @nick012000's link is that marshmallows have cornstarch as an ingredient for the product itself - starch gelatinization is NOT thermoreversible, so they'll keep a good part of the water bound when the gelatin reverses. Nov 17 '21 at 8:56
  • 1
    After further research, it looks like modified cornstarch is commonly used in candy because it can withstand high heats better (this source claims it makes it behave more like "gums", so it could be a little of A and a little of B). ClearJel is a highly accessible modified cornstarch specifically made for withstanding high temperatures while canning. If regular cornstarch doesn't do the trick, I'll give ClearJel a try.
    – cimmanon
    Nov 18 '21 at 1:30
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The missing ingredient is starch. Thanks to hints from nick012000 and Juliana Karasawa Souza, I was able to produce a marshmallow that did not get the cereal wet when it melted.

From what I understand, heating gelatin causes it to release the moisture it has locked inside but starches don't.

Process

I made a small batch here. Ended up with about 400g of marshmallow after it cured.

Gelatin Stage

  • 1/4c cold water
  • 1T gelatin powder
  • 1T (7g) cornstarch

Let the gelatin bloom in the water for about 5 minutes. Add the cornstarch and mix well. Let it come to a boil over medium heat, boiling and stirring vigorously for at least 1 minute. I tried to time this so the gelatin came to a boil about the same time as the sugar syrup was ready.

Sugar Syrup

  • 1/4-1/2c water, didn't really measure it
  • 325g granulated sugar
  • 1/4t table salt
  • 1/4t cream of tartar (probably didn't need this since it's going to come in contact with sugar crystals later anyway)

Mix everything together and bring it to a boil over medium heat. Cook until it gets to the soft-ball stage. Transfer to a mixing bowl and start whipping until it cools to about 212F. Add the gelatin/starch mixture and whip on high until it triples in volume. Pour into a prepared pan (lined with parchment paper is popular, but I greased it with lard and dusted it with straight cornstarch). Smooth it as best you can before it starts setting. Dust with some combination of cornstarch & icing sugar. Let it sit overnight uncovered to cure (I draped a clean towel over it to keep bugs and pet hair out). In the morning, cut into cubes and toss with cornstarch/icing sugar.

Result

I sampled the fluff that was stuck to my whisk and Laffy Taffy immediately came to mind. It was plastic-like, definitely not as good as the non-cornstarch batches. I crossed my fingers and hoped for the best when it finished curing. The finished marshmallows still had that Laffy Taffy taste and texture. I was a little disappointed.

I put a handful into a pot with a bit of butter and let it melt over medium heat. I stirred in a handful of cereal... and it was quiet! I gave it a sample and it was still crispy, definitely more consistent with using store bought marshmallows. Added more cereal until I got the consistency I wanted. I turned it out onto a greased surface and let it set for about an hour. The texture was pretty much perfect, just not crazy about the flavor of the marshmallow.

I also gave this batch the hot chocolate test. They melted much slower than non-cornstarch batches and still had the Laffy Taffy texture. I could live with it if I had to, but I'd rather have the non-cornstarch marshmallows.

Conclusion

I'm not crazy about the taste or texture of this batch, but I think it's possible to tune the recipe to have it taste good and make it work for Rice Krispies Treats.

It is possible that the reason commercial marshmallows use modified cornstarch is because it tastes better than native (ie. unmodified) cornstarch. It's also possible that I used too much cornstarch. In the future, I plan on trying less cornstarch as well as ClearJel, which is a highly accessible modified cornstarch used in canning.

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