An interesting question. Figured that the right place to go would be to go to the folks at Kellogg's -- and here is their response:
"Well I checked with some of our Kellogg's experts and I don't think anyone has tested this scientifically." From Alicia Perdon, a Principal Scientist [at Kellogg's] - "I can think that milk fat may retard water from getting into the Krispies - but there's so much water in all types of milk that it may not make a difference."
I would also suggest that the protein in milk might have a similar effect, but you'd have to come up with a way to measure this. My thought on that would be with sensitive sound equipment.
The question of why Rice Krispies pop in the first place can be found at an earlier posting: http://www.madsci.org/posts/archives/mar99/922638321.Ot.r.html
So it is certainly a researchable topic. Good luck with it if you choose to move forward.
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