I made my daughter's birthday cake this weekend. I noticed a few very small 'crystals' had formed in my crumb coat - they turned the icing lighter right around them. I picked one out with a toothpick to see what it was and tasted it. It was extremely sour / acidic. Almost like a crunchy lemon. Because I was able to see the color difference, I picked the rest out. At least I hope I got them all! Everyone at her party said the cake was delicious, so I think I got them all.

I used the same recipie I always use with no issues before - butter, crisco, powdered suger, cream, merengue powder, and vanilla and almond extracts. Hubby went to the store and only got store brand butter, but everything else was name brand. I don't think that caused it, but I don't really know for sure.

Has anyone had this happen before or know what it is, and how do I prevent it from happening again?
TIA

Are you adding salt to your recipe? I add a pinch and have found it causes the exact problem you are talking about. I try to mix the salt with the wet ingredients to dissolve it.

No, there's no salt in my recipe. It's only the ingredients I have listed above.... maybe hubby got salted butter and it caused it? To be honest, I didn't look at the package very much - just saw it was store brand.