I have a Swiss meringue buttercream recipe that has a water activity of 0.863. I’m trying to reduce the water activity to 0.85 or lower using a humectant so I can keep the frosting at room temperature. Internet research led me to want to use vegetable glycerin, so as not to affect the taste and texture of the frosting. However, I have no idea how much glycerin to use to accomplish this, and would like a better idea before I spend the money to lab test it. Recipe is below. If someone could help me, that would be amazing. Thank you!

160g pasteurized liquid egg whites

4 sticks (453g) unsalted butter

300g cane sugar

2 tsp vanilla extract

pinch of salt

The egg mixture is cooked to 160 degrees before adding butter.

AFS Desk Answered question February 28, 2023