I have some dehydrated store-bought broth mix (chicken and vegetable) that has clumped into a large solid block. I haven't been able to find any information on the Internet about how to fix this.
I suspect it is a matter of hydration (too hydrated or too dehydrated). I could experiment by adding drying agents/water, but I figured I should ask first before making my broth go funky.
The clumping is a result of air and moisture entering the container with the substance. This especially happens if you pour the mix directly from the container over a hot dish - the steam enters and immediately clumps the spices. What you can do is to transfer your mix into a new dry and airtight container. Hope this helps :)
To break the clumps up, just use physical force.
Put the stuff in a sealed, heavy-duty plastic bag and whack on it with a rolling pin or a heavy bottle until it is in smaller lumps, then use your hands to break them down into the original powder.
As Adeline says, this is as a result of moisture (most likely steam) getting into the dry ingredients!
There is nothing wrong with the powder, if I were you I'd just crumble it into your food/gravy jug as and when you need it.
In future (to answer the question in the title) there are a few things you can do to avoid this happening:
(FYI stock = broth and by gravy I mean the British kind)
I would not recommend using the silicon gel pads as someone else has unless they are certified as safe with food. Most contain toxic chemicals that may leach into the powder over time.
Easy fix. In a dry climate, uncap jar for a few days. Then use handle of teaspoon to unclump. If that didn't work, my next step was going to uncap and place in slightly warm oven first; then use spoon handle.
