You can use this method with a host of other berries, fruits and vegetables to create vibrant plating powders. All I did was puree some blackberries in a blender, send the mixture through a sieve to remove any seeds and then smooth the puree over a silpat. The key is to make sure the puree is nice and thinly spread so it dehydrates quickly in the oven.
You can of course use a regular dehydrator but I figured since most people don't have them I'd show you using an oven. Pop the pan with the blackberry puree into the oven set to it's lowest temperature, mine was at 150 F, and let dehydrate for 8-12 hours.
Break a small piece of and let it come to room temperature. If it cracks in your hands with a little snap then the puree is properly dehydrated and ready to blitz into powder. The best way of making powders ( I use this at the restaurant too) is with a coffee or spice grinder which you likely already have.
So break the dehydrated puree up into small shards and place them in the coffee grinder. Blitz until the mix has become a powder then send through a sieve to remove any large chunks. Transfer the powder into an airtight container and store at room temperature (not the fridge it will get too much moisture in it!). Use it to decorate plates, as a powdered colourant or if you're a health nut drop a spoon into your smoothies in the morning.