Rhubarb is a naturally stiff plant, but when frozen and thawed again, it becomes very soft and spongey and loses a lot of water. When attempting to make rhubarb dishes, such as pie or jam, should I attempt to compensate for that lost water or treat it as is?
That’s a tricky question.
While yes, you are discarding some of the juice when straining thawing rhubarb, some rhubarb recipes are struggling with managing the liquid even fresh rhubarb tends to lose when cooked - and it’s likely to lose more than fresh rhubarb with the double damage to the cells, first from freezing, then cooking.
So I suggest a balanced approach:
- For all recipes that have a bit of leeway, can be mushy or liquidy, get down to the desired consistency or thickened, use the juice. Think jams, compote and similar.
- For cakes where the fruit gets stirred in, I tend to strain some of the juice, possibly making up for the difference by using a bit more, so thawing more frozen rhubarb than the fresh kind a recipe may call for.
- And in notoriously fickle (read: moisture sensitive, prone to soggy bottoms) preparations like some pies, I either strain most of the thawing liquid and either discard it or thicken it separately (e.g. cooking it with a bit of starch) and add it back in. Another option to compensate can be adding more dry ingredients that can soak up the liquid, breadcrumbs or ground nuts can work well.
Rhubarb becomes mushy when cooked even if fresh to start with.
If you are not using the liquid that comes with the frozen rhubarb thawing, but discarding it, you are going to screw up any recipe that calls for rhubarb, rather than "frozen and drained rhubarb" and you'll also be discarding a good bit of the flavor. It's not just water.
So, if you have a pound (or half-kilo) of rhubarb, frozen, and a recipe that calls for a pound (or half-kilo) of rhubarb, you include the juice that will thaw, because that's part of the rhubarb called for in that recipe that you froze. So thaw it in a bowl or its freezer bag, and don't discard the liquid.