Too late for this year, but how do you keep horseradish strong?
I don't know what's going on the past few years. Growing up, and all the years I've been married and preparing and going to seders, the freshly grated horseradish was nice and strong, just like maror is supposed to be. Children cried because they were afraid to try it. My brother-in-law's father almost had a heart attack showing off how he could eat a big spoonful at once. All was right with the world and just as it should be.
For the last few years, though, it's certainly strong enough when freshly grated, but a couple of hours later at the seder it has lost all its heat. I'm careful to cover it with plastic so there's no air on the surface, but no matter what I do it's not even recognizable as maror. This year we reorted to cutting it into little chunks, which were strong. But the same horseradish grated - - - nothing.
I'd agree to getting domestically sourced roots. Just as an FYI, my state, Illinois, is the nation's largest horseradish-producing state.
Next, timing is everything. The root is at maximum heat about 30 minutes after grating and then starts to dissipate unless you add vinegar (which, as noted below, is not appropriate for the Marror bracha) to stabilize and maintain the heat level.
So buy local and grate just before the seder starts. Doing it earlier in the day or a day before reduces the potency.
I ask where the horseradish is from. The big chain supermarkets here had horseradish that was imported from South America. It traveled by ship and was aged by the time it hit the stores and lost potency. The local/domestic stuff was far fresher/stronger.
Also, when choosing, buy the thickest root available, it's older and more potent. The thin roots haven't developed enough for our needs.
I finely chop in an old fashioned jar chopper (think vegematic) where the chopped horseradish is not exposed to the air as it accumulates (no grating into a wide open bowl to dissipate), and when I remove the chopping top, I have a jar lid that fits tightly to preserve the strength. I don't use this chopper for anything else.