A few weeks ago I boiled two lobsters for myself and my boyfriend and then returned the shells (head innards included) to the pot along with the original boiling water, a bit more water, an onion, celery, a carrot and herbs. This was my first time attempting lobster stock.
I brought it to a boil and simmered it for quite a while. (I did not roast or broil the shells before bringing them to a boil, as some recipes suggest, since I had just cooked the whole lobsters.) I simmered the whole thing for probably two hours while I watched a movie.
Afterward I removed the solids, strained the stock somewhat and reduced it way down, probably wrongly -- because it then turned an unappealing muddy gray color. Oh well, it would still taste lobstery, I figured. I strained it a few times through a sieve lined with cheesecloth, poured it into a plastic container and put it in the fridge.
A day or two later, when I looked in the fridge, I noticed that it had a lot of sediment at the bottom, similar in proportion and appearance to the sediment that forms at the bottom of a carboy of fermenting wort when I home-brew beer.
I opened up the container with plans to strain the stock some more, but the stuff was head-boltingly stinky -- and not like fish. It didn't even smell like food, really -- more like some weird chemical concoction, or the damp, stuffy smell of subway stations in disrepair. It was seriously gross. It had smelled similar but not nearly as strong right after I'd made the stock.
I was afraid to try it, but I diluted a sip of the concentrated stock with water, heated it and tried it. It tasted slightly odd and musty but not foul like it smelled. It still tasted like stock, but the smell, sediment and color -- and what I'd read about possible seafood contamination -- frightened me. I regretfully dumped the entire batch, and the unsalvageably smelly container.
So... What did I do wrong? Why did the stuff smell so incredibly awful? Was it because I didn't sufficiently strain the stuff right off the bat? Was it because I overreduced it? Was it because I didn't cook the shells in the oven? Or should I have removed all the stuff from inside the heads, or anything else, before boiling the lobster carcasses?
Given how cheap lobsters are (and given that I'm going to Maine soon), I'd love to know how to avoid my awful lobster stock-making screw-ups next time. Thanks!