I know that the majority of you who cook with canned coconut milk- are not the people who need this warning. This is for those of you who, occasionally, use ingredients from your cupboard that are fairly old .Or waaaay old. Uhemmmm.
While I bet that 'too old' coconut milk wouldn't cause you bodily harm, I can assure you that it can RUIN your entire dish. Case in point: I haven't cooked for a while and I have, thank heavens, recently been inspired to end the hiatus. I have been working today on a long project of Coconut Kabocha Squash Soup. Because my very first experience with coconut milk, some 25 years ago, was with a bad can of coconut milk-containing 'Penang Sauce', I tasted both cans of coconut milk before using them, in my soup pot ,and they seemed A.O.K.....( Not.)
But I didn't find this out til AFTER I had cooked squash and onion in the coconut milk, then separated the liquids from the solids and pureed the solids. It was then that I re- tasted the liquid, before adding it to the squash puree. ARGH! Rancid Coconut Milk! Down the drain. (I am guessing that the 'milk' part [this was what I tasted ]was o.k., but it was the separated, solidified, fat part that had gone rancid.) Miraculously, the squash tastes fine.
So I've opened 2 cans of newer, very white, coconut milk. After whisking and heating it, it tastes clean and fresh and strongly of pure coconut. (Rancid coconut milk has a sour tang.)Whew.( Now I've added the freshly purchased coconut milk to the squash cilantro puree, and next comes the corn etc.)
But because I made this dreadful mistake, even though I was on the lookout for rancidity, I wanted to give a shout-out to cooks both new and seasoned. Taste. Your. Food. Often! And watch out for rancid coconut milk that has been on the shelf too long. Before adding a can of coconut milk to a recipe, separately whisk it all together, and then taste before using!
(P.S. This is one place when my "oh, go ahead and use it up" mentality does NOT work! )