Before the Great Western Casa McBardo, there was the Great Eastern Casa McBardo.
And there I did my first trip out to visit and cook over a year ago. We had a spectacular good time in the warmth of the Maryland summer, overlooking tomato plants and blossoming strawberries, preparing a smoked pork shoulder, fresh bread, baby chard and warm mushroom salad, curried tomato soup, even ancho spiced chocolate truffles. But there was one dish that didn't work.
I had this idea of making a savory application for rhubarb. I figured that the tangy herb can be used to flavor a sour fish stew akin to the Filipino sinigang, usually soured with tamarind or unripe guava. Flavorwise, I was able to get it. However, instead of a pink soup I had envisioned, we got this grayish muck that was fortunately served at dusk so people couldn't see it.
What went wrong? Only today did I realize what is going on - the redness in rhubarb is the presence of anthocyanins, water soluble compounds whose colors change with the pH. And when I introduced fish into the equation, the buffering of protein brought the pH to a level where the anthocyanins would be...bluish. Hence, the gray color.
I'll need to re-imagine this dish in the future, where I make a butter and rhubarb sauce to be served atop poached monkfish.