Improved rhubarb compote

A recent Twitter conversation with Laura raised an interesting challenge: Is there any way to make a rhubarb compote that keeps the pieces of rhubarb intact? I’ve often found that cooked rhubarb disintegrates very easily, and I was pleased to know I’m not the only one.

It was tempting to see what a temperature-controlled sous vide approach could offer, but since not everyone has an immersion circulator, I wanted to try a different approach. Conveniently, I’d recently read a blog post about using calcium salts, specifically calcium hydroxide and calcium lactate, to react with the pectin in fruits and vegetables, strengthening their structure to allow them to maintain their shape better when cooked. (You sometimes see this with calcium chloride added to pickles to help them keep their crunch.) This in turn led me to a couple of other blog posts on the same subject. It seemed like a “fruitful” approach to try, even though I know from jam-making that rhubarb doesn’t have huge amounts of pectin.

I started by chopping some rhubarb stalks, then dividing it into two equal piles. One pile was soaked in a 1% solution of calcium lactate (I couldn’t find any calcium hydroxide, aka slaked lime) for 2 hours, and the other pile was soaked in tap water for the same time. I drained both and let them air dry for a while, before putting them into separate saucepans, each with the same amount of sugar and water, and half a vanilla bean. (Maybe not very scientific, but I was going to have to eat this stuff in the end!) I cooked them both at a gentle boil for 20 minutes, stirring occasionally.

The verdict?

The calcium lactate-treated compote is on the left, the untreated compote on the right. The treated rhubarb seemed to maintain its shape better, though it still fell apart somewhat when stirred. The untreated rhubarb disintegrated easily when stirred. Both were very soft when eaten.

I would say the difference was noticeable, but not necessarily significant enough to attribute to the calcium treatment rather than other variables (difference in pan size, evaporation, stirring, or heat regulation, for example). As usual, I realized after I’d done my experiment that I probably should have tried the technique with something that others have had success with in the past, so I would know what to look for. Still, I found this to be a qualified success, and I can definitely see myself trying it again in the future.

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