There’s not enough going on in the garden and greenhouse to support a “Six on Saturday” post today, but I think the first fruit on a strange little plant warrants a post all of its own.
Miracle fruit (Synsepalum dulcificum) is a nondescript little west African shrub with nondescript little white flowers. Its name and its claim to fame come from the red berries which contain a unique glycoprotein called miraculin. Miraculin binds to taste receptors that are responsible for detecting sweet substances and functions as a pH-dependent agonist . In other words, miraculin can activate sweet taste receptors, but only under acidic conditions. The result is that sour (acidic) substances temporarily taste sweet.
This sounded like a lot of fun to me, so about a year-and-a-half ago, I purchased a small. S. dulcificum plant to grow in the greenhouse. After a rocky start when it got badly sunburned, the plant has recovered nicely and recently produced two berries. My initial plan was to cut the berries in half so that all four family members could try them. However, it turned out that the berries consist of a thin layer of white pulp sticking to a large central seed that resists subdivision. In the end, my wife graciously chose to wait for the next crop (or maybe she wanted to use us as guinea pigs). I chewed on a small fragment of skin and pulp shaved off the largest berry, and the kids had one berry each.
The skin/pulp was tart and fresh but didn’t have much in the way of a distinctive taste. After chewing on the berries, the kids and I tried sucking on wedges of fresh lemon and sipping apple cider vinegar. The results were exactly as described in the literature, but it was still startling to experience the effect ourselves. The lemons tasted like wonderfully sweet fresh lemonade. The vinegar was great. I could still smell the volatile acetic acid, but the taste was sweet apple juice. The overall effect was a complex, spicy apple cider.
I see more buds forming on the plant, so hopefully we will soon have a larger crop of berries to experiment with.
 Koizumi, A., Tsuchiya, A., Kakajima, K.-I., Ito, K., Terada, T., Shimizu-Ibuka, A., Briand, L., Asakura, T., Misaka, T., and Abe, K. (2011). Human sweet taste receptor mediates acid-induced sweetness of miraculin. Proc. Natl. Acad. Sci. USA 108: 16819-16824.