Aiyu Jelly

Aiyu is documented in the writings of the Taiwanese historian Lien Heng. According to his Comprehensive History of Taiwan, sometime in the Daoguang reign of the 19th century a merchant traveling through the hills of Chiayi drank from a stream and found a clear jelly floating on the surface, realizing it came from fallen aiyu-fig fruit; he had his teenage daughter, named Aiyu, rub and sell the jelly, and it took her name. The aiyu fig is endemic to Taiwan's mountains.

Aiyu is barely there — a trembling, almost weightless jelly, clear and faintly golden, that slips apart on the tongue with no chew at all. On its own it is nearly tasteless; it lives to carry the bright sourness of fresh lemon and the round sweetness of honey. Over crushed ice it is pure cold refreshment, slithering down in soft, cool sheets.

Aiyu's set is a rare room-temperature gelation driven by an enzyme and calcium, not heat. The seeds are coated in high-methoxyl pectin and the enzyme pectin methylesterase. Rubbing them in water dissolves both out; the enzyme strips methyl groups off the pectin, converting it into low-methoxyl pectin. The divalent calcium and magnesium ions naturally present in mineral water then cross-link the pectin chains into a three-dimensional gel network — which is why mineral water sets it but pure distilled water will not, and why oily or soapy hands, which interfere with the pectin, ruin the set. No heat and no gelatin are needed. This enzyme-plus-calcium cold gelation sets aiyu apart from related plants like the common creeping fig used for bingfen or liangfen, which are a different species and process.