Aiyu jelly

Aiyu jelly (; or ; or simply ), known in Amoy Hokkien as ogio (), and as ice jelly in Singapore (), is a jelly made from the gel from the seeds of the awkeotsang creeping fig found in Taiwan and East Asian countries of the same climates and latitudes. The jelly is not commonly made or found outside of Taiwan and Singapore, though it can be bought fresh in specialty stores in Japan and canned in Chinatowns. It is also used in Taiwanese cuisine.
It's known as Aiyu Jelly or by its local Cantonese dialect, wan tau long. It is commonly served with a slice of lime.
Origin.
According to oral history, the plant and the jelly were named after the daughter of a Taiwanese tea businessman in the 1800s. The gelling property of the seeds was discovered by the businessman as he drank from a creek in Chiayi. He found a clear yellowish jelly in the water he was drinking and was refreshed upon trying it. Looking above the creek he noticed fruits on hanging vines. The fruits contained seeds that exuded a sticky gel when rubbed.
Upon this discovery, he gathered some of the fruits and served them at home with honeyed lemon juice or sweetened beverages. Finding the jelly-containing beverage delicious and thirst-quenching, the enterprising businessman delegated the task of selling it to his beautiful 15-year-old daughter, Aiyu. The snack was very well received and became highly popular. So, the businessman eventually named the jelly and the vines after his daughter.
However, the Austronesian name "igos", coming from Spanish "higo", hints at a possible Austronesian origin for this food.
Harvesting.
Fruits of the creeping fig plant resemble large fig fruits the size of small mangos. The figs grow from flowers pollinated by the Wiebesia pumilae. and are harvested from September through January just before the fruit ripens to a dark purple. The fruits are then halved and turned inside out to dry over the course of several days. The dry fruits can be sold as is, or dried aiyu seeds () can then be pulled off the skin and sold separately.
Jelly making.
The aiyu seeds are placed in a cotton cloth bag, and the bag and its contents are submerged in cold water and rubbed. A slimy gel will be extracted from the bag of aiyu seeds as it is squeezed and massaged. This is known as "washing aiyu" in Chinese (洗愛玉). After several minutes of massaging and washing, no more of the yellowish tea-coloured gel will be extracted, and the contents of the bag are discarded. The washed gel is then allowed to set into a jelly either in a cool location or in the refrigerator. One must keep in mind certain things when making aiyu jelly or else the gel may not set:
Water will slowly seep out of the jelly some time after it sets, and it will turn back to a liquid over the course of several days.
The jelly is usually served with honey and lemon juice but can also be included in other sweetened beverages or shaved ice and is particularly popular as a cool drink in hot summers.
Chemistry.
The gelling agent in aiyu seeds is pectin. Pectines are located in the transparent layer on the surface of seeds and not the inside of seeds, which is why they are extracted by washing and rubbing instead of grounding to a powder. The main component of the water extract was found to be LMP (low methoxy pectin), as opposed to high metoxy pectins prevalent in commercially used sources such as apples or citrus peels. LMP gels in presence of divalent cations, which are found in sufficient amount in water (when it's not distilled), thus causing a creation of jelly.