In a typical, fully-equipped Korean kitchen, you'll find a bottle of honey-like syrup called maesil cheong.

This versatile syrup made from the fermentation of maesil, Korean green plums, serves as both a sweetener in various Korean dishes and a home remedy for an upset stomach or indigestion.

June is the peak harvest season for maesil, which means it’s time for Kwon Sun-ja to prepare for her annual tradition of making the green plum syrup.

"Early summer is when I make maesil cheong. I make sure that I make enough so that I don’t run out and have a few extra bottles to give to my children,” said the 72-year-old living in Anyang, Gyeonggi Province, sharing her recent purchase of 40 kilograms of freshly harvested green plums.

The utensils are also prepared: plenty of glass jars and plastic water bottles, she added.

While Kwon likes to use the homemade syrup as a substitute for “unhealthy” sugar on its own or other sweeteners, she also enjoys having it as a beverage with water and ice during dog days of summer, she said.

Behind her fervent love of maesil lies the popular belief that the fruit has medicinal properties, aiding digestion, boosting the immune system and alleviating inflammation, among others.

In “Donguibogam,” an encyclopedia of medical knowledge and treatment techniques compiled and edited by Heo Jun in 1613, during the Joseon era (1392-1910), maesil is noted for lowering excessive heat in the body, alleviating chest pain, comforting the mind, alleviating thirst and diarrhea, and revitalizing muscles and one's heartbeat.

Maesil, the fruit of the Prunus mume tree, starts out green and turns yellow as it ripens. It is not eaten raw but is typically used only after fermenting or preparing it in other ways. Green maesil smoked and dried to a dark brown or even black color are called omae in traditional Korean medicine. Not only in South Korea but also across East Asia, these smoked plums have been widely used as medicine.

The greatest power of omae lies in inducing sound sleep. The Donguibogam recommends drinking omae tea to help induce a good night's sleep.

In modern days, the efficacy of maesil has been re-evaluated by science. Maesil is rich in organic acids, including succinic, citric and malic acids, which give it its various antioxidant and other medicinal properties. But it also contains a toxic substance known as amygdalin.

Due to this, the Ministry of Food and Drug Safety advises those making maesil cheong at home to follow these instructions to minimize the toxicity.

Below is a recipe based on the ministry’s guidelines.

Instructions

Choose yellowish maesil, as they contain 70 percent less cyanogenic compounds than green ones. If your maesil are still hard and green, leave them at room temperature for a couple of days to ripen.

Wash the fruit thoroughly three times and dry it completely to prevent mold. Remove the stems to avoid bitterness.

Sterilize your storage container using steam or boiling water, and ensure it is completely dry to prevent bacterial growth.

Remove the seeds. This reduces cyanogenic compounds by 95 percent.

Combine the plums and sugar in a 1:1 ratio, ensuring that the maesil flesh is fully covered.

Place the mixture in a sterilized container and stir occasionally. Let it ferment for 3-4 months at room temperature, while occasionally stirring it. After fermentation, use a sieve to remove the solids. Age the filtered syrup for at least 6 months to reduce cyanogenic compounds by an additional 13 percent.

Uses

Beverages: Add the syrup to cold or hot water to make tea; use as a mixer for various mocktails.

Cooking: Use as a sweetener in recipes.