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Fruit from Korea

Maesil-cheong (green plum sugar ferment)매실청

Maesil-cheong starts as a sugar extraction. Green maesil plums are layered with an equal weight of sugar, and the sugar draws their juice out over about three months. It is also a real ferment, because sugar-tolerant yeasts such as Zygosaccharomyces rouxii grow in the syrup and make a little ethanol while it matures for most of a year.

Fully documentedFruit12 months

Recipe

Amounts from a sourceThe amounts are the lab batch in Yoon et al. 2019, made to the method of Choi and Koh (2016). The sources give no household amounts.
Maesil plums, washed and drained400 g[yoon2019]
Brown sugar400 gEqual to the fruit weight; another study layered the fruit with refined sugar[yoon2019][ramalingam2024]
Starterspontaneous

Total time across the recorded steps: 12 months

Start
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15–25 °C

What changes: Plums and sugar go into the jar in layers, and the jar is sealed

Step 1 of 4
Layer the plums with sugar in a sealed jar
Time
Not documented
Temperature
15–25 °C
Reported
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Yeasts
Zygosaccharomyces rouxii
Pichia kluyveri
Flavour
Not documented
Texture
Not documented
Colour
Not documented

Microbes at work in this step

Not documented for this step.

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Maesil-cheong starts as a sugar extraction. Green maesil plums are layered with an equal weight of sugar, and the sugar draws their juice out over about three months. It is also a real ferment, because sugar-tolerant yeasts such as Zygosaccharomyces rouxii grow in the syrup and make a little ethanol while it matures for most of a year. Made in 4 steps over 12 months. The longest step, mature the syrup, takes at least 9 months (Ramalingam S 2024). Zygosaccharomyces rouxii, the main sugar-tolerant yeast, which leads a slow alcoholic fermentation and Clavispora lusitaniae and Pichia kluyveri do most of the fermenting.

Key numbers
Main stepat least 9 monthsReported[ramalingam2024]Mature the syrup
Temperature15–25 °CReported[yoon2019][choi2017]Layer the plums with sugar in a sealed jar

What makes this one different

Maesil-cheong is a sugar extraction, not a brine or lactic pickle. Its only liquid is the juice that sugar pulls from the fruit, and the ferment that follows is slow and yeast-led. Umeboshi and karikari ume use the same fruit with salt instead of sugar.

Related ferments

Variants

  • Ripe-fruit or stoned-fruit syrupMade from ripe or destoned maesil; syrups from ripe fruit had less amygdalin at 3 months [ramalingam2024].
  • Fruit left in for a yearThe fruit stays in the syrup for the whole year instead of being removed at day 90 [choi2017].

Safety

Unripe maesil seeds hold most of the fruit's amygdalin, a cyanogenic compound. In one study, amygdalin in the syrup fell below 5 mg/L after 12 months, and the authors advise at least 9 months of fermentation [ramalingam2024]. By a calculated cyanide yield, they judged all their syrups non-toxic after 9 months. They also cite earlier work that found about 135 to 167 mg/L, a level those researchers reported was not toxic to rats, so a low figure is not guaranteed. The seeds held 42–53 g of amygdalin per kg dry weight, and the authors think the stone's shell keeps it out of the syrup, so do not crack or eat the stones. Ethyl carbamate can form in the sugar extract too; it appeared from day 150, up to 9.7 μg/kg, and was higher at 25 °C than at 15 °C [choi2016]. Biogenic amines were also higher at 25 °C, so a cooler place gives a cleaner syrup [yoon2019].

Hazards the sources name: Amygdalin, a plant compound that releases hydrogen cyanide, over 98 % of it in the seeds; 42.17–66.19 mg/L in the syrup at 3 months and below 5 mg/L at 12 months in one study (a plant toxin, not a microbe).

History and sources

Every number is labelled with how it is known. How this atlas is made

Maesil sugar syrup is a widely used homemade product in Korea, and interest in it has grown in recent years [ramalingam2024].

  1. [ramalingam2024] Ramalingam S., Kumar V., Bahuguna A., Lee J.S., Kim M. 2024, The effect of one-year fermentation of maesil fruit (Prunus mume) sugar syrup on amygdalin level, a natural toxic compound, Foods 13(16):2609, doi:10.3390/foods13162609paper
  2. [yoon2019] Yoon S.H., Koh E., Choi B., Moon B. 2019, Effects of soaking and fermentation time on biogenic amines content of maesil (Prunus mume) extract, Foods 8(11):592, doi:10.3390/foods8110592paper
  3. [choi2017] Choi B., Koh E. 2017, Changes in the antioxidant capacity and phenolic compounds of maesil extract during one-year fermentation, Food Sci Biotechnol 26(1):89–95, doi:10.1007/s10068-017-0012-7 (abstract)paper
  4. [choi2016] Choi B., Koh E. 2016, Changes of ethyl carbamate and its precursors in maesil (Prunus mume) extract during one-year fermentation, Food Chem 209:318–322, doi:10.1016/j.foodchem.2016.04.040 (abstract)paper
  5. [yoon2024] Yoon S.H., Lee S., Lee S.Y., Moon B. 2024, Effect of precursors and stress factors on yeast isolated from fermented maesil extract and their biogenic amine formation, Food Sci Biotechnol 33(1):211–218, doi:10.1007/s10068-023-01328-8 (abstract)paper