Khanom jeen is not Chinese: a Mon name and a fermented rice noodle

Khanom jeen (ขนมจีน) is the round white rice noodle eaten with nam ya fish curry, green curry, nam ngiao or a sweet peanut sauce. The name looks like it means “Chinese”, but the most popular theory says it comes from the Mon people, and that “chin” in Mon means “cooked”. Traditional khanom jeen is also one of the most everyday fermented foods in Thailand. This article covers where the name comes from, how fermented noodles are made, and the science behind their taste and keeping.

Where the name comes from

In Thai, “jeen” (จีน) means China, so many people assume the noodle arrived with Chinese migrants. Several sources agree it more likely came from the Mon, but they do not agree on the exact translation.

Source	Mon word	Meaning given
MICHELIN Guide	kanorm chin	kanorm = a pack sticking together; chin = cooked
Wikipedia	hanom cin	boiled noodles
Kasetsart University and JIRCAS poster	not given	believed to come from the Mon, found in Thai food since the Ayutthaya period

What they share is that the second part means “cooked”. The first part is translated differently. The MICHELIN Guide adds that in old Thai, “khao nom” meant kneading rice flour into dough, which later became “khanom”, a word not limited to sweets.

There is no decisive evidence for where khanom jeen came from. Every source says “believed” or “popular theory”, and so do we.

Evidence that the noodle has been in Thailand a long time comes from place names: a historian quoted by the MICHELIN Guide points to old canals in Ayutthaya called Khlong Khanom Chin and Khlong Namya. The story that Thais overheard Mon people saying the noodles were “cooked” and kept the word is a popular anecdote with no evidence behind it.

Fermented flour versus fresh flour

Khanom jeen in markets today comes in two broad kinds.

	Fermented flour	Fresh flour
Base	Rice or rice flour fermented for several days	Unfermented rice flour
Colour	Darker, slightly brown	White
Taste and texture	Slightly tangy, stickier	Soft, thicker strands
Making	Takes several days	Quicker
Keeping	Keeps longer than fresh	Keeps for a shorter time

Sources give different fermentation times. Wikipedia says the rice is fermented for three days; the MICHELIN Guide says “a few days”; and producers vary by recipe and weather. There is no single right number for everyone.

What fermentation does

A joint research project between Kasetsart University’s Institute of Food Research and Product Development and Japan’s JIRCAS explains that khanom jeen is made from rice fermented by lactic acid bacteria, the same family of bacteria as in yogurt. They make the dough acidic, and that acidity holds back the bacteria that turn noodles mushy and spoil them. If the dough is not acidic enough, the wrong microbes grow instead.

The noodle’s particular flavour and its springy texture come from that fermentation and from its high moisture. The same high moisture is why khanom jeen keeps only about 3-5 days, and one reason proper khanom jeen is hard to find in Thai restaurants abroad.

Worked example: a lab recipe, step by step

A Kasetsart University study published in the Thai Science and Technology Journal (2015) set out its noodle-making steps in detail. It is a good way to see the principle.

1. Wet-mill broken rice with water at 1 part rice to 2 parts water.
2. Ferment the slurry at room temperature; in this study, for 1 day.
3. Make a cooked dough first, weighing 30% of the total flour. For 1,000 g of flour, that is a 300 g cooked dough ball.
4. Knead the cooked dough into the rest of the flour, adding water until the paste is about 60% moisture.
5. Press the paste through a die into water at about 85 °C and cook for 6 minutes.
6. Cool the noodles in water, then drain them on a rack.

The same study found that fermentation time changes the starch. Flour fermented for 1 day and then heat-moisture treated had 5.92% resistant starch (starch that resists digestion); 2, 3 and 4 days gave 4.84%, 4.40% and 1.95%. That is for specially treated lab flour; it does not mean market noodles have these values.

Names and curries by region

It is the same noodle across the country, with different names and partners.

• Central: khanom jeen, with nam ya, green curry, sweet peanut nam phrik, and in hot weather khanom jeen sao nam (coconut milk, dried shrimp, pineapple).
• North: khanom sen or khao sen, with nam ngiao. See northern food: khao soi and nam ngiao.
• Isan: khao pun, with jungle-style nam ya, and pounded into som tam as tam sua. See som tam styles.
• South: eaten from early morning, with hotter curries that often include cumin, plus fresh phak nao vegetables. See southern curries.

Neighbouring countries have similar noodles. The Kasetsart and JIRCAS poster names khao pun in Laos, mohinga in Myanmar and bún in Vietnam.

Common mistakes

• Thinking khanom jeen only goes with nam ya. Each region has its own curries. Order what the stall does best.
• Keeping it for days because “fermented food does not spoil”. Fermentation helps, but it still keeps only about 3-5 days. Mushy, slimy or off-smelling noodles go in the bin. For leftovers, see storing Thai leftovers.
• Mistaking a mild sour smell for spoilage. Fermented noodles normally smell faintly sour. Slime, mush and a strong, changed smell are the warning signs.
• Telling the “Mon said it was cooked” story as history. It is still an anecdote without evidence.

Summary

Khanom jeen did not come from China. The most popular theory traces it to the Mon, with “chin” meaning “cooked”. Fermented khanom jeen is made from rice fermented by lactic acid bacteria, whose acidity gives the noodle its taste and slows spoilage, yet it still keeps only about 3-5 days. Next time you order it, ask whether the noodles are fermented or fresh, and notice the difference in colour and taste.

Sources

• Secret of Khanomjeen (poster) — Kasetsart University IFRPD and JIRCAS
• Application of fermented and hydrothermal treated rice flour to increase resistant starch in rice vermicelli (Kanom-jeen) — Thai Science and Technology Journal
• Khanom jeen and lactic acid bacteria (Thai comic) — JIRCAS
• Get to know how khanom chin conquered Thailand — MICHELIN Guide
• Khanom chin — Wikipedia