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Fresh whole shrimp are fermented with salt and cooked rice or sticky rice, plus chilli, galangal, garlic and vegetables such as carrot, bamboo shoot or papaya. Sealed away from air at room temperature for 4–6 weeks, the shrimp sour and turn brown-red to brick-red but stay whole. A Huế provincial technical regulation sets its salt, shrimp content and safety limits.
Other ingredients named by the regulation; each must have a clear origin[qcdp-tomchua]
Starter
spontaneous
Total time across the recorded steps: 13 months
Start
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What changes:Starting material: fresh whole shrimp with nothing else mixed in
Step 1 of 5
Choose fresh whole shrimp
Time
Not documented
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Lactic acid bacteria
Lactobacillus farciminis
Lactobacillus futsaii
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
Fresh whole shrimp are fermented with salt and cooked rice or sticky rice, plus chilli, galangal, garlic and vegetables such as carrot, bamboo shoot or papaya. Sealed away from air at room temperature for 4–6 weeks, the shrimp sour and turn brown-red to brick-red but stay whole. A Huế provincial technical regulation sets its salt, shrimp content and safety limits. Made in 5 steps over 13 months. The longest step, keep, takes 12 months (Phan Thi Hang G 2024). Salt is up to 10 % (Ủy ban nhân dân tỉnh Thừa Thiên Huế 2020). Lactobacillus farciminis and Lactobacillus futsaii does most of the fermenting.
Unlike salty mắm tôm paste, the shrimp stay whole and sour with cooked or sticky rice, at no more than 10% salt; Huế regulates it as a local product with its own technical standard.
QCĐP 2:2020/TT-H caps sodium chloride at 10%, histamine at 150 mg/kg, E. coli at 3 MPN/g and S. aureus at 10 CFU/g, and Salmonella must be absent from 25 g. Use fresh shrimp, refined salt and rice free of mould. The regulation sets no minimum salt and no pH limit, and a sealed jar does not stop Clostridium botulinum, which grows without air. WHO names fermented fish, not shrimp specifically, among the foods that have carried its toxin. It says the bacterium will not grow below pH 4.6, but that acid does not destroy toxin already formed. So do not eat a jar that has not soured, and do not take sourness alone as proof that a jar is safe.
Hazards the sources name: Salmonella (must not be detected in 25 g); Staphylococcus aureus, Escherichia coli and Clostridium perfringens (capped by the regulation).
In a 2022 article by the Vietnamese intellectual-property news site Sở hữu trí tuệ, Huế food researcher Nguyễn Xuân Hoa says the old records hardly say who created tôm chua Huế, and that folk stories trace it to the south. By the tradition he repeats, Queen Mother Từ Dũ, whose family came from Gò Công, brought the Gò Công sour shrimp to the Huế court, where it was refined and later spread to ordinary households. The same article says a collective trademark for Tôm chua Huế was first sought in 2009 [sohuutritue2022].