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Soy and legumes from China

Red fermented tofu (hong furu, nam yu)紅腐乳

Firm tofu cubes are grown over with mould, salted, then ripened for months in a dressing of red yeast rice (angkak), rice wine, salt, sugar and flour or bean paste. The red rice colours the outside of each cube deep red while the inside turns apricot-yellow and creamy.

Fully documentedSoy and legumes3.8 months

Recipe

No fixed amounts recordedFactory process with no fixed amounts published in the sources read. The dressing of red furu is similar to white furu's plus red yeast rice (Tan 2020).
Firm tofu, cut into cubes[tan2020]
Mould starter (Actinomucor, Mucor or Rhizopus)Sprayed on the tofu to make the moulded cubes (pehtze)[tan2020][han2004m]
SaltA saturated salt solution salts the pehtze, and salt goes into the dressing again[tan2020]
Red yeast rice (angkak)The colourant that makes it red; the white kind leaves it out[tan2020][jgs2024]
Alcoholic drink (rice wine or spirit)[tan2020]
Sugar, flour or soybean paste, and spices[tan2020]
Starterdefined culture: mould sprayed on the tofu; Monascus comes in with the red yeast rice

Total time across the recorded steps: 3.8 months

Start
Drag the bar or press Play
shapes, not to countMonascus purpureus27 °C

What changes: Monascus mould grows through steamed rice and turns every grain red

Step 1 of 5
Make the red yeast rice
Time
20 days
Reported
Temperature
27 °C
Reported
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
Monascus purpureus
Moulds
Mucor circinelloides
Rhizopus microsporus

Output: red yeast rice (angkak).

Flavour
Not documented
Texture
Not documented
Colour
white rice to deep red

Microbes at work in this step

Monascus purpureus grows through the steamed rice and turns it red

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

Firm tofu cubes are grown over with mould, salted, then ripened for months in a dressing of red yeast rice (angkak), rice wine, salt, sugar and flour or bean paste. The red rice colours the outside of each cube deep red while the inside turns apricot-yellow and creamy. Made in 5 steps over 3.8 months. The longest step, add the red dressing and ripen in sealed jars, takes at least 3 months (Han B-Z. 2003). Salt is at least 11 % (Han B-Z. 2003). Moulds that make the pehtze: Actinomucor repens, A. taiwanensis, Mucor circinelloides, M. hiemalis, M. racemosus, Rhizopus microsporus and Monascus purpureus, which grows the red yeast rice added in the dressing do most of the fermenting.

Key numbers
Main stepat least 3 monthsReported[han2003]Add the red dressing and ripen in sealed jars
Temperature27 °CReported[sic-ftofu]Make the red yeast rice
Saltat least 11 %Reported[han2003]Salt the pehtze
AciditypH 5.5–6.8Measured[han2001b]Keep in its dressing

What makes this one different

Red furu is white furu with red yeast rice in the ripening dressing. The rice adds the red colour, and its antimicrobial compounds may be why lactic bacteria rarely grow in it.

Related ferments

Variants

  • Rose sufuWai listed rose sufu next to red sufu among the types he studied in Taiwan.

Safety

Botulism is the serious risk when it is made at home. Commercial red sufu sits at pH 5.50–6.78, so acid does not hold C. botulinum back. In a CDC report, California health officials found botulinum toxin in one home-prepared batch of fermented tofu (boiled shop tofu left under plastic wrap) at pH 6.8, made and kept at room temperature. The report warns that home preparation can cause botulism, and says home-fermented bean products are the commonest food behind botulism in China (63 % of about 2,000 cases, 1958–1989). We found no tested home method. Bacillus cereus was found in every commercial sufu tested, at 10⁵ cfu/g or more in two red samples, which the authors call a potential hazard. One of those samples also held Clostridium perfringens at about 10⁵ cfu/g.

Hazards the sources name: Clostridium botulinum type A and its toxin (in a home-prepared fermented tofu with chilli, at pH 6.8); Bacillus cereus, found in every commercial sufu tested; 10⁵ cfu/g or more in two red samples; Clostridium perfringens (about 10⁵ cfu/g in one commercial red sufu of 12).

History and sources

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

The earliest verifiable Chinese record of fermented tofu is in the Pen-ts'ao kang-mu (1578–97). In 1920 Margaret Church of the USDA first referred to it in English as "Chinese cheese" (Shurtleff and Aoyagi).

  1. [cdc-mmwr-2007] US CDC 2007, Foodborne botulism from home-prepared fermented tofu, California, 2006, MMWR 56(5)gov
  2. [han2001b] Han B-Z., Beumer R.R., Rombouts F.M., Nout M.J.R. 2001, Microbiological safety and quality of commercial sufu, a Chinese fermented soybean food, Food Control 12:541–547, doi:10.1016/S0956-7135(01)00064-0paper
  3. [han2003] Han B-Z. 2003, Characterization and product innovation of sufu, a Chinese fermented soybean food, PhD thesis, Wageningen University (abstract via FAO AGRIS)paper
  4. [han2004m] Han B-Z., Kuijpers A.F., Thanh N.V., Nout M.J. 2004, Mucoraceous moulds involved in the commercial fermentation of sufu pehtze, Antonie van Leeuwenhoek 85:253–257 (abstract)paper
  5. [tan2020] Tan G., Hu M., Li X., Pan Z., Li M., Li L., Yang M. 2020, High-throughput sequencing and metabolomics reveal differences in bacterial diversity and metabolites between red and white sufu, Frontiers in Microbiology 11:758paper
  6. [jgs2024] T/JALNCP 2024 Jinggangshan fermented bean curd (井冈山豆腐乳), group standard, consultation draft, Ji'an Green Agricultural Products Promotion Associationother
  7. [sic-ftofu] Shurtleff W., Aoyagi A., History of Fermented Tofu, SoyInfo Center (chapter of an unpublished manuscript, 2004)book