Sai Krok Isan (Thai Fermented Pork and Rice Sausage)

Sai krok Isan is the sour sausage of Isan, the north-east of Thailand: coarse pork, a large amount of garlic, salt and cooked sticky rice stuffed into thin casing, twisted into little balls, left in the warm for a day or more until it turns pleasantly sour, and then grilled. It is eaten hot with raw cabbage, slivers of fresh ginger, bird’s-eye chillies and roasted peanuts, a bite of each. The diagnostic detail is the rice. Lean pork has almost no sugar for lactic bacteria to feed on; cooked rice gives them a meal, so they acidify fast and hard enough to make the tang and to crowd out spoilage organisms. The sourness is the design, not a fault. Thai research groups have isolated the bacteria that do it — Pediococcus acidilactici and Lactobacillus plantarum — and a 2019 study recorded the pH falling to about 4.9 after three days at 32 °C. This home version runs the same ferment with a commercial culture, cure and a pH meter, and it is always grilled before eating, as it is in Isan. I have not made this one yet; the formula is built from that published control formula and general fermented-sausage practice and is untested.

Ingredients

MEAT BLOCK (2,270 g / 5 lb), % of meat weight

• 1,590 g (3 lb 8 oz) lean pork shoulder, trimmed — 70%
• 680 g (1 lb 8 oz) pork back fat, well chilled — 30%

RICE (% of meat weight)

• 340 g (12 oz) cooked glutinous (sticky) rice, cooled and broken up — 15%

CURE AND SEASONING (% of meat weight)

• 50 g fine salt (2.2%)
• 5.7 g Cure #1 (0.25%) — 2.5 g/kg = 156 ppm nitrite
• 11 g dextrose (0.5%)
• 114 g garlic, finely minced (5%)
• 7 g black pepper, fine (0.3%)
• 0.6 g Bactoferm LHP or another fast lactic starter, at the maker’s dose (a 25 g pack treats 100 kg), in 30 ml distilled water
• 28–30 mm natural hog casing, about 6 m (20 ft)

TO SERVE

• 1 small green cabbage, cut in wedges
• 1 thumb fresh ginger, in thin slivers
• Bird’s-eye chillies and roasted peanuts

Directions

Key ingredients

Black Pepper

1. In the collection: cook the rice as for Thai Sticky Rice (Soaked and Steamed) and let it cool completely. The fresh northern Thai sausage in the collection, Sai Ua Samun Phrai (Thai Sausage), is the unfermented end of the same grill; this one is the sour middle.
2. Wake the culture: stir the starter into the distilled water 20–30 minutes before mixing. Chlorinated tap water can slow it.
3. Grind cold: chill lean and fat to −1 to 0 °C / 30–32 °F and grind through a 6 mm (¼ in) plate. Fat that smears coats the lean and makes the ferment patchy and the texture greasy.
4. Mix: add salt, Cure #1, dextrose, garlic and pepper, mix 1 minute, add the culture water and the cooled rice, and mix 1–2 minutes more until the mass is tacky. Weigh out a 50 g piece, wrap it and keep it for the pH meter.
5. Stuff and twist: stuff loosely into the casing and twist into 3–4 cm (1½ in) balls, or tie 10 cm links. Prick air pockets with a needle.
6. Ferment — the safety step: hang or lay the sausages in a box at 30 °C / 86 °F and 85–90% relative humidity. Check pH from 18 hours on. The target is pH 5.0 or lower (the program floor is 5.3; 4.9 is what the published version reaches). At 30 °C the US degree-hour rule for a fermentation below 32 °C allows (86 − 60) °F × hours ≤ 1,200, so the pH must reach 5.3 inside about 46 hours. If it has not, the ferment has failed: discard the batch rather than cooking it and hoping.
7. Taste the tang: when the pH is down, fry one ball to 71 °C / 160 °F. It should be distinctly sour, garlicky and salty. Too sour means it went too far; it is still safe, and next time stop earlier.
8. Chill: refrigerate at once. The sausages keep 7 days refrigerated or 3 months frozen.
9. Grill: grill over medium charcoal, turning, until browned and 71 °C / 160 °F inside, 15–20 minutes. Eat hot with cabbage, ginger, chillies and peanuts.
10. Sibling recipe: make Naem (Thai Sour Pork, Cooked) from the same pork order — the rind-and-rice parcel and the rice sausage are the two halves of Isan’s sour-pork family.

Notes

Where this recipe came from — and what it isn’t. The backbone is the control formula from a 2019 Thai study of Sai Krok E-san (Asian-Australasian Journal of Animal Sciences, PMC6817787): ground pork 55%, backfat 30%, cooked rice 15%, with garlic 50 g/kg, sugar 5 g/kg, black pepper 4 g/kg, MSG 2.5 g/kg and a ‘prague powder’ at 15 g/kg, stuffed in 28–30 mm hog casing and hung at 32 ± 2 °C for 3 days to about pH 4.89. Deviations: (1) the percentages are restated on the meat block, so the rice is 15% of meat rather than 15% of the whole; (2) the study’s prague powder is a pre-mixed salt-and-cure of unstated strength, so salt and Cure #1 are given separately — 2.2% salt and 2.5 g/kg Cure #1, 156 ppm; (3) a commercial starter and dextrose are added so the acid drop does not depend on whatever bacteria the pork carries; (4) phosphate, erythorbate and MSG are left out (add 2.5 g/kg MSG if wanted); (5) fermentation is shortened to the pH target. Untested.

Traditional method, stated plainly. In Isan the mix is salt, garlic, rice and pork, often with a little saltpetre, stuffed and left out in the warm air or sun for two to four days with no culture, no meter and no fridge. That works most of the time because salt, garlic and a rice-fed lactic ferment are a strong combination; it is still a spontaneous ferment, and the reason it is safe to eat is that it is grilled hot.

Where sai krok Isan came from. It is the sausage form of a family of Isan and Lao sour-pork ferments that use cooked rice as the fermentable sugar — naem, som moo, and fish ferments such as som pla. The rice-as-substrate idea is the same one behind Isan fermented fish. No dated origin is documented. The sausage has research behind it: Thai university groups have isolated Pediococcus acidilactici and Lactobacillus plantarum from ‘sai krok prew’ (sour sausage), identified them by 16S rDNA sequencing, and tested them as starter cultures with bacteriocin-like activity against Staphylococcus aureus.

The name. Sai krok is ‘sausage’ (literally ‘stuffed intestine’); Isan names the region. Sai krok prew (or priao) means ‘sour sausage’ and is the same thing seen by its taste. Sai krok wun sen is a variant made with glass noodles instead of rice.

Variations. Some cooks use pork with rice only; others add glass noodles; some leave out pepper. Shapes vary from marble-sized balls to long links coiled on a stick. Restaurants in Bangkok often sell a shorter-fermented, milder version.

Sourcing and gear. Glutinous rice is sold as ‘sweet rice’ or ‘sticky rice’ in Thai and Lao groceries. Bactoferm LHP (Pediococcus acidilactici and P. pentosaceus) is a fast, warm-temperature culture made for exactly this kind of short, hot ferment; F-LC also works. A pH meter with a meat probe and a box you can hold at 30 °C with humidity — a proofing box, or a cooler with a seedling mat and a wet towel — are the two pieces of gear that make this safe.

Still open. The study’s ‘prague powder’ strength is not stated, so its nitrite level cannot be reconstructed. No published Isan household formula with weights has been compared against this one.

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