Crab Products Crab Paste / Sauce

While not used as widely as Shrimp Pastes / Sauces, Crab Pastes / Sauces are very important in Vietnam, Laos and Issan Thailand. Some forms are easily available in Asian markets, usually from Thailand, but the one most important in Laos and Issan you need to make yourself. Fortunately, the ingredients are now available in North America, though frozen rather than live. Instructions will be found below.

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Thai Crab Paste   -   [Gach Cua Xao Dau An]
Crab Paste with Oil

This is a typical Thai crab paste by a leading Thai brand, Pantai. According to the label, the crabs were caught in the Pacific ocean. The bits of crab in the paste were surprisingly firm.   Ingr: Crab meat (60%), soya bean oil (28%), garlic, salt, pepper, flavor enhancers (monosodium glutamate E621, disodium 5'inosinate E631, disodium 5'guanylate E627) color (paprika oleoresin E160c)

Paddy Crab Pastes / Sauces

In Laos and the Issan region of Thailand, the rice paddies are infested with tiny freshwater crabs. They are disliked by farmers, because they eat young rice shoots. They are hard to get rid of because, when the paddies are dry, they just tunnel into the mud and hibernate until the water returns. On the other hand, they do provide a significant supplementary income for the rice farmers. The crabs are captured, salted and ground up into a seasoning paste that is well liked in Laos, Northeastern Thailand, and southern Vietnam. This paste is usually locally made and isn't much available in North America. These crabs are also sold fresh and unsalted for use in Vietnam's famous Bun Rieu Cua soup.

Rice Crab Sauce for Bun Reiu Soup   -   [Gia Vi Cua Nau Bun Rieu (Viet)]
Commercial Bun Reiu Sauce

So important is the Bun Rieu Soup, mentioned above, that pre-made sauces are exported for use by Vietnamese in other countries where the raw ingredients are hard to find. This sauce was made in Thailand, rather than Vietnam, but this is reasonable. Thailand is a major manufacturer of canned and bottled sauces and similar products for export, while Vietnam is more known for exporting whole natural products. Ingred: Water, onion, crab meat (18%), garlic, soybean oil, peanut, lemon grass, chili, sugar, modified cornstarch E1422, monosodium glutamate E621, salt, paprika natural color E160c.

Rice Crab Sauce   -   [Nuoc Cot Cua Dong (Viet)]
Commercial Crab Sauce

This is a commercial product that recently showed up in the same freezer case with the whole crabs and chopped crabs with sauce that were used in the development described below. The white plastic tub held 1-1/2 cups. Of that, 1-1/4 cup was water (83% water), and 1/4 cup was sediment, about half very fine and half somewhat gritty. Made in Vietnam, Ing: Crab, pure water. In my opinion, my homemade sauce is superior.

Making Rice Crab Pastes / Sauces

I've found incomplete information on making these pastes. I suppose the writers expect an English speaker would not want to do this and/or be unable to get the ingredients. Having studied everything I've found, I believe my procedures are adequately accurate, and I have made these pastes and sauces.

So, you ask, what does it taste like? In my opinion it tastes pretty good - fairly inoffensive, and definitely more crab flavored than similar murky fish sauces. My office assistant noticed a sort of "fishy" smell when I was concentrating the Laotian paste, but didn't find it objectionable.

Rice Paddy Crab   -   [Boo Kem, Bpoo Kem (Thai, salted); Ba Khía Nguyén Con (Vietnam, salted)]
Salted Paddy Crab, whole

This is a salted rice paddy crab. I bought a tray with 14 ounces of them from the freezer cases of a large Asian market in Los Angeles (San Gabriel), 2017 US $3.56 / pound. They are up to 1-3/4 inches across the shell. For use in Green Papaya Salad and the like, the top shell is pried off and discarded along with the gills under it. The rest of the crab is broken up and added to the salad. For pastes and sauces, the whole crab is ground up. For details see our Rice Paddy Crabs page.

Frozen Minced Crab   -   [Ba Khia]
Chopped up Paddy Crabs

Some weeks after I bought the whole frozen salted crabs, the market added 14 ounce tubs of "Frozen Minced Crab" to the same freezer case, 2017 US $3.41 / pound. "Minced" is hardly the word, they were just very coarsely hacked apart as they would be for salads. These were from Vietnam, and had quite a bit of sauce (or salad dressing) included. Ing: Crab, water, salt, sugar, chili, garlic, vinegar.


  • The tub of chopped crab didn't look to be enough for paste, and there was too much sauce - so I decided to grind together the 14 ounce tub and the 14 ounces of whole crabs.
  • Suggestion: Use heavy wire cutters or similar to cut off the white teeth from inside the claws. They are extremely hard and difficult to grind.
  • You need a powerful high speed blender for the grinding. A food processor just doesn't have what it takes. An Indian wet grinder (used to grind rice for idli cakes) would probably be ideal, but those are scarce and expensive in North America.
  • In Laos the Crabs are pounded with Lemon Grass and Guava Leaves (Mak Sida - from real guavas, not pineapple guavas). Lacking Guava Leaves, I decided to just use the liquid sauce from the tub of chopped crabs for flavoring, though there wasn't enough to make much difference. I certainly could have added Lemon Grass, but decided to leave that to be added to recipes separately.

Ground Paddy Crabs

In Laos, the crabs would be pounded in a mortar, a project taking a lot of time and energy, so I used mechanical means. The specimen to the left in this paragraph was ground in a powerful food processor, but was just too gritty, so it had to be reground in a blender. As the blender grinds, you will need to add more and more water so it doesn't bog down and get overloaded. Smoke coming from the blender base is not a good sign. The resulting paste will always be a little gritty, but the grit should be very fine. Commercial products are a bit finer, but still gritty.

In Vietnam
Liquid from Ground Paddy Crabs Solids from Ground Paddy Crabs In Vietnam and parts of Thailand, this is as far as the process might go. The loose paste is strained to produce a liquid sauce (left photo), and the finely ground debris (right photo) is often used to make crab cakes. I wrung out the photo example in a strong muslin bag, making a very fine liquid with no grittiness, but strainers not quite so fine may also be used. The difference from making the broth for Bun Rieu soup in Vietnam is that fresh crabs are used rather than salted and frozen. Salted and frozen are the only ones we can get in North America (California rice growers are very adverse to having these crabs in their paddies). You could desalt the crabs by soaking, but Unsalted crab juice needs to be used right away as it will spoil quickly.

In Laos and Issan Thailand   -   [Nam Bpo]
Partially Dehydrated Paddy Crab Paste

In the countryside it is desired to have a crab paste that will last a long time without refrigeration, as the crabs are not readily available much of the year. For this reason, the ground crab paste is allowed to ferment overnight, then cooked very slowly in kitchen embers for about 24 hours, or until most of the water has evaporated and the paste is dark and very stiff.

Not having kitchen embers available, I put the paste in an open sauté pan and cooked over very low heat, stirring often and carefully regulating the temperature. It should be kept above 165°F/75°C, but below 205°F/95°C. If it goes much above 205°F in the early going it will bubble and splatter without mercy, and in the later going it might burn. The object here is not to fry the paste, but to dehydrate it. It should be a dark, rather stiff paste, but should be taken off the heat and packed before it becomes so dry it breaks up into crumbs. With precise temperature control and frequent stirring it should take less than 6 hours. Kept in a sealed container, the paste needs no refrigeration. My paste didn't come out nearly as dark as it often does in Laotian homes, probably because of very precise temperature control.

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