Allergen guide

Soy in recipes — how Frittu checks and excludes it

Soy is one of the most widely used ingredients in Asian cuisines and processed food manufacturing. It turns up in fermented pastes, finishing sauces, meat alternatives, and even chocolate. This page explains what Frittu's system does, specifically, when soy is listed as an excluded ingredient in a user's profile.

Soy in everyday cooking

The soybean is one of the most versatile ingredients in the world food supply. Whole soybeans appear as edamame and natto. Pressed into a cake, they become tofu. Fermented, they become miso, doenjang, and tempeh. Processed into a liquid, they become soy milk and soy sauce. Extracted as oil, they become a neutral cooking fat. Defatted and extruded, they become textured vegetable protein — a meat substitute used in everything from bolognese to burger patties.

That versatility means soy can appear in a recipe under many different names, in many different roles, and not always the ones you would expect. Miso is a soy product that turns up in soups, salad dressings, and even desserts like miso caramel. Hoisin sauce, a thick sweet-savoury condiment, is built on a soybean base. Gochujang — the Korean fermented chilli paste used in bibimbap and tteokbokki — typically contains soy in its commercial form. Soy lecithin, a food additive derived from soy, appears in many processed ingredients including chocolate.

Because soy spans whole foods, fermented pastes, extracted additives, and processed protein products, it requires a keyword list that is broader than many other allergens. Frittu maintains an explicit list of these aliases so that a recipe for a dish like mapo tofu or Korean fried chicken does not pass through the check on a technicality when soy is excluded.

How Frittu's allergen check works

When your profile lists soy as an excluded ingredient, Frittu applies a two-layer check to every recipe it generates.

Layer 1 — prompt-side instruction.Before sending a generation request to Claude, Frittu builds an exclusion list from your allergen profile. For soy, that list includes not just “soy” and “soya” but also the aliases most likely to appear in a recipe: tofu, tempeh, edamame, miso, tamari, hoisin, oyster sauce, teriyaki, black bean sauce, doubanjiang, ketjap, doenjang, gochujang, natto, yuba, soy lecithin, soy flour, soy protein, textured vegetable protein, and TVP. Claude receives these as a hard exclusion instruction and is directed to build the recipe without them.

Layer 2 — deterministic post-generation scan.After the recipe is returned, Frittu runs a server-side function that checks every ingredient name against a coded keyword list for soy. Short names like “tamari” are matched as whole words so they do not produce false matches on unrelated ingredient names that contain the same letters. If a recipe still contains a matched keyword after generation, it is rejected and Frittu attempts to generate an alternative before the recipe reaches you.

What this check does not cover. The check operates on ingredient names as generated. It does not cover cross-contamination that could occur during home preparation — shared cookware, utensils used across dishes, or incidental contact through kitchen surfaces. It also does not account for ingredients a user adds themselves after receiving the recipe. If you prepare food for someone with a significant soy allergy, kitchen cross-contamination controls remain your responsibility.

Hidden sources of soy in cooking

Common hidden sources of soy in cooking include the following — ingredients that contain soy but may appear in a recipe without the word “soy” being present.

Hoisin sauce — A thick, sweet-savoury sauce made from soybeans, garlic, vinegar, and spices. It is used as a dipping sauce in Peking duck, as a flavouring in mu shu pork, and as a glaze in many stir-fries. The soy content is foundational, not incidental.

Doubanjiang — A fermented broad bean and chilli paste that is the central flavouring in Sichuan cooking — the base of mapo tofu, Sichuan braises, and dan dan noodles. Most commercial doubanjiang is made with both broad beans and soy. Because its soy content is not obvious from the name, it is listed explicitly in Frittu's keyword list.

Doenjang — A Korean fermented soybean paste with a deep, pungent flavour similar to miso. It is used as the base of doenjang jjigae (Korean soybean paste stew), in dipping sauces for grilled meats, and in marinades. It is made from soybeans and salt.

Gochujang — A Korean fermented chilli paste used in bibimbap, tteokbokki, and as a marinade base for dishes like spicy Korean fried chicken. Most commercial gochujang is made with soybeans in addition to rice, chilli, and salt. The soy content is present but not named in most English-language recipes that call for it.

Miso — A fermented soybean paste available in white (shiro), red (aka), and mixed (awase) varieties. It appears not just in miso soup but in salad dressings, glazes (miso-glazed cod or aubergine), butter sauces, and desserts like miso caramel. Its presence as a flavouring ingredient — rather than a named sauce — makes it easy to overlook as a soy source.

Textured vegetable protein (TVP) — Defatted soy flour that has been extruded and dried into granules or chunks. It is used as a meat substitute in bolognese, tacos, and burger patties, and sometimes listed in recipes as “textured soy protein” or simply “TVP.” Frittu checks for both “textured vegetable protein” and “tvp” in the keyword list.

Yuba — The thin skin that forms on the surface of soy milk during heating. It is used in Japanese and Chinese cooking as a delicate wrapper, noodle substitute, or garnish in soups. It is a whole-soy product under a name that does not reference soy directly.

Natto — Fermented whole soybeans with a sticky, stringy texture and a pungent, earthy flavour. A traditional Japanese breakfast food, it also appears in sushi rolls (natto maki) and rice dishes. Its fermented form makes it a distinct ingredient from plain soybeans but it is entirely soy-derived.

Edamame — Young, immature soybeans harvested before they harden. Used as a standalone ingredient in salads, rice dishes, and some East Asian soups. Their green colour and fresh flavour make them look different from other soy products, but they are soybeans.

Soy lecithin — A food additive derived from soy, used as an emulsifier to blend fat and water in chocolate, baked goods, and many processed ingredient products. It appears in ingredient lists of ready-made sauces, cooking chocolate, and packaged pastry. Frittu's keyword list checks for “soy lecithin” as a full phrase to catch it specifically.

Tempeh — A fermented whole-soybean cake with a firm texture and nutty flavour. Used as a meat substitute in Indonesian, Thai, and plant-based Western cooking — fried, grilled, crumbled, or marinated. It is a whole-soy product.

Ketjap (manis) — A sweet, thick Indonesian soy sauce with a molasses-like consistency. Used in nasi goreng, satay, and as a finishing glaze for grilled dishes. It is sometimes written as “kecap manis” or simply “ketjap” in recipe ingredient lists — all forms are soy-based.

Teriyaki sauce — Typically a soy-based glaze sweetened with mirin and sugar, used on grilled chicken, salmon, and tofu in Japanese and Japanese-inspired cooking. Most commercial and recipe-made teriyaki sauces have soy sauce as their primary liquid ingredient.

Oyster sauce — Many oyster sauces use soy as a base liquid alongside the oyster extract. For this reason, oyster sauce appears in both Frittu's soy keyword list and its shellfish keyword list — each allergen check runs independently, so a recipe containing oyster sauce would be flagged by whichever check corresponds to your allergen profile.

Note on tamari. Tamari is widely used as a wheat-free alternative to soy sauce, which is why it matters separately to people who avoid both wheat and soy. But tamari is still a soy product — it is brewed from soybeans, just without wheat as a fermentation substrate. When soy is excluded from your profile, tamari is treated the same as any other soy ingredient: a recipe that lists it is rejected and Frittu attempts to generate an alternative.

Frequently asked questions

How does Frittu's system check for soy in a generated recipe?

Frittu uses a two-layer process. First, before generating a recipe, Claude is given an exclusion list built from your allergen profile. For soy, that list covers the ingredient itself as well as its many aliases — fermented pastes like miso, doenjang, and gochujang; condiments like tamari, hoisin, and teriyaki sauce; whole-bean products like tofu, tempeh, edamame, and natto; and processed derivatives like soy lecithin, soy flour, and textured vegetable protein. Claude is instructed to build the recipe without those ingredients. After the recipe is returned, a server-side function checks every ingredient name against a coded keyword list for soy. Any match causes the recipe to be rejected and Frittu attempts to generate an alternative.

Does tamari trigger the soy check?

Yes. Tamari is a soy sauce brewed without wheat — which makes it the go-to alternative for people avoiding gluten — but it still contains soy. Frittu's check matches "tamari" as a standalone ingredient word so that unrelated ingredient names containing the same letters are not flagged. When soy is excluded from your profile, any recipe that calls for tamari is rejected and Frittu attempts to generate an alternative.

What is doubanjiang and why is it in the soy keyword list?

Doubanjiang is a fermented broad bean and chilli paste that is central to Sichuan cooking — it forms the base of mapo tofu, many Sichuan braises, and dishes like dan dan noodles. Most commercial versions of doubanjiang also contain soy, in addition to the broad beans. Because its soy content is not always apparent from a recipe's ingredient name alone, Frittu includes it explicitly in the soy keyword list. Any recipe that lists doubanjiang as an ingredient is rejected and regenerated when soy is excluded from your profile.

Is oyster sauce in the soy keyword list?

Yes. Many oyster sauces use soy as a base ingredient alongside the oyster extract. For that reason, oyster sauce appears in Frittu's soy keyword list. It also appears in Frittu's shellfish keyword list, because the oyster content is itself a shellfish allergen. Each allergen check runs independently — so if soy is excluded, the soy check flags oyster sauce; if shellfish is excluded, the shellfish check flags it separately. A recipe that contains oyster sauce would be caught by either check when the corresponding allergen is in your profile.

What happens when a generated recipe triggers the soy check?

The recipe is rejected before it is saved or shown to you. Frittu retries the generation automatically. The rejection and retry happen server-side — you see only the final recipe that passed the check. If a generated recipe matches a soy keyword it is rejected and Frittu attempts to generate an alternative; if none passes the check, no recipe is returned for that slot.

What this check covers and what it does not

Frittu's allergen check operates on ingredient names as listed in a generated recipe. It is a keyword-matching system applied to text, not a chemical analysis of food. It does not account for cross-contamination during preparation, incidental contact through shared kitchen equipment, or soy present in ingredients a user sources or adds themselves after receiving the recipe.

The keyword list is maintained and expanded as new recipe patterns are identified, but no keyword list can be exhaustive against all possible ingredient names an AI model might generate. The two-layer design — prompt-side exclusion instruction followed by post-generation keyword scan — is intended to reduce the likelihood of a soy-derived ingredient appearing in a recipe, not to produce a result that can be treated as independently verified.

If you have a significant soy allergy or prepare food for someone who does, the standard precautions around cross-contamination, shared cookware, and label-reading on packaged ingredients remain relevant regardless of what a recipe generator produces.

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