Most ingredients that fail a kosher review are not obviously non-kosher. Nobody submits a formulation with lard in it. The ones that cause problems are ingredients whose status depends entirely on a source you cannot see from the name — and they are extremely common.
This is the list to check your own formulation against before you apply.
Always prohibited
- Pork and all pork derivatives
- Shellfish, crustaceans and molluscs — shrimp, lobster, crab, clams, oysters, scallops, squid, octopus
- Fish without fins and removable scales — catfish, eel, shark, monkfish, sturgeon (and therefore most true caviar)
- Birds of prey and non-traditional poultry species
- Insects, other than a few locust species with an unbroken tradition
- Meat and dairy combined in one product
- Blood
- Meat or poultry that was not slaughtered and prepared under supervision — ordinary commercial beef and chicken are not kosher, regardless of the animal
Depends entirely on the source — the real list
This is where certifications actually get held up.
| Ingredient | Why it is a question |
|---|---|
| Gelatin | Usually from non-kosher hide or bone. Fish and certified-bovine sources exist and are a different product. |
| Enzymes | May be animal, microbial or plant-derived, and microbial ones may be grown on dairy or other media. |
| Rennet | Animal, microbial or fermentation-produced — and cheese carries its own requirement regardless. |
| Glycerin / glycerol | Animal or vegetable. Extremely common in supplements, confectionery and coatings. |
| Mono- and diglycerides | Animal or vegetable. Ubiquitous in bakery and fats. |
| Stearates, stearic acid, magnesium stearate | Animal or vegetable. Standard in tablets and capsules. |
| Emulsifiers (polysorbates, lecithin) | Source-dependent; lecithin may be soy, sunflower or egg. |
| Natural and artificial flavours | A flavour is a formulation with its own ingredients and carriers, often including dairy or grape derivatives. The name tells you nothing. |
| Carmine / cochineal / E120 | Derived from insects. Not kosher. |
| L-cysteine | May be derived from human hair or feathers. Common as a dough conditioner. |
| Whey, lactose, caseinate, milk solids | Kosher, but dairy — they will make a pareve product dairy. |
| Grape juice, concentrate, wine, wine vinegar | Grape products carry their own requirements independent of everything else. |
| Vitamins and nutrient premixes | Carriers and stabilisers are frequently animal-derived; vitamin D3 is commonly from lanolin. |
| Omega-3 and fish oils | Species matters. |
| Bone char-filtered sugar | A question depending on the refinery. |
| Shellac / confectioner’s glaze | Insect-derived; status depends on the view taken and the grade. |
| Activated charcoal, filtration aids, processing aids | Never on your label, frequently on the review. |
| Release agents and pan sprays | Often butter-based. A recurring cause of an unexpected dairy designation. |
Insects in produce — the issue nobody expects
If you process fruit or vegetables, this is likely your biggest exposure, and it is treated seriously.
The obligation to check applies where a vegetable type has a commonly occurring level of infestation. One approach quantifies that at around a tenth of samples; another declines to fix a number and asks instead which vegetables are known in practice to be infested. Where more than half of servings are affected, the prohibition is Torah-level rather than rabbinic.
Three consequences matter commercially:
- A whole insect cannot be nullified. Unlike most prohibited substances, which can be disregarded below a ratio, an intact insect is treated as a distinct entity and no amount of surrounding product dilutes it. A removable fragment cannot be disregarded either.
- You cannot purée the problem away. Deliberately destroying insects by blending to make a product acceptable is not permitted, and a certifier cannot approve it. There is a narrow allowance where a product is cooked or sieved in the way it would be prepared anyway, and the specific batch is not known to be infested — but not where the processing exists to solve the problem.
- Packing in an opaque medium is not a solution. Obscuring insects in thick oil does not address the issue.
Insects invisible to the naked eye are not a concern — nobody is expected to inspect produce under magnification. The difficulty is the middle case: specks visible as dark spots that an ordinary person can learn to recognise with a little practice. Those count.
The practical answers are agricultural and procedural: source from growers with lower infestation, use varieties and growing methods that reduce it, and build a validated washing and inspection process. Products commonly requiring attention include leafy greens, broccoli, cauliflower, brussels sprouts, asparagus, artichokes, berries — raspberries especially — figs, dates and some dried fruit and herbs.
How to use this list
- Go through your full formulation, including processing aids, release agents, filtration media and rework — not just the label declaration.
- Flag every ingredient above. Flagged does not mean disqualified; it means the source has to be established.
- Request a current kosher certificate from each supplier, starting now. This is the bottleneck in every certification.
- Look hardest at flavours, enzymes and premixes, which hide the most sub-ingredients.
- Ask us about anything you are unsure of before you reformulate. Kosher alternatives exist for almost everything here, and it is often a supplier change rather than a recipe change.
Send us your ingredient list and we will tell you which items need tracing and which are straightforward — no fee, no obligation. Get a free quote, or read whether your product needs certification and how long it takes.