Safety notes

1. General rules

• When in doubt, throw it out. Do not taste a product if its smell, look or texture seems suspicious, or if you have doubts about how the process went.
• Wash your hands and use well-cleaned jars, bottles and tools, rinsed of any detergent.
• Use fresh, sound ingredients; discard bruised or moldy parts.
• Label every batch with its contents and start date (fermentLab prints labels with a QR code).
• Recipes from other users are not verified by us: check ingredients, allergens and quantities before using them.
• If you have health conditions or allergies, are pregnant, or serve the products to children, older people or people with weakened immunity, ask a doctor or a professional first.

2. Warning signs

Throw everything away (starters and SCOBY included, if involved) when you see:

• mold: fuzzy or raised spots, green, blue, black, pink or orange, on the surface or on the ingredients;
• a rotten, putrid or solvent smell, very different from the usual sour or yeasty one;
• slimy or stringy liquid, unusual colours, ingredients that turn mushy or fall apart in an unusual way;
• bulging lids or leaking jars when you do not expect them.

A flat, even white film on vegetables ("kahm" yeast) is usually not dangerous but spoils the taste: remove it and make sure everything stays submerged. If you are not sure it is kahm and not mold, throw it out.

3. Lacto-fermented vegetables

• Salt protects the fermentation: it usually stays between 2 and 3% of the total weight of vegetables and water (fermentLab works it out for you). Below 2% the risk of spoilage rises.
• Vegetables must always stay below the liquid: use weights, leaves or brine bags. Whatever floats is where mold grows.
• A good fermentation turns sour: the pH must drop below 4.6 (better around 4 or lower) before long storage or eating. If you measure the pH, log it in the timeline.
• Ferment at a cool room temperature (about 18–22 °C); once done, keep it in the fridge.

4. Kombucha and jun

• Always add a good amount of already sour starter liquid (about 10% of the volume or more): it lowers the pH right away and protects against mold in the first days.
• Use glass or food-grade stainless steel containers. Avoid reactive metals, non-food plastic and ceramics with glazes that might contain lead: the drink is acidic and can corrode them.
• If mold appears on the SCOBY, throw away both the SCOBY and the liquid.
• They contain caffeine (from the tea) and a little alcohol, and are very acidic: drink them in moderation, especially if you have stomach or dental problems.

5. Milk kefir and yogurt

• Use pasteurised or UHT milk. Raw milk can carry dangerous bacteria, especially for children, pregnant women, older people and vulnerable people.
• Respect the temperatures: yogurt incubates warm for a few hours, then goes straight into the fridge. Do not leave milk lukewarm for longer than needed.
• A good product smells fresh and tangy: if it is bitter, putrid or moldy, throw it out.

6. Bottles, gas and second fermentation

Kombucha, water kefir and wild sodas (ginger bug, tepache, kvass…) in closed bottles build up gas: the wrong or a forgotten bottle can burst.

• Use thick bottles made for pressure (swing-top or beer bottles); never decorative bottles, jars or thin glass.
• Do not fill them to the brim and open them every day to release the gas ("burping"), ideally with a cloth on top and away from your face.
• A plastic bottle made for fizzy drinks helps you tell when the pressure is high (it becomes hard).
• When the fizz is right, move everything to the fridge: cold slows fermentation down. Open chilled bottles carefully.

7. Alcohol

Every yeast fermentation produces some alcohol: usually little, but in sweeter, warmer or longer fermentations it can exceed 1% or more. These drinks are not suitable for minors, during pregnancy, for drivers or for anyone who does not drink alcohol for health or personal reasons.

8. Botulism and preserves

• Botulism develops in low-acid, airless preparations. Successful fermentations are acidic and keep it away: that is why the right salt and the pH drop matter.
• Do not store raw garlic, herbs or vegetables in oil at room temperature: they are not fermentations and are among the riskiest preparations.
• Do not vacuum-seal or home-can low-acid preparations without following tested procedures.

9. Starters and swaps

• A healthy starter has its typical smell and look: if it is moldy or smells odd, do not use it or share it.
• If you receive or give away a starter, use clean, closed containers and keep it cool while travelling.
• Every exchange between users takes place under the responsibility of the people involved.

10. If you feel unwell

If after eating or drinking a fermented product you have symptoms such as nausea, vomiting, diarrhoea, fever or, more rarely, blurred vision, difficulty swallowing or breathing, contact a doctor or a poison control centre right away; in serious cases call 112 (the European emergency number). If you can, bring the product or its label with you.