Note: if you are seeing a white coating on the surface of your vegetables, it’s most likely Kahm yeast, and perfectly safe.
How full is your culturing vessel?
Culturing is an active process and the vegetables will expand or push up in the jar. This is especially true of shredded vegetables! Leave space for this to happen.
A trick to keep things settled is to wiggle the jar a couple of time a day during the initial week or two of culturing. This will work the bubbles to the top and settle the vegetables back into the brine.
What was your salt to water ratio for the brine?
While possible to ferment without salt, salt does help to preserve texture, flavor and prevent undesirable growth of yeasts.
Even when using starter cultures, we recommend adding at least 2-3 teaspoons of high-quality salt per quart jar.
What is the room temperature of your culturing area?
Warmer temperatures are not necessarily better for fermenting vegetables. We prefer a low temperature, slow ferment for best flavor.
For more information on how temperature affects lacto fermentation see http://www.culturesforhealth.com/learn/natural-fermentation/basic-formula-fermenting-any-vegetable/
Was your culture near any other bacterial sources (like another culture, garbage can, pets, houseplants, soiled laundry, laundry room, compost, ambient mold)?
It’s not guaranteed to ruin a culture, but all these things have their own microbial life. It’s been known to happen, so we recommend keeping things you plan to eat at least 4 feet away from other possible contaminants.
Were your utensils/containers spotlessly clean? No dishwasher soap/food residue? No anti-bacterial soap?
Other food particles, as well as cleanser residue, can play havoc with cultures. We really don’t advocate sterilizing anything, but a good scrub and thorough rinse is a good practice.
Hands clean when working with veggies?
Yup! This is important too. We do still advise skipping the anti-bacterial soap though.
Was the culture in direct sunlight?
Sunlight is a natural anti-microbial. This is great for line-drying towels, but not so good for culturing. Some light is fine, and cultures do well on kitchen counters. However, it’s important to avoid window sills and direct light.
In short, if a batch of fermented vegetables goes bad, it goes horribly bad. So if your vegetables look and smell pleasant, have a small taste. If they taste pleasant, they are safe to consume.