Fermenting is an ancient form of preserving food - it was around long before refrigerators. Making sure your preparation area, equipment and hands are clean will go a long way to creating a healthy and safe fermenting environment. Having said that, fermented foods have a limited shelf life. Spoiled fermented foods are not good for you. Like any food, if a fermented food smells unmistakenly rancid or putrid, don't eat it.