Fermented dairy products are cultured at room temperature or above. After they reach the desired fermentation, you chill them to slow the fermentation. For fermented dairy recipes, follow the recipe to the letter, taste it, and decide whether to stick with the same storage time based on how well you like the flavor.
Though properly fermented food doesn't go bad, it does eventually become too sour-tasting to enjoy eating.
Serve fermented dairy products at their optimal flavor, especially when you're introducing someone to the idea of home-fermented items. For someone who's new to the taste, the tanginess may be off-putting if the product is overripe.
When serving things like yogurt and kefir, many people expect a highly sweetened taste. To retrain their palate, add natural sweeteners like honey, maple syrup, or organic sugar to the recipe. You can slowly cut back as their taste develops for the unsweetened product.
As with any new food, moderation is key. Try eating (or drinking) your new food in small amounts to gauge your reaction to it. Although you should never feel ill, fermented foods can produce gas or slight bloating in some people at first. A good rule is to start with no more than 1/4 cup of fermented dairy product a day for the first week. Then increase the amount the following week to give your system time to adjust.
If your fermented dairy seems too strong or sour, try reducing the time of fermentation for the next batch. Chilling it, sweetening it, and adding it to other foods are also good ways to help you get used to the natural tang.
As with any fermenting, use nonreactive containers, rather than plastic; glass is the perfect vessel for most of your fermenting. It's easy to clean, it doesn't harbor odors, and you can recycle it. Other choices are stainless-steel and enamel-coated containers or lead-free crocks.