A starter culture is a microbiological culture that actually performs fermentation. Starters usually consist of a cultivation medium — such as grains, seeds, or nutrient liquids — that have been well colonized by the microorganisms used for the fermentation.
Here are various options for some great, nondairy, fruit-fermentation starters:
Finished water kefir: You use this at the same rate as whey: about 1/4 cup per quart of ferment.
Leftover fermented juice: The juice of previously fermented pickles, sauerkraut, or other ferments is rich with bene�?cial organisms. You use it at the same rate as whey, a commonly used fermenting substance from milk. However, keep flavor matching in mind; a pickle juice starter probably won't taste very good inside fruit ferment.
Vegan probiotic starter: You can purchase this easy-to-source powder and mix it with water or nondairy milk to make the equivalent of a whey starter.
Water kefir grains: You use 1 tablespoon extra water ke�?r grains per quart of ferment and scale up from there. Similarly (although not nondairy), you can use 1-1/2 teaspoons of extra dairy ke�?r grains per quart of ferment.
What if a recipe doesn't specify a starter culture and you want to use one? Generally, 1/4 cup of liquid starter works for 1 quart of ferment. Scale up accordingly. If a recipe calls for another amount, by all means follow the wisdom of the recipe author. However, like many aspects of traditional cooking, starter culture usage isn't an exact science, and a range of amounts will probably work.
When using whey in fruit fermentation, recipes just say: No whey, Jose! Whey is derived from cheese and is a milk product. It may be familiar to you as a nutritional supplement; bodybuilders use it as an added protein source. If you do choose to explore using whey as a fermentation starter, keep in mind that the whey used as a nutritional supplement isn't the same type of whey used for fermentations, so you should explore making your own at home.
