If using the starter culture, stir together the culture and water. Let the mixture sit while you prepare the ingredients—around 10 minutes. If using kefir whey, add it when the recipe calls for culture.
Shred zucchini, sweet potato, and onion with a food processor (using a shredding blade) or by hand with a shredder.
Place vegetables together in a bowl, add salt, and toss to mix together.
Add the juice, Cutting Edge Culture or kefir whey, and cover with water, leaving an inch or two at the top.
Seal the container and let it sit on your kitchen counter, out of direct sunlight, for 3 days. After 3 days, place the jar in the refrigerator.
Check the vegetables every day to make sure they are fully submerged in the water. If they have risen above the water, simply push them down so they are fully covered by the water. If any white spots formed because the veggies rose above the water, do not worry. Remember, this isn’t harmful. Just scoop out the vegetables that have the white spots on them and push the rest back under the water.
Storage note: This kraut can be kept in a covered airtight jar in the refrigerator for up to nine months.