Home made yeast.

Prep Time: 10 minutes

Ingredients

Whole wheat flour
Unsweetened pineapple juice (or Vinegar)
Purified water

Instructions:

Step 1. Mix 3 ½ tbs. whole wheat flour with ¼ cup unsweetened pineapple juice. Cover and set aside for 48 hours at room temperature. Stir vigorously 2-3x/day. (“Unsweetened” in this case simply means no extra sugar added).
Step 2. Add to the above 2 tbs. whole wheat flour and 2 tbs. pineapple juice. Cover and set aside for a day or two. Stir vigorously 2-3x/day. You should see some activity of fermentation within 48 hours. If you don’t, you may want to toss this and start over (or go buy some!)
Step 3. Add to the above 5 ¼ tbs. whole wheat flour and 3 tbs. purified water. Cover and set aside for 24 hours.
Step 4. Add ½ cup whole wheat flour and 1/4 to 1/3 cup purified water. You should have a very healthy sourdough starter by now.