I was worried about the preservatives also so I used two packets of yeast. I mixed up the must (juice, blend, bananas, sugar, water, etc) and let it sit 12 hours. During that 12 hours I made a starter (1/2 cup water, 1/2 cup must, pinch of energizer, yeast) and every 2 hours I added another 1/2 cup of must. After 12 hours I had a vigorous starter. I dumped the starter and pitched the second packet on top (Why? Well I dunno for sure but it made me feel good). Worked like a charm.