Grains are by far the most common seeds to use as substrate. I've made it with spelt berries, and barley (the unhulled kind with a thick hull still on it). The spelt rejuvelac turned out better for me than the barley rejuvelac. The original version uses wheat berries. Sprout people recommend rye. But I've also seen references to people using legumes such as lentil or mung. So in the spirit of Dennis Moore, I figured, why not try lupins, and it wound up working ok. I use tap water exclusively because it's convenient, but other recipes I've seen, including the original, recommend using "purified water".
- Soak 1/3 cup of dry lupin seeds for 24 hour
- Drain off water and pick out unswelled seeds (if you soak these longer, they will actually swell eventually but in the interest of time, just take them out)
- Let remaining seeds sprout for 24-48 hours, rinsing and draining every 12 hours or so (I sprouted for 36 hours, but I think that whenever the tails are at least as long as the bean, you should be ok) (the original recipe also specifically says not to rinse, so you can probably get away with skipping that step and it may give you a stronger brew)
- Take out any seeds that didn't sprout
- Cover sprouts with 2 quarts of water
- let sit at room temperature for 4 days (I swirl it around about once a day, but that might not be necessary), or until the rejuvelac is as strong as you prefer.
I drain the finished rejuvelac off into another pitcher, then I refill the first pitcher and make another batch. After the second batch, I cook up the sprouts (which probably causes Ann Wigmore some postmortem restlessness, for which I apologize) and eat them with rice or quinoa.
Conclusion: Lupin actually makes decent rejuvelac, nevertheless, I drink it with a squirt of lemon. It's not as good as spelt rejuvelac, but better than barley rejuvelac. I'm sure the process could be optimized to make a better brew: for example by increasing the amount of sprouts, the sprouting time, or the rejuvelac incubation time. For the purposes of a dinner to be served to guests, I would be hesitant to include this on the menu, at least the current version of this, because it has a taste and smell that I think are too unfamiliar to most people. For myself, I may make it from time to time because it's an interesting flavor and I can cook up and eat the beans afterwards, so it's not as though it is a waste of good lupins.