Wild fermentation with improvised equipment, any advice?

Question

First some background. I am in Indonesia for a bit, separated from my equipment and have had a chance to make the native fermented rice dish tape hitam (basically red rice wine without straining, eaten like a porridge. Yes, this is beer you can eat with a fork, quite literally!). Tape Hitam uses a mixture of cultures similar to Sake or Chinese Red Rice Wine. I have also had Tape Putih, which is fermented cassava root using a similar process. At least with Tape Hitam, typically the rice is just covered with a banana leaf. No full seal or airlock is used, though the fermentation is only a few days at (tropical, no-air-conditioning) room temperature.

A few days ago, I had what I thought at the time was intentionally fermented soursop (you may know the fruit as guanabana). It turned out it was not intentionally fermented, but was tasty anyway and rather intoxicating. So I figured I would try to reproduce this, possibly using it as a basis for wines made from local fruit, etc.

So my current plan (which sounds really odd to me and my 20 years of brewing experience) is to follow the process that lead to the unintentional fermentation and do as follows:

let 1-2 soursops fully ripen and begin to go past their ideal ripening point, then scoop out the flesh (omitting any rotten spots) and put in an enclosed tupperware dish in the refridgerator for 2 weeks. I might add some coconut sugar or honey but haven't decided yet. After 2 weeks I will sample and if it is any good will mix in other fruit as I feel like, and grow the fermented fruit at that point kind of like a sourdough culture, preparing of course for some spoilage at some point. If I can get an airlock (and maybe even if I can't), I hope to try to use this as a culture for making mead as well, probably in one of the water dispenser bottles.

Has anyone done anything like this? Any tips or tricks? Or am I pretty much in uncharted territory here?

Answer 1

Ok, so I went and tried it. Maybe I didn't let the soursop get ripe enough or it didn't get the yeasts, or whatever but after a week and a half in the fridge and no evidence of fermentation I gave up on the wild aspect and cultured it with a few tablespoons of the local fermented rice dish, tape hitam (basically red yeast rice mash). This started the fermentation.

Initially I suspected that the original yeast in the first accidental batch (it had a very different, and more yeasty, flavor) must have come from contamination in the container but I dont think that is the case. Instead now, I think I just didn't get ripe enough soursop and will have to try that stage again.

I have now eaten a third or so of the initial batch. It's good and moderately alcoholic. It is a bit of an acquired taste though (not to worry, the local tape hitam and tape putih --- fermented cassava root --- is also!) but so far I am actually enjoying it a bit. I replaced the soursop I ate with mashed mango, so we will see how different mixed fruits interact with it.

All in all relatively successful outside the fact that I was unable to get results with the wild yeast.