Rwandan scientists develop local yeast for banana wine-makers | Hacker News Reader

Rwandan scientists develop local yeast for banana wine-makers

phys.org

181 pointsPaulHoule80 comments

“The team looked for a fermenting agent that could remain reactive in substances with a temperature of up to 370 degrees Celsius and alcohol of the recommended 16 percent per volume.”

My guess is that the reporter forgot a decimal point and meant 37.0 degrees Celsius. Because finding a yeast that actively metabolizes sugar at 370 degrees Celsius might be somewhat challenging.

Yiest that could survive in volcanic geysers is a bit terrifying to think about.

It turns out that the Yellowstone Supervolcano is actually over-risen bread...

free kombucha!

Still, the research itself is pretty exciting. It’s cool to see traditional methods getting scientific backing

This made me snort my coffee, what backing was needed or lacking? Need peer-review to validate them?

Consistency and reproducibility is important part of scientific backing, too.

Optimal temperature for yeast in general is between 25-30C, for grape wine optimal fermentation is usually between 15-20C (white) 20-25C (red).

So 35C is interesting. 350 would be too much even if it was Kelvin.

Kveik beer yeast often works well far above 35C. Some reportedly tolerate into low 40s.

I don’t know of other yeasts that can do this though.

I was going to say, just throw some kiveik in it. That stuff is practically fool-proof

Mmm, caramel sweet wine, perhaps?

Especially given glucose decomposes under 200C.

New fermentothermal electricity power source discovered!

Bananas are notoriously hard to turn into a cleaner wine, mainly because of the fact that most bananas that are not Cavendish have a lot of latex and turn into goop. Most of the places where banana wine is produced (tropics) ultimately also turn it into banana "gin", and there's an incredibly deep and long cultural history of its production, e.g. it's tied to British colonialism in West Africa funded by liquor revenues, regulation was a hot topic of local protests, and drinking bars used to be hotbeds of nationalist agitation. When Nkrumah's CPP took over Ghana, they legalized homemade wine/liquor as a symbol against the gin drinking imperialists (in 1890 a bunch of countries in Brussels banned liquor importation to Africa).

The other much easier to produce wine and spirit comes from palm sugar (akpeteshie in Ghana, toddy in Indonesia), but the time window of when it is fresh and can be consumed is counted in hours, so it's not stable enough as an agricultural product to sell. Banana wine is an easy way to turn surplus calories into surplus cents.

But fresh palm wine is now bottled for sale in Ghana at least. I know because I've bought some in Ghana several times. Not sure how they preserve the freshness and prevent further fermentation though.

They could pasteurize it or kill the yeast with sulfites like they do with wine.

370 degrees Celsius? Hopefully a typo

Last time I was in Rwanda I had banana wine. It comes in beer bottles.

I think it’s an acquired taste - I didn’t have the acumen to acquire it myself.

Fruit wines are tasty usually. But the hangover is on the next level.

depends on the fruit and how many anti-oxidants managed to survive the brewing process

almost entirely depends on how much water you drink, in my experience

Water is the secret that I wish a younger version of me knew about.

College kids in my day just drank and drank and drank and learned to deal with hangovers.

College kids today tend to alternate one alcoholic to one water. They don't really have hangovers.

They're smarter than we were.

Frank the Tank!

Quasi-mandatory orientation week training about safely drinking really worked – I know college kids who'll eat while they're drinking, and apparently they make make "BORGS" with electrolyte drinks mixed in too.

I just wish they had training about all the avoidable mistakes you'll make in college relationships...

I've heard stories of med students at my former university going on a saline solution IV drip to drink more.

IV therapy is big business in places like Las Vegas.

I find it bewildering that anyone ever didn't know about this. almost like not knowing sex causes babies

Pectin breaks down into methanol. Particularly fruit wines and liqueurs will end up with hyper-concentrated methanol. Water will help but cannot remove the pain of actually passing that methanol.

Granted, it's not so bad with the first glass. But with three, be prepared for a nasty hangover. At least this is my experience with applejack. Professionally-made apple jack may be cleaned up more (I kind of hope it is).

It depends on the aging. The nasty metabolites that affect taste and cause hangovers are slowly converted to less nasty chemicals as the wine ages.

I wish avoiding a hangover was as easy as drinking water.

I get really bad hangover from some wines and beers, and no hangover at all from others. Haven't been able to figure out what the difference is. Wish I could just drink water to avoid it.

However, 400mg of Ibuprofen helps a lot.

All wine is made from fruit.

Unlike classical grape wines, the fruit ones are quite "wet". And sweet alcohol for reasons unknown causes the worst of the hangovers.

It's for the same reason you feel dead after eating a pound of sugar, and compounded with extra dehydration. Take it from a former professional alcoholic, drink your water and take your B vitamins.

is it unknown? sugar competes with aldehyde dehydrogenase.

Isn't "fruit" wine kind of a marketing term for "fruit flavored wine", that is "strawberry wine" is supposed to taste like a treat?

The one alcohol that I've made in large quantities [1] is apple cider [2] which I've always made very dry, even though I perceive it has an apple taste, pear cider tastes like pears, even if it is dry.

In sinosphere adaptations of classical Chinese stories like Romance of the Three Kingdoms people talk about drinking 'wine' but my understanding is that what they drank wasn't made from grapes.

[1] probably drank too much of it one December and might have started to get dependent

[2] on my farm we have a few hedgerows that have apples that are good for eating, seedling apples (in some areas surrounded by hedgerows) are usually yucky for eating, although horses think they are fine and they are great for cider.

For fruit wines: you can ferment any fruit with enough sugar. They tend to be made sweet, as many fruits can have bitter or unpleasant flavors that come out when dry, such as strawberry. That said, one of my favorites was a dry raspberry that my dad made.

The Chinese stories could be referring to rice wine, a spirit similar to sake. If the stories refer to regions along the Silk road though, they could easily also be referring to grape wine.

The Chinese alcoholic drink that I think about today is

https://en.wikipedia.org/wiki/Baijiu

which might have exited in a prototypical form at that time.

That is a distilled spirit.

Mijiu:

https://en.m.wikipedia.org/wiki/Mijiu

is what would be a rice wine. Wikipedia listed it going back as far as 1000 BCE.

It is considered more of a wine than an ale presumably due to the alcohol content, the type of yeast used and how it is usually consumed, despite being a grain beverage (somewhat like barleywine only more so).

Kinda like Japanese Sake?

> Isn't "fruit" wine kind of a marketing term for "fruit flavored wine", that is "strawberry wine" is supposed to taste like a treat?

It shouldn't be, I'm sure there are companies who will sell that as "fruit wine" just as you'll get companies selling industrial alcohol mixed with grape juice as "wine" anywhere where that's legal, but a true fruit wine is made by fermenting that fruit.

Ah ... it has been a long, long time, but I fondly remember imbibing (and then, promptly, exbibing) that great, fruity vintage: Mogen David 20/20.

Toilet-hugging good.

Nope. Rice wine, sorghum wine, barley wine. Those are 3 wines made from grains that I could name off the top of my head.

Barleywine is a beer (it requires malting of the barley) marketed as a wine.

Sorghum wine (baijiu) is a distilled spirit, closer to vodka, mistranslated as a wine.

Rice wine (sake, mijiu) really does seem more like a wine than a beer, apart from the fact that it's made from grain. Not sure what is special about rice that makes it suitable for making wine.

Not true, ever since we had advanced chemistry: https://en.wikipedia.org/wiki/Carbohydrate_synthesis

The phrase I've heard is "country wine" -- e.g., any alcoholic beverage in the ABV of wine (10-18%) but not made exclusively from grapes.

This is because pectin in the fleshier fruits will be metabolised into methanol, which isn't very good for you.

Grapes are less of an issue.

The article mentions that it was provided by SciDev.net.

Looking there you find the original article, and it has the correction to the right temperature: https://www.scidev.net/global/supported-content/rwandan-scie...

> The team looked for a fermenting agent that could remain reactive in substances with a temperature of up to 37 degrees Celsius* and alcohol of the recommended 16 per cent per volume.

> This article was edited on 29/01 to correct the temperature for fermenting to 37 degrees Celsius.

Certain yeasts used in beer brewing produce an ester that is banana-like, especially when brewed at higher temps. It's often considered an off-flavor.

Now I'm really curious to taste banana wine.

Banana is one of those flavors that some people love and some people really hate. Others in this category -- lutefisk, kimchi, certain cheeses -- make sense: their distinctive flavor is associated with decay. Why bananas, though?

My grandfather was a banana hater. His observation on the topic: "I hate bananas, and I'm glad that I hate them, because if I liked them I'd eat them, and I HATE them!"

Bananas are a staple food crop in some parts of Africa.

https://en.m.wikipedia.org/wiki/Matoke

It took me until my 30s to make the connection that bananas cause me intense headaches. I used to love to eat them, but now won't touch them.

I think I'm fine with them cooked, but not raw.

I don't know the mechanism, but if you do searches on bananas and headaches you will find people prescribing them as a cure for headaches, not the other way around.

It could be a latex allergy. Bananas are one of a few fruits that cause latex allergic reactions.

Kiwis. Avocado. Watermelon. Etc etc. the list is long.

I have no problems with those, though. I do recognize the latex "feeling" and irritation, but avocados and kiwis are part of my regular yum-fest

I'm also curious about banana wine… wonder if it leans more toward fresh banana or that overripe, almost fermented taste.

If I had to guess, it would be that fermenting bananas into wine makes them taste like they were fermented.

In all seriousness though, I can’t stand overripe bananas. Bleah.

I went a couple years ago in coutryside Rwanda, where locals brought me to a place where I could have some homemade banana wine, or "Urwagwa" (not sure about the spelling!). That place was someone's house with a few people hanging out and drinking, the wine was served in already-opened glass bottles.

For those curious, it is not very boozy (maybe around 7%-10% abv), but very yeasty - to a point where it kinda numbed my mouth. For those curious the yeast is the dominant flavor, followed by banana. Very earthy taste.

Later on I saw Urwagwa sold in a can at the airport, it was very different, no yeast but bitterness instead. I preferred the homemade one.

The article explains nothing, and has a very suspicious typo. If i heat something organic to 370 degrees i do want it to die :D

The explanation as to why flour yeast and grape wine yeast are unsuitable is a bit of a tautology. I know little about yeast. Can someone explain why one sort of yeast is not suitable for another use? And why is "sorghum, the traditional fermenting agent of banana wine" unsuitable or not acceptable to regulators?

Sorghum is acceptable I believe. It’s the fifth most produced crop in the world. It sounds like what might not have been acceptable is using wild yeasts to ferment it.

It's similar to the malting process. Certain ingredients will contain enzymes and other important metabolites that can break down complex sugars into smaller simpler sugars that can be eaten by yeast (glucose, fructose). You need them to get a fermentation started and warmed up.

Even more confusing: "We mixed the fermenting agent with sorghum flour to keep the traditional color and aroma of sorghum, the traditional fermenting agent of banana wine"

So they developed a yeast to replace the sorghum as the fermenting agent, and then mix sorghum in. What has been gained? Does yeast make for a more controlled fermentation making regulation easier? Or just easier to industrialize?

I suspect that using sorghum for fermentation really means using whatever wild yeast happened to be on the sorghum, and the results too variable to regulate for commercial sale or export.

> I suspect that using sorghum for fermentation really means using whatever wild yeast happened to be on the sorghum, and the results too variable to regulate for commercial sale or export.

Definitely this. Sorghum is not a "fermenting agent": it's not an organism that eats sugars and shits out alcohol and carbon dioxide (actually, it's pretty much the opposite). It's just somewhere wild yeast likes to live.

Different yeasts have different temperature and alcohol tolerance. For example a bread yeast may not continue making alcohol beyond 5-6%, or another yeast may only be productive in a narrow temperature range that’s too warm or too cool for a given application.

To add on, different yeasts also vary in their ability to metabolize carbohydrates. In general, a wine yeast will be less able to metabolize complicated carbohydrates than a beer yeast. Beer yeast tends to be more sensitive than wine to alcohol levels. More importantly, it's possible Rwanda lacks any serious brewer's yeast industry that is suitable. Kveik may be able to ferment at both 37C and up to 16% ABV but that's definitely an unusual trait in a yeast and I would not be surprised if they resulting wine was... funky.

They've been making banana wine from wild yeast presumably for at least a 100 years or longer. It sounds like the regulators in their country are a PITA and won't get out of the way.

There's a million different strains of yeast but they all do the same thing. If you don't add any yeast it will still ferment with the wild yeast.

I was thinking the same. Though wild fermenting works well for small batches, I have no idea of it scales. I was guessing this is a comercial operation if regulators are involved.

Regulation is extremely important, and has been part and parcel of alcohol and wine production since prehistoric times. Besides the health reasons, wine is very easy to cut with synthetic or artificial ingredients, which has important economic and health consequences - hence the use of government bonding for hundreds of years around the world.

But more recently, regulation is vital for setting up geographical indicators for production of items that are locally unique, e.g. Parmesean, Champagne, and the German Reinheitsgebot which are legally protected practices for the reasons in the first paragraph. Being able to identify the specific strains of yeast in this banana wine is a big part for arguing the provenance of it.

You can't create an export market if you product is variable due to your results depending on whatever yeast happened to be used that day.

Lambic beers prove you can do that

So people say. I suspect that as they are made in the same buildings over the decades or even centuries that the yeasts eventually become part of the local ecology and are thus quite stable.

Normally, you ferment at lower temperatures because your drink will taste disgusting… (there will be terrible byproducts) this article has no explanation as to why this traditional drink suddenly tastes fine with a high temperature yeast other than something about regulators accepting some shit. I imagine that traditionally they they didn’t add commercial yeast… they just opened the top of it and prayed.. and the wild yeast which probably where they live Ferments fine at higher temperatures however, I had to make this all up in my head because there is no fucking information in this entire article and certainly no science and I’m amazed it’s number three. What the is this shit

Normally when you make banana wine?

I think you need to try some kveik yeast, that might change your mind on high temperature fermentation: kveik is a Norwegian yeast, somewhat recently (last 25 years) rediscovered but brewed with for centuries, and can handle 37ºC without the byproducts.

Science helping tradition instead of replacing it

bannana wine, just does not work well in.english or bannana beer, or bannana cider, would be interesting to hear the term or terms used localy that might be evocative and perhaps marketable but certain words just dont work together..... like english, and cuisine, ha ha! it is and will forever be english food. rooooll your ooooo's

Sorry, native english speaker here, what is wrong with banana wine?

nothing.....if you can make it work.....but in many native english markets, it wont, cept perhaps the kiddy booze market, where if you mix in enough tuarzine(whatever) and ??? purple blobs of some goo, it will jump off the shelves but as a meal acompanyment, no wait wait, with german desert wines going extinct there could be a market for a desert wine so......go for it, mang!

what they want to achieve? Biofuels?

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