Science Questions

How did our ancestors make wine?

Tue, 20th Nov 2012

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Question

Les in Over asked:

I was wondering how could the Romans and predecessors to their great empire manage to make wine? Hygiene seems to be needed to make it these days!

Answer

Chris -   What an excellent question.  So what you're saying is that these days, when we try to make beverages, then if weíre not careful, they end up contaminated and spoiled. 

The answer is, itís the same when they used to make beer.  In fact, people used to drink a lot of beer in Roman times.  It wasnít the high strength stuff we have today but because the water was so contaminated, the wine and the beer were better to drink because they were less likely to be contaminated because they had alcohol in them. 

Basically, if you take grapes and just pick them off the vine and you have relatively good clean starting water, what you're actually relying on is not having sterility in the system because the yeast all comes from the grapes in the first place.  If youíve ever picked fruit Ė you might have noticed this Les Ė if you look at the surface of a fruit, unless you buy it from a supermarket Ė what does the surface of a picked plum or some grapes look like if you look at them?

Les -   Itís got a little bloom to it usually, almost a coating effect, I suppose you could say.

Chris -   Thatís right and if you were to take some of that coat and then put it under a microscope, what you would see is that thatís mainly yeasts.  So there are microorganisms there, but there are lots of yeasts in particular naturally on the fruit.   If you put those into ideal conditions so the yeast can start to grow, and what the yeast is going to be doing is to consume the sugars in the fruit.  If you do it without oxygen being there, itís going to convert the sugar into alcohol and some carbon dioxide.  Because there's so much yeast there, pretty quickly it will outcompete the other things that shouldnít be there and it will supress their growth because the alcohol they produce is toxic to the other organisms.  The yeast can tolerate it though and so, the yeast outgrows other microorganisms.  You end up fermenting the wine and you make a high alcohol or relatively high alcohol beverage where youíve used the alcohol actually to supress the harmful microorganisms.  This means it's effectively self-sterilising.

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How would you say "wine tasting" in Latin?

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makehomemadewine.org Ribrow, Fri, 22nd Mar 2013

I'm not a microbiologist, but I am an avid home brew hobbyist and a scientist, so I read a lot of geeky stuff about fermentation science.

One thing that Chris didn't touch on is that the Romans weren't necessarily making good wine compared to what we know today.  Most modern alcoholic beverages are fermented with some strain of Saccharomyces cerevisiae to produce desirable flavor profiles in the finished product.  However, there are other strains of yeasts and bacteria that can tolerate the low PH and high alcohol environment of beer and wine (thankfully, none of them cause disease).  They do cause flavors that are generally perceived as "flaws" in finished beer: often described as "barnyard" flavors (yeast in the genus Brettanomyces) or acidic (lactic acid producing bacteria).   

If you innoculate a wine by throwing in a handful of grapes or letting wild yeasts from the air settle into it to begin fermentation, you never know quite what you'll get out.  This is why most modern breweries and wineries rely on sanitization and use only particular strains of yeast in order to have more control over the flavors in their product.  Some wineries and breweries still use traditional methods: in particular, many Belgian breweries use "spontaneous fermentation" which refers to letting yeasts and bacteria from the air land in the unfermented beer in order to start fermentation (a technique that's catching on in many artisinal breweries around the world).  I'm less familiar with the wine world, but I'm sure some wineries do it as well. jpetruccelli, Fri, 22nd Mar 2013

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