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I'm a senior student, experimenting on alcohol concentration of wine using different variables. My variables are white wine yeast and brewing yeast and whilst I know the main role, I would like to delve deeper and know the chemistry behind it.

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This question is possibly far too broad for the scope of this site, but I'll do my best to point you in the right direction.

Other than consuming sugar and excreting alcohol, yeast's abilities vary strain-to-strain (and sometimes even by brand). Lalvin 71B, for example, is known for its ability to consume malic acid. EC-1118 and K1V-1116/ICV K1 are great for dominating other strains and restarting stuck fermentations. Wyeast 1388 is a Belgian strong ale yeast that apparently consumes honey like it's its job. Meanwhile, White Labs WLP001 California Ale Yeast remains relatively neutral, and can be used for a wide variety of beers, meads, and ciders.

To get a better idea of what I mean, check out this PDF from Wine Business about choosing a yeast for chardonnay:

http://www.winebusiness.com/content/File/wbm_Aug2006_yeast_chart.pdf

It lists 39 yeast strains from 11 manufacturers (16 brands) that can be used for making chardonnay, and the different properties they impart on the final product. If you wanted something ester-heavy, for example, you might choose Red Star's Côte de Blanc. If you were unable to regulate temperature and needed something resistant to cold and heat, you could choose Lalvin's EC-1118 and K1V-1116. Those two are also very alcohol tolerant, and can easily make it up to the 18%-20% range through step-feeding fermentables along with a good nutrient schedule and pH management.

If you are interested in the specific biology or chemistry of it (how does a yeast eat malic acid, anyway?), the best place to start is on a particular manufacturer's website. Once you have an idea of what you're looking for, you can find hundreds of studies across the web looking at specific properties in depth.

Interesting side note, the abstract on that malic acid pdf I linked noted that Lalvin 71B consumed 33% of the malic acid in their test without the help of malolactic bacteria, while keeping SO2 production to a minimum. The bacteria converted 100%, sure, but the yeast was still very impressive on its own.

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