Brew With Us ESSENTIALS – yeasts beyond beer

Posted on 23rd June 2022

The Sacc strikes back!

Wild yeast and bacteria are great, but Saccharomyces still has some tricks up its sleeve…

Right back at the beginning of our yeasty journey, we mentioned that Saccharomyces cerevisiae wasn’t just the main yeast used for beer – the same species is used for pretty much every other kind of alcoholic fermentation you can think of. And for making bread. Oh, and that nutritional yeast you can eat? It’s all Saccharomyces.

Mead, wine, and cider

Yeast strains for fermenting mead, wine, and cider are relatively interchangeable depending on the end result you’re targeting (dry or sweet, aromatic or neutral, etc.). These strains can typically stand higher levels of alcohol than beer yeasts (around 15% ABV maximum). They also tend to produce high levels of floral and fruity esters that complement the sugars and fruits in these drinks – honey, apples, grapes, and pretty much any other fruit you can think of.

Wine corks
Pint of cider

These yeasts don’t usually taste that good when used in beer – they are adapted to fermenting sugars from fruit rather than malt and can produce a lot of phenolic and sulphury flavours. They also often produce acetaldehyde, a “cidery” green apple note usually considered a fault in beer. Though some intrepid beer brewers are experimenting with using small amounts of wine yeast in combination with beer yeasts to make beer/wine hybrids, trying to get the best of both worlds – the crisp fruit flavours of wine yeasts without the off flavours.

Keeving

An interesting fermentation technique seen in some artisan ciders is “keeving”. Most cider yeasts finish very dry, so medium or sweet cider has artificial sweeteners added. The keeving process controls the yeast to leave a natural level of sweetness with no need for additives.

The process relies on the pectins found in apples. In many commercial operations, pectin is removed as it can lead to a cloudy end product. When keeving, the pectin is left in, and allowed to form a gel-like cap at the top of the fermenter. Cider yeasts need nitrogen from the air to grow, so with the air blocked off by the pectin cap, fermentation finishes early, giving a complex flavour with some sugar left intact.

This is a very delicate process and not often attempted by home cidermakers – though in theory it is possible!

Spirits

Spirits and liqueurs

You might imagine that the main difference between a yeast for making vodka, whiskey, or rum and one for making beer is the level of alcohol they have to cope with. Spirits are, after all, usually upwards of 40% ABV! But spirit washes (the stage before distillation) are typically no more than 10-15%, and sometimes more like 7-8% – like a strong beer. So the yeasts used here are no more alcohol tolerant than regular beer yeasts.

The first main difference is how dry spirit yeasts ferment. Most spirit yeasts will finish at gravities of 1.000 or even less. They ferment all the sugars available, far more than most beer yeasts (spirit washes are also specially made to be more fermentable).

The second difference is in the flavour. Distilling concentrates flavours over and over, so even tiny notes can become huge. Spirit yeasts are extremely neutral in flavour compared to beer or wine yeasts, but this is a good thing: the big flavours of those other strains would be massively overpowering after distillation. It’s not just pleasant flavours that get amplified, either, so it’s vital for a spirit yeast to finish without even the slightest off note.

Even though spirit yeasts are super clean and neutral, there are differences between strains for different spirits. As with mead, wine, and cider, the yeast strain has to be adapted to the particular kind of sugars in the wash. Molasses contains very different sugars than a barley mash, so it follows that rum yeasts are different from scotch whisky strains.

Hard seltzer

What happens if you use a super neutral yeast – like the ones for spirit washes – and don’t distill the end product? That’s pretty much how hard seltzer is made. A very clean yeast chews through the sugars in a seltzer, finishes dry, and leaves a blank slate for fruit and other added flavours. However, because seltzers are made from simple sugars like dextrose, you can use pretty much any yeast you like, including beer yeasts (even kveik!).

Hard seltzer

Sake

Sake is commonly thought of as rice wine, though in truth the way it’s made is closer to a beer. Just as in beer, enzymes convert starches from a grain (rice rather than barley), then good old Saccharomyces turns that into alcohol, CO2, and flavour! However, where barley contains its own enzymes, rice doesn’t.

This is where koji comes in. Koji is a type of non-toxic mould (the Aspergillus species) that produces the same kind of enzymes as barley. Unlike in beer, though, where we would release sugar from the barley in a mash step completely separate to fermentation, in sake the two steps are done at the same time.

The process starts with gently steamed rice and water. Koji and sake yeasts are added together in a mixed culture called shubo. As the koji slowly releases sugars from the rice, the sake yeast ferments them immediately. More water, steamed rice, and shubo are added to the fermenter over a total of three stages to complete the fermentation.

Sake yeasts are adapted to consume the specific types of sugar released by this process, so like many other yeasts mentioned here, they don’t necessarily produce their best flavours in other contexts – though as always, you’ll find some brewers experimenting!

Bread

Bread ingredients

In the 19th Century, bakers got their yeast from breweries – so there really was no difference between the strains used. Over time, though, the strains used for baking have become quite different. They act extremely fast, partly as a result of the way they’ve been dried: the process makes the yeast lay down reserves of energy, so when the yeast is rehydrated, it burns through its reserves and gets growing immediately, skipping the lag phase typically seen with beer yeasts.

You can use bread yeast for alcoholic fermentation, though it tends to throw some pretty funky flavours out, including isoamyl acetate – the fake foam banana flavour produced by wheat beer yeasts.

Some of the traditional farmhouse brewers in Northern Europe didn’t mind these flavours and abandoned their kveik cultures in favour of cheap and readily available bread yeast. Sahti, a Finnish style of farmhouse ale, is almost always made now using a specific Finnish brand of bread yeast.

SCOBY

Many fermented products use a mixture of yeasts and bacteria, working together. This is often called a SCOBY, which stands for “Symbiotic Colony Of Bacteria and Yeast” – you can see why an acronym is needed!

A good example of a SCOBY is “ginger beer plant”. This is a mixture of a yeast (Saccharomyces florentinus) and lactic acid producing bacteria. The SCOBY forms a gel-like layer after fermentation than can easily be harvested from each batch of ginger beer to be used over and again. You can make also ginger beer with regular bread yeast, or a specific ginger beer yeast, but a ginger beer plant is more traditional.

Kombucha also uses a SCOBY, often termed a “mother” or “mushroom”. These SCOBYs usually include bacteria that produce acetic acid, an important part of the kombucha flavour.

Sourdough cultures are also SCOBYs. Many sourdough cultures are passed down through families, a bit like kveik cultures, and most are unique, with no single standard for what yeasts or bacteria are included.

Kombucha

Show what you know!

We’ve learned about the huge variety of yeasts available.

Now let’s get back to the recipes and see how they’re used!

All content © The Malt Miller 2022

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