Thirteen mini-ferments on the go!
A few weeks ago I brewed a Blonde ale. This batch was slightly oversized, in order to give me enough wort to do a series of mini ferments in beer bottles, using a selection of the yeasts isolated in my first wild yeast hunt. The goal was simple – to brew a light beer that would let the yeast characteristics dominate, while at the same time producing a beer that would act as both a flavour control, and as a lawnmower beer to get me through the beginning of August.
I selected about half of the 25 strains of yeast I isolated as part of my first wild yeast hunt, and grew up 1ml mini-starters, using 1.040 wort (no hops) and a shaker set at 32C. These ‘starters’ were then stored in a fridge for a few days until I could brew the Droit du seigneur Blonde; a low-hop (17IBU), modest-gravity (1.044) ale. I brewed an extra 5L of this beer, in order to give enough volume to setup 13 100ml mini-ferments, which were inoculated with the mini-starters. A month later I ran a flavour testing series, to see what these wild yeasts had produced. A month may seem like a long time, but since wild yeasts can sometimes be slow, a month gives a long enough ferment for even the slowest of yeasts to ferment to completion.
I did not get any particularly stellar yeasts out of this – about half were oxidative yeasts and barely reduced the gravity of the beer. I was more successful than I had expected – finding four strains with potential. But what really came out of this project is a usable method. SWMBO’d has a garden full of veggies right now all of them covered in local wild yeast!
All the nitty gritty below the fold.
While I ended up with 25 strains of yeast, I didn’t test all of them – both because the strains from the earlier days are unlikely to be fermentative (indeed, no drop in gravity was observed until after day 10), and because many of the strains appeared to be similar in terms of their colony and micrograph morphology. As such, I tried to pick a series of samples which were representative of the yeasts from each sample day, with an emphasis on yeasts from the later days as these later-arising yeasts are the most likely to be of interest. As such, I took one each of the small mucoid, medium powdery, and large mucoid from day 4, colonies #1 & #3 from both day 10 and day 20, and all six strains from day 30.
Yeasts are temporarily named by date, colony type (day 4 only) and their isolation number. I.E. D04SM-1 = day 4, small mucoid, colony #1. D10-3 is day 10, colony 3. I’ll give real names to anything good.
For each strain I am noting the bottle appearance,appearance in the sample glass, aroma, taste, final gravity (FG) of the wort, apparent attenuation (Ap. Atten.), and notes on anything else of interest. All samples – including the ‘control’ glass of Droit du seigneur Blonde (fermented with the very neutral US-05) are being drunk warm (room temperature) and uncarbonated. This brings out the taste of the sample – which, as you’ll soon see – is not always a good thing!
Interesting yeasts are highlighted in yellow, otherwise “notable” ones are highlighted in blue.
D20-1 Fluffy yeast-cake Highly cloudy Unpleasant, fungal sour/estery 1.036 18% Minimal ferment, surprisingly not bad taste.
D30-1 Compact cake Mild cloudiness Fruity esters Dry, astringent, bitter 1.002 95% Highly attenuation, but unpleasant. May work as a co-fermenter with ageing.
D30-4T Thin cake Cloudy Yeast & medicinal (phenolic) Mouldy/mousy 1.036 18% Tastes like Bret, but was minimally fermentative.
D30-5T Cotton-ball yeast cake Mild cloudiness Mouldy Sickingly sweet, horrendous flavour notes 1.040 9% Nasty, flavour outside of what I can find words for.
These are strains which are sufficiently attenuating to be used as the sole organisms in a brew.
D30-6T: Medicinal phenolics, esters and highly attenuating. Ma be Brettanomyces.
D30-1: Lots of fruity esters, attenuates strongly but produces an astringent finish.
These are strains with interesting taste profiles, but which lack the attenuation to be used as the sole strain in a fermentation.
D10-3: Ale-like esters, but minimal attenuation. May work as a co-fermenter, but its hard to conceive of a place where it could be used in place of a real ale yeast.
Very cool stuff. You're brave, tasting some of those!
Interesting results from your hunt. Keep up the good work.