You never know what you'll find on a piece of fruit!

You never know what you'll find on a piece of fruit!

In case you hadn't noticed already, I love to get my hands dirty and make/build/grow anything and everything wherever possible. And what better thing to capture and harvest for a brewer than yeast in your very own backyard? It's a good time of year to do this when the flowers are blooming and fruits are abundant in the warmer weather.

Yeast is everywhere. In the garden, on food, on your skin, on your dog… everywhere! This microscopic fungus, specifically the strain Saccharomyces Cerevisae or “Brewer’s Yeast” plays a very important role in beer production with the vital responsibility of converting sugar into alcohol. A side effect of this reaction is that the yeast also produces some delicious (and some not so pleasant) esters. The flavours and aromas developed depend on variables such as the strain of yeast, the temperature of fermentation and the availability of key yeast nutrients in the wort.

The skin of fruit has a plethora of yeasty goodness on it. The apricot tree that we sampled grew a yeast with a delicious sweet apricot aroma... apricot beer anyone?

The skin of fruit has a plethora of yeasty goodness on it. The apricot tree that we sampled grew a yeast with a delicious sweet apricot aroma... apricot beer anyone?

Historically, before the invention of microscopes, the brewer’s would leave the wort to cool outside and voila! Magically, it turned into beer overnight. Of course it wasn’t magic, it was simply science; wild yeast floating about in the air had landed in the wort and couldn’t believe their luck to land in such a sugary feast. Unfortunately there were also a number of undesirable yeast strains and bacteria in the air. These days with technological advances in microbiology, it is possible to collect a sample from a surface and if yeast starts to grow upon incubation, it is possible to isolate the yeast from any other things lurking in the sample and grow the yeast to brew a beer. Some breweries have done this, for example Rogue Brewery in Oregon and the famous “Beard Beer” from the yeast harvested from the head brewer’s own facial hair. In Gisborne, the brewer’s from 7Cent swabbed their navels in order to brew their “Belly Button witbier” (which despite the name is admittedly a delicious brew!).

Alfie!!! Such a sweet innocent looking dog... his tongue... not so sweet! #blackmouldgrowth

Alfie!!! Such a sweet innocent looking dog... his tongue... not so sweet! #blackmouldgrowth

To show how it’s done, we headed over to the lovely Froth Editor Emily Day’s home to swab a few things and see if we could capture some yeast. A variety of things were swabbed or collected in the garden and house, including lavender, an apricot tree, Emily’s hair and a lick from her little dog Alfie.

Agar plates... different nutrient bases encourage the growth of different organisms, so you can undertake specific tests to determine the presence of particular bacteria or yeast.

Agar plates... different nutrient bases encourage the growth of different organisms, so you can undertake specific tests to determine the presence of particular bacteria or yeast.

How to DIY yeast hunting using agar plates:

1.       Make up a solution of agar and set a thin layer onto a sterile plate.

2.       Make some delicious wort to entice the yeast cells to come and party

3.       (Optional) Get yourself a sterile cotton swab

4.       Put on your yeast hunting cowboy hat and clean disposable gloves 

5.       Go and find something awesome to swab!

6.       Wipe your cotton swab onto an item, for example an orange, and then take the lid off the sterile plate and gently swipe the swab onto the plate, careful not to break the agar layer. The reason the swab is optional is because you can also gently wipe the object directly onto the plate. For example, you can let your dog lick the plate (side note: the results from this will be an excellent way to deter yourself or others from allowing the dog to jump up and lick you on the face)

7.       Cover the plate and leave in a dark place.

8.       Check every few days to see if anything has grown onto your plate!

It won’t happen overnight, but it will happen! You can also get some plastic centrifuge vials (or small plastic bottles) and fill them with wort and add a potential yeast host, such as a leaf, flower or some hair. Keep the vial flat side down and still and wait to see if it bubbles – a good sign that yeast is present and being active in the solution (Carbon dioxide is a by-product of the conversion of sugar to alcohol by yeast, hence the bubbles).

It's best to incubate your agar plate samples in a cupboard with a constant temperature of 25C (or an incubator if you have one handy!) but somewhere dry, not windy and not too cold or hot or where your dog won't lick it will suffice.

So our experiment took a few days waiting for yeasty goodness to colonise on the agar plates. The good news is that Emily’s hair showed no signs of bacteria so you're safe reading a copy of Froth magazine with your glass of frothy... unfortunately we can't say the same about Alfie’s tongue… black and blue mould does not belong in your beer! Hair of the dog anyone?! (literally…!)

No... that is not how yeast should look!

No... that is not how yeast should look!

Happy yeast hunting folks!

 

Cheers,

Annabel & Skye (& Rusty!)

Don't worry - this is as close as these two dogs and their tongues ever get to our brewery!

Don't worry - this is as close as these two dogs and their tongues ever get to our brewery!

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