Yeast Comparison: S-04 and S-05 - Side by side.

Yes - it's more about yeasty goodness!

This time, we're doing a true side by side test of Fermentis' S-04 English Ale Yeast and their S-05 American Ale Yeast.

I've been brewing for a touch over a year now and have completed around forty or so brews successfully. They have included a wide range of English and European ales and ciders and some other experimental and speciality beers.

The character of how each yeast behaves in the fermenter, its influence on how fast or slow the ferment is, whether it's a top fermenting yeast or a bottom fermenting yeast, how fast it flocculates out and many other characteristics is very individual. Using the right ingredients with the wrong yeast can render a batch to be like ordinary homebrew made by a novice. I've used some very ordinary ones that came with the cans of goo when I was starting and I've used some delicious exotic White Labs vials that have made for some very surprising successes from some really crap ingredients.

Obviously, one of the first few things you can change when you're getting started is the yeast. That's why I'm taking a closer look at S-04 and S-05 and sharing the results with you.

Here's where you can find the data sheets on each type:

S-04: http://www.fermentis.com/FO/pdf/HB/EN/Safale_S-04_HB.pdf

S-05: http://www.fermentis.com/FO/pdf/HB/EN/Safale_US-05_HB.pdf


>From my point of view, S-04 tends to be typical of an English Ale yeast. Fairly quick ferment, reasonably temperature tolerant (up to 24C according to the pack), willing and ready to make good ales, porters and stouts. As and English style yeast, it tends to accentuate the malt flavours and tends to be a medium to high flocculator, leaving a rather clean and clear product even at the end of primary fermentation.

S-05 is a bit different. As with a lot of global perception of all things American, this is definitely a bold and brassy yeast. It tends to favour the hops moreso than the malt, giving a sharper, cleaner finish to the taste and making the flavouring and aroma hops more pronounced. Sadly, it's not a big floccer so it leaves the beer rather cloudy by comparison to S-04. However, there are clarifying techniques that we can talk about another time to overcome this issue - the simplest of which I will tell you now: time. Leave it sit a few weeks or a couple of months and it will be reasonably clear, excellent tasting and better mellowed.


The yeast can be pitched either by rehydrating it into a cream or sprinkling the dry yeast onto the top of the wort. Either method is rather easy and in my experience equally effective.


So - on to the testing!


So that the comparison is completely fair, the wort and fermentation needed to happen at the same time so that every part of the process would be exactly equal. The style of ale had to be something reasonably 'normal' so that there were no additional complexities which would interfere with the yeast being compared fairly.

Here's the recipe for the wort:

400 g Cracked Carapils steeped @ 70C for 30 minutes
7.9 kg Liquid Light Malt Extract
30 g Pilgrim Hops (10.8% AA) @ 60 minutes
25 g Fuggles Hops (6.1% AA) @ 30 minutes
25 g Fuggles Hops (6.1% AA) @ 15 minutes
... made up to 50 litres.

This gives: OG = 1049, IBU = 34.3, EBC (est.) 14.9, IBU/SG = 0.719.

In plain English, that means an ale that will finish up around 5% alcohol, with a pleasant balance of bitterness and sweetness but leaning slightly toward the sweeter end of the spectrum.

The wort was made in one big batch, cooled to 20C, stirred to homogenise it, divided equally between two fermenters and topped off to 25 litres in each fermenter.

Yeast was pitched, one sachet of each yeast type into each fermenter. Rather than just allowing it to find its way into the wort, it was stirred in aggressively in order to introduce as much oxygen into the wort as possible.

Fermentation was four days at 22C.

FG = 1011.


Here is a pic of the beer drawn off from the fermenter prior to bottling:

Don't you love my high-tech laboratory glassware? :)

As you will notice, the beer on the left is very cloudy indeed. That's the S-05 yeast. The one on the right is S-04.

While this pic might cause you to leap to conclusions about which one you would choose, take a moment to ponder out a few more points:

• The nature of the S-05 tends to create a hoppier, more lively tasting beer which more of the market is accustomed to. It tends to have a slight bite to it. Even at this stage out of the fermenter without bottle conditioning, it's certainly the spicier of the two.
  
• S-04 tends to flocculate out faster and produce a cleaner beer sooner. However, as I've mentioned earlier in this article, it does tend to be more malt driven so you should take this into account and increase your first hopping accordingly to gain more bitterness and let the malt drive the flavour and aroma.
  
• As you notice, the two beers both have quite different colour profiles. The S-04 is a good copper colour and the S-05 is a brighter amber colour. I'm not one to care much about colour but about taste, especially in these beers at the lighter end of the spectrum.

So - what yeast to choose?

That depends on personal taste and your intended "grain to brain" schedule.  

S-04 If speed is your thing and you're OK with a young beer, then I would choose S-04 and a hops schedule to suit. The above hops schedule does not suit. If anything I would increase the first hops either by weight alone or by both weight and boil duration, depending on your taste. I prefer an ESB with an initial hoppy bite, mild aroma and let the sweetness be a lingering afterthought.

As far as speed goes, a fermentation around 18 - 22C would last around four days and after five days of secondary fermentation / bottle conditioning, you're pretty much good to go. Flocculation continues in the bottle and results in a rather bright and clear beer that only improves with time, out to about two months. If you keg, then this is the one to go for. Clean and clear in a hurry.


S-05 If you can spare a month for a rather good, modern style beer that is reminiscent of some of the west coast USA craft brews then S-05 is your yeast. It will take a couple of weeks at least for the yeast to drop out of suspension. Drinking too early while the yeast is still suspended tends to lead to bottom-ripping farts and runny poo. You have been warned.

Again, the fermentation time and temperature is much the same as S-04, but longer secondary fermentation / bottle conditioning will really reap rewards.


In both cases, if you allow a day or two in the fridge prior to drinking you will find the result much better than if you rapidly chill the beer in the freezer for an hour or so and then keep it in the fridge. The technical aspects of this have been explained to me, but I don't recall those in detail. Suffice to say, it works. Try it.


This article is already far too long and probably boring to anyone who isn't a beer nerd, so I will put the pics and tasting notes into another post in a few days.

Take care and happy brewing.


Cheers!!


EDIT (09/12/09): No pics of the finished product, sorry. Drank it. Yummy. :)