This page describes a talk held by David Logsdon, proprietor
of Wyeast Labs,
at Grumpys in Verdun, Adelaide Hills, on 13 June
2004. It's my viewpoint, and I've doubtless missed something.
The meeting was held in a tent outside Grumpys, not an ideal place for a stormy night in the
middle of winter, but we survived. Here are some photos. I know some of the people, and I
should remember the names of more, so I haven't mentioned anybody by name. Please let me
know if you recognize anybody (including yourself), and I'll update the page. Keep clicking
on the images to get progressively bigger versions.
The talk started off with a talk by David Cryer of Cryer Malt, who was sponsoring David Logdson's visit.
He told us about some of the more interesting Weyermann
malts that they stock. It was an interesting talk, but aimed more at microbreweries than home
brewers.
David Logsdon was excellent. He's a fountain of knowledge, and it's a pity we only had two
hours. We also had a number of less interesting questions, prompting Andrew Schultz to show why
people call him “Grumpy One”. Here's an interpretation of the scribbled notes I
made. If you see anything that is obviously wrong, please let me know and I'll correct it.
Notes on the talk
Yeasts need valene, which is present in light malts, but less so in darker malts. Yeast can
generate the valene itself, but this will create diacetyl as a by-product. Yeast also benefits
greatly from oxygen in the wort. Since I've been investigating this myself, I asked some more
detailed questions, in particular about Brew 23, which still hasn't
cleared. As I suspected, the symptoms are all typical of insufficient oxygen, including the
pronounced estery taste. Unfortunately I forgot to ask him what would happen over time.
Talking about Bavarian Hefeweizen, specifically the 3068 Weihenstephan yeast, he noted that
the banana flavour comes from iso-amyl acetate, which derives from the iso-amyl alcohol, a
fusel oil, that is produced at higher temperatures. Others have claimed that it comes from
ethyl acetate.
He then spent some time talking about repitching yeast from previous fermentations. It
seems that it's better for yeast destined for repitching to be removed from the fermenter
before the alcohol level reaches 5.25%: above this level, the alcohol is toxic to the yeast,
and the surviving yeast will create more diacetyl. He suggests draining yeast from the
fermenting wort after 2 to 3 days for ales, or 3 to 5 days for lagers. The effects of
higher concentrations affect the long-term viability of the yeast. In Belgium it's common
to skim from the Kräusen, and in Belgium they will repitch a yeast strain up to 16 to 18
generations; elsewhere it's more like 8 to 12.
On the question of acid washes, he noted that pH of 2.2 can adversely affect the character
of the yeast: it “burns off the hairs” (protrusions from the cell surface).
Apart from other effects, it also reduces the ability of the yeast to flocculate. He
doesn't recommend it, and finds that it's somewhat overkill. He notes that a bit of Trub in
the yeast can be beneficial. It contains fatty acids and amino acids and can help the yeast
produce sterols.
Yeast should be stored between -1° and 0°. To my
question as to whether my 3068 yeast currently in storage will survive a year (well, from
January to October), he thought it wouldn't, but it would be possible. I asked if the resultant
yeast would be any good, or whether it would bear me a grudge and “reach out and strangle
me”. He didn't have an answer to that one, and suggested that I try it and report if
anything happens.
On the subject of pitching quantities, he initially came up with a cell count, until Thomas
Hamann reminded him that most home brewers can't count yeast cells. He then suggested 1
kg/hectolitre (hl) of yeast slurry for ales, but not more than ½ kg/hl for wheat beers.
Overpitching is also bad, though not as bad as underpitching.
On the topic of yeast nutrition, Free Available Nitrogen (FAN) is not really an issue if
you're doing all-grain brews. If you're using a lot of adjuncts, it could become so. On the
topic of minerals, he said that Magnesium up to 500 ppm is beneficial. I asked “but won't
that give you diarrhoea?”. He said yes (laughter), but the yeast won't care. He agreed,
though, that the level I used today (20 ppm) would be sufficient. Other minerals of interest
are Zinc (0.1 to 0.15 ppm), Manganese (0.05 to 0.1 ppm) and Calcium, up to 20 ppm.
To other questions, he noted that more flocculent yeasts also tend to produce more diacetyl,
and that although hops don't seem to interest yeast at all, a starter with 18 IBU or so will
inhibit the growth of lactic acid bacteria, of particular interest to wheat brewers.
On the topic of
fermentation temperatures (a subject of particular
interest to me at the moment), he suggests pitching at a low temperature and allowing it to
rise through the main fermentation, and then drop it at 5° per day to quite a cold temperature
(not stated more specifically, but I got the impression to about 5°). During this time the pH
will drop from initially about 5.3 to 4.0, even to 3.7 for Weizenbier. For an ale, the
temperature might start at 17° and rise to 23° (even 28° for Belgians). For lager, it might
start at 8° to 9° and go through 13° for the main fermentation and finish round 15° to 16° to
clear the diacetyl.
On a question from somebody from the NT about how high you can go, he suggested that
fermentation temperatures could go as high as 23° for lager or 32° for Belgians.
These values sound very high to me, and I'm not convinced that he had his Celsius
temperature conversions right. When I asked him about Fahrenheit temperatures for Weizenbier,
he mentioned 58°F to 72°F (15° to 22° Celsius), which seems more reasonable. I'm sending him
this page for comment, and maybe these values will be changed.
There are a few people on the
German Hausbrauerforum who advocate the use of
baker's yeast, especially for Weizenbier. David said that there were certain similarities,
since both baker's yeast and Weizen yeast generated higher quantities of phenolics. The
difference is that they're subtle in a Weizen yeast, whereas the ones generated by baker's
yeast tend to have a medicinal character.
I asked him about the beer that
to Gordon Biersch
brew. It seem that they no longer buy yeast from him, but he suspects that the Weizenbier
that I had last September was indeed brewed with
the Weihenstephan yeast that he sells as 3068.
Finally Dave gave a bit of his background: he's from Ohio, where they have quite a tradition
of good, flavoursome beers, and when he moved to the West Coast he was somewhat
disappointed. He helped start off a new brewery (missed the name), and also started the
yeast business. Somebody asked if it was true that they
use Coopers malt extract. It is. It's
interesting to note that they use extra pale dried malt extract. I feel vindicated on a
couple of points: firstly, that extract brewing doesn't give you worse quality beers; it
just limits your choices. Secondly, the malt they sell round here is too dark.
