Ranking how different factors affect brewing

I've noticed when people get to arguing about how a particular factor affects beer they always seem to go on as if it is of prime importance. I'm not always convinced. For example, home brewers seem to spend an inordinate amount of time obsessing about liquor treatment, when from what I can see ion balance has a relatively minor effect.

So I was pleased to see that in George Fix's Principles of Brewing Science he classifies a number of factors as being of primary, secondary or tertiary importance. Mastering primary effects he says is crucial for every brewer, whereas the secondary and tertiary effects are fine tuning.

Here's his ranking:

Relevance in brewing:

Primary:

Fermentation
Oxidation

Secondary:

Malt
Maillard products
Hops and hop chemistry

Tertiary
Beer clarification
Water chemistry and water treatment

It's interesting to see where he places things, but when I try and slot things in he doesn't list I keep thinking "it depends", with things such as the beer style and if you do get it wrong how badly being variables. Also as he's talking about brewing other important points such as carbonation and the use of sparklers isn't listed. I shall ponder some more.

The Twelve Point Yeast Management Plan

Reading the second edition of Brewing Yeast Fermenation Performance I realised it was not an update of the first edition but contained completely different content. So I had to go back and read the first edition. I didn't enjoy it as much, perhaps I've been over doing it on textbook reading, but there's a gem right at the end:

Yeast Management and Fermentation Performance: a Brewer's perspective

byWarren Quilliam, Gavin Hulse and Anna Cameron-Clarke

The Twelve Point Plan

1. Ensure that the propagation technique is such as to produce biomass rather than alcohol, and then minimise the contact between the propagated yeast and the alcohol.
2. Top up the various propagation stages at the appropriate times. Each brewery would need to establish their specific exponential growth pattern to determine the ideal top up timing. This should occur towards the middle of the exponential growth curve to expose the yeast to the sugar spectrum it can expect in the main fermentation process.
3. Provide the yeast with the ideal oxygenation regime during propagation to ensure optimal growth potential.
4. Provide the fermentation with enough nutrients (especially FAN) from the raw materials (paying more for better quality malt invariably costs far less at the end of the day).
5. Provide the yeast with stress-free conditions during the fermentation process. This relates to temperature control and rate of oxygenation in particular. The wort should be collected at a temperature suitable for the brand profile. Sufficient oxygen must be provided to enable yeast development but also accommodate the required brand profile characteristics. Starving the yeast of oxygen might give the product a higher level of ester but will also cause the development of stress products.
6. Minimise temperature shocks. If a refrigerant temperature of close to zero degrees Celsius is capable of controlling the fermentation process, it would certainly be of benefit to the growing yeast cells, which would not be subjected to temperature shock if the refrigerant were at a lower temperature. Similarly the cone temperature, which is often controlled at -4 degrees Celsius, could be contributing significantly to yeast autolysis at the interface. Consideration should also be given to a two-phase water chiller for reducing the temperature of recovered yeast, rather than the sudden reduction of temperature using propylene glycol or compressed ammonia at very low temperatures. The rate of chillback of the fermentation should also be prolonged to ensure that the possibility of temperature shock is minimised.
7. Recover the yeast on time. When the fermentation has reached its attenuation limit there is no need to keep the yeast in contact with the product. Yeast which is still in suspension will mop up any residual fermentable sugars that may remain in the beer. More harm than good will result from delaying yeast recovery. It is also essential that all the yeast is removed and that slurry consistencies and crop sizes are monitored as indicators of fermentation performance.
8. Scrap the 'tired' yeast. Phenomenal improvement in yeast performance has been reported if the first 10 to 15% of the recovered yeast is scrapped. Improvements in protease levels, attenuation, pH and flavour were reported after removal of the early flocculating 'tired' yeast from the base of the fermenter prior to recovering the crop.
9. Ensure homogeneity, gas stripping and temperature control in recovered yeast. Gentle but effective agitation is critical to minimising yeast stress through the achievement of homogeneity and the removal of entrapped carbon dioxide. It is also critical that the temperature increase in the recovered yeast is restricted to a few degrees Celsius prior to pitching, or the quality of the subsequent fermentations will be negatively affected.
10. Minimise the recover to re-pitch time. It is not always practical to minimise the occupancy of the recovery and pitching yeast vessels, particularly if the brewery uses several strains of yeast. The longer the yeast spends away from the nutrient, despite the temperature, the more prominent the stress placed on that yeast.
11. Minimise mechanical damage. Consideration has been given to the gentle handling of the product. Care needs to be given to the selection of pumps, the complexity of the pipework, the number of valves, the action of agitators and the design of chillers in order to protect the yeast from unnecessary mechanical stress. .
12. Use the best yeast … scrap the rest. With every fermentation potentially different to the others, it is critical that the brewer responsible for selecting the yeast scrutinises every aspect of the parent fermentations, ensuring that the best yeast is selected for the subsequent fermentations.

So. Farewell then SABMiller.

The world's second biggest brewery has now been taken over by the world's biggest brewery. Their main office is (or should that be was?) in my home town of Woking so I've taken a few pictures.

Now you see it

Now you don't

At the Capgemini building next door to what was SABMiller house the signs have been rebranded with Asahi stickers:

Apparently SABMiller staff are/were in five office blocks in town. As Asahi have taken over Miller Brands some people will be keeping their jobs, but most will be losing them. It's this point I find a lot more troubling than ownership of beer brands I don't drink. Certainly Group Technical will be closing down, and with it brewing science will be diminished.

Get some pork on your tenedor

Work recently took me to Segovia in Spain. It's a pretty town full of historic whatnots.

La única iglesia que ilumina es la que arde

Acueducto not aguaducto. Perhaps a Welsh style mutation from the Spanish?

There's a fortress as well but I didn't get that far.

But what about the beer I hear you ask? Well there was a promisingly named shop:

But sadly it was a clothes shop. We did find a bar that actually had a beer list. The beers all seemed to be from Heineken but it was good to see some interest being taken in beer.

This was a Belgian style beer from Southern Spain

After that we wandered on to a tapas bar to be greeted by a keg font and small glasses. Did this mean we'd stumbled upon a craft beer establishment where awesome ales could be had at enormous expense?

Nah, it was just industrial lager. Dirt cheap mind.

The thing that most impressed me with Segovia though was the fine selection of pork products they had on offer, and the tapas bar didn't let us down. I was delighted to discover the Spanish even have their own version of pork scratchings.  

Chicharrónes

They were somewhat marred by actually having meat on them, which makes them lose the lardy lack of redeeming features of the British variety. I consoled myself by shovelling vast quantities into my mouth.

Green hop beers go back a long way

A very long way in fact. I knew I'd seen an early reference to green hop beers (beers made using fresh, undried hops) before, and I finally re-discovered it when looking into hop taxation history.

In the book Hops AH Burges quotes from Reynold (Reginald) Scot's A Perfite Platforme of a Hoppe Garden, (complete with olde English spelling):

"Some gather them, and brue with them being green and undryed, supposing that in drying, the vertue and state of the Hoppe decayeth and fadeth awaye..."

The book dates from 1574, and is in fact the earliest book in English written about hops, written 50 years after hops started being cultivated here.

Reg wasn't keen on the idea himself continuing:

"...wherein they are deceyved, for the verdure is woorse, the strength less, and the quantitie must be more of the greene Hoppes that are to be brued in this sort"

 He has got a point about the amount of green hops that need to be used for making beer, and I've always used dried hops for bittering, but when used as late hops undried hops really do have something special.

This is the stuff of legends: The Farnham Whitebine

The astonishing resurgence of Farnham hops continues: they're even on the telly now.

Countryfile Anita Rani present visited the hop growers in the Farnham area (yes, both of them), starting with Bill Biddell in Puttenham, and then moving on to see Rupert Thompson in Tongham. 

As one of Britain's foremost Farnham Whitebine historians, I was delighted to see the hop described as "the stuff of legends", and the presenter seemed quite taken with the hop and the beer made with it.

You can watch the programme here, the hops are at 2, 40 and 55 minutes.

Ester synthesis during brewery fermentation

Of late I've been reading Brewing Yeast Fermentation Performace by Katherine Smart*. It's full of fascinating facts and I found it a surprisingly easy read. This may have been helped by skipping the bits where it got into too much detail about genetics. Even I have my limits.

On chapter I particularly enjoyed was Control of Ester Synthesis During Brewery Fermenation. Just look at the start to the introduction:

"The synthesis of volatile aliphatic esters by yeast is of major industrial interest because the presence of these compounts determines the fruity aroma of fermented beverages. Esters represent the largest group of flavour compounds in alcoholic beverages. In beer, the major esters are ethyl acetate, isobutyl acetate, isoamyl acetate, phenylethyl acetate and the C6-C10 medium chain-fatty acid (MCFA) ethyl esters"

Isn't it gripping? And it keeps getting better. One important thing is the concentration of individual esters, rather than the total ester level. Of the esters mentioned only one of them is above the flavour threshold in most lager beers. Now that didn't come as much of a surprise, as I knew the cold fermentations of lagers produce less esters than warm ale fermentations. But who'd have thought that the ester that can be tasted in lagers in isoamyl acetate? That's right, the one that tastes of banana and is particularly known for its high levels in German wheat beer. I'm almost tempted to go an buy a lager just to see if I can notice it.  Almost, I said.

Esters ares synthesised from two substrates: an alcohol and a carboxylic acid, and a number of factors can influence this. They can be divided into: yeast characteristics, medium composition and fermentation parameters.

Selection of yeast strain is important as each yeast strain produces a specific ester profile. Though higher levels of esters are found in ales than lagers this is due to higher fermentation temperature and "there is no conclusive evidence to support the idea of higher production of esters by ale yeast, all other conditions being kept constant". Who'd have thought it?

Contradictory results have been found in studies on pitching rate and yeast performances are variable and can change through successive fermentations.

Here's a handy table about the wort composition and fermentation conditions:

Long chain unsaturated fatty acids (such as oleic acid), which mainly come from trub, decrease ester synthesis. As you'd expect from that aeration/oxygenation also decreases ester levels. Zinc stimulates yeast growth and the production of higher alcohols and their corresponding esters.

Stirring stimulates yeast growth as it increases access to nutrients and decreases carbon dioxide supersaturation. This increases higher alcohol production but decreases ester production. Increased CO2 pressure also increases higher alcohols but decreases esters.

Fermenter size and shape has a large influence on higher alcohol and ester levels. The greater liquid height in large fermenters increases dissolved CO2 with increasing hydrostatic pressure, and the shape of cyclindro-conical vessels encourages stirring. These factors decrease ester levels. Successive additions of wort during fermentation (drauflassen) can increase ester production, particularly if the added wort is not or only minimally aerated.

Increasing fermentation temperature not only increases ester levels, but changes the ester profile. Acetate esters are increased but medium chain fatty acid esters are not. Finally yeast esterases could play a significant role in the final ester profile, particularly with bottle conditioned beers (and in fact even more so if they're conditioned with Brettanomcyes but that's another story).

















* The wife of one of my many bosses so I'll have to say nice things about it. But to be honest I have really enjoyed it.