Monday, 5 January 2015

German brewing in 1966 – pasteurisation and stabilisation

It only seems like several years since we embarked on this journey and now we’ve nearly arrived. Nearly.

What’s my feeling about pasteurisation? I’d rather drink beer that hadn’t been through it, is the simple answer.

“Flash heating of the beer has been introduced in many cases. Supervision is simpler and one is less dependent on the personnel. Such a unit requires approximately one-third of the costs of a sheet filter and provides the same shelf life.

Heating times of up to 60 sec. have been selected. It seems that heating units with pressure beer flow have the best effect. On the other hand, the colloidal stability is reduced and in many cases the flash-heated beers had a protein deposit after 6-8 weeks, whilst the beer had already had a pasteurization flavour for some weeks previously. It may be necessary to stabilize the beers before they have been filtered which will nullify to some extent the low cost of flash pasteurization.”
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, page 22.

That’s pretty honest about why you’d pasteurise rather than filter: it was cheaper, simpler and more reliable. You can’t really argue with that. Except, of course, it can bugger up the flavour of the beer.

Cooling was another way to stabilise beer:

“In many cases it was possible to increase the stability of beers by storing them for a number of days prior to filtration at less than —1° C. so that the colloid particles increased. The deep cooling system is only useful if it is designed to counteract temperature increases in pipelines and filters by chilling the beer as it leaves the storage tank. Filtration after aggressive cooling can result in haze formation in the bright beer tank. The results achieved with chilling were not always sufficient and therefore a stabilization method had to be introduced.”
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, page 22.

I think I understand how that would work. The cooler the beer, the more gunk that will precipitate out. Chilling, filtering and artificial carbonation were the first techniques employed to produce sparkling bottled beers without sediment towards the end of the 19th century. The practice was originally developed in the USA then spread to Europe.

The method of stabilising beers was to add an absorbative material to the beer than would remove unwanted stuff, like protein, which could later cause a haze. German brewers, because of the Reinheitsgebot, had a limited number of options:

“For domestic consumption, only bentonites and silica gels are permitted. Bentonites are only really useful for stabilization in the storage tank. It is necessary to mix the beer with the bentonite by repumping the tank. After the rest period of 5-10 days the stabilized beer is filtered which results in a loss of 5% in sludge deposit.

The strongly swelling alkaline bentonites have a more intensive effect than the weak swelling calcium bentonites, but the latter can be applied in larger quantities and can even be added during filtration. The short reaction time during contact stabilization gives only a limited improvement in chill- and protein-stability, as compared to the rest method; nevertheless, this improvement is sufficient for the required purpose. If the beer requires a shelf life in excess of 2 months, then the rest method must be used.

According to the type of bentonite being used, dosing varies between 50-100 g. for contact stabilization and 30-200 g. per hl. for the rest method. The latter amounts are used for export beers. The bentonite quantity is calculated fairly exactly, partially for economic reasons but also to obtain head stability. It is known that bentonites selectively remove a considerable quantity of haze-forming matter; they also cause a considerable reduction of the total nitrogen and so remove many head-forming products. The danger threshold is fairly low, being at approximately 60 g. per hl. Next to the linear reduction in coagulating protein, the corresponding increase in the Esbach precipitation (picric acid test) is particularly notice able. This test can be used to control the success of stabilization. Bentonites have an effect on flavour; as the dose is increased, a reduction in full-bodied flavour occurs and a slightly harsher after-taste is noticed. The after-taste disappears after some weeks in the bottle. Analytically, the effect is a reduction in bitter values, a lighter colour and increased pH, which is particularly noticeable when alkaline bentonites are used.”
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, pages 22 - 23.

Did you get all that? A lot of it went straight over my head. What the hell is bentonite to start with. This is how the ever-reliable Wikipedia describes it:

“Bentonite is an absorbent aluminium phyllosilicate, impure clay consisting mostly of montmorillonite.”

Not sure I’m much the wiser. In addition to being used to stabilise beer, it’s also eaten by hippies:

“But natural clay, especially the form known as "bentonite clay", has not only been used medicinally for hundreds of years by indigenous cultures around the planet, but has, in recent years, been increasingly used by practitioners of alternative medicine as a simple but effective internal cleanser to help in preventing and alleviating various health problems.”

Not sure I’d eat the stuff myself. Maybe smear it on as a mudpack.

Getting back to beer, it seems as risky thing to use in beer, given that it reduced body, buggered up the head, reduced bitterness, stripped out colour and added a harsh aftertaste. Just a few disadvantages there.

The alternative was silica gel:

“The silica gels are synthetic silicic acid preparations which are popular as contact stabilizers because they can be effective in a matter of minutes. Ideally they should be allowed to act for several hours but in this case re-pumping systems must be used. Silicic acid preparations result in a lesser reduction in total and coagulable protein, the Esbach precipitation increases only slightly, and the amount of ammonium sulphate precipitation increases considerably.

Even though the shelf life of beers treated with small quantities of silica gel (30-100 g. per hl.) is equal to that of beers stabilized with bentonites, the oxygen sensitivity of these beers is somewhat greater. The head retention is not affected and the original full-bodied flavour is retained; reduction of colour is marginal. Recently, patent mixture of bentonite and silicic acid gels have been marketed.

When stabilization products are being used with filtration it is necessary to introduce a reaction tank where the beer can remain for 20-30 min. Nevertheless, the contact method requires twice the quantity of stabilizing products compared to the rest method, without being able to increase the shelf life to more than 10-12 weeks.

Polyamides may only be used for Export beers. In Bavaria these are forbidden.”
Journal of the Institute of Brewing, Volume 72, Issue 1, January-February 1966, pages 22 - 23.

Ah, the vagaries of the Reinheitsgebot. You are allowed to stick bentonites and silica gels in your beer, but not polyamides. I’d love to know the reason why. Thinking that only water, malt, hops and yeast were allowed? Think again. Stuff that supposedly doesn’t end up in the finished beer because it’s filtered out – like bentonites and silica gels – are fine.

I think I’d go with silica gel, myself. Sounds like it has far fewer nasty side effects.

That must be my dullest post ever. Best end with a joke. What do you call a man with a condom on his nose? Fuck knows.

We’ll finish with bottling.

1 comment:

Ed said...

Always interested to see things that shine a light into the dark depths of the reinheitsgebot.