Yeasts require a range of metals for optimal growth, metabolism and fermentation performance. In production of fermented beverages, zinc is of prime importance, with levels of at least 0.3 ppm preferable for optimal fermentation and avoidance of stuck ferments. Zinc is a co-factor for numerous important biosynthetic and metabolic enzymes including, significantly, various glycolytic enzymes and alcohol dehydrogenase. In addition it plays critical regulatory roles through the action of Znfinger DNA binding proteins, and affects yeast-yeast flocculation. Zinc is also known to modulate yeast stress responses, mainly due to its role as a co-factor for the antioxidant enzyme superoxide dismutase. Furthermore, zinc ions are thought to have some effects on stability and dynamics of cell membranes, which may lead to downstream effects on cell permeability and signalling systems. In brewing fermentations, zinc is actively assimilated by yeast from malt wort. However, in most instances its bioavailability may be limiting due to decrease of zinc levels during mashing, lautering and boiling through complexing in precipitated trub. Consequently low zinc levels in wort may lead to slow and incomplete fermentations.
Read up!!!
Its entirely logical that German brewers (and there are some bloody good ones) need training in that area, if they come to the UK to brew and have never used finings.
I dont want the post to be too long and apologies for the hijack.
Malting does not encourage barley to produce starch, it is already there, encapsulated in a protein honeycomb matrix. Malting serves to (yes encourage germination) break down this matrix. These proteins are sub divided into the categories of polypeptides, hydrophobic polypeptides (which create the head on your beer/ale/lager) and the simplest, amino acids. this is started by steeping the grain in water, sometimes with low levels of gibberillic acid, but is normally present in the grain to 'wake' the grain from dormancy, by stimulating the aleurone layer, this then releases the enzymes that break down the protein, releasing the starch. The grain would start to then break down the starh into sugar, which you correctly allude to.
Your statement on water is correc it does acidify the wort ideally 5.3 to 5.5pH, but as I mentioned earlier, and forgive me for generalising (or dumbing down) does bear out the beer styles originating from differing areas, because the water has differing ionic balances.
During mashing, once you have the acidity you need for your beer style, yes enzymes get to work, alpha and beta amylase, (wont go into the others, such as limiting dextrinase), these two enzymes have differing properties, a-amylase breaks down straight chain linkages (if you know the structure of glucose, fructose etc will know they are a 6 long carbon chain) and are joined at carbon 1 and 6.
Beta amylase, which is very temperature and pH sensitive, breaks down the branched 1-4 linkages, if this is denatured by mash pH and temp, this will alter the sugar profile of your resulting wort. you can have more dextrins, complex sugars that saccharomyces cerevisiae, or indeed carlsbergenesis (lager yeasts) cannot metabolise, therefore creating 'body' and mouthfeel, but not sweetness in beer.
Quote 'Magnesium sulphate because yeast likes it.'
in single celled organisms such as bacteria and yeast low levels of Mg manifests itself in greatly reduced growth rates, in yeast excess Mg gives rise to mutation as yeast is a eucarite, which means it has 18 chromasones and therefore DNA.
As to finings Derry, yes I'm well aware of their composition, what they act upon, at what stage, and at what addition rate.
There are numerous, not two types of finings, yes in the context of primary (auxillary alginates, which are a type of fining I mentioned!), and secondary you can use gelatine instead of isinglass, plus vegan approved finings.
Then there's the third!
There are also copper finings (carragenan) to aid 'hot break' (wont bore you) that are derived from seaweed.
Oh yes, ionic principle and fining interaction, the ion involved is Ca2++, Calcium. Yeast would not have a charge without it!
Full apologies to the OP.
Kindest regards
Guy
PS: where was I wrong?
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