Apologies, Wouter. I missed that despite double checking. Thanks for the link.
It made me smile though. The foam in the dryhopped beer only lasted 307 seconds. A glass of a good IPA never lasts that long in my experience.
It does show how complicated the issue is, and that it is a balancing act where the negatives need consideration as much as the positives.
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No you're completely right! Dry hopping is always named apart and I should have been more specific. I was mixing thing a bit up in my head while writing.
Yeah its really interesting. I also have trouble with head many times.
Alright guys, I did my best to compile a more specific list! Most of it is from this paper:
Shokribousjein, Z.; Deckers, S. M.; Gebruers, K.; Lorgouilloux, Y.; Baggerman, G.; Verachtert, H.; Delcour, J. A.; Etienne, P.; Rock, J.-M.; Michiels, C.; Derdelinckx, G. Cerevisia 2011, 35, 85–101.
I've added the paper as a file at the bottom of this post.
I did my best to take the most important points and either explain or remove things that are just too technical. There probably are many other things, but these are the points that the authors thought to be most important. And I added a few other things of more recent times.
If any thing is unclear feel free to ask and I'll try to see if I can explain it better.
Proteins:
Lipid transfer protein (LTP1) is a protein present in grains. The amount of it is dependent on the specific growing conditions.
This component is a
positive influence on foam stability. It does this by enhancing the foam itself, but more importantly by binding fatty acids (which are negative influence).
Hordeins are also present in the grain and are a
postive influence if they are present (they are insoluble unless treated with proteolyltic enzymes).
Protein Z has interaction with other proteins (such as LTP1) and in doing so
enhances the foam stability.
Non-starch polysaccharides:
Arbinoxylan and -glucan or even oligosaccharides
improve foam stability by increasing beer bulk viscosity, thus reducing the drainage of the liquid from foam
Hop acids: Iso--acids of added hops cross-link with protein, and
improve foam stability. But if they are used in large amounts (hydrogenated iso--acids) predominantly tetra hopped beers (this is the stuff that large companies use to hop their beer, degrades less rapidly) will degrade to produce a foam that is like “whipped egg-white icebergs” and foam stability is lost. As these acids can produce bad taste “vulcanized rubber” in the final beer, only low addition of hydrogenated iso--acid hop is a useful tool in optimizing foam quality. A high proportion of
isohumulone to
coisohumulone (Our hop!) will result in more stable foams.
Dry Hopping: Interestingly, dry hopping seems to
decrease foam stability. The reasons are not yet well researched:
https://hopsteiner.com/wp-content/uploads/2016/06/2016-06_TS_Foamstability.pdf.
Cations:
Metal cations
promote beer foam stability and gushing. Multivalent cations (i.e. cations with a charge more than one + or -)
improve foam stability via reversible cross-linking with hop acids and proteins. I.e. you have hop acids and proteins floating around randomly, but the cations sort off pull them together making a network of these compounds (giving foam!)
Lipids: : Sources of lipids in beer are mostly malt but also hops and yeasts. By addition of lipids to beer, at first the foam
destabilizes but after a rest for 24 h, its foam can be either fully or partially recovered. The reason for this reaction is the presence of lipid binding proteins in beer and the degree of recovery is related to the level of these proteins in beer, their state and the amount of lipid. There is no evidence that essential oils from hops have any impact on foam stability at the levels found even in the “hoppiest” products.
Ethanol (alcohol): The higher the percentage of alcohol the more likely it is for ethanol to
disrupt the proteins forming the foam and thus has a
negative influence on foam stability in higher alcohol beer.
pH (acidity): The pH of beer has an important impact on foam stability. The proteins and hop acids change their properties according the pH. There is a sweet spot for the pH at which there properties are
postive which lies between pH= 3.8–4.6.
Amino acids: The building blocks of all proteins! Basic amino acids (arginine > lysine > histidine) interfere with the protein–iso--acid interaction to inhibit lacing of these proteins. Thus it
decreases foam stability. Amino acids in the beer are often the result of
autolysis of the yeast. This is caused by leaving the beer too long in the fermentation vessel. It is yet unclear wether or not autolysis rapidly occurs in such small quantities as we brew.
.
Malt manipulation: Higher colored malt contains less foam active proteins available for extraction into beer. This is because higher coloured malts require more intensive heating which causes the proteins to denature (unfold/break down). Thus this is a
negative effect.
Removing of acrospires: Acrospires include basic amino acids and trans-2-nonenal (cardboard flavour when a beer ages), so removing them will result in
higher foam stability.
Usage of wheat: Addition of wheat to barley causes
more foam stability because of: (a) higher protein content of wheat than of barley. (b) the amount of arabinoxylan of wheat is also higher than in barley. Thus the viscosity of finished beer will be higher which causes
more foam stability. (c) the size of bubbles will be decreased which results in
higher foam stability. (d) the puroindoline (lipid binding protein) level in wheat is high, and in beer there will be less lipids and foam stability will be
higher.
Brewing process
Generally: to produce stable foams in beer it is important to extract proteins as much as possible from malt to beer.
Mashing temperature:
If the mashing temperatures are low (<55 ◦C), the proteolysis remains active and causes loss of foam promoting proteins. More basic amino acids remain present in beer which cause foam destabilization as previously mentioned.
If mashing is performed at high temperature (71 ◦C), protease activity is inhibited. Proteins are less degraded and keep their effect on foam stability. All sorts of other pro-foam processes occur. As a whole, mashing temperatures of 65 ◦C or higher have some benefits on foam stability but over 65 ◦C it results in reduced fermentation (lower yield) because of inactivation of some starch hydrolyzing enzymes.
Milling: Wet milling may improve foam stability, leading to increased levels of polypeptides in wort and beer.
Wort boiling (the best is at 103 ◦C): Wort boiling leads to foam
promoting of beer by different reactions, such as increased hop acid extraction and isomeration, stopping of malt enzymatic reactions, concentration of wort, and increased Maillard reaction. The Maillard reaction
improves foaming stability. The reason is increased glycosylation (coupling of sugars) of protein Z and LTP1 which tends to more flexibility of molecules to move to the air/water interface.
Pitching yeast into high gravity wort: this leads to severe stress on the yeast and reduces secretion of foam promoting proteases, thus
reducing foam stability. Again, higher alcohol beers just hate foam.
Yeasts: yeasts excrete proteinase A, which slowly degrades hydrophobic foam promoting proteins (LTP1), leading to foam
destabilization.
Pasteurization: causes denaturation of enzymes like proteinase A which is detrimental for foam stability (Evans and Bamforth, 2009) and thus it may
favor foam stabilization in beer.
Glassware: Glasses should be clean. Fat residues inside the glass
decrease the foam stability. In addition using nucleated (an edging in the bottom) glass favors foam stability and is widely used these days.
