Aging and Storage

Overview of goals: https://www.facebook.com/groups/MilkTheFunk/permalink/1640076039353937/

BEGIN ROUGH DRAFT

(In progress) For this page, Aging and Storage will refer to the conditioning and aging of beer in its final package (bottle, keg, etc.). The conditioning process includes the changes that take the beer from its state at packing to the state in which it is intended to consumed. The term aging will be used on this page to discuss changes in the conditioned beer as it is aged further. Storage conditions and their advantages and disadvantages will be discussed. Aging of beer before packaging is discussed in various brewing pages on the wiki and will not be discussed here.

For simplicity, this page will mostly refer to what is going on in a bottle, but the same changes and processes occur in other package types, albeit at different rates, and 'bottle' can be replaced with 'keg' or another final package.

Best Practices for Storage

This could be an overview for customers, retailers, and distributors. The sections below can give more technical/detailed information.

See Techniques of Cellaring below for more information.

Bottle conditioning

(in progress)

Bottle conditioning is the process and changes that take a beer at packaging time to beer that is ready to drink. This can include the development of carbonation, microbial growth, development and reprocessing of off flavors, 'bottle shock' and other changes. Bottle conditioning, at least for the initial period where carbonation is generated, is typically carried out at warmer temperatures than extended aging after the conditioning is done.

Techniques of Cellaring

Cellaring, or extended age in the bottle once the beer is ready to drink, is common for many mixed fermentation beers. Cellaring is typically carried out at cooler temperatures.

Bottle Orientation

• Brandon Jones article on corked bottle storage (verticle vs horizontal) with comments from Belgian lambic brewers.
• Pierre Tilquin explains that horizontal storage for corked bottles results in no Pellicle formation in the bottle .
• As with wine and champagne, some recommend storing beer that uses natural corks horizontal to keep them from drying out. This allows them to keep a tight seal and either horizontal or vertical for synthetic corks (it doesn't matter for synthetic corks) .
• Jeff Porn observes accelerated flavor development (good or bad) when comparing bottles that are stored horizontally versus ones stored vertically . This is also the experience of Brasserie Dupont.

Chemical Changes

General Effects of Oxygen

(This is probably the most important thing to talk about first.)

Haze

Also referred to as colloidal instability, haze that forms in beer after packaging is often attributed to the interactions between polyphenols and proteins. Haze generally limits the shelf life of beer. Beer contains much more haze-active proteins than haze-active polyphenols. Haze-active proteins are acidic hydrophilic polypeptides that originate from barley and are rich in proline, glutamic acid, and glycosylated. Smaller phenols such as phenolic acids and flavonols do not contribute to haze, but heavier polyphenols such as procyanidin and prodelphinidin are strong haze inducers. These proteins and polyphenols bind together to form haze in beer. The polyphenol found in hops, catechin, does not form haze immediately but can cause haze after a period of storage. The pH of the beer has a huge impact on this reaction: much more haze is formed at a pH of 4.0 than it is at a pH of 3.0 or above 4.2. Higher ABV beers also encourage more haze formation from proteins and polyphenol reactions. This haze generally forms after a period of storage (called the "lag phase"); the longer this lag phase, the better the beer's colloidal stability. Haze can also be induced by oxidation, the presence of aldehydes, shaking, higher temperature, polyphenol-rich raw materials, light, and heavy metals .

Chill haze (or reversible haze) is the combination of polyphenols and proteins via non-covalent bonds at colder temperatures. This haze generally goes away after the beer is warmed up again, but chill haze can become permanent as well .

Brewers generally remove haze by additives such as tannic acid, papain, or silica gel. Some of these additives can also remove foam forming proteins. Because of this, a chemical known as PVPP is often used because it does not remove foam forming proteins. Several products are available that contain combinations of PVPP and other compounds .

Acids and Esters

Cover microbiologically driven changes: over-attenuation, Brett expression under pressure, autolysis

• "Thoughts on Spitaels and Van Kerrebroeck et al, 2015", by Dave Janssen on Hors Catégorie Blog.

pH change in the bottle?

http://www.sciencedirect.com/science/article/pii/S0740002014002548

Phenols

Phenols are a large class of organic compounds. One way that phenols can be classified is by how many carbon atoms they include (see the phenols Wikipedia article). Examples of classes of phenols include the phenol (the simplest form of phenols with 6 carbon atoms), hydroxycinnamic acids (ferulic acid, caffeic acid, etc.), and complex polyphenols (multiple phenol structure units) .

Many phenols have an impact on beer aging or are impacted by beer aging. They are introduced from malt, hops, and yeast fermentation. Some phenols directly impact the flavor, astringency, haze, body, and fullness of beer. Some phenols also have health properties. Degradation of some phenols leads to the changing of fresh beer taste. Other phenols act as antioxidants and can protect the beer to some degree from oxidative degradation as beer ages .

Phenolic Monomers

Phenolic monomers include phenolic acids (also known as "hydroxycinnamic acids"), flavonols, and volatile phenols (4-vinylphenol, 4-vinylguaiacol, 4-vinylcatechol, and their ethyl derivative) .

Hydroxybenzoic acids (e.g. vanillic acid, gallic acid, syringic acid) and hydroxycinnamic acids (e.g. p-coumaric, acid, ferulic acid, sinapic acid, caffeic acid) are extracted from polysaccharides within the cell walls of malted grains during the mashing process, and are generally considered to have some antioxidant qualities, however at least one study found that they did not positively impact the oxidative reactions in aging beer (some phenolic acids are antioxidants, but others are oxidizers, and the net result is possibly a non-effect of oxidation and preventing oxidation). They generally do not impact flavor because of their high flavor threshold in beer (52 ppm for p-coumaric acid, 66 ppm for ferulic acid - these acids are generally bitter and astringent in flavor when above flavor threshold), however yeast metabolism can lead to flavorful volatile phenols such as 4-vinylphenol (plastic) and 4-vinylguaiacol (clove flavor; 0.3 ppm flavor threshold in beer) . 4-vinylguaiacol can be partially oxidized or reduced into smaller compounds such as vanillan, 4-ethylguaiacol (reduced by Brettanomyces), and guaiacol as beer ages .

The aging of volatile phenols in bottled beer hasn't received much attention from science. One study looked at the evolution of various volatile phenols in several Belgian beers, including one Trappist beer that was conditioned with Brettanomyces (probably Orval). All beers were aged at 20°C/68°F in a dark room. The study found that Belgian beers that did not contain Brettanomyces and that had a high level of 4-vinylguaiacol (4VG) saw a drop of about 50% between months 3 and 6, and then a very slow increase from months 6 to 14. This also corresponded with a fairly sharp increase in vanillan beginning after 6 months. This decrease in 4VG and increase in vanillan was suggested to be caused by both the oxidation of 4VG and acid hydrolysis of glycosides. Both guaiacol (roasted coffee flavor) and 4-methylphenol (burnt flavor) saw a sharp rise after 6 months to 14 months of aging, particularly in the dark Belgian beers (from 6 to 15 ug/L and 2 to 5 ug/L respectfully) . The degradation of 4VG has also been reported to be 25% after 20 days at room temperature, or 50% after 20 days at 40°C/104°F .

For the Belgian beer that was conditioned with Brettanomyces, 4-ethylphenol (4EP), which is responsible for the plastic off-flavor in beers and wine with Brettanomyces, steadily increased from 1500 ug/L to 2000 ug/L from when bottled to 3 months. From month 3 to 6, the level of 4EP was stable. From month 6 to 14, 4EP showed a steady decline from 2000 ug/L to 500 ug/L, indicating that 4EP can age out of bottled beers. The phenol 4-ethylguaiacol (4EG) was steady at 1600 ug/L with only a very slight increase from bottling date until 6 months. From month 6 to month 14, 3EG dropped from 1600 ug/L to 1200 ug/L. This indicates that 4EG is relatively stable compared to 4EP, but is not immune to breaking down .

The volatile phenol 4-vinylsyringol (smokey, burnt) has been identified in lagers that have aged and is thought to stem from the slow acidic hydrolysis of a glycoside during aging .

Polyphenols

Polyphenols are a large group of organic chemicals characterized by many phenol structures combined. Subclasses of polyphenols include tannic acid, tannins, and flavonoids .

Polyphenols have an ambiguous role in the aging of beer. Flavonoids (for example catechin, which comes from hops and is a major source of polyphenols in beer), are antioxidants and protect more sensitive compounds such as isohumulones from oxidation. However, they themselves can also be oxidized over time to possibly create off-flavors. In addition to their own oxidation, hydroxyl radicals that cause oxidation also react highly with ethanol. After a lag period of 5 weeks in the bottle, it was found that levels of tannins actually increase. This is thought to be caused by smaller flavonoids reacting with acetaldehyde. Polyphenols were also oxidized into quinones, which are a stepping stone in the reaction that causes oxidative food browning. The use of polyphenols during mashing and boiling has been shown to decrease trans-2-nonenal (cardboard flavor) and trans-2-nonenal that is protected from fermentation by being bound to proteins (see Tannic Acid below). In two studies, there appeared to be no significant effect on free radical formation by polyphenols, probably due to the fact that they readily react with ethanol .

Higher temperatures increase the rate of oxidized polyphenols. In one study on aged lagers, 6.5% of the polyphenols were oxidized after 5 days at 40°C/104°F, but only 0.6% of the poly[phenols were oxidized after 9 months at 20°C/68°F .

Polyphenols generally contribute to an astringent taste in beer, and this can be intensified at a lower pH (4-4.2). Oxidation of polyphenols might make them more astringent depending on the degree of "polymerization degree" (see this article), although residual sugars reduce their astringency. Sensory analysis of lagers has shown that aged lagers became less bitter and more astringent over time (especially at a higher temperature or a higher pH), probably due to a decrease in IBU's and bitter polyphenols like catechin, and an increase in oxidized polyphenols .

Heavier polyphenols such as procyanidin and prodelphinidin also contribute to beer haze after packaging. See Haze above.

Tannic Acid

Tannic acid is a subclass of tannin (tannins are a subclass of polyphenols). Tannic acid is generally extracted from four sources: Chinese gallnuts, Aleppo gallnuts (these both produce gallic acid), Sumac leaves, and Tara pods (produces quinic acid). Forms of tannic acid can also be extracted from oak galls (seeds from oak trees) and oak bark . Tannic acid extracts are of interest to the brewing industry because they have been found to improve flavor stability through its antioxidant Properties. Specifically, these properties include free radical scavenging activity, bonding of the metals involved in beer staling (specifically iron ions and perhaps copper ions), and preventing oxidative degradation of lipids that produce the aldehydes such as trans-2-nonenal (trans-2-nonenal is responsible for the paper/cardboard off-flavor in stale beer). Tannic acid also increases colloidal stability (clarity over time) by binding with the proline-rich proteins that cause chill haze. The higher molecular weight tannic acids (Chinese gallnuts or Sumac leaves) will reduce chill haze by removing these proteins, while medium molecular weight tannic acids (Allepo gallnuts) can result in a stable haze for beer styles where some haze is desirable such as Belgian Wit or German Hefeweizen .

One study showed that adding gallic acid (tannic acid from Chinese or Aleppo gallnuts) during the mash and sparge water extended the shelf life of beer by reducing off-flavors such as trans-2-nonanol, the aldehyde responsible for the papery taste in stale beer. It also bound to proteins containing thiols that when oxidized during mashing can cause filtering and amylolytic issues, and settled them out during the mashing/boiling which made filtration easier. The study determined that the tannic acid did not have an impact on the saccharification rest or the soluble protein content (including head retention proteins). It did have a very slightly negative impact on yeast attenuation, however the addition of zinc resolved the attenuation issue (it is thought that the gallic acid dropped the zinc out of solution since it binds with metals, and thus negatively impacted the yeast's health) .

The sensory analysis in this study showed that all of the fresh beers with or without gallic acid scored positively by tasters, although they preferred the beers with gallic acid because of their "fullness of taste and mouthfeel". After 5 days of storage at 40°C, the beers with gallic acid continued to rate high while the non-gallic acid beers began to show signs of staling (darker in color, cardboard flavor, slight sweetness, and a sharp unpleasant bitterness). After storing the beers for 10 days at 40°C the non-gallic beers were clearly more oxidized. These results were confirmed by also storing the beers for one year at 4°C in the dark; the beers with gallic acid were always preferred by tasters. The beers with gallic acid added during the mashing and sparging had better flavor stability and better stability of hop compounds such as iso-alpha acids. They also had a higher polyphenol content from the malts (only hop extract was used, so the polyphenol content had to come from the malts). The lipoxygenase activity (LOX), which is the mechanism by which lipids are oxidized to create off-flavors, was also decreased in the beers with gallic acid added. They also found that the "Strecker" and "Maillard" derived aldehydes phenylacetaldehyde, furfural, benzaldehyde were reduced by the use of gallic acid (fatty-acid derived aldehydes were not reduced, but there is evidence that these are already present in malt and are not formed during the mashing process, unlike the previously mentioned aldehydes). Trans-2-nonenal (paper, cardboard staling flavors) was also reduced in beers brewed with gallic acid. The study found that mashing with gallic acid at 62°C and 5.3 pH had the most positive impacts on both flavor stability and the prevention of off-flavor development .

Tannic acid products are now being sold in the brewing industry, such as Brewtan B which contains gallic acid extracted from oak galls without the impurities that can often be found in other commercial tannic acid products. This manufacturer claims that the product enhances initial clarity of wort and colloidal stability of beer over time, stabilizes hop bitterness, reduces aldehyde formation, and increases flavor and color stability over time. The dosage for this product is quite low at 1.5–4.0 g/hL . Author Denny Conn of Experimental Brewing has noted that the use of Brewtan B increases the mouthfeel and flavor stability of beer . Brewtan B specs and usage can be found here.

Hop Compounds

Lightstruck

http://www.scielo.br/scielo.php?pid=S0100-40422000000100019&script=sci_arttext&tlng=es

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.2002.tb00568.x/abstract

http://www.professorbeer.com/articles/skunked_beer.html

Other Flavor and Non-flavor Compounds

Cover lifespan and effects of: THP (reference THP page), diacetyl, proteins, enzymes, gluten(?), effects of different levels of CO2.

Pediococcus 'sickness'

• See the Pediococcus page.

Microbial Survival and Changes

Cover what we know the about survival rate of different microbes, and connect them to the above sections if they have an impact.

See also Commercial Sour Beer Dregs Inoculation.

See Also

Additional Articles on MTF Wiki

• Packaging

MTF Facebook Discussions

• Devin Bell's facebook discussion about aging in bottles
• Discussion about how long it takes to develop carbonation