Low oxygen brewing

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Low-oxygen brewing (LOB) is a holistic approach to brewing designed to preserve the fresh flavors of the malt, hops, and other ingredients by minimizing the negative effects of oxygen end-to-end, from ingredient selection to beer storage. These methods are sometimes referred to as "LODO" (LOw Dissolved Oxygen).

Low oxygen methods don't necessitate a lot of specialized equipment or ingredients, but they do require attention to detail and refinement of a number of brewing processes beyond the basics. As such, low oxygen brewing should be an endeavor for brewers who already have an understanding of the basic all-grain brewing process. Be aware that it will likely take multiple brews to achieve success with the full series of steps required to preserve the fresh flavors from start to finish.

The formation of long-chain staling aldehydes and precursors during malting and mashing is believed to be the main mechanism implicated in causing stale and off-flavors in beer.[1]

The brewing industry have been attempting to maintain beer flavor stability and hence prolong its shelf life by minimising the oxygen content and hence ROS in the process of brewing using varieties of antioxidant compounds such as polyphenols, sulfites, sulfur dioxide and vitamins.[2]

limiting oxidation during the hot-side will be a productive approach to limiting the damaging effects of oxygen only if oxygen is first thoroughly controlled downstream (after fermentation).[3]

Although the evidence is not entirely convincing that limiting oxygen uptake in the brewhouse manifestly benefits flavor stability, there are many brewers who strive to minimize air ingress at all stages in the brewery. It certainly makes sense to take sensible precautions (of the type listed in the box “Factor impacting on flavor stability”); however, to go to extremes such as operating the entire brewhouse under an inert atmosphere is surely overkill. It may even be detrimental—e.g., to haze stability. Intermediate between the two extremes (doing nothing to prevent air ingress or the oxygen-free brewhouse) are precautions such as mashing in with deaerated water or purging the milled grist with nitrogen. To get an idea of the relative worth of each of these, the water may contribute 10 g of oxygen per ton of malt, whereas the grist may have trapped within it some 600 g of oxygen per ton.[3]

Brewers are increasingly concerned to exclude air, or rather the oxygen in the air, from their beers and from the production stream.[4]

Factors Impacting on Flavor Stability[3] Grist

  1. More highly kilned pale malts contain less LOX
  2. Darker malts contain more antioxidant Maillard reaction products
  3. Nonbarley adjuncts (degermed rice and corn grits; sugars and syrups) lack staling precursors

Sweet wort production 1. Milling that preserves embryo tissue undamaged will not release LOX or lipids 2. Milling under inert gas to avoid air ingress 3. Purging of air from milled grist with nitrogen or carbon dioxide 4. Mashing with deaerated water 5. Use of a premasher 6. Mashing-in at highest practical temperature to obviate LOX action 7. Mashing at lower pH (<5.2) to prevent LOX 8. Fewest number of transfers and pumping to minimize opportunity for air ingress* 9. Turning off pumps when transfer complete 10. Filling vessels from bottom* 11. Avoid use of rousers until covered* 12. Copper from copper vessels will promote production of damaging radicals* 13. Inert gas as motor gas 14. Good plant maintenance (e.g., correct leaking pumps)

Boiling 1. Vigorous boiling to purge volatiles 2. Excessive boiling leads to production of “cooked” flavors

Hops/hop products 1. Reduced iso-α-acids more resistant to degradation to carbonyl compounds 2. Trans isomers of iso-α-acids more prone to degradation to stale compounds: ratio of cis:trans is 2:1 for conventional boiling with hops or pellets, but 5:1 for isomerized extracts; so latter may offer more stability

Yeast and fermentation 1. Good yeast husbandry (pitching rates, viability, vitality) to promote scavenging of carbonyls 2. Promotion of SO2 production to bind staling carbonyls—to increase SO2 , increase sulfate supply to the yeast, increase wort clarity, increase oxygenation of wort, reduce pitching rate, reduce fermentation temperature 3. Higher out of fermenter pHs preferable (see below)

Conditioning Filtration and stabilization 1. Use of low-iron filter aids (and other additions and process aids) 2. Divert water used to precoat filters to drain

Packaging 1. Double evacuation, inert gases, tappers and jetters, undercover gassing and other low-air filling protocols 2. Scavenger crown corks

Final product 1. Beer progressively more susceptible to staling as pH is lowered from 4.5 2. Store and transport beer as cold as possible, but short of freezing

  • Applies at other process stages also.

Good quality sweet wort has a fresh flavour and sparkling quality. This freshness is greatly diminished with long mashing times. Wort tastes dull and bland after a few hours and is irreversible damaged due to oxidation processes. The impact on the final beer is a lack of certain positive flavours – less maltiness, greater astringency and overall dull flavour. Other severe forms of staling (cardboard, aldehyde) may result. Fortunately all this is preventable with the simple technique of adding 20-30 ppm KMS to the mash.[5]

Water[edit]

See Water and Brewing pH

Key points:

  • Deoxygenate the strike water

Milling[edit]

See Milling.

Key points:

  • Mill as close to mash-in as possible. This generally means milling the grain yourself.
  • Avoid shredding the husks.
  • Consider flushing the grist with low-oxygen gas (e.g. CO2) to remove air prior to dough-in. This isn't an absolute requirement, but it is a good tweak after you get comfortable with the rest of the process.

Mashing, Lautering, and Sparging[edit]

See Mashing, Lautering, Sparging, Water, and Brewing pH.

Key points:

  • Use active oxygen scavengers
  • Use proper pH control
  • Add the strike water to the grain from below (underlet)
  • Avoid unnecessary splashing and aeration (e.g. do not vorlauf)
  • Make sure hoses and connections are tight
  • Use a mash cap (or inert gas) to reduce air exposure at the surface of the mash

Less important (helpful but not required):

  • Flush grist with inert gas before mash-in
  • Use a multi-vessel system (not BIAB or an all-in-one)
  • Recirculate the mash
  • Do not sparge
  • Use tubing with low oxygen permeability

when wort is in contact with conventional atmospheric conditions, it is critical to minimize agitation.[6] The fewest practical number of transfers of wort should be undertaken. When necessary, transfers should be as gentle as possible, with agitator not employed when they are uncovered and with liquid flows directed in such a fashion as to minimize turbulence (e.g., close to vessel walls, bottom entry). Single-vessel systems employing temperature ramping are clearly more advantageous in this regard than are multivessel decoction vessels and systems using cereal cookers. Pumps should riot be leaky and should be large enough to enable large-volume delivery at low speed and with minimum cavitation. Opportunity for oxygen uptake through seals, valves, etc., should be eliminated by regular maintenance. Transfer from vessels should be carefully controlled to ensure that when vessels are approaching emptiness pumping will not suck air into the system. Clearly vessel and piping geometry should be carefully considered to minimize any opportunity for gas uptake. Brewing liquor may contain substantial dissolved oxygen, and the use of deaerated liquor could be considered, not only for mashing-in but also for lautering. Milling, too, can introduce substantial quantities of air. Dry milling under a nitrogen headspace is practical. Further considerations in wet milling, apart from the use of deaerated liquor, include minimizing agitation and introducing gentle transfers. With regard to the kettle, there is clearly substantial scope for oxygen uptake in a turbulent boil if manhole covers are left open.

most of the brewhouse manufacturers have designed brewhouse operating and transfer systems to minimize the uptake of oxygen:[7] • Mashing and mash transfer systems to the bottom of the vessels • Sparge and lauter re-circulation systems to introduce the wort below the liquid level. • Avoidance of systems with forced aeration during boiling. All these designs reduce oxygen ingress. However by far the largest uptake of oxygen comes from the brewing water (in mashing and sparging) which unless de-aerated will contribute around 30 ppm oxygen per kilo of malt mashed.[7]

These points are difficult to rank in terms of importance.

A direct determination of the oxygen content of the mash is not possible because of the active oxidase systems; The oxygen absorption can be estimated indirectly by simulating the mashing process with the aid of a sodium sulfite solution and the amount of this reagent consumed. Under unfavorable conditions it is up to 200 mg / l during the entire mashing process, with optimized brewing units around 30–40 mg / l.[8]

Sources to review

Active Oxygen Scavengers[edit]

Deoxygenating the strike water alone is not enough to prevent oxidation because the dough-in process can significantly increase DO, and oxygen can diffuse into the wort from the air. Therefore LOB employs additives to actively remove the oxygen that gets into the wort.

Sulfite[edit]

When beginning the transition to low oxygen brewing, the suggested starting amount of sulfite in the mash is 20-30ppm of sodium metabisulfite, which equates to 13-20ppm of free SO2. Sulfite directly eliminates DO.[9] See sulfite usage in beer for more info.

Oxygen uptake during small-scale mashing is around 50 to 200ppm O2.[10][6]

Brewtan B[edit]

Brewtan B is an extract of gallotannins.[11] While this product isn't directly an oxygen scavenger, it does help avoid oxidation by facilitating removal of compounds that may promote oxidation and associated flavors.[citation needed]

Ascorbic Acid[edit]

Ascorbic acid acts by directly with dissolved oxygen and releasing hydrogen peroxide.[12][13] Suggested usage is to match the concentration to the amount of sodium metabisulfite. Ascorbic acid alone is not useful for scavenging oxygen; it must be used in conjunction with sulfite.[13] See ascorbic acid for more info.

AA and sulfite may work synergistically.[14]

If 100 mg/L ascorbic acid in wine reacts completely with oxygen, 62 mg/L SO2 is required to react with the ascorbic acid oxidation product.[13]

Underletting[edit]

Coming soon!

I am milling immediately before dough in and then pouring the grist on top of the strike water. I let it precipitate, or sink in, at its own pace. This seems to me a functional equivalent of underletting, from the perspective of the relative motions of grist and liquor. I end up with the grain nicely dispersed -- I give it a brief stir to confirm, but I find no dough balls at all -- and unlike when I used to stir the grain in rather than just let it sink, I see very little in the way of bubbling and foaming during the process. This indicates to me that the grain is not taking much air down with it. I suppose that if the grist case and headspace could be purged the method would be brought nearer to perfection, but hey, this is one of those points where I let my antioxidants take up the slack. The evidence of the results from the totality of my current process indicates that this is working quite well for me. I pour slowly(ish) but in a single batch. When I'm done pouring there's still a small raft of grain on the surface which gently sinks. It just takes a couple of minutes including a quick homogenizing stir to get all doughed in. Then it's cap on and done.[15]

Capping the mash[edit]

Coming soon!

Preventing Aeration[edit]

Coming soon!

Sparging Techniques[edit]

Coming soon!

A tailored batch sparge method is used successfully by some low oxygen brewers.[16][17]

Boiling and Chilling[edit]

Boiling and Wort chilling

Yeast and Fermentation[edit]

Coming soon!

Dry hopping[edit]

Packaging[edit]

Packaging is one of the most vulnerable points in the entire brewing prices with regard to oxidation. Preventing oxidation on the cold side is important even for brewers who eschew using a low-oxygen hot side process.

Gelatin = not needed for clear beer.

Fast Fermentation Test (FFT)[edit]

Conducting a FFT is the way we measure the ultimate final gravity of the beer before the batch finishes fermention. This is necessary for spunding.

Shortly after active fermentation has begun, drain 100-200mL (or however much you need to read specific gravity) into a small sanitized vessel (like a flask or jar). Cover it loosely or fit with an airlock, and put it somewhere warm. Continuously stirring the FFT because it will cause a falsely low FG. Some people prefer to avoid stirring it so that the FFT reports the true final measurement. Others prefer to stir it so they can start estimating well in advance when they'll be spunding, and they just assume that the main batch will finish about 0.5°P higher than the FFT. (Your mileage may vary.) It may reduce the offer by spinning the FFTs very slow with a short bar, just barely enough motion to keep the yeast from settling. It's been reported by multiple brewers using a slow stir method that the beer will finish within 1.001 of the FFT.[18]

If if you are brewing ales and having difficulty keeping the FFT warm enough to ferment faster than the main batch, an incandescent bulb in a reflector lamp is useful for keeping it warm. Radiant heat is ideal (for FFTs and yeast starters) because anything blowing or circulating air with dust in it around a loosely foil covered flask may introduce microbial contaminants. Choose bulb wattage carefully, the flask has a greenhouse effect too.

Spunding[edit]

Spunding means packaging before the end of fermention, while there is residual fermentable extract. The goal is to package with just enough fermentation remaining to carbonate the beer.

Spunding is the ideal low-oxygen packaging/carbonation method because active yeast help scavenge any oxygen introduced during the transfer, and it avoids using artificial CO2 that has oxygen impurity.

Process

Determine the ultimate FG with a Fast Fermentation Test, and package when the gravity is 3-4 points above the FG. Frequently measuring and recording the s.g. will help predict the timeframe when the batch will reach the spunding gravity. Making a little graph of the daily gravity readings will help a lot with making accurate time predictions.

Using a refractometer is a good option because of the smaller sample size required. Even though it doesn't accurately measure the density it's fine since we don't really need it. The refraction at bottling just needs to be about 1°Brix above the FFT refraction (when it's finished).

This process isn't as hard as it sounds. The most annoying part is when the beer is are expected to be ready to package in the night or some time when you're away. If you have temperature control it’s gives you another lever to pull to slow down or speed up a little to spund at a more convenient time.

Speise[edit]

Speise is German for food; it's what we feed the yeast when packaging.

If spunding is no longer an option because the beer fermented too long, you can add low-oxygen wort that was saved at the beginning. This allows the beer to benefit from the active yeast oxygen scavenging during the natural carbonation process and also achieves proper carbonation.

To save the speise, drain wort (before pitching) from the kettle or fermenter into a sanitized mason-style jar, filling it to the very top (zero headspace). Cap and refrigerate.

When it's time to add it, use a gyle calculator to determine the proper amount. Dump it into the fermenter 15 minutes before packaging.

Kegging[edit]

Coming soon.

Basically: Do the FFT and then spund via closed transfer to a purged keg. Consider using a floating dip tube to avoid the yeast sediment.

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Bottling[edit]

Contrary to popular belief, kegging is not a requirement for a low oxygen cold-side process (although it certainly does reduce oxygen exposure). It is possible to drastically limit oxidation with the right bottling process.

Bottled beer ideally should be spunded (see above). However, if you miss the spunding opportunity, priming the fermenter with sugar or speise is the second best option. You should still bottle as close to the end of fermentation as possible. Add the priming sugar or speise, wait 15 minutes (fermentation should be visibly active), and then bottle straight from the fermenter. Spunding reportedly provides noticeably better results than priming.

Bottling tips

  • Use large bottles (e.g. 22oz) whenever possible because:
    • It reduces the the amount of beer lost (if you like to leave the sediment in the bottle when pouring).
    • There's less oxygen ingress through the cap relative to the amount of beer in the container (less oxidation).
    • There's less headspace relative to the amount of beer (less oxidation).
  • Minimize the amount of headspace by filling bottles to within 1/4-1/2" (1cm) from the top. Less air in the bottle means less oxygen in the bottle.
    • After you fill a bottle, withdraw the bottling wand to the top and gently press the valve against the side of the bottle to fill it higher.
    • Do not fill the bottle completely full because there needs to be a small amount of headspace to prevent explosion if there is thermal expansion.
  • Use oxygen-absorbing bottle caps and activate them immediately before or immediately after capping the bottles. Getting them wet is what activates them.
  • Keep the bottles reasonably warm so that they carbonate quickly, around 70-75°F (21-24°C) is good.
  • Rouse the yeast as often as possible by inverting the bottles and swirling.

Done properly, and with rousing once or twice a day, the bottles will be fully carbonated in 1-3 days! Once carbonated, the bottles should ideally be stored cold. Cold storage slows down oxidation reactions from oxygen that enters through the cap seal. Unfortunately the beer will eventually stale,[19] but, fresh flavors will linger months depending on how well the steps above were followed.

Canning[edit]

Recipes[edit]

Adaptation to modern breweries: In the course of the last few decades there has been a development of breweries which led from the original vessel materials copper or black steel to "inert" stainless steel. This is less eroded than the metals originally used, which also promote the oxidation of components of the mash. An air-free way of working (mashing from below and moving the mash from bottom to bottom) accelerated and intensified the degradation processes, which in turn is countered by higher mashing temperatures or shorter rest periods. There is a reduction in the oxidation of polyphenols, resulting in higher contents of total polyphenols and anthocyanogens. There is also less oxidation of lipid breakdown products, especially unsaturated fatty acids, by the lipoxygenases. The overall shorter contact times - also during lautering - lead to lighter worts and beers. This can promote a more neutral, often less full-bodied beer character and u. Can lead to a “greener” and “unfinished” note. This effect is further supported by the smaller cooking mash portions that are common today, which for reasons of energy saving, as well as the better dissolved malt, are no longer boiled, but only kept hot. Many breweries have also switched to infusion processes.[8]

These findings call for a correction of the malt filling. In the case of light beer types, it would be logical to demand more intensive solidification malts with colors of 3.7 / 6.0 EBC instead of the very light malts of 2.5–3.0 (cooking colors 4.5–5.0) EBC that are frequently ordered . However, these can never be represented quite evenly. So it is better to normal, i. H. Malts hardened at 80–83 ° C with colors of 3–3.3 / 4.7–5.3 and a "basic admixture" of 0.5% dark caramel malt (F = 100 EBC) or 2.0% light caramel malt ( Color 25–30 EBC). These malts have to be dosed evenly when grinding, as a “packaged” fill from the malt house can separate due to the different (glassy) endosperm properties of these specialty malts during transport and storage in the silo.[8]

Notes[edit]

Low-oxygen brewing may enhance the activity of certain enzymes, namely cysteine endoproteases, limit dextrinase, and beta amylase.[20]

General principles to improve beer flavor stability and diminish aldehyde staling:[21]

  • Oxygen uptake should be avoided at all times (except during aeration, of course, when yeast works as an oxygen scavenger requiring oxygen for its metabolism). The construction of the brewing installation should be designed accordingly. All pipes and tanks should be flushed with CO2 or N2 of high purity, air pockets should be avoided, and bottom filling of the tanks should be applied when possible. When all containers are emptied, pulling in air should be avoided. Oxygen-free water should be used as much as possible.18,22,24,76,77,198
  • Heat load should be minimized as much as possible throughout the malting and brewing, because this favors several unwanted processes in regard to flavor stability (e.g., autoxidation of unsaturated fatty acids, Maillard reactions, Strecker degradation). For example, all hot transfers between vessels should be as short as possible.121
  • The presence of iron and copper should be minimized, because they can initiate free radical reactions. The transition metal ions that do end up in the medium, for example, originating from the brewing installation, can be chelated by, for example, amino acids, melanoidins, and phytic acid.24,95,198
  • All adjuncts used throughout the process should contain as few aldehydes and aldehyde precursors as possible. In some cases, the substitution of malt, for example, by maltose syrups, was shown to have a neutral to positive effect on flavor stability 77 Sadly, most adjuncts do not contribute to antioxidant activity, nor do hop extracts.22
  • Antioxidant activity in beer is supplied by different components, the most important ones being polyphenols. Generally around 80% of the polyphenols in beer originate from malt, whereas hops contribute about 20%.199 The majority of oxygen that enters beer and interacts with beer components has been shown to be incorporated in polyphenols (approximately 65%, whereas about 30% was found in the volatile carbonyl fraction and about 5% was associated with bitter acids). Moreover, polyphenols chelate transition metal ions.22,95,200 However, not all polyphenols are antioxidant, such as catechin (3′- and 4′-hydroxyl groups on the flavan ring); some are pro-oxidant, such as delphinidin (3′-, 4′-, and 5′-hydroxyl groups on the flavan ring) due to their ability to transfer electrons to transition metal ions.18,21,95,201 Besides polyphenols, a wide spectrum of valuable antioxidants is present in beer, such as reductones, melanoidins, and vitamins. The upstream production process should aim at promoting and protecting the endogenous presence of antioxidants.43,92,163,199,202−205

Potential measures in malting:[21]

  • The variations in levels of aldehydes, aldehyde precursors, and, for example, antioxidant activity and copper content in barley should be monitored, as these concentrations in the raw material vary with barley variety and growth conditions.18,22,75,77,145,199,206−209
  • Barley batches with low levels of soluble nitrogen and low Kolbach indices should be selected, because a correlation was seen with the appearance of Strecker aldehydes in aging beer.210,211
  • Barley varieties with low lipoxygenase potential should be selected.21,75,78,81,91,212
  • Embryo development should be suppressed by, for example, rootlet inhibitors to reduce formation of aldehydes and aldehyde precursors.21,198
  • “Good malting practice” should be performed in regard to the type of malt: temperature and moisture profiles should be chosen and monitored carefully. For example, malt kilning at high (end) temperature inactivates LOX enzymes, which reduces enzymatic oxidation of unsaturated fatty acids, but promotes, among others, Maillard reactions, Strecker degradation, and imine adduct formation.18,21,22,43,71,75,78,145,163,200,210
  • The different temperature and moisture profiles between top, middle, and bottom layers of the kiln should be monitored. For instance, malt from the bottom layer shows lower LOX activity, but a higher nonenal potential.43
  • Intelligent management of the endogenous microflora and/or inoculation with beneficial micro-organisms will produce, for example, cell-wall degrading enzymes, for more efficient wort production.213
  • Storage of barley before malting and storage of malt before further processing should be limited in time, because an increase in free and triglyceride-bound trihydroxy fatty acids is observed during this storage.74

Potential measures in milling:[21]

  • The malt and the milling installation with CO2 or N2 should be sparged to reduce oxidation.18,22,198 Some studies indicate that enzymatic oxidation of unsaturated fatty acids occurs especially during wet milling, although others contradict this statement.74
  • Milling regimens should be applied that minimize damage to the embryo, activation of lipoxygenases, and production of aldehydes and their precursors.19,42,198,206,212

Potential measures in mashing and wort separation:[21]

  • Mashing-in at higher temperatures, for example, 63 °C, and lower pH, for example, 5.2, should be used to quickly denature lipoxygenases that were not inactivated during malting.18,19,21,22,71,75,87−89,214,215
  • Gallotannins should be added at mashing-in, working as antioxidants, metal chelators, radical scavengers, lipoxygenase inhibitors, and aldehyde binders.77,87,200,216
  • Mashing should be performed with low oxygen levels to prevent enzymatic and autoxidation of unsaturated fatty acids and other oxidation processes.74,76,82,146,215,217
  • The use of an oversized chimney with condensate trap promotes removal and prevents re-entrance of unwanted volatiles, including aldehydes.218
  • The time of wort separation, certainly when performed at high temperature, must be limited. However, a good wort separation is essential to remove aldehyde precursors, for example, lipids, and aldehydes bound to insoluble proteins from the mash together with the spent grains.19,22,75,91,161,215
  • The use of acidified sparging water releases aldehydes from imine adducts, which can be stripped in later stages.42
  • Excessive amino acid concentrations must be avoided, because these can lead to Strecker degradation and imine adduct formation throughout the brewing process and even in the packaged beer.146,219,220

Potential measures in wort boiling and wort clarification:[21]

  • The use of an oversized chimney with condensate trap promotes removal and prevent re-entrance of unwanted volatiles, including aldehydes. Other wort stripping techniques that promote removal of volatiles (e.g., depressurization) are recommended as alternatives.18,22,75,77,121,165,218
  • The oxygen content during wort boiling should be limited, as this process step has been shown to be the main step of autoxidation of unsaturated fatty acids throughout the brewing process.71,161
  • Deintensified boiling, a shorter boiling time, and effective convection in the vessel must be sought, as wort boiling is the main step for Maillard reactions and Strecker degradation, and these are promoted by a high heat load.71,77,121,146,165,198 Furfural and 5-HMF formation rates increase with increasing boiling time, and Strecker aldehyde formation proceeds at a pseudo-zero-order rate, whereas lipid oxidation hardly proceeds.121 Heat should be added via the smallest temperature difference and through the biggest exchange surface area.121
  • Boiling should be performed at a lower pH, which promotes aldehyde production from precursors in this step, but subsequently removes them from the wort by stripping. This approach limits carry-over of precursor compounds further downstream, where removal is more difficult. Moreover, Maillard reaction initiation is reduced at a lower pH.121
  • Instead of wort boiling (e.g., during 1 h), mashing-off at 95 °C, membrane-assisted thin bed filtration of the wort derived from fine-milled malt, injection of clean steam (in-line and in-kettle), stripping of the wort, and decantation via a combination vessel should be performed. This speeds the wort production process (fast wort filtration and no wort boiling) and lowers the heat load on the wort.218
  • Fresh hops, rather than aged hops, should be used, because the latter contain more aldehydes and aldehyde precursors.71
  • The use of high-tech hop products (e.g., tetrahydro-isoα-acids) has been shown to be at least neutral to flavor stability and positive in terms of other attributes such as iso-α-acids utilization, bitterness quality, and bitterness stability.139,144,146,221,222
  • Addition of sulfites to the filtered wort showed a suppression of lipid oxidation and imine formation.19,42,159
  • Clarification time should be limited, but a good wort clarification is essential to limit carry-over of aldehyde precursors (such as lipids) to the pitching wort and to maximize the removal of aldehydes bound to insoluble trub particles.22,71,75,198,205,215 However, a complete removal of lipids will negatively influence the yeast fermentation process.22,82

Potential measures in cooling, aerating, and fermentation:[21]

  • The time between the end of boiling and cooling should be limited.215
  • Swift cooling of the wort slows all aldehyde formation processes.77
  • Excessive aeration must be prevented, as it suppresses SO2 secretion by the yeast.146 Moreover, introduced molecular oxygen is depleted rapidly, but excesses might initiate oxidation processes before uptake by the yeast.22
  • A yeast strain with a high aldehyde reducing activity should be selected.193
  • A yeast strain with a larger cellular volume should be used, which appears to promote a higher pH further downstream.223 A higher beer pH generally leads to prolonged flavor stability, because it increases iso-α-acid stability, reduces oxidation of higher alcohols, and reduces protonation of the superoxide radical to the much more reactive perhydroxyl radical.138,214,224−227 Moreover, the binding of aldehydes in imine adducts is enhanced at a higher pH.224 Furthermore, improved flavor stability might also be related to the higher ploidy of the larger yeast cells.223
  • A yeast strain with a high SO2 secretion should be combined with the application of a relatively high fermentation temperature, which also promotes SO2 secretion.146,215
  • Alternatively, an attempt to minimize SO2 secretion should be made to reduce the formation of aldehyde− sulfite adducts and allow the yeast to reduce the free aldehydes. Addition of exogenous SO2 before packaging provides antioxidant activity and aldehyde masking.198

Potential measures in packaging:[21]

  • The lowest O2 concentration possible in the packaged beer (no more than 50 ppb) must be achieved, for example, by purging the beer containers with CO2, fobbing the beer prior to closing the container, and limiting headspace air.18,22,75,76,228
  • Antioxidants, for example, sulfite, ascorbic acid (E300), ferulic acid, catechin, and/or the enzyme glucose oxidasecatalase, should be added, although their capabilities are often contradicted.18,22,146,159,171,201,229,230
  • Arginine should be added, which can (theoretically) perform nucleophilic attacks on α-dicarbonyls and/or aldehydes by its two adjacent end-standing amino groups, thereby acting as a Maillard reaction inhibitor and/or an aldehyde scavenger. Lower aldehyde and Maillard intermediate contents were observed upon the addition of arginine, but this effect may (in practice) be caused by the pH increase associated with the excessive amounts added to the beer in this research.121
  • Enzymes that are able to reduce α-dicarbonyls, either directly or throughout the aging process, should be added, and/or so-called Amadoriase enzymes that degrade Amadori compounds should be added.121 The feasibility of this measure still needs to be proven, however, as research on this topic still needs to be performed.
  • Yeast should be added to the bottle for refermentation (“bottle conditioning” or “bottle krausening”). Its reducing activity significantly improves the flavor stability, even without the addition of fermentable sugar and at low cell counts (10000 cells mL−1 ). Aged lager beer has been shown to be difficult to separate from fresh beer, and haze formation is only limited.152,153,231 An additional advantage is the oxygen scavenging activity of the yeast, thereby protecting beer components from oxidation.232
  • When pasteurization is performed, limit the pasteurization temperature.36
  • A crown cork liner for beer bottles, which efficiently excludes oxygen ingress, preferably with oxygen scavenging ability, should be used.21,22,75,228,233 The undesirable effects of light are reduced significantly (but not eliminated) by the use of brown glass, which is, therefore, favored over, for example, green glass bottles.205
  • Beer packaged in cans showed a lower Strecker aldehyde increase, compared to glass and PET bottles, which can be kept in mind in the selection of the beer container type.228

Potential measures in transportation and storage:[21]

  • Refrigerated temperature (e.g., ≤7 °C) should be maintained during transportation and storage to slow all chemical reactions causing staling.18,22,36,75,110,146,198,229,230
  • Exposure to sunlight and intense shaking should be prevented.22
  • Stock turnover must be made in a timely manner.24

See Also[edit]

Podcasts

YouTube

Articles

Potential sources

References[edit]

  1. ↑ Guido LF, Boivin P, Benismail N, Gonçalves CR, Barros AA. An early development of the nonenal potential in the malting process. Eur Food Res Technol. 2005;220:200–206.
  2. ↑ Wu MJ, Clarke FM, Rogers PJ, et al. Identification of a protein with antioxidant activity that is important for the protection against beer ageing. Int J Mol Sci. 2011;12(9):6089–6103.
  3. ↑ a b c Lewis MJ, Bamforth CW. Chapter 12: Oxygen. In: Lewis MJ, Bamforth CW, eds. Essays in Brewing Science. Springer; 2006:131–142.
  4. ↑ Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
  5. ↑ Kallmeyer M. To mash or not to mash Kurz/Hoch. Drayman's Brewery website. 2016. Accessed online March 2024.
  6. ↑ a b Bamforth CW, Muller RE, Walker MD. Oxygen and oxygen radicals in malting and brewing: a review. J Am Soc Brew Chem. 1993;51(3):79–88.
  7. ↑ a b O'Rourke T. The role of oxygen in brewing. Brewer International. 2002;2(3):45–47.
  8. ↑ a b c Narziss L, Back W, Gastl M, Zarnkow M. Abriss der Bierbrauerei. 8th ed. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA; 2017.
  9. ↑ Guido, Luis. "Sulfites in beer: reviewing regulation, analysis and role." Sci. agric. (Piracicaba, Braz.) vol.73 no.2 Piracicaba Mar./Apr. 2016
  10. ↑ Bamforth CW. Enzymic and non‐enzymic oxidation in the brewhouse: A theoretical consideration. J Inst Brew. 1999;105(4):237–242.
  11. ↑ "Brewtan B." Wyeast.
  12. ↑ "Impact of Oxygen on Quality of White Wine." 2013
  13. ↑ a b c Zoecklein, Bruce. https://www.apps.fst.vt.edu/extension/enology/EN/133.html
  14. ↑ https://pubs.acs.org/doi/10.1021/acs.jafc.8b04690
  15. ↑ "Milling into strike water"
  16. ↑ http://www.themodernbrewhouse.com/forum/viewtopic.php?f=2&t=1025
  17. ↑ http://www.themodernbrewhouse.com/forum/viewtopic.php?f=2&t=1167
  18. ↑ http://www.themodernbrewhouse.com/forum/viewtopic.php?f=3&t=1469
  19. ↑ http://www.themodernbrewhouse.com/brewing-methods/bottle-cap-oxygen-ingress-real/
  20. ↑ Evans E. Mashing. American Society of Brewing Chemists and Master Brewers Association of the Americas; 2021.
  21. ↑ a b c d e f g h Baert JJ, De Clippeleer J, Hughes PS, De Cooman L, Aerts G. On the origin of free and bound staling aldehydes in beer. J Agric Food Chem. 2012;60(46):11449–11472.
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