Views: 16 Author: Site Editor Publish Time: 2022-10-08 Origin: Site
Both commercial brewers and homebrewers are doing their best to reduce the oxygen content in the finished beer. The oxygen in the finished beer will destroy the long-term stability of the beer’s flavor and clarity, as well as cause peculiar smells. The oxidized beer will show a paper peculiar smell or even a sweet stone fruit smell.
Oxygen In Fermentation And Finished Beer
Before the fermentation process, oxygen is usually a good thing. Enough oxygen is needed during the fermentation process to allow the yeast to grow healthily. This is why many brewers aerate the beer before adding the yeast. Unless you use pure oxygen, it is difficult to over-oxygenate the wort before fermentation. In the early stage of yeast growth, the yeast actually removes all the oxygen in the beer and uses it to grow and expand.
But, after the yeast starts to ferment, oxygen is usually considered a pollutant. When oxygen enters the fermented beer, it may spoil the beer within 24 hours. Even a small amount of oxygen is not good for the finished beer, it will quickly destroy your beer, and it will also damage the long-term flavor stability of the beer. Also, the clarity of beer with free oxygen will be affected. Because oxygen will interact with the polyphenols and tannins in beer, resulting in cold fog in the beer, and eventually a permanent haze in the beer.
After the fermentation is completed, a protective layer of carbon dioxide heavier than air is placed on the beer to prevent the beer from oxidizing. If you don’t shake the fermentation tank, then this protective layer will protect the beer from oxidation. For home brewers, it is very easy to introduce oxygen when transferring beer from one container to another and bottling or barreling. Excessive splashing during the transfer process, siphoning or leakage of the brewing system, etc. may cause excessive oxygen.
How Is Papery Off-Flavor Formed In Beer?
The main compound that causes papery off-flavor is trans-2-nonenal. Because the amount of dissolved oxygen present in the packaged beer is usually high, storage at high temperatures (above 40℉) for any time will usually develop this flavor in the package.
The more oxygen the beer is exposed to, the faster the oxidation will destroy the beer. Colder storage temperatures will slow down the process. If you do not handle your beer properly, for example, if your storage temperature is high, you will notice an increase in oxidation.
Unsaturated fatty acids in wort can also react with oxygen to form carbonyl compounds, which are oxidized flavor compounds. Generally, these carbonyl compounds bind to proteins during boiling. This is not a big problem, but further oxidation will cause these bonds to break and increase the carbonyl compounds and oxidized flavor in the beer.
How To Cut The Production Of Papery Off-Flavor?
To avoid papery off-flavor is to avoid oxygen in the finished beer as much as possible. A simple strategy is to avoid diverting your beer as much as possible. Many winemakers choose to skip the secondary fermentation altogether and bottle directly from their fermentation tanks. Commercial brewers use conical fermentation tanks so they can remove excess yeast and sediment without transferring beer. For commercial brewers, it is also a very good idea for commercial brewers to use food-grade wort pumps to transfer the beer to bright tanks and to conduct secondary fermentation.
Also, if you want to ferment or store beer for a long time, please use a suitable oxygen-blocking container. Glass and metal are good oxygen barriers, so if you plan to store beer for a long time, use glass or stainless steel fermentation tanks. Plastic is breathable to a certain extent, and oxygen can enter beer through the molecular distance of the plastic. So, plastic fermentation tanks should not be used to store or ferment beer for a long time.
Splashes generated during transfer and bottling are also important sources of oxygen. When a poorly sealed automatic siphon device is siphoning, it usually sucks in oxygen through the seal. This can be seen as a bubble in the attachment of the siphon seal. If your automatic siphon is leaking, you should discard it or add sterile water to the seal to absorb water instead of air when needed. For commercial breweries, it is necessary to pay special attention to whether the equipment is leaking. If there is a leak, the brewing needs to be stopped, and the brewery equipment should be inspected and maintained.
When filling the barrel, you need to cut splashing and use CO2 for a good purge after filling the barrel. You can do this by holding the keg upright and simply releasing the pressure relief valve a few times when opening the gas. The heavier CO2 will replace the oxygen in the keg, thereby protecting your beer.
When bottling, you should try to keep the headspace to a least (usually an inch or so is enough). Avoid splashing beer when filling, and if possible, use oxygen bottle caps. Also be sure to carefully adjust and check the caps on some bottles, because even a small leak can make your beer under carbonate and oxidize.
It is very difficult to remove all oxygen from beer, especially during the packaging process. Under normal circumstances, brewers and packaging line operators need to review their processes and ensure that the oxygen content is minimal. The easiest and most important way to avoid oxidation is to store beer properly at low temperatures. Oxidation is a thermodynamically driven process, and temperature plays a vital role in the shelf life of beer. Keep beer cold for longer storage time—for every 10°C/18°F increase in storage temperature, the freshness will decrease by 2-4 times.