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How to avoid exposure of beer to oxygen during fermentation?

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    Oxygen is everywhere, but it shouldn’t be in the finished beer. Exposure to oxygen is usually a good thing before beer ferments. In fact, sufficient oxygen is also needed early in the fermentation process for healthy yeast cell growth, which is why breweries aerate the cooled wort.

    Oxygen affects beer quality
    Oxygen affects beer quality

    In the beer production process, which links can be in contact with oxygen?

    Maybe, my friends will point out that the yeast needs oxygen during the reproduction period. good.

    In fact, there is another link, that is, the respiration of wheat grains in the malting stage also needs oxygen.

    In addition to this, other processes of beer production (raw material crushing, saccharification process, beer post-fermentation, wine storage, sake filtration, packaging process) must prevent contact with oxygen. Because as long as it is in contact with oxygen, it will inevitably have an adverse effect on the quality of beer.

    1、Adverse Effects of Oxygen on Beer Quality


    Adverse effect 1: Beer is oxidized, which intensifies the formation of cold turbidity and oxidative turbidity, affects the abiotic stability of beer, and shortens the storage period of beer.

    Adverse effect 2: After the beer is oxidized, the flavor changes, resulting in bad tastes such as stale taste and astringent taste.

    Adverse effect three: After the oxidation of polyphenols, the color of beer is deepened.

    Adverse effect 4: Oxygen can also increase the diacetyl of finished beer, causing beer to produce rancid rice and creamy taste.

    Brew beer using brewing equipment
    Brew beer using brewing equipment

    2、Factors Affecting Beer Oxidation and Protective Measures


    Oxygen uptake during saccharification reduces the antioxidant capacity of mash or wort

    Oxygen content of beer brewing water: beer brewing water refers to water for saccharification, gelatinization, and water for washing lees. If the oxygen content is high, it will consume a large amount of reducing substances in mash or wort. Using deoxygenated water as brewing water will reduce saccharification Process oxygen intake.

    Stirring times and stirring speed during the saccharification process: Appropriately reducing the stirring times and stirring speed will reduce the oxygen inhalation.

    Replenishment time of washing water: During the washing process, the washing water should be added in time before the washing layer is exposed to the liquid surface, so as to avoid the large area contact between the washing layer and oxygen, which will reduce the oxygen inhalation.

    Wort boiling time: Wort is easily oxidized at high temperature, so the wort boiling time should be reasonably controlled, not too long, generally controlled within 90 minutes, preferably within 75 minutes. Excessive boiling makes the wort taste rough and increases the color of the wort.

    Wort whirling sedimentation time: shorten the time for wort to be pumped from the boiling pot to the whirling sedimentation tank; under the premise of ensuring the whirling sedimentation effect, shortening the sedimentation time will reduce the heat load of wort and reduce the oxidation and reduction substances of wort Loss.

    The method of feeding mash to each tank of saccharification: the mash or wort is sent from the bottom of each tank, which will reduce the inhalation of oxygen in the process of transporting mash or wort.

    Closing of the manhole door of each saccharification tank: During the saccharification operation, after the addition of materials or sampling is completed, timely closing the manhole door of each saccharification tank will reduce the inhalation of oxygen.

    Stirring and closing time of the mash pump: When the mash or wort pumping is about to end, stop stirring in advance or reduce the stirring speed; when the mash pumping ends, turn off the mash pump in time to prevent the mash from inhaling a large amount of oxygen.

    3、Oxygen control during fermentation


    Wort dissolved oxygen and yeast activity: According to the concentration of wort, control the dissolved oxygen in wort, not only to ensure the activity of yeast, but also to prevent oxygen from consuming reducing substances in the wort in the early stage of fermentation.

    Backup pressure gas for sake tanks and buffer tanks: Using carbon dioxide or nitrogen to back pressure the sake tanks and buffer tanks can effectively reduce the increase in dissolved oxygen.

    Conveying pipeline and pipeline exhaust: use deoxygenated water or carbon dioxide to exhaust the pipeline for the wine to be filtered, the sake filter and its pipeline, which can reduce the increase of dissolved oxygen.

    Pipeline introduction and topping of wine: After the pipeline is exhausted, use deoxygenated water or carbon dioxide to lead and top wine, which can reduce dissolved oxygen.

    beer brewing process
    beer brewing process

    4、Oxygen Control in Beer Packaging Process


    Exhaust of the wine delivery pipeline: Before filling, use deoxygenated water or carbon dioxide to push out the air in the wine delivery pipeline and the wine vat of the wine filling machine, which can reduce the inhalation of oxygen.

    Back pressure: Carbon dioxide or nitrogen is used for back pressure filling, which can effectively reduce the oxygen inhalation during the wine filling process.

    The tightness of the wine valve: the tightness of the wine valve is better, otherwise it is easy to cause oxygen inhalation.

    Oxygen control in beer production runs through almost the entire beer brewing and packaging process. Strictly control oxygen inhalation in each link to ensure dissolved oxygen in raw beer wine and bottleneck air. The finished beer will have good oxidation resistance, non-biological stability and flavor. Stability will also be greatly improved.

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