About Cold Wort Oxygenation

Oxygenation of cold wort seems to be a very simple process, but the control of the way and amount of oxygenation of wort has great influence on the normal fermentation of yeast, the smoothness of the production process, the quality stability and flavor characteristics of beer products. etc. are of vital importance. Improper oxygenation will definitely cause a series of changes in the fermentation process, and even lead to bad fermentation results and flavor defects.

Control of the amount of wort oxygenation The amount of oxygenation in wort is controlled according to the degree of oxygen demand of the yeast strain and fermentation process used. Different yeast strains and fermentation states have different oxygen demand levels. The conventional practice is to control the dissolved oxygen in cold wort at 5 ~ 8mg/L, and make necessary adjustments according to the actual needs of yeast propagation, generally rarely exceeding 10mg/L. The amount of oxygenation of wort is generally controlled by the conditions such as oxygen flow, pressure, time and oxygenation equipment during oxygenation.

The effect of wort oxygenation is related to the control of oxygenation time. The use of unqualified or crude oxygenation devices may not achieve the actual oxygenation effect, and the amount of oxygenation is not necessarily proportional to the actual dissolved oxygen content of cold wort. In this case, some beer lovers tend to extend the oxygenation time to ensure the oxygenation effect. In fact, the dissolved oxygen in cold wort is not only related to the oxygenation time, but also related to the wort concentration and wort temperature. The lower the wort temperature, the lower the original wort concentration, the better the oxygenation effect, and the shorter the oxygenation time. One point; the oxygenation time of wort is related to the oxygenation equipment used, the sterile air pressure, and the flow rate. If the pressure is high, the flow rate is large, the emulsification effect is good, and the oxygenation time can be shorter.

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However, the oxygenation time actually controlled by large-scale production is not only combined with the dissolved oxygen content that needs to be controlled, but also combined with the dissolution and distribution of oxygen in the wort. For example, most of the cold wort batches with added yeast are oxygenated throughout the process, and the cold wort batches without added yeast can be oxygenated by time intervals, or the oxygenation time is reduced, or even no oxygenation. As long as the amount of dissolved oxygen required for yeast reproduction can be met, over-oxygenation is not advocated. The budding cycle of yeast is about 12 hours, and it should stop oxygenation after 12 hours. Yeast budding can synthesize linoleic acid by itself.

The control of oxygenation mode has several significances:

Firstly,One is the location for oxygenating the cold wort. The correct oxygenation position should be near the place where the yeast is added, that is, install a device on the cold wort pipeline that can both oxygenate and add yeast at the same time, and can fully mix, so that oxygenation, yeast contact with oxygen and absorb oxygen The effect is the best; however, breweries generally use the form of installing a Venturi tube on the cold wort pipeline. Before adding yeast, the cold wort is oxygenated, so that the cold wort containing dissolved oxygen enters the tank, and then the yeast is inoculated immediately. This is also a better way.

Secondly, during the wort cooling process, a relatively small flow rate can be used to oxygenate the wort throughout the process, which can evenly distribute dissolved oxygen. It is not recommended to concentrate oxygenation on the wort with a large flow rate, because the oxygen dissolution of the latter is not good.

Third, all batches of wort with yeast added can be oxygenated in the whole process or in stages, and batches of wort without yeast are not oxygenated in principle; considering the needs of yeast reproduction, for multiple batches of full tanks For large fermenters, the batch of yeast added can be oxygenated in the whole process or in stages. After adding yeast, the oxygenation amount can be appropriately reduced, or the oxygenation amount and oxygenation time can be adjusted according to the yeast reproduction situation. increase or decrease. If multiple batches of wort enter the tank, the last batch of cold wort enters the tank without oxygenation in principle. However, if it is found that there is unevenness in the wort entering the tank, it can be filled with sterile air at a lower flow rate and lower pressure for 5-10 minutes.