Brewery Setup Blog

How is wort oxygenated during beer brewing?

We know that fermentation requires a large amount of yeast, and yeast reproduction requires oxygen to facilitate the proliferation of yeast and enter the fermentation stage at the same time. For this, we must provide enough oxygen (in the form of air) to the yeast. If oxygenation is delayed, it is not conducive to the proliferation of yeast and the normal progress of fermentation speed.

Wort aeration is the only time during beer brewing that oxygen is provided to the yeast. The yeast can consume the supplied oxygen within a few hours without damaging the quality of the wort.

In order to dissolve the air into the cold wort, very small air bubbles must be introduced and mixed with the cold wort in a vortex. Otherwise, the air bubbles are too large, the air will overflow from the wort, and the purpose of fully oxygenating the wort cannot be achieved. The amount of ventilation has a great influence on the quality of beer. If too much oxygen is passed in (greater than 12mg/L), the yeast will proliferate in large numbers, and less ethanol will be formed, and the wine will appear weak; if too little oxygen is passed in, the dissolved oxygen will be too low (less than 6mg/L), which will affect the reproduction and fermentation performance of the yeast.

To make the dissolved oxygen in the wort reach 8~9mg/L, a large amount of air must be used. In theory, about 3L of air is needed per hectoliter of wort, and 10 times the amount is needed in actual production. Because some of the bubbles are insoluble in the wort; in addition, the distribution of the air introduced is not completely uniform.

Compressed air must be sterile. Therefore, a sterile air filter should be installed before oxygenation. Unsterile air can lead to yeast contamination.

Ventilation devices are generally installed at the outlet of the cold wort of the plate heat exchanger. After the compressed air is decompressed, it enters the wort oxygenator after passing through the air flow meter and the sterilizing air filter, and the wort is fully mixed with the air, and then enters the fermenter. Yeast is best added in the wort pipeline to better evenly mix with the wort.

Method of oxygenating wort

There are many ways to oxygenate wort, which are widely used. At present, there are two commonly used methods:

(1) Venturi tube

The use of venturi tubes for wort aeration is a common method used in breweries. The structure of the Venturi tube is shown in Figure 3-143. It has a narrow pipe diameter section to increase the flow rate, and the air is sucked through the nozzle. The wort forms a vortex in the widening section of the pipe diameter, so that the wort is fully in contact with the dispersed and fine air bubbles and mixed evenly. Using a Venturi tube can make the wort reach the dissolved oxygen content required by the process. The mixing ratio of wort and air is generally 1:(0.3~0.7).

2. Titanium rod oxygen charging device

Small breweries and craft breweries usually use titanium rods to oxygenate the wort; the titanium rod is inserted in the middle of the wort outlet, and cold wort flows around it. The oxygenation effect of the titanium rod is good because the porous structure formed by the molecular gap can disperse the air or oxygen into fine bubbles, which is beneficial to the fusion with the wort.

Venturi vs Titanium Rod Oxygenation

1. The porous structure of the titanium rod helps to increase the solubility of oxygen, but it is also difficult to clean and easy to block. It must be removed after use and soaked in alkaline water to clean off the organic matter attached to the surface;

2. Venturi tube oxygenation is generally used in conjunction with an air compressor, a three-stage filter and a sterile filter to inject the filtered and purified sterile air into the wort. CIP can be used for cleaning in place.

3. When the same gas is selected, the effect of the titanium rod oxygenation device will be higher than that of the Venturi tube oxygenation device, and the waste of gas is smaller. However, considering the maintenance cost, the Venturi tube oxygenation device is easy to maintain.

4. In terms of gas selection for oxygenation, pure oxygen is often used for small-volume brewing; sterile air is used for large-volume breweries. This is because the use of air oxygenation often requires more wort mixing, and the oxygenation time is long. If the wort production is insufficient, the expected oxygenation amount cannot be achieved.

5. Therefore, for oxygenation of wort, titanium rods and pure oxygen cylinders are used for small equipment; Venturi tubes, air compressors, three-stage air filters and sterile air filters are used for brewery equipment. However, for breweries with limited investment in the early stage, it is also possible to use a Venturi tube and pure oxygen cylinders for oxygenation first, and then add air compressors and other equipment later.

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