Oxygen Absorption in Beer Bottling
Oxygen Absorption in Beer Bottling: Modern Bottling Technology as an answer to known challenges
Brewers know: Beer is probably the drink that is most sensitive to oxygen. The so-called oxidation taste occurs when oxygen intake is too high. Trendy beers with the rediscovered dry hopping, previously called “hopping”, change their taste quite quickly when oxygen is absorbed. But ordinary light beers are also particularly sensitive to oxygen. Darker beers, on the other hand, often show a considerable taste tolerance to oxygen levels beyond 0.1 mg/l.
The oxygen absorption during beer preparation begins when the malt is crushed and does not end when the beer leaves the brewery, because oxygen penetrates, for example, seals in crown caps - until the beer is consumed. Beer ingredients react so quickly with oxygen that measurements of dissolved oxygen are necessary immediately after the respective processes such as tank filling, filtration or bottling. An oxidized beer with the typical taste changes often has barely measurable oxygen levels, and yet the loss of quality is significant.
The use of additives such as bisulfite or ascorbic acid as oxygen scavengers is common in other countries outside of Germany, especially for filling in PET bottles. Because these containers and the PE or PP closure most commonly used for them allow oxygen to migrate in relevant quantities in a short time. However, as an antioxidant for beer, ascorbic acid is a double-edged sword. Oxidation processes - not only in beer, but also in other beverages such as soft drinks or juices - are complex processes with many intermediate stages, and therefore much more than the transfer of oxygen to a specific recipient molecule. Are the polyphenols in malt or hops beneficial antioxidants or harmful clouding agents? This is a chapter in itself,
To meet this challenge, breweries are developing different approaches to quality assurance: from low-polyphenol malts to polyphenol-rich cone hops or from preservation strategies to precipitation to the reduction of polyphenols using PVPP.
Avoiding or reducing oxygen intake for flavor stability
Experts agree that avoiding or reducing oxygen intake is the most important part of achieving the longest possible taste stability. For this purpose, tanks are preloaded with inert gas, and they are often cleaned under this substance in order to avoid any corresponding losses. If the inert gas is CO2 , only acidic cleaning is possible while preserving the gas. If N2 is used, dissolved N2 contents in the beer must be taken into account in order to achieve undisturbed filling performance and not to produce atypical foam structures for the consumer. Alternatives such as argon would be extremely expensive. Basically, tank pressures should be chosen as low as they correspond to the CO2 partial pressure of the beer and pumps should be used to increase the pressure if necessary. When filtration it is recommended to work with degassed water. Oxygen contents of less than 0.2 mg/l should be aimed for - also for discharge water, for example in short-term heating - because non-degassed water has around 10 mg/l.
Oxygen measurement when testing exhaust processes with mixed phase separation reveals a problem much earlier than, for example, original wort measurement. Today’s requirements and possibilities make it seem sensible to even abandon the usual unit mg/l (~ ppm) for oxygen intake and switch to the more manageable unit µg/l (~ ppb 1 ) . Beers before bottling often have 5 µg/l and below, which is less than 0.005 mg/l. Just a few years ago, filling systems that achieved total oxygen absorption of 150 µg/l were common, but with the appropriate technology even 20 µg/l are now possible.
Precise determination of total oxygen
Total oxygen, often referred to as TPO for “total package(d) oxygen,” includes both the oxygen dissolved in the beer and that found in the headspace of a sealed container. The method of determining the “air in the headspace” by transferring this headspace gas into a burette filled with lye to adsorb the CO2 is still used today for reasons of simplicity. But the gas composition in the headspace does not only consist of CO2 and air with the usual oxygen content. This means that the “air in the headspace” is less suitable for determining the TPO. For a precise determination of total oxygen, measuring devices are now available that can more or less automatically measure both the headspace oxygen and the oxygen that is dissolved in the drink. Together with temperature and complex pressure measurements, the headspace volume, CO2 content and even other dissolved gases are calculated fully automatically.
Almost 40 years ago, master brewers Uhlig and Vilachá at the Polar Brewery in Caracas, Venezuela, developed a formula to determine TPO with high precision using a dissolved oxygen meter and determining temperature, headspace and filling volume. For this purpose, the containers must be brought into a gas equilibrium state, which is achieved by shaking. This method has the great advantage that all process steps in beer preparation and bottling can be controlled with one and the same portable device; even gas-in-gas measurements are now possible; For measurements from bottles or cans, all that is required is an additional piercing apparatus with an inert gas supply. The dissolved oxygen of a gas-equilibrium beverage in a bottle or can must ultimately be multiplied by a calculated factor to obtain the TPO.
For common containers and filling temperatures, this factor is between 2 and 3. Modern filling machines achieve measured values ??of dissolved oxygen that are even below those measured in front of the filling machine on shaken containers. In comparison, measurements on unshakable containers provide information about the effectiveness of the essential foaming before closing or the design and setting of the under-lid gassing in a can seamer. Modern filling machines achieve dissolved oxygen readings on shaken containers that are even lower than those measured before the filling machine. In comparison, measurements on unshakable containers provide information about the effectiveness of the essential foaming before closing or the design and setting of the under-lid gassing in a can seamer. Modern filling machines achieve dissolved oxygen readings on shaken containers that are even lower than those measured before the filling machine. In comparison, measurements on unshakable containers provide information about the effectiveness of the essential foaming before closing or the design and setting of the under-lid gassing in a can seamer.
This comparison reveals: With modern filling systems, the filling process itself only contributes 10 to 20 percent of the total oxygen in a filled and sealed container. The oxygen absorption during filling must always be seen in relation to the necessary inert gas consumption. While previously such low oxygen intakes were not possible, even with high consumption, and were perhaps not considered necessary, significant improvements have now been achieved.
Depending on the necessary or selected filling process, the use of N2 is also possible - today this can be produced at an attractive price using molecular sieves.
From practice: Development of sustainable technologies for outstanding beer quality
With modern technology, breweries achieve reliable quality in the production of their beers with a low oxygen content. Above all, this makes the use of additives such as bisulfite or ascorbic acid as oxygen scavengers unnecessary. This is exactly where KHS started with the development of the modular Innofill Glass DRS ECO filling system. This has long been in practice. The OeTTINGER brewery in Mönchengladbach, among others, relies on the solution. According to the customer, the filler allows low-oxygen filling, which was previously not available in this form.
Less oxygen, lower CO2 consumption
The new filling machine allows less oxygen into the beer - and requires less CO2 than its predecessor, rather than more. When filling bottles, a new type of hollow probe filler makes it possible to achieve even lower oxygen absorption on the other side while significantly reducing the CO2 requirement on the one hand. First, the container is evacuated via the vacuum channel and then flushed with CO2 gas. A rinsing process patented by KHS is used here. The container is then pre-stressed to filling pressure with the inert gas as usual. This makes the extremely low total oxygen absorption of 20 ppb possible with a CO2 consumption of 160 g/hl. With further reduced CO2- Consumption at, for example, 110 g/hl, which is half as much as usual, a very low total oxygen intake of 40 ppb can still be achieved. The desired total oxygen intake can literally be selected: For example, an automatic type change can be set to a particularly oxygen-sensitive cold-hopped beer, a less oxygen-insensitive dark beer or even to a completely different filling for lemonades with the greatest possible CO2 savings .
Many breweries have to buy carbon dioxide. Due to the rising price, this is a growing cost factor. The lower the consumption for the filled bottle, the more efficient the production, and the lower the oxygen absorption, the better the product quality. KHS has optimally harmonized these two points with the Innofill Glass DRS ECO. In addition, digital and automated systems ensure that the filling processes are synchronized and thus significantly increase efficiency.
There are currently 23 Innofill Glass DRS ECO reference systems worldwide.
1 ppb = parts per billion (German: parts per billion); For example, 1 ppb corresponds to 1 µg per 1 kg
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