Kegging lines range from systems so simple that washing, inspecting, and filling of each keg are done by hand, to fully automated systems that require virtually no human attendance. The output of a kegging operation ranges from a single-head machine giving an output of 15 kegs per hour, to multi-head machines with outputs more than 1,000 kegs per hour. The scope of a kegging operation is typically all-inclusive and can be divided into the following steps.
Kegs can only be transported on pallets and moved to the keg line by a forklift truck. For this reason, kegs are de-palletized by pushing the kegs together and lifting the layer with pneumatically operated grippers. When a keg comes back from the trade they are tested for internal pressure.
External Keg Cleaning
Keg are externally washed to remover labels, soil, grime and to make it more presentable (Figure 19.4). External keg cleaning involves the following operations: (1) spraying the kegs with a strong (2–3%) caustic solution, (2) allowing the caustic solution to drain off of the keg and back for reuse, and (3) rinsing the kegs to get rid of the caustic soda and reclaiming the rinse water.
Caustic cleaning solutions are used in the brewery because they are relatively inexpensive, can be recycled (re-used) and do a good job of removing protein-based soils. They do not, however, address calcium and magnesium hard water scale deposits nearly as well as acidic cleaning solutions. Non-caustic cleaners tend to cost more per pound than caustics do but they do not promote beerstone (calcium oxalate or C2CaO4) formation as much as caustics.
Internal Keg Cleaning and Sanitizing
The total cleaning cycle of the inside of the keg consists of a pre-rinse reusing the final rinse water, a detergent wash for removing biological and inorganic contamination, and a final rinse. The purpose of the final rinse is not for cleaning but for removing chemical contamination from the previous steps. The next step is to sterilize the inside of the keg with water that is at least 80 to 85 degrees C (176–185°F) or steam.
For physical wash action and chemical cleaning, the actual detergent and wash cycles needed will depend on the concentration of soils and inorganics (e.g., beerstone, water scale) in the kegs. Critical detergent parameters include temperature and working range, pH, conductivity, and activity of caustic. pH and conductivity need to be monitored regularly—any carry-over or faults can easily dilute the detergent tank. Activity of caustic is vital for biocidal efficiency and must be measured by titration, not pH.
Some brewers prefer to use steam rather than caustic and acid detergents for sanitation. The “steam” school view is that detergent sanitation works but requires a thorough understanding of detergents (e.g., with surfactants, sequestrants), concentrations, caustic activity, pH, temperatures, application times, and within range/tolerances to assure that sanitation cycles on every head are executed as intended. Steam must be pure—any included air or gas will degrade the effectiveness of disinfection in proportion and there may be a risk of oxygen being carried over towards the fill cycle.
The internal cleaning and sanitizing of kegs has many variants and is influenced by the keg’s valve style and shape, and the product to be processed. However, the following steps are commonly used in breweries worldwide for most kegs.
Prior to filling, the keg must be purged of all oxygen and steam, using carbon dioxide or mixed gas, and counter-pressurized. For nitrogenated beer, the use of nitrogen or high-nitrogen mixed gas blend may be employed. The gas is introduced upward into the keg through the spear tube and is vented out through the gas port. Any tiny amount of air not purged by gas will cause problems of dissolve oxygen in the beer.
Kegs can be filled in the upright or the inverted position. However, all automatic kegging systems today fill single valve kegs (SVK) or “Sankey” kegs in the inverted position. When the keg is upside down, it is filled through the keg valve’s gas ports and the beer is brought in slowly, forming a pool of beer at the bottom. Gas is vented through the spear via bleed-off venting valves, releasing the counterpressure gas against a backpressure control. Forming the pool of beer initially avoids a lot of foam from being established in the hot, sterilized keg and also allows a cushion for a faster rate of beer to quickly fill most of the remaining volume. SVKs can be filled in the upright or inverted positions but all automatic kegging systems today fill SVKs in the inverted position.
Metering versus Fill by Weight Methods
As mentioned, the correct amount of beer in the keg can either be measured by a metering system or by a “fill by weight” system. The various types of metering systems include turbine, volumetric, magnetic flow, or mass-flow metering. In many counties; however, volumetric measuring methods do not meet fill regulatory requirements and brewers are required to use a “fill by weight” system for measuring the beer.
Capping and Labeling
Before a keg leaves the brewery, a plastic cap is applied to the neck to protect the filling and dispense valve from dirt and to deter tampering. Labels on kegs are important in providing the customer with information as to the beer quality in the keg and its “best-before” date, the brewer, and the customer with complete traceability of the container. Barcodes applied to paper labels are essential to contain this information.
Once palletized, the full kegs are transferred either by conveyor or forklift into cold storage and held at approximately 4 or 5 degrees C (39–41°F) to prevent the development of live beer spoilage organisms that might affect the desired flavor and color profile.
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