Milk has evolved over the last few decades into many attractive varieties meeting the demands of new consumer generations. Two product types – UHT milk and ESL milk – have been particularly important for the continued success of the “white gold”.
UHT milk has energized the milk world by providing a product that combines longevity and convenience without sacrificing flavor or nutrition. This type of milk undergoes high-temperature treatment, allowing it to be shipped, bought, and stored without refrigeration. As a result, milk can be enjoyed by more people than ever before, regardless of location or infrastructure.
Another success story is the rise of ESL milk, offering a modern twist on the traditional beverage by significantly extending its shelf life. Like the classic fresh milk, ESL variants are gently pasteurized and then refrigerated in a cold chain until consumption. However, new high-purity processing methods ensure that the milk retains its immediate freshness for several weeks rather than just days. This innovation has resonated with consumers worldwide.
Valves can be seen as crucial gateways and switchboards, directing the flow of the milk through the various processing stages in the dairy plant. The journey begins with the reception and initial distribution of the raw milk. This is followed by various separation and homogenization steps to extract by-products such as whey or cream and ensure the milk’s consistent quality.
Heat treatment – either UHT or pasteurization – is the essential next step to minimize the impact of microorganisms on the product. Afterwards, the milk proceeds to filling and packaging unless it is destined for further processing into cheese, yogurt, ice cream or other refined products.
Given the high sensitivity of the natural product, the equipment used in dairy operations is subject to stringent official regulations and constant improvement efforts. Valves, in particular, play a critical role. Directly contacting the milk, they must be designed and built to be hygienically cleaned after each batch. For some processing applications, the valves must also be equipped to completely close off the product path from the atmosphere, keeping out germs and other substances that would otherwise affect food safety.
Achieving this aseptic level is challenging, because valves contain a stem that moves in and out of the product area, potentially allowing impurities to enter the flow path if not properly sealed. It took an alliance of dedicated engineers and renowned chocolate manufacturers to make uncompromisingly aseptic valve technology a reality.
In the mid-1960s, a team of valve engineers in Kirchberg, Switzerland, introduced advanced design features to enhance the safety of processing valves. As is often the case, they were inspired by increasing demands from dairy producers, this time spurred on by their ongoing collaboration with well-known, quality-focused Swiss chocolate manufacturers.
One of the team’s key innovations was equipping process valves with a stainless-steel bellows to isolate the valve stem from the atmosphere. Firmly welded in place, this creates a hermetic seal against contamination. This design has become a hallmark of aseptic valves to this day. Metal bellows are subject to wear, but by filling the inside with steam or sterile liquid, any changes in temperature or level can be monitored to detect possible cracks early on.
A few years after the initial innovations, another development emerged from the same team: the aseptic double-chamber valve. This new valve type made more complex aseptic processing setups possible, particularly efficient clean-in-place (CIP) cycles. Double-chamber valves allow incompatible media to flow alternately through the same valve chambers without the risk of mixing, using steam-protected intermediate spaces between the different pathways.
Keeping the quality and safety of dairy products in mind is always essential when equipping dairy process with valves, because even minor defects can alter the taste and consistency of milk, potentially causing consumer concern. Additionally, an impaired batch can cause production downtime and result in the loss of unprocessed milk.
Aseptic valves as described above can be used to safely cover all dairy processing stages, but their primary application is in the sensitive steps following heat treatment. Prior to pasteurization or UHT, the defense against germs is less critical, as these processes will render them harmless.Extended Shelf Life (ESL) milk must also be protected against re-contamination after pasteurization to stay fresh for longer periods. This standard has been named "UltraClean". Suitable valve options for this hygienic class can be aseptic valves or specialized UltraClean valves with stem diaphragms, such as the GEA D-tec® series. The choice often depends on the valves already in use at a given dairy company: Adapting a familiar valve approach to UltraClean/ESL processes can be more economical than starting from scratch with a different one.
For numerous applications in dairy processing, highly versatile valves in the "Hygienic" class offer the most economical solutions. The modular GEA VARIVENT® series provides unlimited combination options, suitable for all milk variants and applications before heat treatment, as well as for selected processes beyond.
The Kirchberg facility, where aseptic valve technology was first pioneered, remains a hub of innovation and advancement in the field. The direct successors of the originators, now a part of the global GEA Group, continue this story of progress with the current GEA Aseptomag® product line. The range includes aseptic shut-off and divert valves as well as special variants for sampling and control applications. Additionally, pigging systems are available, allowing manufacturers to recover valuable product residues from pipelines before cleaning.
Sustainability has become an increasingly important requirement when equipping technical processes. The Kirchberg facility supports this goal with a dedicated service workshop. Although metal bellows need regular replacement, the welded-on valve inserts do not have to be discarded. In the workshop, these components can be separated, refurbished, and cost-effectively returned to the user, reducing waste, and lowering costs.
Protected by advanced valve technology, popular modern dairy products such as UHT milk and ESL milk retain their flavor and consistency to the satisfaction of discerning consumers. The promised quality and shelf life is safely achieved by keeping harmful microorganisms at bay. The GEA Aseptomag® valve series traces its roots to the origins of this development and demonstrates the strength of aseptic valve technology for dairies today and in the future.