Imagine a world without the goodness of cheese, the silkiness of your favorite yogurt, or the refreshing simplicity of a cold glass of milk. From fruity gelato to the cream in the coffee, milk is at the heart of delights cherished across the globe. But this staple is also at the forefront of technological advancements aimed at optimizing its quality, safety, and shelf life. Join us as we explore this story of ongoing progress and the special role of aseptic valve technology in it.

Modern milk variants for an evolving world

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.

Process valves – gateways in the dairy journey

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.

Aseptic pioneers, driven by chocolate

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.

After heat treatment, UHT milk is the product type that requires the highest level of protection, as it is not refrigerated. This standard is defined by the hygiene class "Aseptic", which mandates hermetically sealed and regularly sterilized flow paths to keep the product safe. Aseptic valve technology is thus considered indispensable for UHT milk. In other industries this highest hygienic class is associated, for instance, with baby food, medical nutrition, and biotechnology products.

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.

Manufacturing and customizing the Swiss-made valves has also remained in the experienced hands of the local workforce. All designs are based on a consistent modular system and thus can be re-combined and adapted to individual requirements, such as different pipe diameters, higher closing pressures, or special material requests. Complete valve blocks are pre-assembled and delivered to the customer ready for use. Unless otherwise requested, the valves are equipped with digital GEA T.VIS® control tops for future-proof integration into automated process environments.