Across the world, food processing is understandably one of the most critical industries. Along with the medical industry, food processing calls for factors of hygiene that would otherwise be overlooked in areas such as automotive, chemical or oil & gas. With the advent of automation, food processing is increasingly seeing the need for materials that are FDA approved and that will not in any way degrade during operation. In addition to this, food processing usually involves heat, which means the materials used cannot deform or melt during operation.
Whether we look at large-scale food processing or kitchen top processing, high-performance food safe polymers have found a way into nearly all aspects of this industry. Not only are polymers food-grade and non-contaminating, they also allow for a significant reduction in noise and weight – both of which are paramount, especially when dealing with home level food processing equipment. We take a look here at some of the key areas in which high-performance polymers find application.
PEEK valves for Coffee Machines
High-end coffee machines are built keeping the final taste of the finished brew as the most critical parameter. Traditional machines used valves made of aluminium, which routed the high-temperature liquid within the machine. However, as consumer palates became more discerning, the manufacturers realized that aluminium valves caused a faint metallic taste to be left in the mouth.
In the hunt for a high-temperature material that is compatible with coffee and FDA approved, PEEK was used as a replacement for the aluminium. It should be said that PEEK being an expensive material, the price of a PEEK valve is many multiples of what the aluminium component costs. However, with the PEEK Valve, the taste of the coffee is preserved. PEEK Valves are now a mainstay of any high-end coffee machine
PTFE and Acetal Rotary Seals and Shafts
Most food processing equipment involves some rotary motion. Whether it is the gentle kneading of dough or the high RPM mixing and grinding of spices, all rotary motion causes some amount of friction and thereby, heat.
Polymers in food equipment are essential in such cases. PTFE and Acetal (POM/Delrin) seals and shafts are preferred in these applications. Not only are these materials lightweight in comparison to metals, but they are also self-lubricating, implying no need for external lubrication and minimal noise creation.
PTFE+Molybdenum-di-sulphide is possibly the most preferred material in rotary applications, as it possesses a low coefficient of friction, while also having superior wear resistance. In addition to this, parts can be machined to close tolerances, allowing a good fit between the polymer seal and the moving parts that minimize vibration.
PTFE Wiper Seals
Many food processing applications involve foods that are sticky and may not easily separate. The equipment may process the food and place it on a non-stick pan; however, an additional member is needed to move the food either out of the equipment or to another part of the apparatus for further processing. In such cases, PTFE wiper seals are used to push or move the food around. Since PTFE is non-stick, the wiper seals do not themselves allow any food particles to adhere to themselves. This is beneficial not only because the food can be moved without deforming or affecting its shape in any way, but also because food particles that get stuck pose a hygiene issue.
PTFE is also unique because it can withstand up to 250°C of temperature. This means that even if the food is hot, there is no chance it will affect the PTFE seal. With so many benefits, it is no wonder that PTFE is among the most valued polymers for food processing.
PTFE Tubes for liquids
PTFE tubes are both chemically inert and have a service temperature of 250°C. The transfer of hot fluids is often essential for food processing. In addition to being able to take the temperature, the polymer tube needs to ensure that it does not react in any way with the food. In some cases, liquids may collect within the tube for long periods, if the equipment is not used often. PTFE not only stays non-reactive over long periods of time, but its non-stick nature ensures that once the equipment is re-started, there is little chance that any residual fluids will remain stuck within the tube.
PTFE and PEEK Stirrers and Impellers
Much of food processing involves the mixing of various ingredients. While most stirrers are made using metals coated with a non-stick material, some applications do call for the stirrers themselves to be made of inert materials. This may be needed in applications where the material being mixed may be abrasive and cause the non-stick coating on the metals to chip. Since both PTFE and PEEK are FDA approved and will not chip or degrade when in contact with foods, they are preferred as stirrers and impellers in many mixing operations.
Fundamentally, the combination of chemical inertness, food grade, non-stick and high-temperature capabilities means that there are many more applications within food processing where high-performance polymers could find use. As food processing moves further into the realm of robotics and automation, the devices created will need an increasing number of food-safe polymers to be incorporated to ensure both hygiene and long-term performance can be guaranteed.