Cleanability: how to ensure things are clean and safe

Up to 30% of time in food and beverage is spent cleaning. Any reduction in this time that does not compromise the quality of the outcome directly contributes to a company’s bottom line.

So, it is not surprising that processors place great importance on the cleaning-friendly design - hygienic design - of the machines during the purchase of new equipment. They want to achieve optimal hygienic conditions while minimising their investment in time and cleaning agents and by selecting machines ‘geared up for hygiene’ they gain a twofold benefit - increased food safety and increased productivity.

The central idea of hygienic design can be summed up fast: it is always about preventing microorganisms or impurities of any kind from affecting a food product using constructional measures. A central aspect here is that the machines and systems are easy to clean. However, what might seem simple is in fact no easy task. EHEDG, 3A or material specifications of the FDA - the list of hygiene requirements is long.

For Dr Jürgen Hofmann, hygienic design is, however, not a book with seven seals but quite simply the answer to the question: how can the system be optimally cleaned? According to him, many sources for the danger of impurities can be avoided using simple constructional details. “One only has to talk to a member of the cleaning staff to understand that sharp edges are less favourable than smooth transitions,” stated Hofmann. His engineering office advises mechanical engineers and food producers who want to gear up their systems for improved hygiene. The chairman of the German division of the European Hygienic Engineering & Design Group (EHEDG) knows from years of practical experience what has to be taken into account so that these are easy to clean: namely, particularly avoiding gaps, recesses, constructional cavities and flow-free zones, because here there is the increased risk of deposits and biofilms.

FrieslandCampina took into account these typical design features when it came down to putting the new dessert and yoghurt line in Gütersloh into operation. Almost 2000 actuators and valves ensure that the networked system comprising pipes, heaters and stainless steel tanks works accurately - in the heart of the sensitive process field, where cleaning agents and water are regularly used. Valve terminals by Bürkert, which were installed into the hygienic design casing, make the ‘short cuts’ to the actuators and sensors possible. The switch cabinets offer protection against the toughest washdown attacks with high-pressure cleaners. A blue silicone seal, which is resistant to all types of cleaning agents, guarantees absolute impermeability. Overhanging sloping roofs with a 30° angle and horizontal drip edges on the casing ensure that liquids drip off quickly and reliably.

Stainless steel = hygienic design?

In addition to construction in accordance with hygienic criteria, the selection of the materials that are used for building the machines and systems also plays an important role. Stainless steel is generally considered to be the most hygienic material of all; however, Jürgen Hofmann warned: “Stainless steel corrodes too under certain conditions!” Chlorides that are found in cleaning agents and even in the food itself are the cause. The corrosion depends on the state of the surfaces. Hofmann said: “It is essential that the areas that come into contact with the products are good quality. Initially passivation, for example electropolishing, and a medium surface roughness of max. 0.8 µm guarantees this.” An own working group of the EHEDG occupies itself with the chemical treatment of stainless steel surfaces. It is responsible for one of the numerous guidelines that define the criteria for cleaning-friendly design. Furthermore, the EHEDG certifies components which satisfy these requirements.

However, this alone is no guarantee that the system is in a hygienic state. Even on installing a certified sensor, it is possible for the entire measuring point to become unhygienic. The weakest link always determines the ‘cleanability’ of a system - which can slow down any optimised clean-in-place (CIP) process.

But when is CIP cleaning possible and when do the systems have to be hand-cleaned because product residues can’t be completely flushed out? This is when being able to dismantle the system easily, another facet of hygienic design, becomes essential.

If you are attending the giant food processing exhibition Anuga FoodTec, being held in Cologne between 24 and 27 March, you may find attending the following forums on hygienic design worthwhile:

• 24/3/2015 - 1.00-2.35 pm - Forum 3 - Why hygienic design (Boulevard North)
• 24/3/2015 - 3.33-5.05 pm - Forum 5 - Hygienic and cleaning aspects of bulks/containers and trucks (Congress Centre North)
• 25/3/2015 - 3.30-5.15 pm - Forum 14 - Aspects and specific areas in hygienic processing (Congress Centre North)