Effective Sanitizing

Sanitizing Tunnel

COVID 19 has raised public awareness of the need to sanitize and adopt best practices to maintain a clean environment in which to work and socialise. It may be a shock to most, but some of these controls have been in operation within the food industry for many years. Low Risk and High Care are the 2 general areas within a food facility, and transfer of goods and personnel between the two has always been an important control point. However, there is also the risk of transfer of bacteria and pathogens into the facility from outside sources, such as transport of raw materials and packaging.

In order to alleviate these risks of products potentially transferring bacteria and organisms between areas and facilities, it is normal practice to introduce a sanitizing tunnel, which attempts to kill any harmful bacteria at point of entry. Attempt? Yes that is correct term as there are several different systems and machines on the market that offer themselves as Sanitizing tunnels, but like most things in life, there are good and bad systems out there. In the following points we are going to discuss several areas where some sanitisers are not as good as you may think, and what Unitech Washing Systems offers to overcome some of these issues.

Sanitizing Processes

There are 2 main processes for sanitizing products, and both have their advantages. UV sanitizing is a non-chemical and non-thermal cost effective system and is also excellent where products can be adversely affected by aqueous chemicals and have to remain dry during the process. However, the main issue with this method is that the light can only sanitize correctly where there are no shadows, which can sometimes be difficult when dealing with packaging and complex shapes. In addition to this, the residence time within the tunnel is dependent on the power of the lamps used and can be a lengthier process than aqueous sanitizing.

Aqueous sanitizing is where the items pass through a curtain of liquid, which covers the product as it passes. The advantages of aqueous sanitizers is that the solution remains on the product for a period of time after exiting the tunnel, ensuring that the chemical has suitable time to take effect, which also means that the residence time within the system is greatly reduced. This is the system that we will discuss further, and that Unitech Washing Systems have significant experience with.

Aqueous Sanitizing

When supplying a sanitizing unit, consideration needs to be taken in respect to product being handled, water usage and chemical usage. The make-up of the item to be sanitized can dictate whether it needs to be sanitized with a mist spray or a re-circulated flush system, as due to the larger jet size on a re-circulated system, it may be too much pressure for delicate items.

Mist sanitisers tend to be one shot units, where water and chemical are mixed, sprayed over the product and then allowed to flow to drain. This type of unit is generally the cheaper priced of the 2 options of machines offered, and due to fresh water being used, the jet size and flow can be quite small, minimizing the water and chemical usage.

Re-circulated sanitizers, are initially charged with the water and chemical mix, and re-circulate the solution with a pump. Filters are used to remove particulates that may come from the products, and higher flow jets can be used to circulate the water over the item to be sanitized, usually ideal for items such as ingredient tubs, packaged cheese blocks and similar items. Replenishment of the sanitizing solution is automatic, as when solution is carried out on the product, and the reservoir level eventually reduces, it is topped off from the mains via a proportional doser, which allows the correct mix of sanitizing solution into the reservoir water supply. With a re-circulated sanitizing tunnel, the water and sanitizing fluid usage is generally a fraction of that of a one-shot mist sanitiser, as the only fluid loss is that carried out on the product, making them a cheaper option in the long term.

Conveyor Systems

In either of the above options, products are loaded onto a conveyor belt in the Low Risk Area, and are transported through the spray jets into the High Care area. This is where conveyor design can affect the efficacy of the process.

If the conveyor is a solid PU belt, which is used in some basic units, the product may only be sanitized on the upper surfaces, leaving the base unaffected, which if coming from transportation pallets, can probably be the most critical area of contamination. An argument for this can be that the belt itself is wetted, so the product base does come in contact with the solution, but this depends on the package design, and on some ingredient buckets this would not be the case.

So, what about modular open belt designs? This type of belting is certainly more suited to the sanitizing process, allowing fluid to be sprayed through the belt, and onto the base of the product, basically giving a 360° flow. However, certain areas of the product can still be shielded from the flow of solution by the parts of the belt that are in contact with the product base. This method is employed on many units available on the market today.

Sanitizing Tunnel Figure 1

Fig 1

In order to be certain of full coverage, it is recommended that belt contact is removed from the product in order to allow an uninterrupted flow of solution to all faces. This can be achieved in 2 ways, by either having 2 conveyor belts, or having a conveyor design that removes the belt and then re-introduces it following the spray bar – see Fig 2.

Sanitizing Tunnel Figure 2

Fig 2

With the 2-belt option, it allows separation of areas (Low Risk/High Care) meaning that the high care conveyor belt does not enter Low Risk, and can also facilitate bi-directional operation, allowing packaging or other items to be transferred back to Low Risk in a controlled manner, isolating the fluid flow in the reverse operation. With the 2 belt system, a counter drive is used, by means of a chain or meshing sprockets, which on some sanitizers can in itself introduce an additional issue with cleanability of the unit if correct hygienic design principles are not considered.

The Unitech Conveyor Solution

A single belt system can be employed and still allow full 360° coverage, with the Unitech Washing Systems divert belt design. This eliminates a counter drive (for one directional units), improves cleanability of the machine and also sanitizes the belt on the return, with the re-circulated units fully immersing the belt into the reservoir ensuring a completely sanitized belt is offered to the product at the infeed. – see fig 3

Sanitizing Tunnel Figure 3

Fig 3

Additional Considerations

There are several other issues to be considered in the design of a sanitizing systems. For instance when transferring from Low Risk to High Care, there may not be an operator to receive the product at the end of the process, so it is important that a photocell or sensor is employed, stopping the conveyor belt to prevent goods either ending up on the floor, or if a physical stop is used, preventing product from continually rubbing on the belt.

Cleanability of the units, ease of maintenance and hygienic construction are also important, and are often overlooked or compromised on many systems worldwide. So, as the above points demonstrate, there can be several differences between a well-engineered, specifically designed sanitizing unit, and a unit that performs the task inadequately. Employing the correct unit and principles can ensure your facility remains free of pathogens and bacteria that could easily be unintentionally introduced from outside sources.

For more details on the Unitech Washing Systems’ sanitizing units or any other of our wash plants, please contact us and we would be more than happy to discuss any applications that you may have.