Air tunnels with UV disinfection.
Contamination Control by UV-C light for access to clean manufacturing environments.
BASIS OF DISINFECTION BY ULTRAVIOLET LIGHT
This is a disinfection method that uses short wavelength light (UV-C, between 100 and 280 nm) to kill or inactivate microorganisms by destroying nucleic acids and interrupting their DNA, leaving them unable to perform vital cellular functions such as their own reproduction.
The wavelength found in commercial lamps is 254 nm. Type C ultraviolet light is not in principle visible to the human eye since it is outside the visible light spectrum. However, many ultraviolet lamps emit a marginal part of their light in the area adjacent to the visible spectrum, giving them a violet colour.
This ability of ultraviolet light to disinfect has been used for years in the food, pharmaceutical, etc, industries for various disinfection processes. This article shows the possibilities of achieving robust and rapid disinfection processes, without hazardous waste, that allows the validation of disinfection in the transfer of materials in hygienic manufacturing processes.
DISINFECTION LEVELS WITH ULTRAVIOLET LIGHT
The disinfection that can be achieved with ultraviolet light will depend on the dose of light applied to each surface to be disinfected. For this reason, it is vitally important to analyse adequately the incidence of light on the surfaces to be disinfected. It is therefore fundamental to analyse the luminous intensity to be contributed and the incidence time. The multiplication of these two factors results in the dose of light applied. With different doses, different levels of microbial load reduction are achieved. According to our experience, it is possible to achieve up to 5 Log10 microbial reductions for plant cells and spores with exposure times of up to eight minutes. These conclusions have been reached with the following microorganisms: E. Coli, Staphylococcus aureus and Bacillus pumilus.
The results that can be obtained will therefore depend on the following factors:
- Luminous intensity measured on the surface to be disinfected, measured in energy/surface units.
- Exposure time (t).
- Dose: (energy/surface) * t.
- Geometry of the body or surface to be disinfected.
FOOD INDUSTRY NEEDS
The contamination that can be found in food can be defined as any substance not intentionally added to the food which is present as a result of the production, manufacture, processing, preparation, treatment, packaging, transport or storage, or as a result of environmental contamination. It is therefore a fact that contamination will be present in the manufacturing process and we have to make sure that the level of contamination is controlled.
The possible origins of the contamination are usually:
– Tools and equipment.
– The operators.
– The manufacturing environment.
– The flow of materials throughout the production process.
These risks can be mitigated out with the actions described in Table 1.
|SOURCES OF CONTAMINATION||RISK MITIGATION ACTIONS|
|Tools and equipment.||Cleaning, validated CIP, sanitisable equipment.|
|Users||Procedures and training.|
|Manufacturing environment.||Controlled contamination environments. *|
|Material flow, raw material flow and semi-finished materials.||Safe and efficient transfer systems.|
* Clean rooms.
Here we want to emphasize the possibilities that the adequate use of UV light offers to reduce the contamination coming from the material and raw materials and the semi-finished product flow in the production process.
The efficiency of these disinfection processes will depend on the possibilities of influencing the UV light on the surfaces to be disinfected. For them, if we analyse the types of packaging in which we introduce the raw materials in the production areas, we find the following possibilities:
Undoubtedly, each packaging format requires a specific study of its geometry and behaviour in handling for its disinfection by UV light but it is also true that rapid and waste-free microbial load reductions can be achieved .
On the other hand, we must analyse the materials flow that the production process requires, which means the number of units per hour to be treated. For high throughput, continuous treatment equipment can be configured.
Based on the analysis of these factors, disinfection equipment can be selected to ensure a validated disinfection process.
EFFICIENT DISINFECTION EQUIPMENT
Bags, sacks, boxes and drums equipment for low throughput.
When the need for disinfection throughput is for a few units per hour, we can choose a pass box of sufficient size to enter the loads to be disinfected inside.
In this equipment we can get a throughput of 35 units/hour for a microbial load reduction of 3 Log10.
Figure 1. Pass box – Albian.
Bags, sacks, boxes and drums equipment for high throughput.
When the need for disinfection throughput is for a high demand (units per hour), it is possible to opt for a continuous pass box of sufficient dimensions to introduce the loads to be disinfected.
In this equipment we can achieve a throughput of between 150 and 250 units per hour for a microbial load reduction of 3 Log10. This performance fork is for different lengths of the treatment tunnel (see Table 2).
Figure 2. Disinfection tunnel – Albian.
|Table 2. Different lengths of disinfection tunnels.|
EQUIPMENT FOR BIG-BAGS
When the disinfection of large volumes such as big-bags is required, we can opt for an integral pass box solution of sufficient size to introduce the big-bags to be disinfected with an integrated crane system. Figure 3 shows an integral solution for the passage of big-bags between two manufacturing zones, including a pallet exchanger, from wood to plastic.
In this equipment we can achieve a throughput of up to 14 big-bags per hour, for a microbial load reduction of 3 Log10 on their outer surface.
Figure 4. Big-bags disinfection model.
The validation protocol for these disinfection processes using UV light is based on the following concepts:
- Measurement of the light intensity at the least favourable points (UV-C): mW/cm2
- Setting a cycle time.
- Calculation of the dose: mW * · s/cm2 and comparison with the usual disinfection pattern (based on previous experiences).
- Performing a microbiological test to measure the reduction of the microbial load (coli, S.Aureus, B. Pumilus). The usual acceptance criterion is between 2 and 5 Log10.
Microbiological tests can be performed in two ways:
A. Through culture plates prepared with specific microbial loads.
Figure 5. Example of control plates with microbial loads of 104 103 102 101 y <10 cfu/plate.
B. By strips with spores.
Figure 6. Bacterial spore test strip.
UV light disinfection is an option to consider in the processes of material transfer between areas of different classification or cleaning levels, in the pharmaceutical, food and other related industries.
It is a quick solution without residue.
Microbial load reductions of up to 5 Log10 can be achieved in reasonably short cycle times.
If the morphology of the packaging to be disinfected is studied carefully, the shadow areas which the light does not affect and which will not be disinfected can be minimised.
We cannot say sterilisation, but yes, there is an important microbial load reduction.
Albian pass boxes can disinfect a large number of containers, from small containers, bags, sacks to even big-bags.
De-dusting treatment can be combined in the same pass box.
Albian Equipment, R&D Department, study of PBOX family for UV disinfection: 15043-2017.