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Cleaning programmes and Coronavirus control: - lessons learnt
John Holah, Principle Corporate Scientist, Kersia
Prior to undertaking a cleaning programme in the food industry for food processing equipment, a number of considerations are required. Firstly, the objective of the cleaning programme should be determined, and 10 or more objectives may be realised (Holah, 2018). This could include the need to remove visual soiling for organoleptic reasons, the need to remove soils for brand protection issues such as different meat species, the need to control food spoilage microorganisms or the need to control hazards such as allergens or pathogens.
Secondly, a risk assessment should be undertaken to assess the choice of cleaning chemicals required and application techniques. This can include the chemical nature of the food soil and the food processing conditions that has led to its formation, the chemical compatibility of the surface the soil is formed on, the hardness of the water supply, where the soil is (open or closed surfaces), the application method (manual or automated), the rinsing method and pressure, and any impact on effluent treatment plants present.
Thirdly, more practical aspects should be considered such as production implications (length of cleaning window available) and costs. Following these considerations, a cleaning method and chemicals are chosen that meets the programmes cleaning objectives, and that has minimal impact on other food processing and environmental activities. This cleaning programme might be a single stage (gross soil removal, pre-rinse, detergent clean, post-rinse) or a two stage (gross soil removal, pre- rinse, detergent clean, post-rinse, disinfect) programme. The majority of cleans within the food industry for food processing surfaces are likely to be two stage cleans.
The current COVID-19 pandemic has done nothing to change these considerations (the original cleaning objective must still be met) and to thus attempt to change current food processing equipment cleaning programmes, without due consideration, may be counterproductive. In addition, the recommendations from the WHO (WHO1 2020), CDC (CDC 2020) and EFSA (EFSA 2020) remain that there is no evidence that COVID-19 is transmitted by food (or its packaging).
What has changed with COVID-19, however, is the need to consider additional environmental and personal hygiene measures. These are primarily to prevent person to person transmission via touching fomites that could have been contaminated from an asymptomatic or pre-symptomatic COVID-19 case. In particular: -
In relation to COVID-19 decontamination, early studies on the survival of SARS-CoV-2 on stainless steel and plastic surfaces (e.g. van Doremalen et. al., 2020) suggested a decimal reduction time of approximately 17 hours, but more recent studies have suggested survival is much longer, particularly at low temperatures, e.g. a decimal reduction time of 163 hours at 4oC (Guiellier et. al., 2020). Practical advice has thus gone from the potential to leave an area fallow for 72 hours to ensure SARS-CoV-2 decontamination to the fact that fallow time per se is insufficient and that surface disinfection is always required. Holchem has produced generic cleaning instruction cards (CICs) to cover these additional COVID-19 controls, both within food production and in ancillary areas, and these are available on the Holchem website.
It may, however, be prudent to ask the question as to whether current cleaning programmes for food processing equipment have any effect on SARS-CoV-2.
Cleaning and disinfection are well understood for their impact on bacteria and all stages of the cleaning programme have an impact on bacterial control. Gross soil removal and pre-rinsing remove many bacteria that are associated with the food soil. Detergent application can remove bacteria from food contact surfaces and the detergents themselves have known impacts on bacteria. This is due to extremes of pH (acidic to caustic detergents) outside the tolerance of the bacteria and the effects of surfactants on bacterial cell walls which could affect cell permeability. Disinfection, undertaken on pre-cleaned surfaces where the level of soiling is much reduced, is well established with a number of European disinfectant tests available to assess the antibacterial activity of biocide active ingredients and formulated finished products (e.g., EN 1276 and EN 13697.). Indeed, a combined cleaning and disinfection programme for microbial control has been described as a unit process and a combined 5 log reduction or more of bacteria present on the surfaces is expected (Holah, 2014).
However, as foodborne viruses have only recently been identified as a potential issue in food safety, our knowledge of viruses on food contact surfaces and their associated removal via cleaning programmes is poor and COVID-19 has only now brought this into focus. Viruses embedded in the food soil will be removed via the rinsing and detergent steps from surfaces. How strongly viruses attach to food processing surfaces and how well they are removed from them via detergency is, however, not well known, as is the potential effects of detergents on the virus structure or its infectivity (technically the virus is not ‘alive’ so it cannot be ‘killed’).
One of the lessons that we have learnt about the control of COVID-19, and well broadcasted to the public (WHO2, 2020), is that “washing your hands with soap and water dissolves the virus”, which is based on established facts (e.g. Sickbert-Bennett et. al., 2005). Some detergents may, therefore, influence coronaviruses.
As part of its programme to provide guidance on hygiene procedures to control COVID-19, Holchem have commissioned studies to look at the effect of a range of Holchem detergents on coronaviruses. Studies were undertaken by the Perfectus Biomed Group (Daresbury, Cheshire, UK) who have the ability to work with one of the human coronavirus strains, strain 299E (HCoV-299E). Six detergents were chosen to reflect the type of detergents commonly used in the food processing and food service industries, to include caustic, alkaline, neutral and acidic products. The detergents were tested against the HCoV-299E using the method of the European virucidal disinfectant test EN 14476, under dirty conditions, according to their recommended concentrations and contact times. Note: EN 14476 was chosen as a test method not to make any disinfection claims, but as a simple way of assessing any virucidal activity of the detergents using an accepted test method. The results are shown in Table 1.
The results show that all of the detergents show virucidal affects, with a range of between 1.5-3.67 log orders of loss of infectivity (96.8-99.98% reduction) within their in-use concentrations. The surfactant-based products were the most effective, within their 5 minute contact times, rather than the extended contact times (20min) of the caustic and acidic products. In some way this endorses the WHO position that “washing hands with soap dissolves the virus”. The acidic product was more effective than the caustic detergents.
Any virucidal activity realised in practice from detergents, however, will be inconsistent and will depend on the level of soiling present on the surface. Whilst the studies were undertaken under ‘dirty’ test conditions (within the context of EN 14476), these are meant to be reflective of poorly cleaned, rather than uncleaned, surfaces. We can say, however, that detergency will have some role in reducing the presence (removal) and infectivity (of remaining) coronavirus, particularly after much of the soiling present has been removed from the surfaces.
As noted above, disinfection is only ensured following cleaning, when the vast majority of the soiling has been removed, and this work emphasises the need for disinfection to further reduce the infectivity of any viral particles present. And just for clarity, even though the detergent action may have virucidal properties, detergents should not be seen as a replacement for disinfectants – combined cleaning and disinfection programmes must continue where currently advocated.
Detergent generic description
Contact time (min)
Caustic detergent used in CIP, soak or boil-out operations
Chlorinated caustic detergent used in CIP, automated tray washing, soak or boil-out operations
Low alkalinity detergent used in foam applications or in manual cleaning
pH neutral surfactant-based detergent for manual cleaning
Surfactant-based detergent for manual cleaning
Phosphoric acid based detergent used in CIP, automated tray washing, soak or boil-out operations
Table 1 – loss of infectivity of HCoV-299e expressed as log reduction or percentage reduction, following exposure to a number of detergents
We have long recognised the general disinfectant resistance patterns between microorganisms likely to be found in food establishments, with an established order as proposed by McDonnell and. Denver (1999) and shown in Figure 1.
Figure 1 – Relative resistance of microorganisms to biocides
As coronaviruses, including SARS-CoV-2, are enveloped viruses, they are thus the least resistant to disinfectants of the microorganisms found in food etablishments.
The World Health Organisation have recommended 1000ppm sodium hypochlorite and 70-90% alcohol as effective disinfectants for coronaviruses (WHO3). Since the onset of COVID-19, there has also been a number of scientific publications that have considered the resistance of coronaviruses to disinfection and disinfectants including QATS, sodium hypochlorite, hydrogen peroxide and ethanol have all been shown to be effective (Ijaz et. al., 2020, Han et. al., 2021). It is likely, therefore, that many of the disinfectants that have been approved for bacticidal action and that are used in our current cleaning and disinfection programmes for food processing equipment will also be effective against coronaviruses.
In addition, specific disinfectant product performance claims can be made for virucidal activity against the European disinfectant test, EN 14476, which requires a 4-log reduction of infective viral particles in 5 min. The performance claim is dependent on the viruses chosen as test microorganisms. If a surface disinfectant product passes EN 14476 against Adenovirus, Murine Norovirus and Poliovirus, a claim can be made that the product is virucidal and is likely to be active against all known viruses. If a product passes EN 14476 against Adenovirus and Murine Norovirus only, a limited spectrum virucidal claim can be made against all enveloped virus and some non-enveloped viruses, e.g., Norovirus. Finally, if a product passes EN 14476 against Vacciniavirus, a limited spectrum virucidal claim can be made against all enveloped viruses.
Disinfectants used for additional environmental decontamination (as advocated above) and decontamination following any known COVID-19 cases, must be EN14476 approved.
The detergency studies (Table 1) and general knowledge on viral disinfection enhance our knowledge of the overall potential programme of routine processing equipment cleaning and disinfection programmes (to meet their established cleaning objectives) whilst providing additional assurance that they are also controlling SARS-CoV-2. Existing CICs for food processing equipment should thus be adequate to control the potential small challenge of any SARS-CoV-2 being present on pre-cleaned surfaces, arising from pre-symptomatic or asymptomatic COVID-19 suffering food operatives.
A holistic approach of a combined virus surface removal via detergency, together with detergent and disinfectant virucidal affects, should meet the 5 log reduction expectations for bacteria and, due to the lower biocide resistance of enveloped viruses, may well exceeded this. Due to the expected high coronavirus removal and inactivation via a combined detergent and disinfection action, frequent cleaning and disinfection of surfaces is recommended as the best surface coronavirus control strategy.
The monitoring and verification of routine processing equipment cleaning and disinfection programmes to ensure original cleaning objectives are met, e.g. via visual assessment, ATP testing or TVC or pathogen sampling, should remain as is. The monitoring and verification of specific SARS-CoV-2 removal from surfaces is possible, though the development of appropriate test methods is in its infancy. A rapid antigen-based, monitoring detection kit, which will provide a detection of any SARS-CoV-2 present in 15 minutes and works on the same principles as an allergen lateral flow device, has been developed called the COV-Hygien Xpress. However, the detection limit is approximately 5000 viral particles, which may equate to the level present on uncleaned surfaces, and the test does not infer anything on the infectivity of the viral particles, only that there is evidence of their presence.
Verification of SARS-CoV-2 removal can be undertaken by polymerase chain reaction (PCR) based kits, and these are now widely available to the public sector. These kits detect the presence of portions of the RNA from probably single viruses and, as for the antibody-based kit, the test does not infer anything on the infectivity of the viral particles, only that there is evidence of their presence. The downside of these tests is their expense and their timescales, which may be up to 48 hours or more for surface swabs to be returned to the testing laboratory, processed and a result reported. Both the antigen and PCR based test kits maybe more relevant for post COVID-19 decontamination management.
Looking to the future, hopefully, the additional practices the food industry has undertaken associated with environmental surface disinfection and enhanced hand hygiene noted earlier, have helped in their intended COVID-19 control. However collectively, these changes are perhaps the biggest change in hygiene practices within the food industry for many years. Is it possible that these changes could also have brought additional benefits in terms of food safety or personal health? Fewer microorganisms in the food process environment (including operatives’ hands) might lead to reduced levels of general microorganism indicators (TVC, Enterobacteriaceae) and reduced levels of environmental pathogens, particularly Listeria. This could reduce levels of cross-contamination of microorganisms from the environment to the food product, resulting in the food showing lower counts of general microorganism indicators (TVC, Enterobacteriaceae) and lower pathogen incidence. Practically, at the food manufacturer level, this could lead to enhanced product quality, reduced spoilage, improvements in shelf life and fewer customer complaints. Fewer other, non-SARS-CoV-2, respiratory viruses on the hands could also lead to fewer cases of respiratory diseases (colds and flu) resulting in less absenteeism.
Is there any evidence of enhanced food safety? In the wider community, Public Health England (PHE 2020) published cumulative data up to week 30 for common gastrointestinal infections in England and Wales (Table 2).
Cumulative to week 30
Cumulative to week 30
Table 2 – Cumulative laboratory reports of common gastrointestinal infections in England and Wales reported to Public Health England to week 30 for 2019 and 2020
Table 2 shows that the general incidence of gastrointestinal infections in the population was approximately one third lower in 2020. Similarly, the number of Listeria recalls alerted by the FSA in the 2018, 2019 and 2020 is shown in Table 3.
Number of Listeria recalls
Table 3 – FSA Listeria recalls, 2018, 2019 and 2020
Listeria incidence, the organism most likely to be controlled by frequent environmental disinfection in food factories, was also reduced in 2020. This position is not unique to the UK and other countries have also shown a reduction in pathogen incidence in the community, typically reported in Food Safety News (FSE 2020) including Finland, the USA and Australia.
The reasons for the reduction in cases of gastrointestinal illness in the population is complex. Perhaps not as many cases of illness have been reported due to difficulty in accessing GPs (and therefore fewer stool tests), or people are not eating outside the home in restaurants so much, or the diet of people spending more time at home has changed? There may also be changes in the food factory or the manufacturing procedures that might enhance food hygiene. For example, reduced food product volumes, fewer product SKUs, fewer staff, more use of gloves, longer hygiene windows to enable enhanced cleaning. Equally the opposite may be true, with food manufacturers increasing production, particularly at the start of the pandemic, with an increased pressure on maintaining hygiene windows.
It would be very useful, therefore, for both individual food manufacturers and the industry at large, to try and gain evidence from food industry data to see if these major changes in food hygiene practices have had additional benefits to food safety or personal health. Should our current, extended cleaning and disinfection practices become the new, post-COVID-19 pandemic, norm?
BS EN 1276:2019 – TC Tracked Changes. Chemical disinfectants and antiseptics. Quantitative suspension test for the evaluation of bactericidal activity of chemical disinfectants and antiseptics used in food, industrial, domestic and institutional areas. Test method and requirements (phase 2, step 1)
BS EN 13697:2015+A1:2019 – TC Chemical disinfectants and antiseptics, Quantitative non-porous surface test for the evaluation of bactericidal and/or fungicidal activity of chemical disinfectants used in food, industrial, domestic and institutional areas. Test method and requirements without mechanical action (phase 2, step 2)
BS EN 14476:2013+A2:2019 Chemical disinfectants and antiseptics. Quantitative suspension test for the evaluation of virucidal activity in the medical area. Test method and requirements (Phase 2/Step 1)
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WHO3 (2020) Which surface disinfectants are effective against COVID-19 in non-healthcare setting environments. https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-cleaning-and-disinfecting-surfaces-in-non-health-care-settings