Barrie Trevena, an independent Environmental Health Consultant and Director of Kernow Enviro-Wise Ltd, explores the main methods of disinfecting hand and food surfaces and the effectiveness of these methods.

There are two main methods to disinfect food and hand contact surfaces in food businesses: heat and chemical. The ‘E. coli O157 Control of Cross-contamination’ Guidance for food business operators and local authorities gives specific guidance and I will explore two aspects relating to the effectiveness of such disinfection. My comments are based on anecdotal observations during audits and inspections of numerous food businesses across the catering sector.

Effectiveness of commercial dishwashers

Over the last three years, since acquiring a DishTemp® dishwasher thermometer (which is shaped like a small plate and indicates and holds the maximum temperature of the water in the dishwasher, i.e. the rinse water cycle), I have endeavoured to check the final rinse temperature of all commercial dishwashers operating in the various food premises I have had access to, either as an independent EHO advising a client or as a local authority contracted EHO inspecting a food business.

Unfortunately, because conducting a regularised survey was not the reason for the checks, I have no hard evidence to confirm my observations, but many dishwashers tested registered less than than 70°C for the final rinse temperature, and less than 10% achieved the recommended 75°C (i.e. for circa 30 seconds rinse cycle) to achieve effective disinfection. Invariably the rinse water indicator, where there was one, registered 82°C+ as would be expected but clearly there is a significant drop in that initial heater temperature where the sensor is normally situated, following the water travelling through the pipework and spraying out onto the items being washed.

My great concern is that the Food Standards Agency confirms heat is the most reliable way to disinfect and that ‘if the same utensils and equipment are used for both raw and RTE foods at separate times, they should be heat disinfected or put through an adequate dishwasher cycle between uses’. No advice is given as to what constitutes an ‘adequate dishwasher cycle’ and I fear, in fact I know, that most food business operators believe their dishwasher is working effectively.

Almost all will confirm that the dishes ‘come out so hot you can’t hold them’ but we all appreciate that water at 60°C is too hot to keep ones hand in, so that observation is no reliable indication of an adequate rinse temperature being achieved. There are also dishwasher temperature strips available which have little windows which change colour according to which temperature has been reached. The benefit of these strips is they can be peeled off the metal dish they were attached to for the test and stuck in the daily diary for due diligence records, as the colour change is permanent. Businesses should be reminded that if they put temperatures of dishwashing in as a Critical Control Point in their Food Safety Management System they need to be careful that they are achieving this.

Effective disinfection in businesses without a commercial dishwasher

I have concerns regarding how food businesses that handle and prepare raw and ready-to-eat foods satisfy the requirement for effective disinfection when they don’t have a dishwasher. Some have only one sink, or maybe two, in which everything gets washed including hands! Should we be insisting on at least an old-fashioned but effective ‘sterilising’ sink, or at least a commercial grade sanitising detergent for washing up?