In Summary
- Effective cleaning must be carried out for sanitisation to be effective.
- To validate a sanitisation scheme, there are various factors that must be considered, contact time, chemical concentration, temperature, and presence of neutralisation chemicals.
- Sometimes, companies which manufacture chemical sanitisers may already have validated their product’s effectiveness, and a grower can validate it in their process rather simply.
- If a grower needs to verify for themselves, they may consider doing microbiological tests before and after the sanitising treatment.
- When verifying sanitiser effectiveness, try to replicate the real growing environment as closely as possible.
Validation of Sanitation
Effective cleaning is a pre-requisite for effective sanitation, as it is almost impossible to sanitise a dirty surface. A "validated as effective" sanitation scheme is considered important for a particular use because there are a number of factors that can influence a sanitising chemical's kill effectiveness. Factors which affect kill effectiveness includes: contact time, chemical concentration, temperature and the presence of neutralising chemicals. For example, areas with high iron content in water can't use some chlorine-based sanitisers without experiencing precipitation problems which effectively lower the sanitiser concentration and require longer contact times. Iodine based sanitisers rapidly lose activity at alkali pH not much greater than pH 7 and so can't be effectively used on surfaces which could have alkali residue from (for example) a previous cleaning chemical.
It is important that growers (or their chemical suppliers) undertake some basic testing to ensure that the sanitising chemicals that they are using are suited to the application they are being used for. In many cases, the chemical manufacturer will already have undertaken the required testing as part of their 'due diligence' before bringing their product to market. In such cases, obtaining the required validation data might be little more than a paper filing exercise.
For those growers that need to undertake verification for themselves, the following information may be helpful. The purpose of the validation is to show (or not show) that the sanitiser that is being used is effectively killing bacteria and other microorganisms on tools, harvesting equipment and food contact surfaces.
The traditional way to demonstrate an effect is to take microbiological samples from different parts of surfaces before and after the sanitising treatment and compare the counts of indicator bacteria. Any decision for appropriate indicators to use lies with growers; but likely candidates are total aerobic counts or Enterobacteriaceae for general hygiene and E. coli for surfaces with the potential to be contaminated by faecal material. What constitutes an effective reduction in indicator numbers is again something that should be decided by growers. General information on comparing reductions in bacterial numbers using statistical methods is available on the help page dealing with the validation of sanitisers.
When undertaking a verification of sanitiser effectiveness, it is important to try and mimic what generally happens in a growing environment as closely as possible. It is also important that the surface being sanitised is visibly clean.
Changing a chemical's concentration or using a new type of sanitising chemical requires a new validation to be undertaken.
Further reading with far greater detail on how to validate a sanitising chemical for use in a food harvest or packhouse environment can be found in the International Standard ISO 1276:2019.
