Process validation

• Effective cleaning is a prerequisite for effective sanitisation.
• Process validation depends on predetermined and strictly adhered to key factors: contact time, chemical concentration, temperature, and presence of neutralising substances.
• Process validation trials should replicate actual growing and packing conditions as closely as possible.
• Some sanitisers are already validated by manufacturers, and growers may only need to ensure suitability for their process.
• Where process validation is not pre-existing, microbiological testing before and after sanitising is a recommended method.

Effective sanitisation cannot be achieved without thorough cleaning. Dirt and organic matter shield microbes from chemical agents, rendering sanitisers far less effective. A validated sanitation scheme confirms that microbial contamination is reduced to acceptable levels under real-world operating conditions.

The ability of a sanitiser to kill bacteria and other microorganisms is influenced by several key variables:

1. Contact time - the length of time the surface remains wet with the sanitiser.
2. Chemical concentration - too low may be ineffective; too high may leave residues or damage surfaces.
3. Temperature - some sanitisers work best at specific temperature ranges.
4. Neutralising substances - such as residues from other cleaning products or minerals in water (e.g. iron), which can inactivate certain sanitisers.

Chlorine-based sanitisers may form precipitates in water with high iron levels, reducing effective concentration. Iodine-based sanitisers lose efficacy above neutral pH, so cannot be used effectively on surfaces with alkaline residues (e.g. from some detergents).

In many cases, chemical manufacturers have already validated their sanitising products under standard conditions. For growers, this means the validation process may simply involve obtaining documentation and ensuring the sanitiser is appropriate for the specific application.

If growers need to verify the effectiveness of a sanitiser themselves, whether due to changing products, application methods, or because of customer requirements, the following approach is recommended: take microbiological samples from surfaces both before and after sanitisation, then compare microbial counts. This approach can demonstrate whether the sanitiser achieves an acceptable microbial reduction.

Suitable surfaces to test include food contact areas, harvesting tools and equipment, and high-risk zones where contamination is more likely. The following organisms are recommended indicator organisms:

1. Total aerobic counts – general hygiene
2. Enterobacteriaceae – hygiene and sanitation efficacy
3. Escherichia coli – for surfaces with faecal contamination risk

Growers must determine their own acceptable levels of reduction, based on risk assessments or customer specifications.

For further detail on statistical analysis of bacterial reductions, refer to the guidance on the trending of microbiological data.

When conducting a process validation trial, ensure the surface is visibly clean before sanitising and replicate real-world conditions as closely as possible (e.g. the same equipment, water quality, contact times).

Re-validate if there are any changes to the sanitiser, including switching to a different chemical, altering concentration, and/or changing application method (e.g. spraying vs. dipping).

For growers seeking more detailed technical procedures, refer to International Standard ISO 1276:2019 Chemical disinfectants and antiseptics - Quantitative suspension test for the evaluation of bactericidal activity in the food, industrial, domestic and institutional areas. This standard provides in-depth information on how to conduct effective validation of sanitising chemicals in food production settings, including packhouses and harvesting environments.