Sanitizers for Flume and Spray Bar Wash Lines

Flume and spray bar wash lines typically use chlorine, chlorine dioxide or peracetic acid to achieve disinfection. They are used to reduce microbial load on the product or prevent cross-contamination between batches of produce where wash water is re-used.

In both flume and direct spray systems, minimum concentration limits must be maintained to satisfy legal or operational requirements regarding microbial safety. Maximum limits are implemented to prevent oxidative damage to produce or impact on employee safety.

Contamination through failure to control sanitizer concentrations in flume or spray water used in postharvest processing has been associated in multiple fresh produce outbreaks or food safety recalls.

Accurate onsite test results can be used to control sanitizer concentration and water quality at effective levels to ensure food safety, cost savings and reduced environmental impact.


  • Get repeatable and reliable results each time. Kemio minimises user input to deliver consistent results from all operators.
  • Reduce uncertainty of test results by enabling operators to act on clear pass/fail results based on your specification.
  • Kemio is suitable for all users, with clear visual instructions which requires user training. Clear visual instructions guide the user and minimises chances for error.
  • Suitable for all sample types, Kemio is not affected by coloured or turbid samples.
  • Reduce expensive laboratory tests with Kemio spot checks.
  • Measure free chlorine, combined chlorine, total chlorine, chlorine dioxide, chlorite and PAA on one instrument.
  • Personalise your Kemio by adding your unique test and application information to improve traceability and provide a complete dataset.
  • Go paperless and protect your data to meet your compliance requirements. The integrated data log summarises 10,000 results to provide a traceable, auditable dataset.
What is the US-FDA maximum concentration of PAA allowed in fresh produce wash waters?

21 CFR 173.315 states that peracetic acid concentrations must not exceed 80 ppm for fruits and vegetables that are not raw agricultural commodities. Rinsing with potable water is not required to remove residual PAA.
Raw agricultural commodities are generally defined by 21 U.S. Code § 321 as “any food in its raw or natural state, including all fruits that are washed, coloured, or otherwise treated in their unpeeled natural form prior to marketing”.

Which sanitizer is best to use for flumewash water?

Each sanitizer has its own unique advantages and drawbacks regarding cost, efficacy and disinfection by-products for each product being washed.

Chlorine is the most cost-efficient to dose at high concentrations in flumes. Although the weakest oxidiser of the three, chlorine will persist in wash waters for longer periods of time due to its reduced volatility.

Chlorine dioxide is significantly more expensive than chlorine, but much lower levels are required, typically 0-5 ppm. This increased reactivity makes it more effective against bio-film build-up and chlorine resistant pathogens.

Peracetic acid (PAA) is often the most expensive sanitizer but it provides highly effective disinfection, even against chlorine resistant pathogens. In addition, it requires less complex dosing equipment than chlorine dioxide.

Which sanitizer is best to use for direct spray disinfection?

Direct spray applications, where the product is not rinsed further, will typically use peracetic acid as the breakdown products are either already food-grade (e.g. acetic acid) or generally regarded as safe (GRAS).

Other chemical disinfectants applied to produce surfaces may leave behind by-products harmful to health but are still useful where additional rinsing may take place before packaging or consumption. They may be preferred due to their lower cost compared to peracetic acid.

The best disinfectant to use will therefore depend on the process being used, the produce being sprayed and whether it has regional approval.


Why does Europe not allow disinfectants to be applied to meat and poultry during processing?

Disinfectants are applied to meat products during processing to reduce microbial contaminants, such as salmonella, which can occur during rearing or harvest. These processes are often called microbial intervention, direct intervention or pathogen reduction treatments – and all are banned within the European Union.

Industry bodies within the European Union argue that, whist safe to human health, the use of chemical disinfectants at the abattoir can encourage poorer hygiene practice at the farm during rearing of the animal and at point of harvest. It is claimed that a more holistic ‘farm to fork’ approach can achieve safe meat products without the need for chemical disinfection.

Where should I take my sample from?

The first thing to always consider when sampling from spray bars and flumes is ensuring it is both safe for the operator to do so and does not compromise produce or wash water quality. Never sample using glass vials or jars.

For flumes, if it is safe to sample directly from the flume this will provide the most representative sample. Look to sample downstream from where the chemical is being dosed to give time for it to disperse and reach a homogenous concentration. For longer flumes, multiple points should be tested to ensure the correct disinfectant residual is present even at the end of the line. If it is not safe to sample directly from the flume, water should be taken from a sampling port or run-off point on the line.

For spray bars, sampling from the nozzle itself will ensure that the concentration measured is exactly what is being applied to the produce. However, spray nozzles are often high up and the applied disinfectant may be applied at a high concentration and under pressure – so it is common to have sample ports built into pipework feeding spray bars for safety reasons.
When sampling from a port, rinse you sample container at least 3 times with water from the port – this removes contamination from the sample and ensures the water being tested hasn’t been sitting in the pipe.

Should I choose an online testing system or an offline test system for my flume and/or spray bar?

Online systems for testing spray systems at the point of application are not available, though some systems may be installed close to the point sanitizer is added to the pipework feeding spray systems.
For all applications, even with an online system, an offline system will always be needed for verification and calibration.
For more information about what you should consider when choosing a test method, read our advisory piece here.

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Why Kemio Technology?

Kemio technology offers significant advantages compared to alternative techniques for sanitizer control in food and beverage. Unlike traditional methods, Kemio has no user subjectivity and minimal user input which minimizes potential operator errors and variation in results.