Why is it important to monitor disinfection in fresh produce washing?

Fresh produce must be washed to remove dirt, pesticide residues, and microorganisms responsible for quality loss and decay. Washing fresh cut produce with potable water helps remove microorganisms to a certain extent but a sanitiser must be used to ensure complete produce safety.

Disinfection must be monitored to ensure the correct amount of sanitiser is present. Without regular testing you may be overdosing or underdosing your sanitiser, both of which can cause problems. Underdosing can compromise cleanliness and safety, and overdosing can affect product quality and increase chemical costs.

What are the main sanitisers used in fresh produce washing?

Chlorine

Chlorine sanitiser products are widely used due to its effectiveness and relatively low cost. However, chlorine is strongly affected by pH, temperature, and cleanliness of the wash water, and therefore needs to be carefully monitored.

The efficacy of chlorine is reduced with increasing turbidity and is less effective on certain biofilms and microbes. In addition, light and metals can cause breakdown of chlorine.More chlorine is required in dirty water because chlorine is de-activated by organic matter. The amount of this de-activation is known as the chlorine demand.

Peracetic Acid

The use of peracetic acid, also known as peroxyacetic acid or PAA, has grown in use as a sanitiser. Approvals from the US Environmental Protection Agency (EPA) and U.S. Food and Drug Administration (FDA) support the use of PAA in fresh produce washing applications. Additionally, PAA is popular due to reduced levels of disinfection by-products – none of which are harmful to the environment or health.

PAA is effective against a broad spectrum of microbes and remains active when the organic matter load is high. It is effective even at low temperatures. An independent study, by CEBAS, identified Palintest sensor technology as the best method for testing PAA in produce wash water. For fresh produce treatment PAA is typically applied between 30 ppm and 80 ppm in wash water, with higher concentrations used for surface sanitation. PAA at high concentrations can be hazardous to the health of workers, and therefore should be handled with care and monitored regularly.

Chlorine Dioxide

Chlorine dioxide is a gas used to sanitise various food and beverage wash systems. It is around 2.5 times more active than hypochlorite based sanitisers and is less affected by pH and organic matter compared to chlorine. Chlorine dioxide is highly effective as a sanitiser meaning a lower residual is usually sufficient for treatment.

Chlorine dioxide is less corrosive than chlorine but can lead to potentially harmful disinfection by-products including chlorite. With effectiveness at lower residuals, it is important to regularly monitor concentrations of chlorine dioxide to ensure the system remains within operational limits.

Ozone

Ozone is a colourless gas that is a strong oxidizer. It is highly effective at killing microbes but is not suitable for all fresh produce processing systems due to operational limitations.

Ozone is quickly broken down to oxygen in contact with water and is de-activated rapidly by organic matter. Once de-activated, there is no residual control for microbes, and ozone becomes ineffective. The effectiveness is strongly determined by contact time and residual concentration. Ozone can be hazardous to the health of workers, and therefore should be handled with care and regularly monitored.