Thinking beyond chemicals for sustainable fresh produce disinfection

Microorganisms can contaminate salads, fruits and vegetables from any number of sources – fertilisers used for growth, water used for irrigation, the use of pesticides and bacteria from animals can all impact the cleanliness of the fresh produce. It is vital, therefore, that before being placed on the market, fruits and vegetables must be thoroughly and suitably washed to reduce the health risks of contamination from bacteria, such as E. coli.

Sanitising produce

For several decades, chlorine has been used to wash fresh fruit, vegetable and salad products (M.E. Parish, 2003, p. 164) to kill microorganisms and remove pesticides. Even today, chlorine is heavily relied upon for sanitation purposes – but it does have disadvantages. Chlorine’s limited effect in destroying microorganisms on the produce surface means that high dosages of chlorine are often used, sometimes with limited added benefit (M.E. Parish, 2003) and often leaving a residue on the produce to be consumed by customers (Xu, 1999).

While the use of chlorine at high levels in processing non-organic fresh produce is still permitted, there are many reasons why food manufacturers should look for alternative products and processes for cleaning and disinfection. Reasons to avoid the use of chlorine include improving the safety of the fresh produce due to health concerns of the carcinogenic by-products of chlorine use (Jennifer L. Banach, 2015), and the increasing environmental concern around the levels of chlorine in discharged waters (A Abarnou, 1992).

Some EU countries have already taken steps to limit the use of chlorine in washing processes of fresh produce, with the UK limiting free and total chlorine levels in wash water, as well as the produce to water ratio (Jennifer L. Banach, 2015).

Clean without chemicals

An efficient and more environmentally-focused alternative to chlorine, Ozone is a powerful disinfectant that offers the benefits of effective microbial quality control of circulatory water, without the need for halogen-based chemical biocides or disinfectants.

Ozone is an inorganic molecule, (O₃), and an allotropic form of oxygen which can be formed naturally in the atmosphere by the discharge of electricity during a thunderstorm. When produced within an Ozone generator, a high voltage of electricity is passed across a gas stream containing oxygen. The energy of the high voltage splits an oxygen molecule (0₂) into two oxygen atoms (0) which recombine with ordinary molecules of oxygen (0₂) to form ozone (0₃).

Ozone gas treats the water using a process called Ozonation. With Generally Regarded as Safe (GRAS) status granted by the United States Food and Drug Administration (FDA), Ozone can be used for all food products without restriction (excluding milk, which has its own specific regulations). Tests have shown that Ozone controlled at 2 mg/ltr in the wash water can achieve a greater than 99 percent reduction in surface microbial populations, equal to or better than that achieved with chlorine at levels of up to 50 mg/ltr. Ozone is particularly effective against E. Coli, the food pathogen of most concern in the produce industry (C*T for 99 percent de-activation, 0.02 for ozone against 0.4-0.75 for chlorine dioxide).

Additionally, it’s not just about Ozone’s capacity to disinfect. Ozone is a tried, tested and examined method, with research showing it is 1.5 times stronger than chlorine (Xu, 1999). In fact, Ozone can also control the taste and smell of the fresh water (Xu, 1999) without the risk of a risk of hazardous by-products, as the breakdown component is oxygen.

Where Ozone is used as a direct replacement to halogen-based products, any procedure requiring a Cleaning in Place (CIP) process has downtime dramatically reduced, as there is no neutralisation step given that the Ozone by-product is oxygen. ROI on such an initiative is often less than a year (dependent on process and volume), and the principle of Ozone disinfection can be used in a plethora of applications, including bottling and canning.

The benefits of sustainable production

Within the food industry, safety is the most important factor. However, as with any organisation, sustainability, energy efficiency and corporate responsibility are increasingly important focuses. The processing of fresh produce involves high water usage through cleaning, sanitisation, manufacturing and refrigeration.

In a bid to minimise water consumption, organisations can recycle water, but it is vital to ensure anything recycled is safe to use. In food production, wash-water quality can be compromised as a result of soil and other contaminants on the fresh produce. After being used to wash fruit and vegetables, contaminated wash-water will require treatment to bring it up to drinking water standard, if not higher.

Not only can Ozone treat water without the use of traditional halogenated chemicals, it can also support any organisation’s objective to minimise water consumption. The Ozone gas is produced ‘in situ’ within the Ozone generator to refresh and sanitise the water without contamination – an ideal water treatment option for reuse and recycling. Better yet, using Ozone treats water to a degree of purity and freshness that is unachievable by any other means, destroying by-products, pesticides and toxic organic compounds without leaving toxic residues, in addition to conftrolling the taste and smell of the water (Xu, 1999).   

Toxin-free

With Ozone, there are no residual compounds or toxins left on the product or in the rinse water. This is because ozone has a short half-life, lasting only 10 to 20 minutes before it breaks down to natural oxygen. Halogen-based products such as chlorine and chlorine dioxide cause concern when discharged into the environment, limiting the ability for recycling and reusing wastewater. Ozone’s lack of residual contamination means that Ozone-treated wash water can be discharged to the environment or used for other applications without any need for additional treatment or decontamination of areas or products.

While chlorine and other chemical compounds may seem like the easier option due to the lower capital costs, Ozone has shown to be more effective than chlorine and other disinfectants when used on a range of microorganisms (Xu, 1999). Therefore, investing in long-term solutions can support sanitation objectives, as well as meet other business goals by reducing operating costs and minimising the overall impact on the environment through reduced water usage and cleaner wastewater discharge.

Bibliography

A Abarnou, L. M. (1992). Chlorinated waters discharged to the marine environment chemistry and environmental impact. An overview. Science of The Total Environment, 173-197.

Jennifer L. Banach, I. S.-K. (2015). Effect of Disinfectants on Preventing the Cross-Contamination of Pathogens in Fresh Produce Washing Water. International Journal of Environmental Research and Public Health, 8658-8677.

M.E. Parish, L. B. (2003). Methods to Reduce/ Eliminate Pathogens from Fresh and Fresh-Cut Produce. COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY , 161.

Statistica. (2016). Statistica. Retrieved 11 21, 2018, from Statistica: https://www.statista.com/statistics/263156/water-consumption-in-selected-countries/

Xu, L. (1999). Use of Ozone to Improve the Safety of Fresh Fruits and Vegetables . Food Technology, 58-62.