salad washing

Salad washing

The washing of fresh cut fruit & vegetables is important because there is no opportunity with salads or fruit to carry out a thermal reduction step for control of microorganisms.


Both pathogenic and non-pathogenic microorganisms have been shown to form intimate attachments and/or form biofilms on fruit and vegetable surfaces, as well as on food contact surfaces on processing equipment. Such interactions allow the microorganisms to effectively resist the antimicrobial activity of applied disinfectants and therefore provide a source of further contamination of produce.


Chlorine based disinfectants

Chlorine-based disinfectants are most commonly used in the fresh cut fruit and vegetable industry.  Benefits include their low cost, ease of use and numerous studies demonstrating the ability of chlorine to reduce microbial numbers by up to 2 logs. Nonetheless, there is a drive to minimise the use of chlorine in the industry due to environmental concerns, potential health implications of chlorine by-products and consumer reticence. Coupled with this is a need to reduce water consumption, whilst ensuring that the safety and quality of products is maintained.

The chlorine solution may be made up with sodium hypochlorite and water but more commonly in a kitchen environment with rapid dissolving chlorine tablets.


Chlorine alternatives

Washing with clean water has been shown to typically reduce microbial loading by 1 log.

Ozone has been proposed as a useful disinfectant solution in water. In principle, because it is a powerful oxidiser it should be effective as a disinfectant.  However, it will be rapidly deactivated by any organic material it comes into contact with (for example food debris). Ozone leaves no residues to taint or contaminate food and passes only oxygen and water to the environment.  

Peroxy acetic acid based disinfectant are effective against a wide spectrum of micro-organisms, including vegetative and sporing bacteria, moulds, spores, yeasts and viruses.  They are suitable for a wide variety of vegetable, salad, and fruit washing operations, it is particularly suited to automated dosing systems. At typical use concentrations the biocidal efficacy of peroxy acetic acid based disinfectants (such as Crystal) is several orders of magnitude better than that of comparable concentrations of sodium hypochlorite. They are low foaming and can be used in soak and recirculation systems. Unlike hypochlorite based disinfectants, they do not cause pitting corrosion, and do not precipitate brown stains of iron and manganese, and are effective without the need to modify pH by the addition of organic acids. Peroxy acetic acid based disinfectants break down to form water and acetic acid; no chlorinated organic compounds are produced.