The bacteriophage mix making up Biolyse®-PB has been developed over a number of years of intensive sampling, addressing the need for an effective, sustainable alternative to chemical biocides used widely in the fresh-produce industry to reduce spoilage, shelf-life failures and associated economic losses. It has been proven microbiologically, visually and by excellent customer feedback.

The bacteriophage mix is applied as a fine mist to washed potatoes on a roller table prior to bagging. Application midway-along the roller table ensures that the potatoes are no wetter when bagged than without treatment or with the application of a chemical biocide.

Microbiological analysis of potato samples taken pre- and post-bacteriophage application indicates that the Biolyse® treatment significantly inhibits bacterial growth, below the threshold that soft rots and breakdown are observed. Furthermore, these reductions in rot-causing bacteria on the potato surfaces are subsequently reflected in reduced shelf-life failures for the packers and fewer complaints regarding quality from the end user.

Log counts of Pectobacterium bacteria (per ml of peel extract) from potatoes collected before and after treatment with Biolyse

Example of retailer customer complaints due to "rots" on Jersey Royal potatoes supplied by 3 different suppliers, with "supplier 3" having treated their potatoes with Biolyse

bagged salads: reducing spoilage

Bagged salads are a relatively new and rapidly growing (7% p.a.) category for the UK’s retailers, with product development and innovation central to success. The industry, however, is hampered by short shelf life and bacterial rots, causing losses throughout the supply chain; on farm, in the factory and in the home. APS has applied its skills in isolating bacteriophage and creating effective mixes to formulate a bacteriophage product suitable for use with bagged salads, reducing bacterial breakdown and also, presenting a solution to growing issues associated with chlorate residues on foods such as salads routinely washed with chlorinated water to reduce bacterial loading. The main spoilage bacteria on salads are Pseudomonas spp.

The process can be summarised:

A five-bacteriophage mix was prepared after sampling a variety of salad leaf varieties commonly found in mixed salad bags, isolating the rot-causing Pseudomonas bacteria from them and “enriching for bacteriophage active against these pathogens.

  1. In the laboratory, treating salad leaves with the bacteriophage considerably reduced the growth of rot-causing bacteria compared with a water-only treatment.

  2. In a factory trial, where “failure” in shelf-life testing is taken as >10% defects, treatment with the bacteriophage mix extended the shelf-life by 3 days; highly significant in a product that routinely has such a short shelf life.

1. LABORATORY TRIAL: Counts of Pseudomonas bacteria (cfu/g tissue) from salad material treated with a 5-bacteriophage mix, compared with a water-only control and no treatment

2. FACTORY TRIAL: % Defect of bagged salad, "date of packing + x days". Failure is taken as >10%. Bacteriophage treatment extending the shelf life from DOP+ 5 in the controls to DOP+ 8