Reducing waste and enhancing safety of fresh produce by hydraulic shock washing

This project aims to improve the efficiency, sustainability and safety of bagged salad production, worth over £450M retail
sale value in the UK, through more effective processing of fresh produce. A novel hydraulic shock washing process
designed to be installed in commercial washing systems will be investigated. The process has the potential to extend the
shelf life of prepared salads and other foodstuffs prone to microbially driven spoilage. The process can also reduce the total
amount of water used, and the environmental impact of toxic biocides used in many wash systems. The consortium will be
led by a leading salad producer, and involve members of the salad packaging, retailing, and equipment manufacturing
industries, supported by one of the UK's leading surface biofilm research teams, thus demonstrating integration across the
food manufacturing industry, and the research base.
The existing laboratory Pulsifier works on the principle of a plastic bag containing food and diluent inside a metal ring which
is cycled to generate the required shock waves. This project will build on the success of the laboratory equipment to
remove biofilms with minimal tissue damage, to develop a robust continuous flume system. The innovation therefore is in
developing a system which will work in a continuous mode, and can be assimilated into a typical contra-flow washing
process (rather than the batch process in which the lab Pulsifier works). There is no such system in place today, and hence
the new equipment and process will be completely novel.
UoS will lead the laboratory validation and be involved with on-site factory testing when hydraulic shock prototypes are
being evaluated. Overall the project will involve 9 WPs with UoS involved in WPs 1, 3, 5, 7 and 9:
WP1. Assess the Pulsifier in the laboratory (determine effects of varying Hz, amplitude and duration parameters on
physical performance and microbial removal)
WP2. Develop prototype 1
WP3. Assess prototype 1 in the laboratory (benchmarked against the Pulsifier performance)
WP4. Develop prototype 2
WP5. Assess prototype 2 and consider scale up challenges
WP6. Installation of equipment in factory line
WP7. Factory testing
WP8. Final assessment of performance
WP9. Project management (Quarterly review meetings, assess business plan and risk register)

UoS will lead the laboratory validation and be involved with on-site factory testing when hydraulic shock prototypes are
being evaluated: (i) Lab development: the energies required to release the natural biofilm, Enterobacteriaceae and E. coli
on fresh produce such as lettuce and spinach, and samples spiked with important pathogens such as E. coli O157,
Salmonella Typhimurium and Listeria monocytogenes will be evaluated in a HG2 containment laboratory. Detachment will
be assessed by standard culture recovery techniques of the water used post treatment and advanced light microscopy
techniques such as Episcopic Differential Interference Contrast (EDIC) microscopy of the treated leaf surface for biofilm
presence together with epifluorescence (EF) microscopy of green fluorescent protein-labelled pathogens so that they can
be tracked during processing; (ii) Commercial development: On-site factory validation: factory scale prototypes of the
hydraulic shock equipment made by Ambit will be evaluated by visiting Vitacress on-site and collecting leaf and water samples; (iii) Samples from the commercial facilities will be returned to the laboratory for examination, specifically
quantification of pseudomonads and Enterobacteriaceae using culture recovery techniques and EDIC microscopy for
remaining biofilm presence on leaves; (iv) Validation: These techniques will be used to confirm that the scaled up
equipment works successfully in the factory setting and maintains quality on the supermarket shelf in Vitacress and SSL
trials; as such samples will be returned to UoS for the detailed microscopy and microbiological analyses described above.

The project will investigate decontamination of biofilm and zoonotic pathogens on the salad leaf phylloplane for enhanced
food security and safety. Thus, the project provides a major opportunity for UK PLC, firstly through its delivery of safe,
nutritious food products which helps the government meet its healthy eating challenges. While there is scope for new
product development in bagged salads, improvement in nutritional value per se is essentially a public good benefit for
which industry would be unlikely to invest alone. Secondly, benefits to the wider industry from this research in terms of
reduced chemical use. Thirdly there is a potential new export opportunity for the UK manufacturing base since the work
requires development of a new Pulsifier design whcih can be translated into the factory. Consequently, all of the skills of
the partners are required to make the project a success and all will share in the IP and licensing agreements.
Immediate beneficiaries will include all fresh produce suppliers and retail outlets in the UK and internationally. The
producers will better comply with international sanitary standards for the sale of fresh produce and will benefit from reduced
water use during washing due to improved bacterial removal and reduced use of sanitisers when water has to be recycled;
the retailers will benefit from improved customer confidence and sales, and extended shelf life due to reducing the biofilm
spoilage (costing one UK supermarket chain £9 million per year). The consumer will benefit since it is critical to establish
the safest means of salad production from the farm to the fork to protect the public health, improve their diet, and maintain
consumer confidence following the regular reports of salad-borne disease outbreaks. Thus, directly impacting on the
nation's health, wealth and culture.