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Enhanced prediction of susceptibility to mechanical damage in harvested and stored potatoes - LK0931

Potatoes are an important UK crop with a retail value of ~£3 billion. Blackspot bruising is a major problem for potato growers and processors resulting in an average 18% of the crop being devalued or discarded. Bruising arises through mechanical damage to tissues in the tuber cortex resulting in blue-black discoloration as the result of enzymic and oxidative reactions producing melanin-based pigments. The problem manifests itself in susceptible tubers mainly during harvesting and transportion as the result of mechanical damage. Bruising significantly lowers tuber quality (appearance and taste) making them unacceptable for direct consumer sales or for processing leading to considerable financial losses. Damaged crops also lead to a major disposal problem and wasted resources.
Susceptibility of potatoes to bruising is dependent on a complex combination of factors making it impossible to predict the predisposition of a crop to mechanical susceptibility. Accurate prediction of the susceptibility of a crop would allow sympathetic harvesting, transport and handling to minimise actual damage incurred and bruise development. Present predictive methods involve sampling tubers from the field, exposing them to impacts (for example by tumbling), incubation for 15-48h in a 'hot box' (37°C) followed by a visual assessment of the level of bruising after peeling. For many years potato scientists have searched for convenient measurable factors correlated with bruising potential including tyrosine levels, enzyme activities and tuber properties, but none of the proposed correlations has proved reliable or sustainable. In a current programme sponsored by BPC and DEFRA, we have investigated the detailed biochemistry of the early responses of tuber tissues to impact and have discovered that the damaged cells generate superoxide radicals. Significantly, quantitation of radical production has established an excellent, direct correlation with tuber bruise indices (a measure of the susceptibility of tubers to bruising) of 5 different potato varieties exhibiting differing bruising status. This relationship (See Appendix A1) is highly reproducible and the correlation coefficient of R=0.97 compares with the previous ‘best’ of R=0.75. Furthermore the overall assay is rapid, taking only about 30 minutes following a 2h tuber incubation. Associated prototype devices designed for testing tuber explants have been developed, including an 'impactor' designed to impart a standard energy of impact to test tubers; and a 'corer', designed to excise a standard plug of impacted tissue for detection of radical generation. The potential value of the IPR as a detection system for the diagnosis of bruising susceptibility has been recognised and is protected by UK and international patents. The research is now at a stage where further development involving the direct participation of relevant branches of the potato industry will benefit the progress towards the establishment of a practical, predictive assay system.

9.2 Aim of the project
The overall aim of the project is the development of predictive tests for the susceptibility of potatoes to bruising. This will be achieved by the introduction of a novel, rapid and accurate test for measuring the predisposition of tubers to mechanical damage. The test will be tailored to industry's needs and on project completion, it is anticipated the test will take the form of a commercial kit of reagents and associated hardware.
Project Documents
• Abstract : Enhanced prediction of susceptibility to mechanical damage in harvested and stored potato tubers: Summary for growers   (123k)
Time-Scale and Cost
From: 2003

To: 2006

Cost: £184,572
Contractor / Funded Organisations
Martin Lishman Ltd, Tesco Stores Plc, Branston Potatoes Limited, Greenvale AP PLC, University - Durham, MBM Produce Ltd, British Potato Council, McCain Foods (GB) Ltd, ADAS UK Ltd.
LINK Programme              
Sustainable Farming and Food              
Sustainable Production              
Fields of Study