‘Of shoes – and ships – and sealing wax’: forensic biology in the international fruit trade

Over 20 members and their guests attended the East Anglia Branch soiree on 26 January at Churchill College, Cambridge.  Following an enjoyable buffet with wine and soft drinks Anna Snowdon talked about her work as a forensic biologist.

Dr Snowdon has almost 40 years experience of investigating the problems associated with the shipping industry and transport of stored fruit and vegetables.  Most of the fruit and vegetables imported to the UK now come by sea.  These are usually in refrigerated and controlled atmosphere containers, though in some cases palletised cargo is still transported in sealed holds.  Like field plant pathology, the key it seems is to look for spatial and temporal patterns in the distribution of problems.

Historically, serious problems were first diagnosed when that well known plant pathogen Sclerotinia sclerotiorum became associated with carrots imported to the UK from Cyprus in the 1960s.  Like most problems this arose when a series of unconnected circumstances coincided.  The primary issue was a lack of understanding of basic biology by shippers, exporters and importers.  The second problem was a series of poorly worded instructions prepared by individual exporters to individual ships’ masters, each capable of mistranslation and interpretation in several ways.  These problems were then compounded by use of cargo ships with non standard ventilation and temperature control.  In some cases the resulting high temperatures resulted in precooked carrots arriving in the UK.  The resulting smell and mess in the hold does not bear thinking about!

A classic problem arose when refrigerated ships were first used to import apples to the UK.  In this case, unadapted ships, without opportunities for ventilation, resulted in CO₂ building up on the voyage and inducing senescence with dark brown tissue collapse in the core of the fruit.  This has led to subsequent improvements in design of storage and transit with controlled atmosphere techniques which are standard in terrestrial fruit and vegetable stores.

An important part of the talk dealt with the banana trade and the range of conditions, from field diseases to transport, which can affect the quality of the final product.  Most of us had probably not appreciated the importance of starting at the point of export with hard green fruit and the way in which temperature needs to be monitored and managed during the voyage to ensure that we get fruit at optimum ripeness on our supermarket shelves.

When the formal part of the evening concluded members and guests continued to regale Dr Snowdon with questions and discussion for some time.  All in all an enjoyable and informative evening in pleasant surroundings.

 Robert Cook