Marine transport of some tropical food cargoes to cold climates: maintenance of quality (NRI Bulletin 69)

Problems of quality maintenance are encountered in the marine transport from tropical and sub-tropical to temperate climatic zones, of hygroscopic durable foods such as cocoa beans and similar commodities, particularly in winter in the Northern Hemisphere. Cargoes frequently display damaging mould formation and insect infestation on unloading. This publication indicates the likelihood of the incidence of these problems for different modes of transport by ship (bulk, bag and box container). Interpretations are based upon the principles of heat and moisture transfer and experimental observations of several shipments. The mould problem is usually interpreted as arising from the migration of moisture from the interior of the cargo to its sides. It occurs when a temperature difference develops between the cargo interior and the frame of the ship's hold. With bulk commodities, the moisture problem can occur at the sides of the cargo if this is in direct contact with the sides of the ship. With bagged commodities, similar difficulties can arise, but they are less pronounced because of the beneficial effect of air circulation around the bags, particularly if dunnage is present. For box-container transport, the major risk of quality deterioration occurs in winter following offloading on the dockside. Dew can rapidly form on the underside of the container roof, and 'internal raining' with subsequent wetting and mould formation can occur with the associated risk of mycotoxin production. Closed box containers present the greatest hazard. Naturally ventilated and open-sided containers together with suitable modifications to handling practices are considered to be more suitable for the avoidance of this problem. General recommendations for good practice are also included in the text.