MAINTAINING THE COLD CHAIN Air Freight of Perishables Maintaining the Cold Chain during the handling and transportation of fresh produce for export by air. DISCLAIMER This chart was prepared by the South Australian Research and Development Institute (SARDI) and is reproduced under licence by the Victorian Airfreight Council (VAC) and the Victorian Sea Freight Industry Council (VSFIC) which is proudly supported by the Victorian Government’s Food Victoria. For further information contact the Victorian Airfreight Council, phone (03) 9651 9154. While all reasonable care has been taken in preparing this chart, SARDI, VAC and VSFIC accept no liability resulting from the interpretation or use of the information set out in this guide. THE IMPORTANCE OF THE COLD CHAIN The Cold Chain is the management of produce temperature, from harvesting through to the consumer, to maintain the quality of the product. Maintenance of the Cold Chain is the best way to minimise all forms of deterioration after harvesting, including Weight loss resulting in wilting and limpness Softening Bruising Unwanted ripening Colour changes Texture degradation Development of rots and moulds. Good Cold Chain management results in the consumer receiving a product of “fresh” quality, leading to greater satisfaction and increased demand. The export of fresh produce often involves long journey times and frequent handling. This makes effective Cold Chain management more difficult but even more essential to ensure the product offered for final sale retains maximum freshness. It’s Everyone’s Responsibility Maintaining the Cold Chain is the responsibility of everyone who handles fresh produce, from production to retail sale. A breakdown in temperature control at any stage will impact on the final quality of the product, although the effect may not be visible until several days later. Without the cooperation of everyone involved in handling fresh produce, the consumer will not be able to enjoy the produce in the best possible condition. Air Freight Exports The use of air freight allows perishable produce to be rapidly transported around the world. By using the right combination of packaging, cooling agents, handling procedures, and land and air freight services, the Cold Chain can be maintained, delivering “fresh” quality produce to the end user. FRESH PRODUCE FACTS • Fresh fruit and vegetables are living products. After harvest they continue the process of respiration which produces carbon dioxide, water and heat. • The heat produced by respiration results in warming of the produce unless it is actively kept cool eg by refrigeration. • The rate of deterioration of the product is largely determined by the rate of respiration. Respiration needs to be slowed to minimise product deterioration but respiration can never be completely stopped. • The rate of respiration is temperature dependant. Produce which is kept cool will have a low rate of respiration with limited heat production and low rate of deterioration. However, produce which is not actively cooled will gradually warm from the heat released during respiration, which will lead to increasing rates of respiration and deterioration as the produce continues to warm. • Different products have different rates of respiration. Those with higher rates are more highly perishable and temperature control is very critical for these products. • Ethylene is produced by many plant products and can trigger ripening and deterioration in some products. Keeping produce cool reduces the production of ethylene. Also, cooled produce is less sensitive to ethylene. PRODUCT PACKAGING Packaging selection is the responsibility of the exporter and the following factors should be considered. • Ensure that packaging used meets airline requirements for fresh produce, especially in regards to containment of liquids. • Determine the temperatures likely to be encountered by the produce. This includes tarmac conditions at departure and arrival airports, and aircraft cargo hold temperatures. Aircraft temperatures should be available from the airline. • Consider the use of insulation to help maintain correct produce temperature. The main forms are produce packaging (eg. styrofoam boxes) or flexible sheets lining the interior of the ULD (Unit Load Devicea) • If cooling agents are to be used (see following page) packaging must be suitable and meet airline requirements. • Packages must be clearly labelled with the nature of the produce and the temperature range required. a Unit Load Device - this term covers all containers and pallets used on aircraft. These come in a variety of sizes and shapes to suit individual aircraft types. Check with the freight forwarder or airline to determine which ULDs are used on the routes chosen. PACKAGING - COOLING AGENTS • Consider the inclusion of cooling agents (often referred to as refrigerants) such as wet or dry ice or gel packs to assist in maintaining correct produce temperature during nonrefrigerated transport stages. • When using refrigerants, ensure the location and amount used will not cause freezing or chilling injury to the produce. • Ensure refrigerants and packaging used are coordinated and meet airline requirements. Wet ice requires packaging which will contain liquids. Dry ice requires sufficient ventilation to prevent a build-up of CO2. • If using wet ice, ensure that the form used (chipped, flaked, block) will not cause damage to the produce during packing, handling or transport. • If using dry ice, the airline must be notified of its use via the air waybill as it is classified as dangerous goods and is harmful to most fresh produce and living organisms. • Refrigerants may be either included in the produce packaging or added to the interior of the ULD at packing. If the latter occurs, allow enough space around the produce to ensure sufficient air circulation to cool the entire container. • Insulated and refrigerated ULDs are available with some airlines and may be considered for highly perishable, high value products. Refrigerated ULDs are insulated containers which contain dry ice to produce cold air which is then circulated by a fan. COOL FACTS • Dry ice produces carbon dioxide (CO2) gas which, if allowed to accumulate, can be damaging to some fruit and vegetables. However, for a few products, a raised level of CO2 is beneficial. ULD PACKING FACILITIES The ideal facility for consolidation and loading of ULDs will ensure that produce pulp temperature never falls outside the optimum carriage temperature range for that product. This will require: • Multiple cold stores which can be set to various temperatures (including a freezer at -18oC), suitable for holding boxes, pallets and packed ULDs. • One or more refrigerated or at least air conditioned working areas for the various handling activities including loading ULDs, AQIS inspections and weighing. • Loading docks which allow trucks to dock directly onto the cold room or refrigerated working area. • A rapid cooling facility for produce received warm or to recool produce warmed during handling. The use of a forcedair cooling system is recommended for a wide range of packed produce. • Regularly calibrated electronic thermometers with a metal probe, for taking produce pulp temperatures at receival and other times as required. See section “HOW TO MEASURE PULP TEMPERATURES”. The facility must also meet legal requirements for the handling of foodstuffs. If no cold storage facility is available, these procedures will help to minimise produce warming: • Keep the produce in the coolest position possible, ie out of the sun and away from warm breezes. • Use insulated blankets which have been designed to cover ULDs. • Depending on the airlines schedule, handle the produce during the cooler times of the day. LOADING INTO ULDs • Minimise the time the produce spends out of the cold room by completing all preparations for loading before removal of the produce. • Check that all items of equipment (eg containers, pallets, cargo nets) are clean and in good condition. • Check if any special packaging materials are required by exporter (eg dry ice, insulation or wadding) and ensure it is at hand. • If AQIS inspection is required, coordinate timing and preparation to minimise the time the produce spends out of the cold room. • Loading and weighing should be carried out in a cooled packing area. • Do not load produce into hot ULDs. If the ULD has been in the sun, open it in the loading area and allow it to cool before loading. • Ensure that the load is secure and will not shift during transport. Pallets need to be neatly stacked with no crushing and secured using cargo nets and possibly rigid corners. Containers need to be packed so that there is no movement of boxes. • Where possible, place the ULD back into cold storage after packing. MIXED LOADS Avoid mixed loads in ULDs whenever possible. If mixed loads are necessary, make sure the compatibility of the products is fully understood. The following factors should be considered. • Product temperature – warm/ambient produce will speed the warming and thus deterioration of cooled produce. Also treatments such as icing may cause chilling or freezing injury in other products. • Ethylene production/sensitivity – ethylene is released by many fruit and vegetables during ripening and can cause unwanted ripening or loss of quality in other products. Products which produce ethylene generally should not be carried with those that are sensitive to it. • Odours and off flavours – the contamination of produce with odours or off flavours may not be visible but leads to a loss of quality for the consumer. • Time – the longer the journey, the greater the deterioration of the produce if compatibility is poor. AIRCRAFT LOADING • Protect the ULD from the elements as much as possible by minimising on-tarmac time and using any available shelter. The use of an insulating blanket during on-tarmac time (including during transport) is recommended. • Where possible, temperature sensitive produce must be stowed in the area of the aircraft hold where the temperature will be closest to the required carriage temperature of the produce and where there is sufficient ventilation. • Product compatibility in terms of temperature, ethylene production and/or sensitivity, and dry ice content/sensitivity needs to be considered. • Loading of perishable cargo onto the aircraft should occur as close to take-off time as possible. • If the cargo requires special attention at transit stops (eg replenishment of ice or placement in a cool room) ensure that the arrival and transit cargo terminal operator are informed of this, and ensure cargo is in an accessible position. TIME LINES/DELAY • Airport cut-off times for receival of goods vary with the airport and whether the produce is loose or unitised. The freight forwarder should be able to provide this information. • For Adelaide airport the cut-off times are currently 4 hours for loose and 3 hours for unitised goods, unless special prior arrangements have been made. In the event of flight delays, consider putting in place the following precautions, depending on product type, length of delay and facilities available: • Move the entire ULD back into cold storage. • Provide air-conditioning to the aircraft hold if the cargo is already loaded. • In the case of longer delays it may be necessary to re-book the produce onto another flight. • Whatever action is taken, monitor the temperature of the produce and adapt plans as required. • Inform the exporter of the delay and any action taken. HOW TO MEASURE PULP TEMPERATURES • Pulp temperature measurements require an electronic thermometer with a metal probe attached. This thermometer needs to be calibrated using an iced water slurry at least every 4 weeks. • Take several measurements through the consignment and average these to get a representative measurement of the pulp temperature. Ensure measurements are carried out at different levels and on different faces of the consignment. • Insert the metal probe into the densest tissue of the produce, avoiding any seed cavity. Allow the thermometer to stabilise before reading the pulp temperature. • When taking multiple readings over a period of time, use the same pieces of produce repeatedly to minimise damage. ROLE OF THE FREIGHT FORWARDER The freight forwarder has an important role in organising the export transport route and ensuring necessary paperwork is completed. However, a freight forwarder handling perishable produce should also assist the exporter in ensuring that the cold chain is maintained through out the journey. This may involve some or all of the following. • Select an export route which is not only economical but minimises potential breaks in the cold chain. Issues to be considered include length of journey, reliability of service, number of times produce will be handled, length of transit stops and facilities available at these stops. • Assist the exporter in determining the environmental conditions likely to be encountered by the produce (on aircraft and in transit) and advise on suitable packaging. • Communicate with the airline the required carriage temperature and any special requirements eg sensitivity to dry ice. • Check compatability of products before consolidating consignments into ULDs (see section “MIXED LOADS”) • If cargo is trans-shipped, and the waiting period is beyond an agreed time, ensure that appropriate steps are taken to maintain produce temperature. This may include booking cold room space or ordering extra refrigerants, and informing the relevant people to ensure this is carried out. • In case of delays, inform exporter of delay and discuss alternative arrangements. It is recommended that contingency plans be determined prior to shipping.