Most perishable products are still alive and respire to maintain their physiological functions during the voyage. Deep frozen and most processed foods, although dead, also require special conditions to maintain quality. The Master and crew can only ensure that all equipment is functioning within the specified parameters. Some important aspects that require continuous attention during the voyage are highlighted in this chapter.
1. Carrying Instructions
The exporter selects the required carrying conditions. These conditions are based on extensive research, product condition, and market requirements. Optimum temperatures or regimes and fresh air ventilation are defined and codified (reefer code) to comply with standardized shipping documents and procedures. The process to ensure correct carrying conditions is initiated at booking (see Chapter 6, par 1.2). It is important to ensure:
- The ship’s crew fully understands the carrying conditions as defined in the reefer code.
- The temperature control thermostat is set correctly to deliver air at the specified carrying temperature.
- The fresh air intake is set to supply a prescribed volume of fresh air per container or to maintain carbon dioxide below 0.5% in conventional shipping spaces.
- Controlled atmosphere conditions, if required, are set according to product requirements and shipping line specifications.Note: For chilled produce, temperature control should be on the delivery air; for deep frozen produce, on the return air.
2. Temperature Management
Historically, chilled produce was stored and shipped at a single temperature, defined as the optimum storage temperature (actual pulp temperature). However, storage and transport at the optimum temperature may still contribute to quality problems. For example, internal breakdown in plums stored at -0.5°C can be reduced by changing the storage or carrying temperature.
Shipping at a defined maturity stage and manipulating ripening during storage and transport is a management tool to obtain optimum shelf life and meet ready-to-eat requirements. High reliability in supply is required; losses due to incorrect shipping and handling cannot be tolerated. Procedures have been developed to monitor carrying conditions and ensure optimum equipment performance.
The temperature management system developed by PPECB, in cooperation with shipping lines and the fresh produce industries, considers all relevant product and shipping factors. The system is based on the evaluation of air temperatures and their changes. Temperature management based on actual product pulp temperatures is more accurate, but pulp temperatures are only available for special and in-transit cold treatment shipments. The system starts in the orchard and continues into the marketplace.
2.1 Preharvest Actions
Optimum results with temperature management are only possible when the product is at the most optimum physiological stage and correctly prepared to minimize quality losses during the voyage and subsequent distribution. Important steps:
- Determine the storage and transport potential of the specific cultivar or variety.
- Determine product behavior, such as ripening and ripening rates.
- Quantify the effect of climate, growing, maturity, and handling conditions and procedures.
2.2 Preshipment Actions
The product and shipping equipment must be prepared to operate optimally during the two to three week storage and voyage period:
- Packaging and palletizing must provide adequate product protection and maximum air circulation in both horizontal and vertical planes to ensure efficient removal of product heat.
- The load must be efficiently precooled to the optimum loading temperature.
- Transport and shipping equipment must operate correctly at the specified temperature and fresh air circulation set points.
- The product must be handled, transported, and stored within the prescribed temperature tolerances.
2.3 Actions Required Prior to and During the Voyage
2.3.1 Prior to Sailing
Voyage temperature management starts when the container or deck is loaded. Both product and shipping space must now be within specification. The following steps become operational:
- Final check to ensure all relevant controllers are set according to the required carrying condition as defined in the reefer code.
- Delivery (DAT) and return (RAT) air temperatures must be recorded as soon as refrigeration is applied.
- DAT and RAT of containers still to be shipped must be recorded at least once every four hours. These readings must be verified by PPECB at least once every twelve hours.
- All DAT and RAT readings (and other required shipping information) must be reported to the PPECB prior to sailing.
2.3.2 During the Voyage
The Master must ensure the following actions are carried out:
- The temperature set point must be according to the temperature regime requirement as specified in the reefer code.
- The DAT and RAT of each deck or container must be recorded every morning and relayed to the PPECB office as indicated on the PPECB letter of confirmation of carrying conditions.
- The difference between the RAT and DAT should be as small as possible but not more than 1.5°C.
- A cold blast must be applied as soon as the RAT/DAT difference approaches 1.5°C.
- During the cold blast, the DAT is reduced by 0.5°C and maintained for three hours, after which the DAT is reset to the reefer code specification and maintained for at least three hours.
- The cold blast procedure must be repeated until the RAT/DAT difference is reduced to less than 1.5°C, but not more than four (3-hour) cycles.
- The PPECB must be informed of the cold blast procedure applied.
It is the responsibility of the PPECB to communicate temperature deviations, as received from the Master, to the owner of the product. A corrective action procedure must be formulated and relayed back to the Master by the PPECB. The corrective action procedure must be regarded as an amended PPECB carrying instruction and immediately implemented.
2.4 Maintenance of Product and Air Temperature
For fresh produce, the product is almost always warmer than the air in the immediate surroundings. This product/air temperature differential is affected by many factors but should preferably not be more than 0.5°C at temperature equilibrium. In practice, this means the DAT should be 0.5°C colder than the required optimum product (pulp) temperature.
2.5 Raising and Lowering of Carrying Temperatures
Some carrying temperature regimes require that the carrying temperature be raised (e.g., plums) or lowered (e.g., avocados) at certain stages during the voyage. These DAT changes must be effected on the dates specified in the PPECB letter of confirmation of carrying instructions (reefer code). The temperature change should take place as quickly as possible, especially for plums, to minimize exposure to the temperature range 2°C to 6°C.
3. Logging of Carrying Conditions
It is a legal requirement that all temperature logs and other relevant information on the carriage of perishable produce be immediately made available to the PPECB. Minimum requirements:
3.1 Temperature Logs of Conventional Vessels
- Temperatures in all shipping spaces must be logged at least once every hour until stabilization, and thereafter at least once every eight hours.
- Temperature logs must be safely stored by the shipping line for at least one year and made available immediately on request to the PPECB.
- Other legislation may require logs to be stored for longer periods.
3.2 Temperature Logs of Container Shipments
3.2.1 Integral Containers
- Fitted with either a chart (Partlow) recorder or an electronic data logger.
- Partlow charts must be stored for at least one year and the original chart made available on request to PPECB.
- Electronically logged data must be stored for at least three months and immediately made available to the PPECB on request.
3.2.2 Ventilated Containers
- Usually not fitted with temperature or other recorders.
- Important to keep accurate records of voyage conditions such as:
- Ambient day and night air temperatures (minimum and maximum)
- Relative humidity of the ambient air
- Weather conditions (rain, sun, fog)
- Ocean conditions (seawater temperature, swell heights)
- Air inlet and exhaust temperatures to and from ventilated spaces
- Operation of air extraction fans
3.2.3 Controlled Atmosphere Containers
- Fitted with carbon dioxide and oxygen data loggers.
- Data must be made available to the shipping line, which is responsible for safe keeping for at least one year.
- Data must be made available to the PPECB on request.
3.3 Logging of Other Voyage Conditions
All information pertaining to the shipment of perishable products must be kept and stored by the shipping line and made available to the PPECB on request. Important information to be logged includes:
- Voyage conditions such as air and seawater temperatures, rain, and fog.
- Maintenance carried out on the refrigeration equipment and data sensors, controllers, and loggers.
- Commencement and termination of refrigeration in all decks and containers.
- Breaks in the cold chain (e.g., power and refrigeration shutdowns, defrost cycles).
4. Transshipment and Restows
Transshipments and restows always result in a break in the cold chain and often in delays. Every effort should be made to minimize additional handling of cargo. Important factors requiring attention during transshipments and restows are summarized below.
4.1 Transshipments
4.1.1 General Conditions
- The export agent must ensure a copy of the carrying instructions is handed to the Master of the ongoing vessel and to the shipping agents responsible for handling the produce in the transfer port.
- The Master of the ongoing vessel is responsible for applying the carrying conditions and keeping the prescribed logs.
- If the transshipment takes place in a South African port, PPECB responsibilities include:
- Re-inspection of the produce according to the Agricultural Product Standards Act if the product exceeds the maximum stipulated time between initial inspection and actual shipping date.
- Re-inspection of the container or cargo according to the PPECB Act and regulations to ensure the cargo is still in sound condition and within the prescribed temperature tolerance.
- Ensuring prescribed temperatures are maintained and breaks in the cold chain are within the Time Temperature Tolerances specified in Chapter 8, par 3.
4.1.2 Ventilated Cargo
- Ventilated cargo is often transshipped in South African ports.
- Changes in shipping schedules may result in ventilated cargo being exposed to uncontrolled ambient conditions for extended periods.
- Transshipment of ventilated cargo is not recommended. If it must occur:
- Containers with ventilated cargo must be stored in well-ventilated stores and protected from the elements.
- The total shipping period from first to last port of 10 days may not be exceeded.
- The cargo must be suitably stabilized to allow opening of the doors during the transshipment period.
4.2 Restows
Products may sometimes be restowed for various reasons. Ensure the following conditions are followed:
4.2.1 Restow of an Integral Refrigerated Container
Necessary when the original container malfunctions or when drastic temperature deviations occur. Ensure:
- PPECB cleanliness and pre-trip inspection (PTI) certificates are still valid (see Chapter 4, par 3).
- Cargo still meets the quality criteria stipulated under the Agricultural Product Standards Act.
- Cargo temperatures and condition are within specification.
- Necessary records are kept to support food traceability requirements.
- Correct carrying temperature reefer code is registered and the Master is informed accordingly.
- All relevant documentation is passed on to the PPECB.
4.3 Reporting on Deviations
The sooner detailed information on deviations, delays, and other conditions that may affect the age and quality of the product are known, the better the chances to rectify the problem. All deviations must be reported to the PPECB, who will, in cooperation with the exporter and owner of the product, formulate corrective actions.
4.4 Availability of Logs
It is the responsibility of the shipping line(s) who accepted and carried the cargo to make all logs and notes pertaining to all shipments available to PPECB. If such logs are not made available within two months of a written request from the PPECB, it will be assumed that the logs were deliberately destroyed.