The main research question that the study aimed to answer is where along the export cold chain of navel oranges were temperature profiles not optimally managed? It was evident from the analysis and observations undertaken that the transportation segment from the pack house to the cold store was not optimally managed. The other stages along the export cold chain where optimal management of the export cold chain is lacking were the drenching, loading and inspection phases. Temperature breaks were also evident during the loading of the two reefer vessels that were analysed in the study. Thus, the study showed that temperature breaks do occur in the different stages of the export cold chain.
The sub-research questions of the study aimed at answering what causes temperature breaks in the cold chain?; how can temperature breaks be minimised?; what impact do these breaks have on the quality of navel oranges? and which best practices can be undertaken to ensure the effective management of temperature along the export cold chain stages? The results of the study showed that the main determinant of temperature breaks was due to exposure to weather elements, for instance, exposure to direct sunlight and high winds during drenching, transportation and loading. Another cause for temperature breaks was the rise in ambient temperature, which affected the pulp temperature of fruit, causing a rise in temperature that resulted in temperature breaks. In addition, during the fruit drenching stages bin liners were not utilised when navel oranges were placed inside bins and left to dry. This could also be noted as a possible contributor to the cause of quality problems since bin liners minimise the level of oleocellosis. The export season also proved to be an abnormal season in terms of weather patterns. This led to difficulties with navel oranges at the start of the cold chain as effects
147 of the drought and heat waves experienced in the Citrusdal region resulted in the navel oranges bursting open and dropping from the tree and thus no longer being viable for export.
The question of whether temperature breaks have an effect on fruit quality was answered through the testing of a hypothesis formulated for the study. The Kruskal-Wallis test employed proved that there were no (significant) links between fruit quality and temperature breaks. However, there are factors which influence the quality of fruit, which may be related to low temperatures.
From the results derived during data analysis, it was clear that there is room for improvement in terms of optimal management of the export cold chain. To respond to the last two sub-research questions, the study explored good cold chain best practice guides developed in previous studies undertaken. The aim of the practices developed is to assist the fresh fruit industry in minimising cold chain breaks. 7.3.1. Exploration of good cold chain practice guides developed in previous studies
Haasbroek (2013) and Freiboth (2012) developed good cold chain best practice guides to assist in minimising cold chain break incidences and identify areas in the cold chain, which could further be improved. Suggestions were made for each individual stages of the export cold chain. The cold chain best practice guides developed in the previous studies can be adapted and applied in the export cold chain of navel oranges. In the guide developed by Freiboth (2012), a differentiation between unavoidable and avoidable breaks is made. Therefore, the aim is to avoid the breaks that can be avoided and to minimise the occurrences of those that cannot be avoided. Leaving fruit to stand for more than 24 hours after drenching is an example of an avoidable break. For the navel orange cold chain, an example of an unavoidable temperature break is the loading of vessels, which could be minimised through efficient operations.
Both guides suggest that it is crucial for a cold chain to be maintained from the point of harvest as quality starts deteriorating soon after the fruit is harvested from the tree. Fruit has to be harvested during cool hours once the pulp temperature of fruit has decreased after being exposed to the day’s heat. Navel oranges are picked at any time of the day as long as it is determined that the fruit is dry. However, picking navel oranges when temperatures are high has been known to increase the Vapour Pressure Deficit (VPD) levels and the occurrence of oleocellosis. Therefore, picking navel oranges once the pulp temperature of fruit has cooled down could help minimise the occurrence of temperature breaks as such incidences can be avoided.
Once navel oranges have been harvested, it is important that they are removed from the orchard into a shaded area. As much as citrus fruits are non-climacteric, meaning the rate of respiration is lower,
148 holding them for a long time under high temperatures after harvesting leads to decay producing organisms and fruit may also undergo changes that may render them unattractive. Hence, moving fruit to a sufficiently shaded area would help avoid temperature breaks and also preserve fruit quality. According to the good cold chain best practice guides developed, pack houses tend to be warmer than necessary. Pack house temperatures should be maintained between 18-25°C. There should be sufficient air cooling systems and temperature monitors placed to continually monitor the temperature. Pack houses utilised for packing navel oranges have fairly shaded areas where fruit is placed before and after degreening. In order to minimise the incidences of exposure to direct sunlight, the areas where fruit is placed before pack line processes start should be fully shaded. Minimising the exposure to direct sunlight minimises the chances of temperature breaks.
The port segment, which proved to have the most temperature breaks, is also addressed in the good cold chain best practice guides. Although it addresses concerns that arise in the container terminal at the Port of Cape Town, some of the suggestions on improvements that can be made can be applied in the Multipurpose Terminal and during the loading of conventional vessels. For instance, fruit should be pre-cooled to optimum temperature before loading. If fruit is not properly cooled, there are higher chances that temperature breaks will occur.
Staging of pallets is another recommended solution. Before pallets are taken out for loading, they could be staged per conventional vessel compartment; this would reduce the amount of time pallets stand outside during loading.
As mentioned, a study conducted by Haasbroek in 2013 found similar results of temperature breaks during the transportation and loading segment. Although, the study conducted by Haasbroek was on fruit shipped through reefer containers. Looking into the different vessels that can be used could help minimise the occurrence of temperature breaks. For instance, conventional vessels are vessels that have compartments in which fruit pallets can be stacked. Conventional vessels carry loads up to 5000 pallets and each deck is individually operated. Conventional vessels can carry loads in their compartments and on-board the deck. The advantages of conventional vessels are its abilities to carry larger loads and have each compartment individually operated, which minimises the chances of income losses. However, container vessels have gained more prominence over the years. Container vessels carry their loads in truck-size intermodal containers, a system known as containerisation. Container vessels carry less loads than conventional vessels, which means they are easier to load. Container vessels require an external power supply for its operation. The disadvantage of container
149 vessels is that once the door has been shut after loading, breaking the seal almost guarantees a temperature break (Simpson,2017).
The good cold chain best practices that were developed in previous studies proved to be crucial in putting forth recommendations on the avoidance and minimising of temperature breaks. These best practices can be undertaken to further ensure continued success of the navel orange export cold chain. Therefore, this discussion responded to the last two sub-research questions that this study aimed to answer. It is clear that temperature breaks are to a large extent minimised by role players in the citrus industry. For example, after harvesting, citrus fruits are placed under a shaded area, fruit is cooled to optimum temperature before loading and pallets are staged before loading in reefer vessels.