Temperature trials

For the purposes of the study, temperature trials refer to the gathering of data through the insertion of temperature monitors inside the pulp of fruit, inside fruit cartons, thus allowing the monitoring of fruit throughout the export cold chain of navel oranges. Temperature monitors utilised measured both pulp and ambient temperature of the fruit inside the carton. Temperature monitors were provided by Company X. For the rest of this chapter, temperature monitors are referred to as iButtons®. The data

80 set recorded by iButtons® was divided into two, namely, the first phase and the second phase of the cold chain. The first phase is from the orchard (point of harvest) until cold storage, before fruit were accepted for cold storage processes. The latter phase is from the cold store until the port of destination. This means that for the first phase, temperature spikes are analysed and for the second phase, temperature breaks are analysed.

Temperature spikes were analysed from the orchard to cold store since the cold sterilisation treatment starts from the point when conventional vessel compartments are closed with all three major temperature probes reading -0.6°C until end destination. Temperature spikes were analysed as each stage of the cold chain influences the next. For the purpose of this thesis a temperature spike was defined as “any time temperature rises along the export cold chain”. The temperature has to rise by 2°C or more for the rise to be significant and influence the fruit quality (Goedhals-Gerber et al., 2017). Temperature breaks were analysed from the cold store until the port of destination and temperature breaks were defined as “a temperature deviation above 0.0°C or below -1.5°C”. Monitoring of fruit from the point of harvest until port of destination was deemed ideal as it accounts for the different factors influencing the occurrence of temperature spikes or breaks along the export cold chain as well as the final quality of the product.

To determine what qualifies as a temperature break for the steri-market section of the export cold chain, an upper pulp temperature limit had to be chosen. PPECB steri-market protocols stipulate that pulp temperature may vary between -0.6°C to 0.0°C, but if temperatures exceed 0.0°C, it is considered a steri-breach and the cold treatment is extended so that temperature is brought back down to -0.6°C. If the temperature exceeds 1.1°C, cold sterilisation treatment is nullified (PPECB, 2012). Therefore, for the purpose of this study’s data analysis, a temperature break for steri-protocols occurs when the pulp temperature of the navel oranges rises above 1.1°C.

It is worth noting that regardless of the researcher inserting iButtons® into the pulp of fruit for the measurement of temperature, protocols are validated on special probes inserted into the fruit by the PPECB. These probes record temperature on a system on the vessel, which is then verified by USDA. Each probe must show that the temperature was kept below the stipulated specification for the required duration. For conventional vessels, 62 temperature probes are inserted into fruit per deck by PPECB and if any of these probes record a temperature beyond 1.1°C, the temperature is nullified. In the orchard, drenching and degreening stages iButtons® were randomly placed into bins. From the pack house to the cold store, iButtons® were placed in the first (bottom), fourth (middle) and seventh (top) cartons that were staged on pallets, but were not placed somewhere specific in the reefer vessel.

81 iButtons® were set to record at 30-minute intervals. A program called ColdChain Thermo Dynamics was used to record the readings from iButtons®. Figures 22, 23 and 24 depict the locations of iButtons® in fruit bins and fruit cartons on pallets. Figure 22 illustrates iButtons® used for the study and how they were probed inside fruit. Figure 23 illustrates the location where iButtons® were inserted in fruit bins from the orchard to pack house, and Figure 24 illustrates the location of iButtons® in fruit cartons on pallets from pack house to the cold store. Since data was collected in different phases, the same locations for iButtons® were utilised in all collection phases.

Figure 22: Illustration of iButtons® probed inside a navel orange and ambient recording iButtons® with a red string attached.

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Figure 23: Pulp and ambient iButtons® in bins at the orchard

Source: Photo taken by researcher

Figure 24: Ambient and fruit pulp iButtons® location from pack house to cold store

Source: Photo taken by researcher

Top Middle Bottom Bin Markings Pulp temperature iButton® Ambient temperature iButton®

83 iButtons® were inserted immediately after navel oranges were harvested from the tree until the pack house and were removed after the degreening process was completed. iButtons® were removed before fruit journeyed through the pack line, because of the perishable nature of fruit and to avoid major losses of iButtons®. Pack lines involve a lot of tossing and turning, especially during washing, drying, fungicide application and waxing. A slit was cut open on the rind of the navel oranges for insertion of the iButtons® and wrapped around with insulation tape to keep it secure. Even though the fruit were secured by insulation tape, it does not prevent the iButtons® from falling out. Therefore, the pack house managers and the researcher decided that to avoid the loss of iButtons®, re-probing would take place after pack line processes were complete. Fruit was re-probed with iButtons® whilst inside fruit cartons before transportation to the cold store. All temperature trials were conducted in the Citrusdal region at Farm X and Pack house X.

Temperature was monitored throughout the export cold chain phases until arrival at the port of destination. iButtons® were manually removed from inside the fruit and fruit cartons by USDA officials and were sent back to the researcher for the data to be downloaded and analysed. Unfortunately, out of the 280 iButtons® used for data collection for the study, only 49% were retrieved.

Table 7 displays iButtons® probing information during the different data collection phases. It is important to note that iButtons® were re-used during the phases where fruit was re-probed, rather than inserting new temperature monitors. For instance, iButtons® used on 19 May had been removed and re-probed from fruit that was used on 10May.

Table 7: iButtons® probing phases

Fruit Type Date of

Probe

iButtons® Inserted

Location Probe usage Vessel

Navel orange 03 May 2017 70 Bins at pack

house

56 pulp & 14 ambient

Santa Lucia

Navel orange 10 May 2017 70 Plastic bins at

drenching area

56 pulp & 14 ambient

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Navel orange 19 May 2017 70 Pallets: top,

middle and bottom carton

56 pulp & 14 ambient

Santa Lucia

Navel orange 31 May 2017 70 Bins at drench

area

56 pulp &14 ambient

Regal Bay

Navel orange 9 June 207 70 Pallets: top,

middle and bottom carton

56 pulp & 14 ambient

Regal Bay

Navel orange 14 June 2017 70 Bins at drench

area

56 pulp & 14 ambient

Regal Bay

Navel orange 22 June 2017 70 Pallets: top,

middle and bottom carton

56 pulp & 14 ambient

Regal Bay