Maintain quality by accurate temperature management
Importance of temperature management in stone fruit
Most notably, stone fruits are susceptible to chilling injury, which manifests itself as one or more symptoms including a dry or mealy texture, leatheriness, failure to ripen, flesh browning, translucency, and dark discoloration of the stone cavity. Since chilling injury is most severe after prolonged exposure to temperatures of 2-8°C, it is important to reduce temperature below this range and maintain it at close to ~0°C throughout the supply chain.
High temperature injury will result in rapid softening, excess dehydration and increased susceptibility to other disorders as also evident in Table 1. Consequently, it is imperative to avoid delays in cooling and stone fruits should be cooled to near 0°C within several hours after harvesting. The fruit should ideally be sorted and packed in the cold storage after cooling to near 0°C, but if this is not possible, then the fruit should be cooled to an intermediate temperature of 5-10°C and then further cooled by forced air cooling to 0°C after sorting and packing. Room cooling s generally too slow to afford protection to stone fruits and should preferably be avoided. 7/8 cooling times (The time required for fresh produce to cool to 7/8 of the original difference in temperature between the produce and the cooling medium) can be as high as 30-60 hours. Hydrocooling is the fastest method for cooling stone fruits since water can hold more heat energy per unit of weight than air. Hydrocooling may be of the shower type or by immersion. Most stone fruits are generally tolerant of wetting but care must be taken to maintain sanitation and avoid spread of postharvest diseases and remove excess moisture from the surface after wetting (which will also be conducive for decay ) before packing. Cherries respond well to hydro-cooling due to their susceptibility to stem shrivel and browning resulting from water loss. Due to the large surface area to volume ratio, they will 7/8 cool in as little as 10 minutes. Large peaches will 7/8 cool in 35-40 minutes. Although slower than hydrocooling, forced air cooling is considerably faster than room air cooling and 7/8 cool times of 4-6 hours are typically achieved for stone fruits. it also offers the advantage that fruit are not wetted. Humidifiers should be considered to reduce weight loss during forced air cooling.
After cooling the stone fruit, failure to maintain a correct temperature regime will compromise quality, the consumers eating experience and will result in increased wastage in the supply chain for reasons that are evident in Table 1. Conventional
means for monitoring temperature in the fresh produce chain include Strip chart recorders with which the visual output is a strip of paper that contains a recorded graph of temperature vs. time. Alternatively, data loggers are used, which is the
digital answer to strip chart recorder with programmable functions. Data can be downloaded using these devices with appropriate software. The limitations are that
they are typically used only during transport and not throughout the supply chain, the temperature is typically not measured throughout the truck/container, but rather at localized points (temperature may vary considerably across a truck); the temperature that is measured is typically that of the environment and not of the produce; Data is reviewed post-mortem when it is often too late to undertake
corrective actions. The advent of RF technologies has opened up a whole new window of opportunities for temperature monitoring. Active RF tags enable produce temperature and other data to be captured, stored and reported automatically
in real-time as long as there is a receiver in the vicinity. Xsense real time monitoring system is of the most advanced active RF based technologies currently available is
being used by shippers of stone fruits for monitoring temperature in real time throughout the supply chain at the pallet level and undertaking corrective actions as
and when need be to maintain quality at a premium throughout the supply chain.
For more information:
Stepac
Tefen Industrial Park
P.O. Box 73
Bldg. 12
Tefen Israel 24959
[email protected]
www.stepac.com