Testing packaging design changes in kiwifruit packaging for reefer container conditions : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Palmerston North, New Zealand
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Date
2021
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Massey University
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Abstract
Refrigerated transport is widely used for export in the New Zealand horticultural industry, valued to be over NZD $9.5B in 2019, to maintain the quality of perishable produce from farm to consumer. New Zealand’s horticultural industry mostly uses refrigerated containers (reefers) to deliver the goods. In which, generally, the precooled produce in stacked boxes will be stored as pallet units, where the refrigeration unit and a fan circulate air into the container. Normally the air inside the reefer is to achieve a homogenous controlled environment around the produce as well as in the container through flow in vertical directions (from bottom to top) towards every corner of container in order to preserve the fruit quality and prolong its shelf life. Packaging design plays a crucial part in the cooling performance, especially in ventilation (i.e vent size and vent location over the design) with respect to the direction of air flow within the cooling unit. Even though vertical ventilation has its impact on the cooling performance of a design, the modular bulk packaging of polylined kiwifruit has not been equipped with vertical ventilation despite the kiwifruit industry being the largest horticultural sector in New Zealand (worth NZD $ 2.3B in 2019). To understand the effects of vertical ventilation on a kiwifruit MB box design in a reefer condition, an apparatus was designed and constructed of a single column of MB boxes with similar airflow considerations as a standard reefer. For experimentation purposes artificial kiwifruit simulators were used in place of real kiwifruits. Fruit temperature was used as a variable to understand the cooling efficiency of the box design by using 20℃ or 25℃ as initial temperature and pumping 0℃ reefer condition airflow into the apparatus. In addition to vertical ventilation, the experimental setup also considered polyliner bags and different air flow modes as a design variable and reefer variable respectively. For single column MB boxes at reefer conditions it was found that 3% vertical ventilation has no significant effect on the cooling profile of the boxes in both economical (40 air renewal/hr) and normal (75 renewal/ hr) air flows. Additionally, removal of polyliner form the design reduced the half-cooling time of the boxes in economical flow ranging from 36-56 %. Where the smallest and largest change was observed in the middle box and the base box. With the addition of vertical ventilation to the polyliner scenario, an added effect of reduction in the half- cooling values ranging 46-52% was observed.