Browsing by Author "Berry, Tarl Michael"

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    Optimisation of multi-scale ventilated package design for next-generation cold chain strategies of horticulture produce
    (Stellenbosch : Stellenbosch University, 2017-03) Berry, Tarl Michael; Coetzee, Corne; Opara, Umezuruike Linus; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: Corrugated fibreboard boxes (cartons) are used extensively in the cold chain to transport fresh produce from growers to consumers. These ventilated packaging systems have multi-scale structures and should facilitate suitable cooling of produce to preserve quality, protect against mechanical damage and enable efficient handling and transport. However, current designs often do not incorporate these factors and improved designs have been identified as part of new strategies to reduce postharvest losses and enhance overall cold chain efficiency. The aim of this thesis was to develop improved fresh produce packaging designs through the use of a novel multi-parameter evaluation approach, within the scope of a multi-scaled packaging system. To this end, computational fluid dynamics (CFD) models and experimental box compression tests were used to evaluate new packaging designs, to quantify spatio-temporal moisture distributions in cartons during shipping and to increase packing densities in refrigerated freight containers (RFC). Three new vent hole configurations were proposed and compared against an existing carton used for handling pome fruit. Results showed that the presence of trays reduced cooling efficiency by 31% in the standard commercial design. Conversely, the use of the newly proposed vent designs considerably improved both cooling efficiency and cooling uniformity by 48% and 79%, respectively. Next, the effect of vent hole area and board material was investigated. Results demonstrated that significant improvements in both cooling efficiency and carton strength are possible, using alternative vent hole designs. Additionally, a significant interaction, with respect to mechanical strength, was observed between board material properties (board type) and the vent hole design. This finding indicates that high humidity conditions (i.e. refrigerated transport) can substantially influence the expected mode of failure in cartons (mechanical performance). Furthermore, a CFD model was developed to predict spatio-temporal moisture distribution in cartons loaded in a RFC. The study of a standard shipping scenario showed that moisture gradients were relatively small, indicating that mechano-sorptive creep is likely not a major factor in this case. However, larger gradients are expected during less desirable conditions. These findings can be used as baseline conditioning treatments for future carton compression protocols. Lastly, two unique packaging system strategies were proposed and evaluated for cooling efficiency. Although both showed generally improved performance, the “Tes” design increased packing density by 12% and forced-air cooling efficiency by 29%, compared to standard designs. Findings also showed improvements in vent hole design for vertical flow (RFC) are still possible. Overall, research reported in this thesis contributes towards the development of a more optimal ventilated packaging design for use in the fresh produce cold chain. Significant advancements were also made with respect to the implementation of a multi-parameter evaluation approach, which should be further extended to future assessments of fresh produce supply chains both in academia and in commercial practice. Finally, significant knowledge gaps were revealed with respect to the mechanical performance of cartons under high humidity conditions. Future studies should therefore concentrate on the development of new predictive approaches to better assess the integrated performance of cartons under cold chain conditions.
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    Resistance to airflow and the effects on cooling efficiency of multi-scale ventilated pome fruit packaging
    (Stellenbosch : Stellenbosch University, 2013-12) Berry, Tarl Michael; Opara, U. L.; Delele, M. A.; Meyer, Chris J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Horticultural Science.
    ENGLISH ABSTRACT: Inadequate cooling of produce after it has been packed into ventilated packaging can result in inconsistent fruit quality. Misalignment of ventilation holes during stacking as well as the use of internal packaging, such as trays, polyliner bags and thrift bags reduces airflow distribution through the packaging. Consequently, the complex needs of maintaining the cold chain of perishable produce and the considerable variations in packaging designs have made it challenging to find an optimal ventilated package and stacking arrangement. The aims of this study were, therefore, to assess the status of ventilated packaging in the South African pome fruit industry, and to characterize the effects of package design and multi-scale packaging components on the resistance to airflow and cooling performance of apples under forced-air cooling conditions. A survey of the pome fruit industry identified over twenty packaging designs which were grouped into eleven unique designs and further categorised into either ‘display’ or ‘telescopic’ designs. Although South African fruit industry standards recommend ventilation areas of at least 5%, the ventilation areas of package designs identified from the survey varied considerably between <1 and 11%. Furthermore, the study showed that use of stacking renders many of the ventilation holes ineffective, due to blockages from adjacent cartons. The contribution of each component of the multi-scale packages used for handling apples was determined by analysis of pressure drop during forced-air cooling. The results showed when utilising a combination of cartons, fruit trays and plastic liner bags, the total pressure drop contribution of the cartons (8%) and fruit trays (3%) was minimal, while the use of plastic liner bags contributed 89%. However, in a carton and thrift bag packaging combination, the thrift bags contributed 66% to the pressure drop while the carton contributed 34%. The cooling results indicated a negative correlation between the total stack ventilation area and the cooling heterogeneity. In addition, the airflow velocity was correlated positively with fruit cooling rate and negatively with total moisture loss. Fruit packed inside polyliner bags had cooling rates four times slower than fruit on trays and three times slower in thrift bags. The use of liner bags blocked the ventilation holes, thereby reducing the airflow velocity. As a result of the longer cooling times in the polyliner bags, fruit remained at higher temperatures for longer periods, resulting in up to three times more moisture loss during forced-air cooling. In addition, a temperature gradient formed due to a progressive increase in air temperature through the stack, thereby resulting in a similar gradient of moisture loss. This research showed that airflow velocity and distribution were the most important factors contributing to the effectiveness of fruit cooling in multi-scale packaging. From a cold chain perspective, future packaging designs should therefore focus on optimising ventilation characteristics and alignment during stacking to ensure adequate airflow. Given the contribution of internal packaging to high resistance to airflow, such packaging components should be used with caution and only when necessary to meet physiological and market requirements.