Masters Degrees (Horticulture)

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Browsing Masters Degrees (Horticulture) by browse.metadata.advisor "Botes, Wilhelmina Jacoba"

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    Investigation of the effect of cooling and delays as well as CO2 concentrations during storage on internal browning in 'Fuji' apples
    (Stellenbosch : Stellenbosch University, 2024-03) Kriegler, Anmari; Botes, Wilhelmina Jacoba; Jooste, Mariana; Crouch, Elke; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: High-quality apple fruit is expected from various markets throughout the year. The use of controlled atmosphere (CA) storage is implemented to increase the availability of high-quality apple fruit. Unfortunately, the storage conditions required during CA also cause the appearance of physiological defects such as internal browning (IB) that lead to several market and financial losses. Since CA storage conditions contribute to IB occurrence, the possible use of stepdown cooling treatments was investigated in the first objective to determine if it influences IB as well as the fruit quality of ‘Fuji’ apples. Harvest maturity played an important role in the development of physiological defects since bitter pit occurred when fruit were harvested closer to optimum maturity while IB occurred when fruit were harvested at a more post-optimum maturity. Ethylene influenced bitter pit development since the stepdown treatments had the highest ethylene concentration and bitter pit levels. The study concluded that fruit should be harvested at optimum maturity and be room cooled under regular atmosphere (RA) for 49 d at 0.5 °C immediately after harvest and should be stored for longer than 4 months in CA (1.5 kPa O2 and 0.5 kPa CO2) to prevent IB and bitter pit development. The second objective was to determine the effect of delayed cooling and delayed CA establishment on CO2 injury and fruit quality of ‘Fuji’ apples. Again, the importance of harvest maturity was emphasized since CO2 injury developed in 2022 when fruit were harvested at post-optimum maturity and had an overall effect on fruit quality. This study found that rapid cooling of fruit after harvest is important to maintain fruit quality and several fruit quality and biochemical parameters were affected by the delayed cooling treatments. The development of CO2 injury was significantly affected by the storage duration, especially after shelf-life. Several findings of the first objective were confirmed during this study. During the third objective the possibility of predicting CO2 injury after long-term CA storage (6 months) by subjecting fruit to a short-term exposure of 3 d to high CO2 concentrations after harvest was investigated. In 2022, when fruit were harvested at post-optimum maturity, CO2 injury developed during short- and long-term CO2 treatments. However, 0.5 kPa CO2 treatment resulted in the highest CO2 injury after each evaluation period. The harvest maturity and the CO2 concentration play important roles in the development of CO2 injury during long-term CA storage and had an impact on overall fruit quality. The study concluded that a short-term treatment involving high CO2 and low O2 stress after harvest is not an accurate method for predicting CO2 injury development during long-term CA storage. Furthermore, the results suggested that harvesting ‘Fuji’ apples at optimum maturity not only prevents CO2 injury, but also enables the use of lower CO2 concentrations while maintaining fruit quality.