Masters Degrees (Horticulture)

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

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    Understanding soft scald and bitter pit development in ‘Scifresh’ apples
    (Stellenbosch : Stellenbosch University, 2024-03) Ladegourdie, Jason; Crouch, Elke; Botes, Anel; Jooste, Mariana; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: The South African pome fruit industry annually contributes approximately R11.47 billion to the country's economy. Effective storage techniques are essential to maintain fruit quality and remain competitive. This study focused on two storage disorders, namely soft scald and bitter pit, both of which significantly impact the South African apple industry. Soft scald is becoming increasingly problematic. Although a great deal of research has been conducted on bitter pit, it remains a common issue. 'Scifresh', a relatively new apple cultivar, was used in this study and is particularly susceptible to soft scald and bitter pit. This study comprises of a literature review and four scientific papers, with a focus on soft scald and bitter pit development under South African conditions. The main aim of the study was to understand the factors that influence disorder susceptibility and propose strategies to minimize the risk. The first paper assessed the impact of various storage regimes on 'Scifresh' apple quality and investigates biochemical indicators such as reactive oxygen species, internal ethylene concentration, total phenolics, total antioxidant capacity, and apple volatiles. Harvest maturity and cooling rate after harvest were identified as factors in soft scald and bitter pit development. Stepwise cooling limited the incidence of soft scald but increased the risk of bitter pit. Ethylene reduction methods are suggested for further research to address bitter pit in regular atmosphere storage whilst stepwise cooling is used for soft scald reduction. The second paper evaluated the effects of regular and controlled atmosphere (CA) storage, storage times, and 1-methylcyclopropene (1-MCP) on post-storage quality. The results indicate that 1-MCP reduced bitter pit in fruit stored under regular atmosphere. Post-optimum harvested fruit treated with 1-MCP that was stepwise cooled and CA stored long-term (6-8 months), had an increased risk of bitter pit development. This was not a risk for 1-MCP treated fruit that was cooled immediately and CA stored long-term (6-8 months). The third paper investigated the effects of forced-air cooling (FAC) after packing on 'Scifresh' apple quality, with a special focus on potential chilling disorders during the re-cooling process. FAC after packaging did not affect fruit quality compared to passive cooling, when re-cooling remained below 10 °C. The fourth paper investigated the effect of different fruit harvest maturities on post-storage fruit quality. It was found that ‘Scifresh’ apples must be harvested at optimum maturity to mitigate the risks of soft scald and bitter pit. Blush colour cannot be used as a single harvest maturity index but rather in combination with other harvest maturity parameters. The recommended harvest maturity includes a narrower starch breakdown window of 30–40 %, TSS > 12 %, firmness > 8 kg with a 40 % blush colour and F4 colour intensity according to the ‘Scifresh’ colour swatch. In conclusion, the research provided valuable insights into the storage disorders, soft scald and bitter pit, offering recommendations for optimal storage protocols and harvest practices of ‘Scifresh’ apples.