Doctoral Degrees (Horticulture)

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Browsing Doctoral Degrees (Horticulture) by browse.metadata.advisor "Fawole, Olaniyi Amos"

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    Formulation and application of novel bioactive edible coatings to extend storage and shelf life of pomegranate whole fruit and arils
    (Stellenbosch : Stellenbosch University, 2022-12) Kawhena, Tatenda Gift; Opara, Umezuruike Linus; Fawole, Olaniyi Amos; Tsige, Alemayehu Ambaw; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: The growth of the pomegranate (Punica granatum L.) fruit industry is limited by high postharvest losses along the supply chain caused by weight loss and incidence of physiological and pathological disorders. Although several postharvest technologies have been applied to reduce these losses, substantial losses still occur, causing negative financial impact on all pomegranate industry stakeholders. Therefore, the development and application of new science-based technologies to reduce postharvest losses in pomegranate fruit is a priority. The overall aim of this research study was to formulate bioactive edible coatings for pomegranate whole fruit and arils to extend storage and shelf life. In Section I, Paper 1 and Paper 2 highlighted the potential of edible coatings as a postharvest treatment for pomegranate fruit during cold storage and shelf life. Section II studies (Paper 3 and 4) applied gum Arabic and methyl cellulose coatings enriched with either thyme or lemongrass essential oils on pomegranate whole fruit and arils. Gum Arabic (1.5% w/v) coatings combined with thyme oil (0.25 or 0.5% w/v) significantly (p ≤ 0.05) reduced weight loss, microbial proliferation and maintained postharvest quality of arils for 8 days of storage (5 ⁰C and 95 ± 2% relative humidity). Similarly, gum Arabic (1.5% w/v) coating containing pomegranate peel extract (1% w/v) and lemongrass essential oil (0.1% v/v) significantly (p ≤ 0.05) reduced respiration rate and incidence of decay for 6 weeks of storage (5 ± 1 °C and 90% relative humidity). Section III (Paper 5 and 6) followed up on the results in Section II by optimizing selected coatings developed in Paper 3 and 4. In Paper 5, lemongrass essential oil was the best antifungal agent against tested microbes (Botrytis cinerea and Penicillium spp.) and the minimum inhibitory concentrations against Botrytis cinerea and Penicillium spp., were 1.5 (% v/v) and 3 (% v/v), respectively. Sodium alginate and chitosan-based coatings formulated with lemongrass essential oil (1.5 or 3% v/v) completely inhibited spore germination and reduced the decay severity of ‘Wonderful’ pomegranate during shelf life. In Paper 6, response surface methodology was used to develop an optimized coating containing gum Arabic (0.5% w/v), maize starch (0.5% w/v), lemongrass oil (3% v/v), and glycerol (1.5% v/v). In Section IV (Paper 7 and 8), the optimized coating developed in Section III was applied on whole ‘Wonderful’ pomegranate fruit and the moisture loss characteristics (Paper 7) and the effects when combined with different polyliners (Paper 8) were investigated. The optimized coating significantly (p ≤ 0.05) reduced weight loss by minimizing the rate of increase in transpiration rate. In Paper 8, the combination of coatings with Xtend® polyliners was the most effective treatment to maintain the quality of ‘Wonderful’ pomegranates during storage (5 ± 1 °C and 95 ± 2% relative humidity). Overall, this research showed that edible coatings minimized postharvest losses in pomegranate whole fruit and arils. The study provides important scientific information to assist prospective studies to develop edible coatings for other fruit types for future application at packhouse level and other food industries.
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    Quantity and quality losses of 'Crimson Seedless' grape and 'Packham's Triumph' pear along the supply chain and associated impacts
    (Stellenbosch : Stellenbosch University, 2022-04) Blanckenberg, Anelle; Opara, Umezuruike Linus; Fawole, Olaniyi Amos; Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: Postharvest loss and waste (often referred to as wastage) is a global problem affecting all produce along the supply chain from farm to plate. These losses not only decrease food supply but also mean that huge amounts of the resources and effort used in the production of horticultural crops are squandered. From an economic perspective, addressing postharvest losses is not only helpful to producers aiming to sell more, but also to consumers who could save money as the available food becomes more affordable. To date, there is little scientific data available on the incidence and magnitude of postharvest losses of fruit and other food crops in South Africa. The aims of this study were to assess postharvest losses in quantity and quality of ‘Crimson Seedless’ table grape and ‘Packham’s Triumph’ pear along the supply chain and quantify the associated economic, environmental and resource impacts in order to inform mitigating actions. The base measurement for table grape losses occurred in the packhouses of four farms in the Western Cape during the commercial harvest. The highest quantity (%) of physical losses in the supply chain was found to occur at this level when compared to the cold storage (2 or 4 weeks at -0.3°C ± 0.7°C and 81.3% ± 4.1% RH), retail (10 days at 5.4°C ± 0.6°C and 83.7% ± 2.9% RH) and consumer/home (ambient) storage (25.1 ± 1.3°C and 46.6 ± 6.0% RH) stages. There were large differences between the 2017 and 2018 seasons, with the 2018 season’s losses being half that of the first. The main reason for losses at the packhouse level was mechanical damage (7.1% in 2017 and 3.09% in 2018) due to rough handling of crates and could be improved by making workers more aware of the necessity to handle crates with care. Harvest timing is also essential, as delayed harvesting reduces shelf life and increases postharvest losses, as evidenced by this research. The farm that sustained the highest losses in 2017 (23.3%) harvested later than was optimal, and therefore, the bunches stayed on the vines too long. In 2018 the harvest occurred two weeks earlier than in 2017, and the grapes were in better condition leading to fewer losses on farm level (5.85%). Among all supply chain scenarios, the main quality problem was rachis and stem browning at temperatures higher than -0.5ºC. This caused berries to drop faster and bunches to look less fresh, as well as causing bunches to weigh less when sold. While 500 g and 1 kg punnets are routinely kept at around 5ºC at the retail level, during peak season 4.5–10 kg cartons are often stacked on the floor under ambient conditions. Therefore, the table grapes would have a maximum shelf life of seven days before the stems have browned and too many berries per bunch are decayed to sell. Therefore, it is advisable to keep cartons at -0.5ºC and high RH and only place bunches in punnets in 5ºC display fridges as the stock sells. The base measurement for losses of pear occurred in the orchard of two farms in the Western Cape during commercial harvest. It was found that 18% of the harvest on the one farm and 19% of the harvest on the other, did not reach the minimum quality standards. The main reasons were deformed fruit and too small size. The only decay, among all supply chain scenarios, occurred when pears were kept under ambient conditions (25.1 ± 1.3°C, 46.6 ± 6.0% RH) where 3.3% were decayed after seven days and 6.6% after 10 days. The majority of physical losses were due to weight loss with a 3.9%, 3.6 and 3.7% decrease in weight for supply chain Scenario B (to local retail markets), supply chain Scenario C (to export retail markets) and supply chain Scenario D (simulated ‘abusive’ treatment of fruit within the export chain) respectively. . Of the data gaps in the existing knowledge on global food loss and waste, the largest gap is the lack of available data on postharvest losses, retail and household level (shelf-life) food waste data. Therefore, this study contributed to the advancement of new knowledge by generating primary data on postharvest quantity and quality losses along the supply chain to manage the food loss and waste problem better.