Doctoral Degrees (Horticulture)
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Browsing Doctoral Degrees (Horticulture) by Author "De Beer, Tarryn"
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- ItemAlternative postharvest technologies for the maintenance of ‘Parthenon’ broccoli quality during export and domestic marketing.(Stellenbosch : Stellenbosch University, 2022-04) De Beer, Tarryn; Crouch, E. M.; Crouch, Ian; Theron, K. I.; Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture.ENGLISH ABSTRACT: Broccoli is prized for its nutritional quality. The green colour and a compact head symbolise freshness. Export and domestic marketing of broccoli is limited by its high perishability. The aim of this study was to investigate the use of two 1-methylcyclopropene (1-MCP) application methods in combination with packing to maximise broccoli storage life under different temperature regimes typically found in the export and domestic handling chains. Under simulation of domestic handling chains, optimal temperature storage (0 °C) of broccoli (cv. Parthenon) in combination with 1-MCP and packaging [Xtend™ modified atmosphere packaging (MAP) or macro-perforated high-density polyethylene (HDPE) liners] resulted in a maximum storage duration of 30 days. In a second season, optimal temperature storage with MAP (RipeLock™) allowed for 42 days storage. Storage at suboptimal temperatures (viz. 7.5 °C or 12 °C), in mixed loads with ethylene is, however, common during domestic handling. Under such environments 1-MCP prevented broccoli (cv. Parthenon) yellowing that occurred with increasing storage temperature from 0 °C-7.5 °C and 7.5 °C-12 °C. Furthermore, 1-MCP alone or in the presence of ethylene extended shelf-life of broccoli (cv. Parthenon) compared to controls, at both temperatures. This research showed how an in-box treatment system of 1-MCP can be used as a viable alternative to the traditional, bulk, in-room application method, having a similar effect in reducing yellowing compared to controls. Sensory quality of broccoli was maintained in MAP (RipeLock™) at 0 °C and 7.5 °C. At 12 °C, where sensory quality was the poorest, 1-MCP reduced the perception of ‘sulphur odour’ compared to untreated and ethylene exposed broccoli. Dimethyl trisulphide (DMTS), an off-odour related volatile, was the most abundant volatile measured at all storage temperatures. The oxidative state of broccoli increased with an increase in storage temperature from 0 °C to 7.5 °C to 12 °C. Ascorbic acid and glutathione were oxidized with an increase in storge temperature. Glutathione, however, had a consistently higher percentage oxidation compared to ascorbic acid. Under simulated export conditions, broccoli was stored at 0 °C in various MAP types with or without 1-MCP. 1-MCP was either applied in-room before packaging or in-box during packaging. Results showed that extended storage without packaging is not recommended due to excessive weight loss. Across two seasons variations in shelf-life were noted. In the first season, a maximum storage duration of 25 days was realised with broccoli stored in Xtend™, or a generic HDPE MAP film with 1-MCP. In the second season, the maximum storage duration was 35 days, irrespective of MAP type or 1-MCP treatment. Here, the limiting factor for shelf-life was sensory quality. At optimal temperature volatiles related to off-odour were negligible, indicating that sensory deterioration was not related to fermentation in the MAP environment. In the second season it was reported that if good quality broccoli is stored at 0 °C, RipeLock™ or Xtend™ MAP in combination with 1-MCP should yield no benefit over untreated broccoli in non-specific, generic liners bags (15 μm HDPE).