Browsing by Author "Botes, Johane"

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    Impact of shade netting on internal and external quality of ‘Nadorcott’ mandarin fruit
    (Stellenbosch : Stellenbosch University, 2018-12) Botes, Johane; Cronje, P. J. R.; Hoffman, L. (Lynn) (Horticulturalist); Zacarias, Lorenzo; Stellenbosch University. Faculty of Agrisciences. Dept. of Horticulture.
    ENGLISH ABSTRACT: In the export-focused citrus industry of southern Africa, the production of high quality fruit i.e. good size, well-developed rind color, blemish-free fruit and good taste is of utmost importance to remain sustainable. Shade nets are a preharvest technique implemented to protect crops against excessive sunlight, wind and hail damage. Shade nets are effective in reducing sunburn, but inconsistent results from previous studies arise about fruit size, rind color and internal quality. Furthermore, the impact on postharvest fruit quality with regard to developing rind physiological disorders and to maintain the physical integrity of the rind as a protection layer against moisture loss and decay development, is not known. Three experiments were conducted to determine how 20% white permanent shade netting would influence, firstly the fruit quality development, secondly the postharvest behavior and lastly the rind physical properties of ‘Nadorcott’ mandarin fruit produced in Citrusdal, over two seasons (2016 and 2017). In the first experiment, results indicated that the fruit size, rind color and internal quality development patterns were similar for both shade-net exposed and control fruit. Shade netting, however, resulted in an increased fruit size over the 2017 development period, but with no influence on rind color or maturity. Sunburn incidence was effectively reduced by shade nets. During cold storage at 4 and -0.6 °C over a period of 34 days, storage duration did not influence the postharvest quality of shade net fruit differently compared to control fruit in terms of rind color, internal quality parameters and fruit weight loss. In addition, no negative effect of shade netting was evident for the above-mentioned parameters or the incidence of staining. In the third experiment inconsistency occurred with regards to the effect of shade netting on fruit rind strength at harvest. A higher firmness was recorded for shaded fruit in the first season. However, during cold storage, there was some indication that the shade net fruit was more susceptible to deformation and required a lower force over the whole storage duration to puncture the rind, compared to the control fruit. However, a lower force required may also be beneficial as it could be indicative that the fruit may be easier to peel. The firmness of shade net-produced fruit was differently influenced by cold storage in 2016, within the first 14 days of storage, compared to the control. In 2017, control fruit were recorded to have a higher firmness over the storage duration. Both results indicated that the control fruit possibly stored better than shade-net fruit. To conclude, shade net was effective in reducing sunburn without negatively affecting any external and internal quality parameters. The postharvest storage potential of fruit from shade netting did not differ from the control at both storage regimes. Results regarding the impact of shade netting on the physical properties of the rind provides some first guideline threshold force values required before damage is inflicted on the fruit. Knowledge of typical forces applied during the commercial harvest- and pack house processes is, however, required before these values can be compared to commercial practices to determine its importance. The use of shade-netting shows potential as a preventative technology ensuring high quality, unblemished fruit, but requires future studies taking into account the effect of various cultivars, tree age, bearing positions and the microclimatic effect on fruit production and postharvest storage behavior.