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Physiological Defects

    The main internal quality defects receiving research attention are heat damage in plums and lenticel breakdown, mealiness, superficial scald and internal browning in apples and pears. Research is aimed at understanding the underlying causative factors (both pre-and postharvest) and biochemistry of these defects to allow the development of technology to limit or prevent their occurrence. In this regard, an ambitious new project by Dr Elke Crouch is studying the climate factors during early fruit development that give rise to radial internal browning in Cripps Pink apples and cultivars derived from it. Other aims are to generate best practice

    guidelines for handling fruit both pre-and postharvest and to develop indicators to predict the risk of various defects in each season.

    Expertise: Physiological Defects Workgroup

    Research team

    • Dr Elke Crouch
    • Dr Elmi Lötze
    • Dr Ian Crouch
    • Dr Ashwil Klein
    • Ms Anél Botes
    • Mr Daniël Viljoen
    • Ms Nolubabalo Mzizi - MSc student
    • Mr Alone Hlungwani – PhD student
    • Ms Monja Gerber – PhD student
    • Dr Thirupathi Pandian – Postdoctoral research fellow

    Projects list

    • Compilation of a photographic compendium of stone fruit disorders in a South African context. (I Crouch)
    • Quantification of the effect of near-harvest temperatures on pitburn and heat damage in cold stored plums and prediction method development. (H Viljoen)
    • Scanning plum cultivars for CO2 sensitivity and effect of closed vents in shipping containers on relative humidity and CO2 levels. (H Viljoen) – see Packaging and Logistics
    • The impact of relative humidity in commercial cold rooms during accumulation of pallets for shipping on shrivel with plums. (H Viljoen)
    • Superficial scald on Granny Smith - understanding the mechanisms and limitations of the storage protocols used by industry and assess risk indicators in storage for scald development (E Crouch, A Botes, A Klein, D Viljoen, T Pandian, M Gerber and A Hlungwani) [Abstract]
    • Assessment of a lenticel breakdown prediction method for the South African pome industry (D Viljoen) [Abstract]
    • Influence of fruit micro-structure on gas exchange and tissue damage (E Crouch) [Abstract]
    • Compilation of a database of high-quality images of pome fruit disorders from South African growing and storage conditions to contribute to the further development of software-based determination (APP) for the detection and reduction of bearing damage in fruit (I Crouch) [Abstract]
    • Quantifying the role of vapour pressure deficit in the development of lenticel breakdown in Braeburn apples. (E Lötze, D Viljoen and N Mzizi)
    • Assessment of fruit density as an indicator for internal browning susceptibility in Fuji apples (D Viljoen) [Abstract]
    • Identification of factors involved in the expression of internal browning in Fuji apples and the development of a strategy to reduce risk of incidence. (D Viljoen) [Abstract]
    • To assess Internal Browning development potential from high watercore incidence FEMA Forelle. (D Viljoen) [Abstract]
    • Summary of Fuji Browning Study and Literature Review (I Crouch)
    • Quantification of lenticels in Japanese plum cultivars and their effect on total fruit peel permeance (I Kritzinger)*
    • Stone hardening and broken stones in Japanese plums (Prunus salicina Lindl.) evaluated by means of computed tomography scans (E Lötze)*
    • Detection of internal heat damage and identification of techniques to prevent the expression of the disorder in plums. (H Viljoen) – also Storage techniques [Abstract]
    • Determining ‘Forelle’ pre-harvest mealiness/cavity development stage, due to environmental factors and exploring prevention of mealiness developing after storage and ripening. (E Crouch, L Schoeman and L-M Dippenaar) – see Growing season climate [Abstract]
    • Compilation of a photographic compendium of stone fruit disorders in a South African context (I Crouch) 
    • SAFJ Feb/Mar 2022: Mouton, A. Internal heat damage in Laetitia: p. 58.
    • SAFJ Apr/May 2022: Mouton, A. Interne verbruining in Cripps Pink: p. 76.
    • SAFJ Apr/May 2022: Mouton, A. Wat leer ons uit navorsing: p. 78.
    • SAFJ Apr/May 2022: Mouton, A. Die beste praktyke vir Cripps Pink: p. 80.
    • SAFJ Apr/May 2022: Mouton, A. Internal browning in Fuji: p. 84.
    • SAFJ Apr/May 2022: Mouton, A. Die beste praktyke vir Fuji: p. 86.
    • SAFJ Apr/May 2022: Mouton, A. Interne verbruining vanuit die pakhuisperspektief: p. 88.
    • Hortgro Technical Symposium Day 3 – 8 June 2022



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