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Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear
Thesis (MScAgric)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867614095571681280 |
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| access_status_str | Open Access |
| author | Dippenaar, Liza-Mari |
| author2 | Crouch, E. M. |
| author_browse | Crouch, E. M. Dippenaar, Liza-Mari |
| author_facet | Crouch, E. M. Dippenaar, Liza-Mari |
| author_sort | Dippenaar, Liza-Mari |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScAgric)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132164 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:46:35.680Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132164 Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear Dippenaar, Liza-Mari Crouch, E. M. Jooste, M. M. Moore, J. P. Steyn, W. J. Schoeman, L. Tsige, A. A. Stellenbosch University. Faculty of AgriSciences. Dept. of Horticultural Science. Forelle pears -- Breeding -- South Africa Pears -- Postharvest technology Pears -- Ripening -- Quality Fruit -- Physiological aspects Fruit trees -- Effect of temperature on Plant cell walls -- Composition Plant canopies -- Climatic factors UCTD Thesis (MScAgric)--Stellenbosch University, 2025. Dippenaar, L. 2025. Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/dcbe54c6-af41-4364-a829-9e68a1ce1c82 ENGLISH ABSTRACT: ‘Forelle’ pears play a crucial role in South Africa's pear industry, ranking as the second most cultivated variety and the leading blush variety, contributing significantly to the country's economy. ’Forelle’s success is attributed to their long-term storability, blush colour, and sweet flavour. However, a key challenge limiting the market competitiveness of ‘Forelle’, is the development of mealiness, a textural disorder characterized by a dry, floury mouthfeel and lack of juice. To address mealiness, this study investigated the environmental, physiological, and cell wall compositional factors contributing to the disorder. The first trial explored the effects of shading time (14-4 and 13-3 weeks before harvest) and microclimatic conditions on mealiness and blush development. Results showed that pears exposed to higher irradiance and fruit surface temperatures (FST) in the outer canopy exhibited higher blush percentages and larger sizes but were more prone to mealiness. Some shading periods reduced mealiness but often compromised the essential blush colour required for commercial standards. Furthermore, the study identified key links between fruit size, pore structure, and mealiness. An F-test highlighted that average pore size and porosity were the most critical variables influencing mealiness, with higher temperatures and irradiance improving fruit size especially of outer canopy fruit, leading to higher porosity and weaker cell-to-cell adhesion. These findings underscore the trade-off between fruit growth, blush colour development, and textural quality in 'Forelle' pears. In the second trial, white and black nets of various densities were tested as a strategy to reduce mealiness while preserving blush colour. While the 20% white net (54% shading) showed commercially sufficient blush colour and lower mealiness compared to outside canopy fruit, mealiness levels remained too high to be commercially viable. Black nets effectively reduced porosity and mealiness after 7 d of ripening but failed to meet blush colour standards. These findings demonstrated that while shading reduced mealiness, it presented significant trade-offs in fruit quality attributes crucial for marketability. The third component of the study focused on cell wall compositional differences between mealy and non-mealy fruit. Comprehensive microarray polymer profiling (CoMPP) revealed that non-mealy tissues had higher levels of homogalacturonan pectins, contributing to stronger cell adhesion. Mealy fruit exhibited evidence of pectin breakdown, leading to weaker cell wall integrity and increased porosity. These findings align with previous research linking mealiness to structural weaknesses in the cell wall. In conclusion, this thesis demonstrated that mealiness in ‘Forelle’ pears is influenced by complex interactions between environmental factors, fruit physiology, tissue structure and cell wall composition. No shading treatment fully prevented mealiness while maintaining blush colour, emphasizing the challenge of balancing these factors. The study confirmed that practices such as prolonged cold storage beyond 12 weeks and the use of 1-methylcyclopropene (1-MCP) remain the most viable strategies for mitigating mealiness. This research advances the understanding of mealiness development and provides valuable insights for optimizing post-harvest management practices and improving the market competitiveness of ‘Forelle’ pears. AFRIKAANSE OPSOMMING: ‘Forelle’ is die belangrikste blospeer en die tweede mees verboude peerkulitvar in die Suid-Afrikaanse peerbedryf en maak ‘n aansienlike bydrae tot die land se ekonomie. Die sukses van die kultivar word toegeskryf aan sy lang houvermoë, bloskleur en soet smaak. Die kulitivar se geneigdheid om ʼn melerige tekstuur te ontwikkel beperk egter sy mededingendheid in die mark. Melerigheid is ʼn tekstuurafwyking wat gekenmerk word deur ’n droë, meelagtige mondgevoel en ’n gebrek aan sap. Hierdie studie het omgewings-, fisiologiese en selwand-samestellingsfaktore wat tot melerigheid lei, ondersoek. Die eerste proef in die studie het die uitwerking van die periode van vooroes oorskaduing (14-4 en 13-3 weke voor oes) en die boommikroklimaat op melerigheid en bloskleurontwikkeling ondersoek. Die resultate het getoon dat pere wat aan hoër bestralingsvlakke en vrugoppervlaktemperature blootgestel is, ʼn oër blospersentasie en groter vrugte gehad het, maar meer geneig was tot melerigheid. Sekere oorskaduingsperiodes het melerigheid verminder, maar dikwels ten koste van die noodsaaklike bloskleur wat kommersieël vereis word. Verder het die studie belangrike skakels tussen vruggrootte, poriestruktuur tussen die vrugselle en melerigheid identifiseer. ’n F-toets het gewys dat gemiddelde poriegrootte en porositeit die belangrikste veranderlikes is wat melerigheid beïnvloed, met hoër temperature en vlakke van bestraling wat v die grootte van veral buitevrugte verbeter het, maar tot hoër porositeit en swakker sel-tot-sel-bindings gelei het. Hierdie bevindinge het die kompromie wat tussen vruggroei, bloskleurontwikkeling en tekstuurkwaliteit in ‘Forelle’ pere bestaan, uitgewys. In die tweede proef is verskeie foto-selektiewe skadunette getoets om te bepaal of dit melerigheid kon verminder sonder om bloskleur negatief te beïnvloed. Terwyl die 20% wit net kommersieël voldoende bloskleur en laer melerigheid in vergelyking met buitevrugte getoon het, was die melerigheidsvlakke wat in die behandeling ontwikkel het steeds nie kommersieël aanvaarbaar nie. Swart nette het porositeit en melerigheid ná 7 dae se rypwording effektief verminder, maar die vrugte het nie aan die kommersiële bloskleurstandaarde voldoen nie. Hierdie bevindinge het getoon dat skadu melerigheid verminder het, maar dat dit belangrike vrugkwaliteitseienskappe negatief beïnvloed. Die derde komponent van die studie het op selwand-samestellingsverskille tussen melerige en nie-melerige vrugte gefokus. Die studie het getoon dat nie-melerige vrugte hoër vlakke van homogalakturonan-pektiene gehad het wat sterker sel-tot-sel bindings tot gevolg gehad het. Melerige vrugte het tekens van pektienafbraak getoon wat tot swakker selwandintegriteit en verhoogde porositeit gelei het. Hierdie bevindinge stem ooreen met vorige navorsing wat melerigheid aan strukturele swakhede in die selwand gekoppel het. Ten slotte het hierdie tesis getoon dat melerigheid in ‘Forelle’ pere beïnvloed word deur komplekse interaksies tussen omgewingsfaktore, vrugfisiologie, weefselstruktuur en selwand-samestelling. Nie een van die skadu-behandelings wat in die studie getoets is, het melerigheid ten volle voorkom en terselfdertyd bloskleur behou nie. Die studie het bevestig dat praktyke soos langtermynkoelopberging van meer as 12 weke en die gebruik van 1-metielsiklopropeen (1-MCP) steeds die belangrikste strategieë bly om melerigheid te voorkom. Die studie het ʼn belangrike bydrae gemaak om die ontwikkeling van melerigheid in ‘Forelle’ pere beter te verstaan en bied waardevolle insigte vir die optimalisering van na-oesbestuurspraktyke en die verbetering van die markmededingendheid van die kultivar. Masters 2025-05-28T10:03:18Z 2025-05-28T10:03:18Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132164 en Stellenbosch University xiv, 118 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Forelle pears -- Breeding -- South Africa Pears -- Postharvest technology Pears -- Ripening -- Quality Fruit -- Physiological aspects Fruit trees -- Effect of temperature on Plant cell walls -- Composition Plant canopies -- Climatic factors UCTD Dippenaar, Liza-Mari Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear |
| title | Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear |
| title_full | Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear |
| title_fullStr | Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear |
| title_full_unstemmed | Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear |
| title_short | Pre-harvest shading treatment effects on post-harvest mealiness of ‘Forelle’ pear |
| title_sort | pre harvest shading treatment effects on post harvest mealiness of forelle pear |
| topic | Forelle pears -- Breeding -- South Africa Pears -- Postharvest technology Pears -- Ripening -- Quality Fruit -- Physiological aspects Fruit trees -- Effect of temperature on Plant cell walls -- Composition Plant canopies -- Climatic factors UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132164 |
| work_keys_str_mv | AT dippenaarlizamari preharvestshadingtreatmenteffectsonpostharvestmealinessofforellepear |