Manipulating harvest maturity and ethylene to extend storage life of feijoa : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand

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Massey University
In New Zealand feijoa (Acca sellowiana) are harvested by touch-picking and can be stored at 4 °C and 90% RH for up to 4 weeks with a subsequent shelf life of 5-7 d at 20 °C. Extending the storage potential of feijoa can enable export to new marketplaces through sea freight. The objective of this work was to extend the storage life of feijoa. Harvest maturity, variability within batch and ethylene all have the potential to influence postharvest storage performance. Harvesting feijoa earlier not only makes touch-picking irrelevant but will necessitate changes to the present grading standards of feijoa. Harvesting feijoa 2 weeks prior to touch-picked maturity consistently enabled storage life extension for up to 6 weeks at 4 °C with a subsequent shelf life of 5 d at 20 °C. However, these fruit were low in SSC with high TA suggesting that their taste profiles may be altered and hence a consumer taste acceptance investigation is recommended. There is also a need to identify a ripening index for feijoa while redefining grading criteria suitable for both local and export markets. This work demonstrates that feijoa having higher °hue (> 122) at the time of harvest possessed longer storage potential than those with lower °hue (< 122) that are ready-to-eat. Blocking ethylene responses of touch-picked or early harvested feijoa by postharvest 1-methylcyclopropene treatment had minimal effect on physiology (ethylene production and respiration rates) or quality after storage. Feijoa were also insensitive to exogenous ethylene application while CA technology stimulated surface injury. However preharvest Aminoethoxyvinyl glycine (AVG) application reduced fruit drop and delayed maturity (retaining firmness) of feijoa at the time of commercial harvest. AVG suppressed ethylene production during storage without altering quality attributes (firmness, SSC, TA or flesh colour). A conceptual model was developed to summarise feijoa responses to ethylene manipulations. Postharvest ripening in feijoa appears to be substantially ethylene-independent. Storage life of feijoa was extended by harvesting fruit earlier than current touch-picking maturity. Segregating feijoa by skin colour change would allow sea freight of less mature fruit. However, taste acceptance of these fruit and commercial trials of preharvest AVG are required before practical recommendations can be made to the industry.
The following articles were removed due to copyright restrictions: Rupavatharam, S., East, A.R., Heyes, J.A. (2015), "Combined effects of pre-storage 1-methylcyclopropene application and controlled atmosphere storage on 'Unique' feijoa quality", New Zealand Journal of Crop and Horticultural Science, 43:2, 134-143 Rupavatharam, S., East, A.R., Heyes, J.A. (2015), "Re-evaluation of harvest timing in 'Unique' feijoa using 1-MCP and exogenous ethylene treatments", Postharvest Biology and Technology, 99, 132-159 Rupavatharm, S., East A.R., Heyes, J.A., (2013), "Opportunities to manipulate harvest maturity of New Zealand feijoa (Acca sellowiana) to enable sea freight export", Conference paper, Acta Horticulturae (under publication).
Feijoa, Acca sellowiana, Feijoa harvesting, Feijoa storage, Fruit shelf life