Understanding the storage potential of two blueberry cultivars grown in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Horticulture at Massey University, Manawatū, New Zealand. EMBARGOED until 31st August 2025.

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Date
2023
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Massey University
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Novel blueberry cultivars such as Eureka (EU) and First Blush (FB) are usually picked, packed, handled, coolstored and commercially sold in the same punnet. However, these cultivars possess different fruit physiological and morphological attributes and consequently may behave differently as influenced by postharvest storage conditions. Two independent experiments were designed to provide a better understanding of the modes of failure (water loss, softening, and rots) as influenced by storage conditions. It is expected that these investigations will facilitate the blueberry industry to decide if these cultivars should be picked, packed and handled differently in the commercial supply chain. Experiment 1 was setup with four storage temperatures (0.5°C, 1.5°C, 2.5°C, and 3.5°C) as treatments using EU and FB cultivars. Response variables of weight loss (WL), firmness and rots were monitored at weekly intervals over 28 days. WL increased over time with highest WL (3.8-6.1%) at 3.5°C and the lowest WL (1.8-4.3%) at 0.5°C. Cultivar differences were observed with higher WL in the EU cultivar than the FB cultivar. Firmness decreased in both cultivars over time when stored at 2.5-3.5°C. When compared to at-harvest firmness, values after 28 days in storage did not decrease significantly at 0.5-1.5°C. Rot incidence was numerically higher at 3.5°C than 0.5-1.5°C for both cultivars, but could not be statistically verified. Experiment 2 investigated the effect of storage extension technologies, such as, modified atmosphere packaging (MAP) and sulphur dioxide (SO₂) pads on both cultivars and WL, firmness and rots monitored at weekly intervals when stored at 2°C over 42 days. Blueberries stored in MAP+SO₂ showed sevenfold less WL (1.5%) than control fruit (6.9-10.9%). In addition, MAP+SO₂ treatment had significantly less rots than the control. Cultivar differences were also observed with higher number of rots in the EU cultivar. However, MAP+SO₂ treatment caused SO₂ bleaching to both cultivars observed at all storage timings and hence the use of SO₂ pads is not recommended in these cultivars. Commercially, the blueberry punnets are packed with approximately 1-2% extra weight at packing to account for the WL during storage and handling. Results from these experiments demonstrate that both cultivars should be packed separately due to propensity of the EU cultivar to lose more moisture affecting the quantity of extra weight. The use of storage extension technologies (MAP and SO₂) did not show a significant commercial benefit. Future studies should focus on comparing the efficacy of using MAP vs a standard polyliner and/or creating SO₂ pads with a slower release rate.
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Embargoed until 31st August 2025
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