- Title
- Estimation of the storage potential of blueberries under modified atmosphere conditions
- Creator
- Ulloa, Patricio
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Masters Research - Master of Philosophy (MPhil)
- Description
- Blueberries are a major global horticulture crop and also in Australia. Over the last 20 years, blueberry production has significantly increased and is one of the fastest growing fresh produce categories. The main drivers of this expansion are blueberry fruit unique taste, convenience and well-publicised health benefits. While blueberry consumption is increasing, there is also an expectation by consumers that blueberries should be available year-round. However, there are certain periods during the year when fruit is not available in sufficient volumes to satisfy the market demand, particularly in Australia where imports are limited. Conversely there are other times in the year, where there is often an oversupply of fruit which causes significant issues for industry. In order to regulate and manage fruit supply onto the market, long-term cold storage under modified atmosphere conditions has been utilised to meet the market needs. However, improper storage can negatively affect final fruit quality with poor flavour and soft fruit. It is important to precisely estimate the storage potential of different cultivars and batches to allow optimal storage and marketing programs. This concept has been used by some horticultural industries, such as the cherry industry in Chile which developed a storage potential matrix based on cultivar type, firmness, and soluble solids. But, even though a predictor would be quite useful, there is no quality predictor for blueberry storage. The primary aim of this study was to identify fruit quality variables at harvest that could be used as indicators of blueberry storage potential under modified atmosphere cold storage conditions. Four important commercial cultivars were used in this study: highbush cultivars (SHB-111 and SHB-222) and Rabbiteye cultivars (Brightwell, and Powderblue). SHB-111 and Brightwell were studied for two consecutive seasons (2015/16 and 2016/17) while SHB-222 and Powderblue were only studied in the 2015/16 season. To examine the effects of fruit maturity on final fruit quality, fruit were harvested at three different stages of maturity. Fruit were harvested at either: 6, 12 or 18 days after the ‘50% pink’ maturity stage. This harvest schedule was then repeated three times during each growing season (early, mid-, and late season). After harvest, fruit were stored at 0ºC in commercial modified atmosphere storage conditions for 20, 40 and 60 days before a further one week shelf-life assessment at 7ºC. Fruit size, berry firmness, total soluble solids (TSS) levels, titratable acidity (TA), and TSS/TA ratio were determined for fruit quality. The results showed that delaying harvest did not always result in significantly increased fruit diameter. However, it must my acknowledged that any increase in fruit could be commercially advantageous, particularly if the fruit volume is considered. The delay in harvest did not affect fruit firmness (as measured with the Firmtech), but there was a slight increase in TSS and decline in TA during the delay in harvest time. The results also highlighted significant differences among cultivars particularly in the quality variables, fruit firmness and TSS/TA ratio. For example, SHB-111 showed superior fruit quality at both harvest and following storage. However, no significant correlation was detected when any of the variables in any cultivar against the overall product quality score after storage. A significant correlation was detected with initial fruit firmness against firmness after storage, but this relationship was only observed when the fruit was stored for 40 days and was not detected when the fruit was stored for 60 days. The apparent lack of relationship between fruit quality at harvest [fruit firmness (as measured by Firmtech), TSS and TA] and the final quality score after storage indicates that developing a suitable and effective estimation matrix is more complex than initially anticipated. Future work needs to be conducted to better define the components of texture for each relevant cultivar, the mould load at harvest, and the sensitivity to CO2 injury. Additional and more sophisticated statistical modelling may also assist in the development of the model. Until that work is carried out, fruit firmness at harvest and the TSS/TA ratio can provide an incomplete and limited estimate of the storage potential of blueberries under modified atmosphere conditions.
- Subject
- blueberry; blueberries; modified atmosphere; cold storage; long-term storage; storage potential
- Identifier
- http://hdl.handle.net/1959.13/1418761
- Identifier
- uon:37392
- Rights
- Copyright 2020 Patricio Ulloa
- Language
- eng
- Full Text
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