Location: Physiology and Pathology of Tree Fruits Research
Project Number: 2094-43000-008-044-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Mar 1, 2023
End Date: Feb 28, 2026
Objective:
Extending ‘Bartlett’ pear storage is a highly ranked Fresh and Processed Pear Committee (FPPC) priority, ideally achieving quality fruit at and beyond 6 months storage postharvest (industry communication). ‘Bartlett’ fruit are currently harvested at 19-17 lb; fruit intended for late-season marketing are stored in controlled atmosphere (CA). Recent research in extending ‘Bartlett’ storage longevity via CA is sparse, although one report indidcates ‘Bartlett’ fruit harvested at 18 lb and stored at 1.5% O2 + <0.5% CO2 begin to deteriorate after 4 months and quality can be market-limiting by 6 months postharvest (Bai et al., 2006). Older research (Claypool, 1973) on California ‘Bartlett’ pears indicated that storage of fruit at ultra-low oxygen (ULO) (0.5% O2 + 0% CO2) could extend storage of early harvested fruit to 6-7 months postharvest. However, ULO was far less effective for extending storage duration for late-harvested fruit (Claypool, 1973). Since firmer fruit typically have higher storage potential, when determining optimal harvest maturity for fruit, decisions must take into account rapidly increasing fruit size (as much as 2.5% size increase per day, according to (Claypool, 1973)) with decreasing firmness. Importantly, a valid concern is that any increase in tonnage due to delaying harvest may not be worth the quality lost (Hansen and Mellenthin, 1979). Alternatively, fruit could be harvested too early to ripen properly.
Present knowledge gaps regarding ‘Bartlett’ storage extension include:
1) optimal CA conditions for long-term stored fruit
2) optimal firmness or maturity indicators for fruit destined for long-term CA
3) the effectiveness of post-storage cold chain solutions
To address these knowledge gaps, this research project proposes experimentation in three areas relevant to ‘Bartlett’ storage: 1) determining relative benefits of long-term ULO-controlled atmosphere (CA) storage compared to more standard long-term low-oxygen CA storage, 2) determining the optimal harvest maturity of ‘Bartlett’ for long-term CA, and 3) evaluating post-storage modified atmosphere packaging (MAP) to enhance storage longevity for ‘Bartlett’ pears. New technologies could allow for commercial application of ULO, and updates to the research CA system underway at USDA-ARS Hood River Worksite will facilitate ULO research. The CA system at USDA-ARS Wenatchee also had a recent upgrade to its nitrogen generator, allowing for larger scale CA-research than was previously possible.
Proposed research activities align with the following highly ranked Fresh and Process Pear (FPPC) research priorities:
• extending ‘Bartlett’ pear storage
• organic strategies for pear storage
Approach:
1. Evaluate ultra-low oxygen in comparison to other controlled atmosphere (CA) regimes for long-term ‘Bartlett’ storage.
Activities in this objective will determine if ultra-low oxygen CA (0.5% oxygen (O2) + <0.1% carbon dioxide (CO2)) offers significant storage extension without loss of quality relative to other CA programs. Research activities will compare these specific CA regimes:
0.5% O2 + <0.1% CO2
0.8% O2 + <0.1% CO2
1.5% O2 + <0.1% CO2
2.5% O2 + <0.1% CO2
Control fruit (no CA)
2. Determine optimum maturity for long-term CA storage for Bartlett.
Research activities in this objective is will systematically evaluate the optimum firmness for long-term low-oxygen CA (~1.5% O2 + <0.1% CO2) for ‘Bartlett’ pear. Fruit size distribution for early (22.5 pound (lb) firmness)), on-time (19.5 lb), and late (17 lb) harvests will be determined by harvesting whole trees, and the effects of maturity on storability will be evaluated by storing fruit at 1.5% O2 + <0.1% CO2. Fruit quality and samples collected in this objective will contribute to research for molecular maturity indicators and the utility of California ‘Bartlett’ maturity indices (Mitcham et al., 1996) evaluated.
3. Evaluate the influence of modified packaging (MAP) (LifeSpan, Amcor, Australia) on fruit quality post long-term CA storage.
Research activities in this objective will determine storage longevity and fruit quality of ‘Bartlett’ fruit held at 30, 36 and 42 °F in boxes with MAP liners post-long-term CA storage. Although research indicates utility for certain types of MAP for ‘Bartlett’ when used immediately after harvest, whether MAP continues to provide significant benefit and retains aroma and quality in late-term storage post-CA has not been examined.
