Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2020
Publication Date: 12/30/2020
Citation: Mattheis, J.P., Rudell Jr, D.R. 2020. ‘Honeycrisp’ apple (Malus domestica Borkh.) fruit response to controlled atmosphere storage with the low oxygen limit established by monitoring chlorophyll fluorescence. HortScience. 56(2):173-176. https://doi.org/10.21273/HORTSCI15404-20.
Interpretive Summary: Cold storage of apples is a technologically advanced process that results in fruit being available for months after harvest. Cold storage is central to extending fruit storage life, but additional tools including a controlled atmosphere (CA) environment where oxygen is kept well below that of air and/or treatment with an inhibitor of ripening, 1-methylcyclopropene (1-MCP) add to the ripening-delay effect of low temperature. All apple varieties respond differently to storage conditions and to date the way to determine what combination of temperature and CA environment is best is a variety by variety exploration. In this study ARS scientists evaluated how 'Honeycrisp' apples react to CA with very low oxygen concentrations. As oxygen decreased, particularly below 1% oxygen, the chance of internal browning developing in the apples increased. At higher CA oxygen concentrations up to 2% there was less internal browning and fruit quality was superior to that of fruit stored in air. Treatment with 1-MCP also impacted browning and quality. The results show CA during cold storage with or without 1-MCP treatment can provide an extension of 'Honeycrisp' storage life compared to fruit stored in air enabling this variety to be available for consumers over a longer marketing period.
Technical Abstract: Postharvest management of apple fruit ripening using controlled atmosphere (CA) cold storage can be enhanced as CA oxygen concentration is decreased to close to the anaerobic compensation point (ACP). Monitoring fruit chlorophyll fluorescence (CF) is a technology to assess fruit response to low O2 CA conditions as fluorescence increases as pO2 reaches a critically low concentration. Use of very low CA pO2 can enhance post-storage apple fruit quality for many cultivars due to better firmness retention and prevention of superficial scald compared with fruit stored at higher pO2 during CA. ‘Honeycrisp’ is a cultivar with little risk of firmness loss or superficial scald during storage, however, other aspects of fruit quality loss during storage including soluble solids content (SSC), titratable acidity (TA), peel greasiness, and physiological disorder development may be impacted by CA pO2. A two-year study was conducted to identify what if any impacts CA storage of ‘Honeycrisp’ with low pO2 CA setpoint determined using CF has on post-storage fruit quality. ‘Honeycrisp’ apples were held 7 d at 10 oC after harvest then at 3 oC. Some fruit in year two were exposed to 42 µmol L-1 1-MCP the day of receipt. CA was established 48 h after transfer to 3 oC. In both years, fruit CF increased when pO2 decreased to ~0.3 kPa O2 and then decreased after pO2 was increased to 0.5 kPa. Additional CA pO2 concentrations above 0.3 kPa were also maintained for other fruit. Fruit internal disorder incidence increased as pO2 decreased and with 1-MCP use. Changes in SSC, TA, and peel yellowing were inconsistently reduced by storage at lower pO2. Peel greasiness did not develop in either year. CA did not impact incidence of chilling disorders regardless of pO2. Results indicate some aspects of ‘Honeycrisp’ fruit quality can be enhanced as storage pO2 decreases, however, storage at pO2 above the low pO2 threshold did not prevent internal physiological disorder development.