Cox’s Orange Pippin (and clones) – benefits
- SmartFreshTM application provides a significant (>2-fold) extension to the storage life of fruit held in refrigerated air storage.
- A combination of a lower storage temperature (1.5oC) and SmartFreshTM application was particularly beneficial to the quality of air-stored fruit.
- SmartFreshTM application consistently improved retention of firmness and reduced weight loss in store.
- Occasionally SmartFreshTM application resulted in reduced yellowing, higher soluble solids and acidity levels and less bitter pit.
- Greatest effects of SmartFreshTM application were achieved on fruit picked at the correct stage of maturity for medium to long-term storage.
Cox’s Orange Pippin (and clones) – constraints / limitations
Stem end russet browning
In some commercial consignments of Cox treated in the UK and also in New Zealand the russetted areas of the fruit have darkened in response to SmartFreshTM application. This is known as stem end russet browning.
- The precise cause of the disorder is unknown although it has been hypothesised that 1-MCP causes a stress response in the skin cells which leak cell contents that are rapidly oxidised to brown coloured compounds (McCormick and Streif, 2008).
- Development of browning symptoms is inhibited by low temperatures and low oxygen conditions so fluctuations in temperature or atmosphere after treatment should be avoided.
- Commercial experience also suggests that early picked fruit are particularly at risk from stem end russet browning.
- Tables of storage conditions for Cox contain information to remind growers of practices that minimise this disorder.
- It is advised by the suppliers (Landseer Ltd.) that SmartFreshSM application should be restricted to fruit where starch coverage is 70% or less.
- This is to minimise the effects of stem end russet browning and encourage fruit above 75% starch and a pressure greater than 8.6 kg to be stored for March marketing without the use of SmartFreshTM.
Core flush
Perhaps the most significant adverse effects of SmartFreshTM is the increased susceptibility of stored fruits to core flush and flesh breakdown which has important limitations on the storage life of Cox stored in CA conditions.
- In air storage, core flush was evident in fruit treated with SmartFreshTM after 90 days but not after 60 days.
- It is difficult to set a precise termination date for air-stored Cox apples treated with SmartFreshTM.
- It is currently advised that marketing should be concluded in December although regular monitoring of fruit condition will help determine more precisely the termination dates for particular consignments.
- The life of Cox apples treated with SmartFreshTM and stored in CA conditions is limited by the development of core flush and flesh breakdown.
- The termination month for treated fruit is set at January but it may be possible to extend storage of some consignments, particularly in years where climatic conditions have conferred a low potential for core flush and low temperature breakdown.
- It is possible to make a general assessment of risk based on seasonal weather (Johnson and Ridout, 1998) but careful monitoring of the condition of the stored fruit is required to determine when to conclude storage.
The storage of SmartFreshTM-treated Cox beyond January
Growers wishing to extend the storage of SmartFreshTM-treated Cox beyond January are advised to store in CA conditions of 1.2% O2 and <1% CO2 and to ensure that fruit temperature is above 3.5oC in all parts of the store.
- Carbon dioxide levels should remain below 1% for the entire period of storage i.e. from the day of sealing the store.
- The practice of allowing carbon dioxide levels to rise initially after store loading is to be avoided.
- In previous work pre-treating Cox apples with high concentrations of carbon dioxide for 15 days prior to low ethylene, low oxygen storage increased core browning and flesh breakdown (Stow, 1990).
- In view of the general heightened sensitivity of SmartFreshTM-treated apples to carbon dioxide and low storage temperatures it seems sensible to adopt the strategy suggested for storage beyond January until further work can be done to optimise store environment parameters for maximum storage life of Cox.