Research firmer for 3 to 4 days at ambient temperatures . However , after 5 days shelf life there were no differences between treated and untreated fruit .
The effects of 1-MCP were even more short-lived when nectarines were stored 3 weeks or more , with apparent gains disappearing once the nectarines were transferred to 20 ° C . In this study the Fantasia nectarines developed severe chilling damage after 4 weeks at 0 ° C . Treatment with 1-MCP reduced pitting and some internal symptoms , but did not prevent them .
As previously noted , if fruit have already started to ripen this will also reduce the impact of 1-MCP . An example of the effect of harvest maturity is shown below . This shows that peaches that are harvested early are more likely to respond to treatment , whereas softening fruit showed little response .
Apricots
As with other stonefruit , the effect of 1-MCP on apricots varies considerably among different varieties . While some cultivars respond , others are relatively insensitive to 1-MCP . Although softening of stored fruit is reduced , ethylene production and respiration rates can be virtually unaffected by treatment . Moreover , one study found that 1-MCP increased internal browning from 3 % to 40 % of fruit 7 .
Apricots are treated with SmartFresh in Europe in order to extend marketable life . However , treatment protocols are specific to variety and need to be thoroughly tested before use .
Can we apply 1-MCP in Australia ?
In Australia , SmartFresh is registered for treatment of nectarines and plums . This season has seen increased use on plums , with fewer applications to nectarines . The recommended application is 0.5 μl . L-1 for 24 hours at 0 ° C . Increasing the dose doesn ’ t necessarily increase the effect ; once the ethylene receptors are saturated , any more just goes to waste .
In Australia , SmartFresh is registered for treatment of nectarines and plums . This season has seen increased use on plums , with fewer applications to nectarines .
One of the issues with SmartFresh is the relatively long treatment time needed . Californian researchers 8 have found a way to treat plums faster , by adding 1-MCP during forced air cooling . In this case 6 hours treatment with moving air proved just as effective as 24 hours in still air . Moreover , the SmartFresh treatment allowed plums to be stored at 10 ° C instead of 0 ° C , avoiding potential chilling injury and resulting in significant energy savings .
AgroFresh ( owners of SmartFresh ) have recently developed an “ InBox ” application system . Sachets containing SmartFresh are simply added during packing into lined cartons . Liquid 1-MCP dips are also on the horizon , along with other innovative delivery systems .
So why don ’ t we treat more fruit ? The answer probably lies in our strong emphasis on the domestic market . After all , why extend the storage life of one variety when others are coming onto the market ? However , as we shift focus to flattening fruit supply , longer transport distances and export markets , this situation may well change .
In Summary
• Treatment with 1-MCP can extend storage life and reduce chilling injury
• The effects of 1-MCP vary by cultivar , according to harvest maturity , and even between orchards
• 1-MCP works best on plums , but needs to be confirmed by variety
• Although the effects of 1-MCP on peaches and nectarines tend to be relatively transient , they may still be commercially significant in some circumstances
• 1-MCP is not currently registered on apricots . summerfruit . com . au April 2017 | Australian Stonefruit Grower 27