Extended cold storage of Abate Fetel pears for EU market

The objective of the study is to successfully store Abate Fetel under controlled atmosphere (CA) and/or regular atmosphere (RA) for 6 months after harvest, without compromising the fruit quality, with emphasis on the prevention of superficial and soft scald development.

Abate Fetel pears treated with SmartFresh^SM after harvest and stored under regular atmosphere (RA) conditions for 6 months, were evaluated for post storage quality, in comparison to pears treated with SmartFresh^SM after harvest, followed by 3 months controlled atmosphere (CA) storage and 3 months of RA storage (partial CA). Control fruit were stored in CA for 6 months with no SmartFresh^SM (2012 and 2013 season) or 6 months in RA with no SmartFresh^SM (2014 – 2015 season). Fruit from five different populations (sources) were evaluated for regularly used ripening parameters and storage disorders, directly after storage at -0.5 °C (start of shelf-life) and after 7 days at 20 °C (end of shelf-life).

2012

Fruit subjected to SmartFresh^SM were generally of better quality compared to the untreated control fruit, regardless of storage regime. Fruit from all three treatments (6 month CA without SmartFresh^SM, 6 month CA with SmartFresh^SM, 3 month CA + 3 month RA with SmartFresh^SM) ripened to an eating ripe firmness of 1.5 to 4.0 kg. This was due to the high ethylene levels that indicated that fruit were respiring and able to ripen. Results demonstrated the limitations of long term CA storage of Abate Fetel due to high soft and superficial scald incidence and senescent breakdown. The ability of 3 month partial CA storage in combination with SmartFresh^SM application to reduce scald-type external disorders on long term stored Abate Fetel fruit was clearly demonstrated.

2013

Fruit subjected to SmartFresh^SM were generally of better quality compared to the untreated control fruit, regardless of storage regime. Fruit subjected to SmartFresh^SM exhibited no soft or superficial scald, regardless of storage regime. Fruit from the 3 month partial CA storage in combination with SmartFresh^SM application exhibited lower incidence of internal browning and CO₂ damage than the other two treatments. Fruit from all three treatments ripened to an eating ripe firmness of 1.5 to 4.0 kg. This was due to the high ethylene levels that indicated that fruit were respiring and able to ripen.

The 3 month partial CA storage in combination with SmartFresh^SM application could potentially be a solution for long term storage of Abate Fetel pears, because of the reduction in scald-type external disorders, and lower incidence of internal browning and CO₂ damage.

2014

Overall fruit quality was improved after storage in 2014 compared to the fruit quality in 2012 and 2013. Fruit that was stored under CA conditions still looked appealing on the outside, but was not acceptable for consumption due to the internal browning and CO₂ breakdown incidence.

The trial indicated that fruit subjected to SmartFresh^SM could be stored for extended periods because superficial and soft scald incidence were inhibited and internal fruit quality was good. However, RA storage should rather be considered over CA storage.

2015

The advantage of using SmartFresh^SM applications for retention of flesh firmness, green skin colour and reduction of progressive disorders of Abate Fetel pears, was demonstrated. However, SmartFresh^SM treatment in combination with RA storage for 6 months could not consistently suppress superficial scald development during shelf-life simulations below commercially acceptable levels. Although the best results in terms of external appearance and reduction of superficial scald, soft scald and senescent scald were observed in fruit stored in partial CA, fruit were susceptible to (internal) CO₂-breakdown (≤ 18.2%).

2016

Fruit subjected to 300 ppb SmartFresh^SM within 4 days after harvest and RA stored for 6 months resulted in the best quality fruit of the three different treatments. This treatment however, is not fool proof since in two of the populations, high incidence of flesh decay developed during cold storage. This could have been due to no phytosanitary dips after harvest. In two of the populations fruit did not ripen to firmness’ lower than 4.0 kg. Fruit with no SmartFresh^SM, RA stored for 6 months, had high incidence of superficial scald and should not be considered as an option for long term storage. The partial CA storage treatment poses the risk of internal CO₂ breakdown in fruit. A shorter CA period, or delay in CA start should be considered for this treatment. Fruit also did not ripen to firmness’ lower than 4.0 kg.

Long term (6 months) storage of Abate Fetel pears, with no SmartFresh^SM application in RA or CA, should not be considered, for superficial and soft scald can develop during storage or shelf life.

Partial CA storage (3 months CA followed by 3 months RA) of Abate Fetel pears treated with SmartFresh^SM after harvest resulted in firm pears with little to no superficial and soft scald development. However, internal CO₂ breakdown was a major defect in fruit of this storage regime. In some instances fruit also did not ripen during shelf life to firmness’ lower than 4.0 kg. It is recommended not to follow this regime and should partial CA storage be considered, more research on shorter CA periods, delayed start of CA and lower SmartFresh^SM concentrations should be considered.

SmartFresh^SM treated fruit stored for 6 months in RA gave inconsistent results over the seasons. In the 2016 season however, little to no superficial and soft scald was detected on this fruit. It is thus the method with the best potential. It is recommended to first do research on what is the causative factors of superficial and soft scald in this method (e.g. maturity, climate, etc.) before these pears be stored commercially under this regime.

It is recommended to determine the maximum storage duration of Abate Fetel pears by storing fruit for 5, 6 and 7 months in RA (with SmartFresh^SM). It is also recommended to determine the effect of delayed CA or shorter partial CA periods on the quality of fruit.

Should the market accept light green pears, it should be considered to store fruit at higher temperatures to solve the ripening issues. Fruit can be subjected to a SmartFresh^SM application after harvest and stored at +0.5° C in RA. One to 1 ½ months before selling the temperature can be raised to 2° C. This method however, will not be suitable should the pears be sold as green.