A new and convenient pear conditioning system results in ripe pears with more flavor and aroma than conventional ­conditioning methods, a New Zealand researcher reports.

Dr. Keith Sharrock of HortResearch conducted tests at Underwood Fruit Company, White Salmon, Washington, with an aerosol can containing ethylene, which he calls an "ethylene release capsule." The device is designed to treat a pallet of pears and is a larger version of devices he invented for conditioning pears by the individual box or clamshell. The capsule contains an internal valve that releases compressed ethylene at a constant rate for up to seven days.

Sharrock conducted two trials at Underwood Fruit—one on d’Anjou pears that had recently been picked (which are typically difficult to condition properly) and the second on pears from controlled-atmosphere storage.

Reporting to the Washington Tree Fruit Research Commission, which has supported his research, Sharrock explained that the capsule was placed on top of the boxes in a pallet under a standard polyethylene ­pallet cover. The continual release of ethylene gas from the capsule ­compensates for ethylene lost through the cover.

Fall trial

For the fall trial, green d’Anjou pears were harvested at commercial maturity on September 13 last year and kept in cold storage until grading and packing 12 days later. The cartons were returned to 30°F storage overnight and then stacked in a pallet and treated with the capsule in an unheated storage room, where the temperature was about 60°F. The ethylene level within the pallet reached about 50 parts per million within four hours of sealing and climbed to 100 parts per million within a day. Ethylene levels stayed above 100 parts per million for the entire conditioning period of up to seven days. After conditioning, the fruit were ripened in the same storage room, and the aroma of the pears was ­monitored with ripeSense sensor labels.

For comparison, some fruit from the same lot was conditioned the conventional way, which consisted of one day of warming and two days of ethylene treatment from a catalytic generator in Underwood’s conditioning room.

Sharrock said aroma production during ripening was much greater in fruit that had the longer exposure to ­ethylene during conditioning (the fruit treated with the capsule). Eating quality was judged to be excellent, even though the fruit had been harvested only ten days before conditioning treatment. The treatment had no apparent detrimental effect.

The conventionally conditioned pears softened to the same extent, but developed very little aroma as they ­softened.

Winter trial

The d’Anjou pears in the winter trial had been picked in September of 2006 and held in controlled-atmosphere storage until early February. After packing, they were held in regular storage at 30°F until the trial began six days later. The cartons of fruit were placed inside sealed pallet covers. Some pallets had ethylene capsules under the cover, and some did not. After conditioning, the pears were ripened. Sharrock found no relationship between the rate of ethylene production during ripening and whether or not they had been treated with ethylene. After five months of storage, the fruit was able to produce its own ethylene, he deduced. Differences in aroma between the treated and untreated fruit were subtle. Blind taste tests revealed differences in flavor, with the flavor of the treated fruit being more intense and attractive, he reported, but the differences were less marked than in the fall trial.

Sharrock said the ethylene release capsules are expected to be available soon for commercial use from Balchem Corporation of New Hampton, New York, and may provide a number of benefits apart from better-tasting fruit. The system does not require a capital investment, as the sealed pallet becomes the ripening room and the treatment can be done almost anywhere. Small orders can be ripened on demand. The capsules could provide additional conditioning capacity during peak shipping times, Sharrock said. There’s also the potential for using the system in transit.