FORCED HOT AIR TREATMENT OF STONE FRUIT TO INHIBIT THE DEVELOPMENT OF MEALINESS

Treatment with high temperature forced air (HTFA) was tested as a potential alternative to the industry practice of preconditioning stone fruit at 20°C for 2 days to slow the development of mealiness during cold storage.
Preconditioned (PC) fruit and non-PC fruit were treated with HTFA (final temperature = 46°C) for 1 to 4 hours and placed into cold storage for 2 to 4 weeks at 1°C. Juiciness of the fruit was quantified after ripening by measuring the percentage of free juice (FJ) present.
Fruit stored for 2 weeks were juicy regardless of treatment, although 3 to 4 hours of HTFA treatment was needed for the percentage FJ in non-PC fruit to be similar to that present in PC fruit.
After 3 weeks of storage non-PC fruit that had not been heated had a FJ value of 27% as compared to 50% for non-heated PC fruit and had become mealy.
Heating slowed the loss of FJ and maintained juiciness, although 3 hours of heating or more was required to have an effect and the FJ value for the non-PC fruit heated for 4 hours was still 7% less that that from non-heated PC fruit.
Both PC and non-PC fruit had become mealy by the end of 4 weeks of storage and had low FJ values.
Exo-polygalacturonase, endo-polygalacturonase and pectinmethylesterase activities in the tissues were affected by PC and heating but did not change in a manner that indicated that these enzymes could be responsible for the differences in FJ. Preconditioning increased the abundance of the protein expansin in non-heated samples but HTFA treatment strongly inhibited its accumulation.
High temperature forced air can effectively reduce the incidence of mealiness but further research is needed to determine if the technique could be useful commercially.

V International Postharvest Symposium

D.M. Obenland, P.M. Neipp

polygalacturonase, pectinmethylesterase, expansin, preconditioning, peach

https://doi.org/10.17660/ActaHortic.2005.682.155