Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2004
Publication Date: 6/30/2005
Citation: Obenland, D.M., Neipp, P.W. 2005. Forced hot air treatment of stone fruit to inhibit the development of mealiness. Acta Horticulturae 682:1171-1178 Interpretive Summary: Peaches often develop a dry, mealy texture during extended cold storage that destroys the marketability of the fruit. High temperature forced air (HTFA) treatment at 46C for 1 to 4 hours was compared to pre-ripening for 2 days at 20C prior to cold storage for its effectiveness in inhibiting the development of this disorder. After 2 weeks of storage, untreated fruit had begun to lose juiciness while pre-ripened and HTFA-treated fruit did not. Following 3 weeks, treated fruit lost juiciness but to a much lesser degree than untreated control fruit, with the pre-ripening treatment being slightly superior to the HTFA treatment. All fruit became mealy after 4 weeks of cold storage. Changes in enyzme activities related to cell wall breakdown did not appear to be responsible for the differences in flesh juiciness induced by treatment. High temperature forced air is a viable means of reducing the incidence of mealiness in peaches that is nearly as effective as pre-ripening but requires less time and produces fruit with a lesser susceptibility to decay.
Technical Abstract: Treatment with high temperature forced air (HTFA) was tested as a potential alternative to the industry practice of preconditioning stone fruit at 20C for 2 d to slow the development of mealiness during cold storage. Preconditioned (PC) fruit and non-PC fruit were treated with HTFA (final temperature = 46C) for 1 to 4 h and placed into cold storage for 2 to 4 weeks at 1C. 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 h 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 than 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. Forced hot air can effectly reduce the incidence of mealiness but further research is needed to determine if the technique could be useful commercially.