should be developed. Postharvest heat treatment has been used to reduce fungal rots in apples ( Ferguson et al., 2000 ; Saftner et al., 2003 ; Sholberg et al., 2000 ). Decay caused by P. expansum can be avoided by heating fruits at 38 °C for 4 d
Ibrahim I. Tahir, Eva Johansson, and Marie E. Olsson
Michael J. Mahovic, Rajya Shukla, Renée M. Goodrich-Schneider, Michael V. Wood, Jeffrey K. Brecht, and Keith R. Schneider
Infantis (F4319), when treated with hot water at 70 or 97 °C for 60 s, resulted in a 2.0- or 3.4 log 10 cfu/cm 2 reduction of Salmonella , respectively. Any heat treatment used to reduce microbe populations on produce must be effective without exceeding
Valeria Sigal Escalada and Douglas D. Archbold
; Halder-Doll and Bangerth, 1987 ; Mir et al., 1999 ; Stover et al., 2003 ). Heat treatment after harvest has shown potential for inhibiting ripening and extending cold storage life. In climacteric fruit, heat might act through its effect on enzymes
Hui-juan Zhou, Zheng-wen Ye, Ming-shen Su, Ji-hong Du, and Xiong-wei Li
to CI and quality rapidly deteriorates—this requires appropriate safe postharvest treatments and storage techniques to extend storage and shelf life. Heat treatment can be used postharvest for many different fruits ( Lurie and Pedresch, 2014 ). A
Harvey T. Chan Jr. and Eric Jang
Heat treatments have been used to control diseases and insect infestation of fruit. The development of heat treatments have been the result of empirical experiments based on the efficacy on the insects coupled with parallel experiments on the phytotoxicity of host fruit. Such heat treatments while approved as quarantine treatments have occasionally produced fruit of poor quality. Thermal processing of foods, an established science, employs kinetics of enzyme inactivation, thermal death times evaluation of various time-temperature relationships to determine the adequacy of the heat process to ensure the safety of the product as well as minimize over-processing to preserve the products quality. There is a need to develop thermo-processing guidelines in the development of quarantine heat treatments and also to enhance product quality. We will report methods that we have developed to determine the thermal death kinetics of insects, fruit pathogens and kinetics for thermotolerance of the fruit.
T. Gregory McCollum, Salvatore D'Aquino, and Roy E. McDonald
`Keitt' mango (Mangifera indica L.) were kept at 38C for 0, 24, or 48 hours before storage at 5C for 11 days. Nonheated fruit developed severe rind pitting and discoloration, whereas chilling injury symptoms decreased with increased duration at 38C. Respiratory rates were slightly higher in nonheated than in heated fruit. Nonheated fruit produced a transient burst of ethylene evolution following transfer to 21C; heated fruit did not produce a similar burst. Firmness was similar in nonheated and heated fruit at the time of transfer to 21C for ripening, but was slightly higher in nonheated fruit after 3 and 6 days of ripening. Soluble solids concentration was higher in heated than in nonheated fruit at the time of transfer to 21C, but was similar after 9 days at 21C. Commission Internationale de l'Eclairage a* and b* flesh values were higher in heated than in nonheated fruit. Results of this study indicate that mango tolerance to chilling temperatures may increase after prestorage heat treatment.
J. O. Strandberg and J. M. White
Tolerance of carrot seeds (Daucus carota L.) to heat treatments that could eradicate seedborne pathogens was investigated. Germination and emergence of seedlings from seeds treated in hot water at 35, 40, 45, 50, or 55C from 4 to 20 min were not affected, but seeds treated at 60C for 8 min or more were affected adversely. At 45 and 50C, treatment durations as long as 48 min did not affect emergence, but >20 min at 55C reduced emergence. Similar results were obtained when seeds were treated at the same temperatures in water containing 1.1% sodium hypochlorite (NaOCI). Emergence of seeds treated in hot water or 1.1% NaOCl and planted within 5 days generally was similar to that of treated seeds stored for 90 days at 20C in 60% RH before planting. Any existing differences were small and not clearly related to temperature–duration treatment combinations. Percent emergence from seeds of 19 out of 25 hybrid cultivars treated at 50C for 15 min was reduced by an average of 2.9%, but differences for untreated seeds ranged from −13.3% to +4.8%. Emergence from hot water-treated seeds was reduced after 6 weeks of storage at 70% and 80% RH, but not at 20% to 60% RH. Prolonged treatment and the higher temperatures were particularly effective in reducing populations of seedborne Alternaria dauci.
John S. Hu, Diane M. Sether, H. Michael Harrington, and Diane E. Ullman
Thermotolerance of pineapple crowns (`Champaka 153') to 50C and above was increased with a 30-min first treatment at 30, 35, or 40C. Pineapple crowns receiving a 30-min heat treatment, before a second heat treatment at 50 or 55C, exhibited significantly less leaf damage than controls receiving no first treatments (P ≤ 0.05). The degree of thermotolerance was dependent upon the season in which crowns were harvested; greater thermotolerance occurred in crowns harvested in April than those harvested in October. Maximum thermotolerance occurred after an interval of at least 8 h between the first treatment and the higher temperature heat treatment. Thermotolerance was stable for at least 24 h.
Joshua D. Klein and Susan Lurie
Commercial, ecological, and agrotechnical considerations have recently renewed interest in the use of physical rather than chemical means to maintain postharvest quality of horticultural crops. This review discusses prestorage heat treatments that protect against physiological disorders, enhance natural resistance to pathogen infection, reversibly inhibit fruit ripening, and permit flexibility in storage temperatures.
R.E. McDonald, T.G. McCollum, and E.A. Baldwin
Mature, green tomatoes were either gassed or not gassed with C2H4 for 24 h, immersed in 42C water for 60 min, or held in 38C air for 48 h or not treated, and then stored at either 2C or 13C for 14 days before ripening at 20C. During ripening, the fruit were evaluated for color development, internal quality, and decay and for volatiles when full ripe. Both high-temperature treatments reduced chilling injury and inhibited decay. Days to ripen after removal from storage at 2C or 13C was not influenced by heat treatment method. Color development, lycopene content, and internal quality characteristics of fruit were similar at the ripe stage, irrespective of heat treatment. Of 15 volatiles analyzed, seven showed decreased levels of concentrations as a result of C2H4 gassing, nine showed decreased levels when stored at 2C prior to ripening, and most were unaffected by the heat treatments. Heat treatments appear to be beneficial for maintaining tomato fruit quality.