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  • Author or Editor: Harvey T. Chan Jr. x
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Abstract

Susceptibility to chilling injury in ‘Kapoho’ papayas (Carica papaya L.) was reduced by ripening the fruit before storage at 5°C. The relationship between the decrease in chilling injury (CI) and postharvest ripening time at 24° was found to follow first order kinetics, hence, the half-lives for reducing the symptoms of CI of scald and hard core are 14.8 and 33.5 hr, respectively.

Open Access

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.

Free access

Abstract

Cucumber fruit (Cucumis sativus L. cv. Burpee Hybrid II) were more tolerant of hot water immersions (30 to 60 min at 45C or 30 to 50 min at 46C) after being conditioned at 32.5 ± 0.5C in air for 24 hr. This increased tolerance was associated with a significant decrease in surface pitting. Hot water-treated cucumbers held for 3 days at 24C after storage at 10C for 7 days were yellower than untreated fruit. Degreening was greatest for the 30-min immersion and decreased with increasing immersion times.

Open Access

Chilling injury symptoms were reduced when `Sharwil' avocados (Persea americana Mill.) were held at 37 to 38C for 17 to 18 hours and then air-cooled at 20C for 4 hours before storage at 1.1C for ≥14 days. In contrast, nonheated fruit developed severe surface discoloration and pitting. Chilling injury symptoms were reduced further when the heated fruit were stored in perforated polyethylene bags during 1.1C storage. No treatment equaled or surpassed the quality of fruit in nontreated controls.

Free access

Abstract

Papayas (Carica papaya L.) were stored at 5° or 10°C for 1, 4, 7, 14, or 21 days. Chilling injury was detectable as visible skin discolorations after 4 days at 5°. Differences in electrolyte leakage and Hunter “L” values between fruit stored at 5° and 10° were not significant until after 7 days of storage. Fruit stored at 5° for more than 4 days also produced more ethylene upon transfer to warmer temperatures than did fruit stored at 10°. Differences in ethylene production between fruit stored under chilling temperatures, 5°, and nonchilling temperatures, 10°, increased with length of storage. Papayas chilled for 14 days at 5° retained a capacity to convert ACC to ethylene.

Open Access

Abstract

Viable larvae of the Oriental fruit fly (Dacus dorsalis Hendel) were found in Carica papaya L. ‘Kapoho’ fruit after hot water double-dip quarantine treatment in Hawaii. Two types of blossom end defects, navel and definite pinhole, were responsible for the failure of the quarantine treatment. These defects resulted from abnormal placental growth near the blossom end of fruit. Defective fruit also had higher incidences of internal infection by Cladosporium sp. and Fusarium spp. A survey conducted in the Puna district of the island of Hawaii showed that the incidence of trees bearing defective fruit ranged from 5.3% to 31%.

Open Access

Thermal death kinetics, decimal reduction times (D-values), and rate constants, k, at 43 to 49 °C were determined for spore or cell suspensions of Colletotrichum gloeosporiodes (Penz.) Penz. & Sacc. in Penz., Guignardia psidii Ullasa & Rawl, Guignardia sp. Viala & Ravaz., and Enterobacter cloacae (Jordan) Hormaeche & Edwards. D-values for Monilinia fructicola (Wint.) Honey, Rhizopus stolonifer (Ehr.: Fr.) Vuill., and Stemphylium lycopersici (Enjoji) Yamamoto were calculated and extrapolated from published reports. We compared the relative heat resistances of the various postharvest pathogens to their expected survival during quarantine heat treatments and found that Guignardia, Rhizopus, and E. cloacae could be expected to survive quarantine heat treatments.

Free access

A reduced heat shock period for `Sharwil' avocado (Persea americana Mill.) before quarantine cold treatment is described. The shortened heat pretreatment period of 8 to 12 hours, rather than the originally recommended 18 hours at 38C, is effective in reducing chilling injury symptoms when the pulp is at ≤2.2C during 16 days of storage. The reduced durations and the range of pretreatment hours affords packinghouses greater efficiency and more flexibility and will reduce handling costs relative to the longer exposure.

Free access

The disinfestation protocol for fruit often requires a delicate balance between suppression of the pest and avoidance of fruit damage. In Hawaii both hot-water and hot-air treatments are used for papaya destined for export. A computer simulation of the heat flow can be used to obtain the temperature Tα(x,t) at every point x in the papaya and every time t for any given heating protocol α. The activity of the ethylene forming enzyme (EFE) has been used as a measure of fruit damage and the “kill” of fruit-fly larvae/eggs as a measure of pest control. The degradation of the EFE measured experimentally for a fixed temperature T and at several times t can be analyzed to yield a rate expression R1(T,t). Similarly the survival of fruit-fly larvae/eggs can be used to establish a rate expression R2(T,t).

The temperature space-time expression, Tα(x,t), for a chosen heating protocol α, and the rate laws R1(T,t) and R2(T,t) can be used to calculate the effect on EFE activity, EFEα(x,t), and pest control, PCα(x,t), at every point in the fruit and time of the protocol. For example the effect of different heating schedules, different heating fluids or even the role of “pre-conditioning” can be assessed.

Free access