Fruit Core Temperature Research Articles

Heat transfer in large bins during the apples cool-down process

The preservation of apples in cold storage relies deeply on understanding the thermal dynamics governing their environment. Within packaging, apples engage in complex thermal interactions, between themselves and the environment, affecting convective and conductive heat transfer pathways. Challenges escalate in industrial cold storage facilities, manifesting as temperature stratification and non-uniform cooling. Nonetheless, a comprehensive understanding of heat transfer dynamics is vital for optimizing cold storage equipment design and enhancing cooling system operation efficacy. Building upon previous studies validating the use of Peltier elements for detecting and quantifying heat flux in individual apples, this research extends its application to industrial cold rooms. By strategically selecting locations within the apple bin and the storage cold room and comparing changes in total heat content obtained by a conventional method and comparing with the Peltier element for its validation. Results of the convective heat transfer coefficient in an upper-layer bin were in the range of 2.7-5.9 Wm-2 K-1 while in a bin at door level were 5.0-7.0 Wm-2 K-1. The higher values found in the position near the door can be correlated to the faster air speed experienced between the apples in this position. By applying these values in the transient heat transfer model to predict the fruit core temperature during the cooling process, a relatable prediction was found, with apple temperature difference <0.9 °C between predicted by the Peltier element and experimental cooling curves. This study can aid understanding of thermal dynamics in cold storage environments, and support future development for more efficient and sustainable cold storage practices.

Cold treatment for guava fruits infested with oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae)

Guava (Psidium guajava Linnaeus) is an important horticulture crop in tropical and subtropical regions. However, guava transportation to the fruit market is regulated due to the risk of fruit fly infestations. The oriental fruit fly [Bactrocera dorsalis (Hendel), Tephritidae, Diptera], which damages numerous horticulture fruits, is the primary pest in guava. For fruit export, phytosanitary treatment is necessary to prevent the potential oriental fruit fly infestations through pest-infested fruits. In this study, cold treatment was administered to eliminate oriental fruit fly infestations in guava fruits. The optimal egg inoculation density was 200 eggs per fruit, and third instar larvae displayed the highest cold treatment tolerance. On assessing the efficacy of cold treatment, none of the third instar larvae in the fruits survived at a constant fruit core temperature of 0.5–1 °C for 11 days. A confirmatory test revealed that on maintaining a fruit core temperature of 0.5–1 °C for 12 days, 100% mortality was achieved among the fruit flies. In fruit quality assessment, guava fruits exposed to cold treatment still maintained their market value. Thus, cold treatment effectively disinfested guava fruits with possible fruit fly infestations, making it a viable quarantine treatment for guava fruits prior to their export.

Development of heat treatments for two species of Samoan fruit flies (&lt;i&gt;Bactrocera &lt;/i&gt;spp., Diptera: Tephritidae)

Of the seven species of Bactrocera fruit flies found in Samoa, only two (B. kirki (Froggatt) and B. xanthodes (Broun)) are of economic importance. These species attack a range of fruit, including papaya (Carica papaya), breadfruit (Artocarpus altilis), eggplants (Solanum melongena) and citrus. The presence of these two species limits export market access for Samoan produce. Eggplants and breadfruit infested with the eggs of B. kirki and B. xanthodes, respectively, were treated using a high-temperature forced-air (HTFA) protocol to heat the fruits to core temperatures of 40oC, 42oC, 44oC or 46oC. No B. xanthodes pupae emerged from fruit treated at 42oC or greater. Pupae of B. kirki were found from fruit treated at temperatures up to 44oC, but failed to survive treatments at 46oC. The HTFA protocol previously approved for treatment of other Pacific fruit flies (fruit core temperature to 47.2oC for 20 min) works without modification for treatment of the two combinations of fruit flies and commodities tested. However, less intense HTFA treatments are worth investigating, if required to enhance fruit quality.

Forced hot-air treatment against Bactrocera papayae (Diptera: Tephritidae) in papaya

The Asian papaya fruit fly, Bactrocera papayae Drew and Hancock, was treated with hot-water immersion and forced hot air to develop a phytosanitary heat treatment schedule. Hot-water immersion tests were conducted with 12- and 24-h-old eggs and with first and third instar larvae to compare the relative thermotolerances of this fruit fly among these life stages. The 24-h-old eggs, the most thermotolerant among the four life stages tested, were subjected to time and temperature tests using cage-infested papaya fruits in a forced hot-air chamber. Heating the papayas to a minimum core temperature of 47.7 °C (95% confidence interval 47.2–48.3 °C) was estimated to induce probit-nine mortality based on a probit analysis of the data. Confirmatory tests in which papayas infested with 24-h-old eggs were heated to a minimum fruit core temperature of 47.2 °C that was maintained for 0–30 min followed by hydrocooling to a fruit core temperature of ≈25 °C resulted in the complete mortality of an estimated treated population of 43,425 eggs aged 24 h (99.9931% mortality at the 95% confidence level). Therefore, heating the papaya fruits to a core temperature of 47.2 °C for a minimum dwell time of 30 min, which was the longest dwell time in the confirmatory tests, may serve as a phytosanitary heat treatment schedule for the control of B. papayae in papaya fruits.

Low-dose methyl bromide fumigation as a quarantine disinfestation treatment for nectarines against Queensland fruit fly (Diptera:Tephritidae)

White nectarines (Prunus persica var. nucipersica) were fumigated with methyl bromide (MB) at a nominal treatment dose of 18 g m-3 at 18°C for 5 h and 30 min as a quarantine disinfestation treatment against Bactrocera tryoni, the Queensland fruit fly. Three large scale trials were conducted against each of the four immature lifestages, eggs and first, second and third instars. There were no survivors from the estimated 43,614 eggs, 41,873 first instars, 41,345 second instars and 33,549 third instars treated, thereby resulting in an efficacy of GROTERDAN99.99% mortality at the 95% confidence level for each lifestage. Of the 12 trials reported herein, the highest concentration of MB, sampled from the chamber headspace analysed by gas chromatography, was 18.7 g m-3. The maximum chamber temperature from 5 min readings was 19.7°C and the maximum fruit core temperature was 19.5°C. The treatment time for all trials was exactly 5.5 h. Thus the recommended treatment dose to disinfest nectarines from B. tryoni is 19.0 g m-3 MB at 20.0°C for 5.5 h. Fruit quality trials were conducted on white nectarines at three combinations of treatment parameters: 15 g m-3 MB at 19°C for 5.25 h; 18 g m-3 MB at 19°C for 5.5 h and 21 g m-3 MB at 19°C for 5.5 h. The fruit were stored at 0, 4 and 8 days at 4°C and 8 days at 4°C followed by 4 d at 22°C. They were then were assessed for skin colour, flesh colour, skin defects, flesh defects, fruit weight loss, flesh firmness, total soluble solids, titratable acidity and rots. There was no significant difference between untreated control and MB treated fruits in any of the parameters measured. Thus the treatments did not have adverse effects on fruit quality.

Desain dan Kinerja Unit Perlakuan Uap Panas (VHT) untuk Disinfestai Lalat Buah pada Penanganan Pascapanen Mangga

Formerly, chemical fumigation was used for disinfestation treatment, but now had been replaced bychemical-free disinfestations treatment such as vapor heat treatment (VHT). The objectives of this researchwere (1) to design the VHT Unit and testing its performances, and (2) to study the effect of the VHT methodand waxing on the fruit quality during storage of mango. The designs of VHT unit consist of water tank, filter,heater, water pump, differential pressure fan, atomizer, control panel and treatment chamber. Performanceof the unit showed that the temperature of the VHT chamber increased from ambient temperature of 30OCto setting point of 47OC in 70 minutes. Relative humidity of the VHT chamber was very high (more than90%) indicating the VHT unit was successful in being used for fruitfly disinfestations of fruit product. Usingsetting point of 46.5OC, the mango fruit core temperature reached temperature of 45.5-46.3OC in 130minutes. Mango ‘Gedong gincu’ were treated at 46.5OC for 10, 20, 30 minutes and control and then followedby waxing. The results showed that VHT of 10-30 minutes were not significantly affect the fruit quality.There were no significant changes in the fruit weight losses, hardness, color, soluble solid content, watercontent and vitamin C. VHT at 46.5OC for 20-30 minutes was effective to kill the fruitfly infested inside themangos and VHT followed by waxing was able to maintain mango quality during storage.Keywords : mango, fruit fly, heat quarantine treatment, vapor heat treatment (VHT)Diterima: 15 Januari 2008; Disetujui: 27 Agustus 2008

Lama Pemanasan Metode Vapor Heat Treatment (VHT) dan Pelilinan untuk Mempertahankan Mutu Pepaya Selama Penyimpanan

Horticulture products are host for Tephritidae fruitflies that are considered a quarantine risk by many importing countries. This research was conducted to find out the specific condition for the heat treatment using vapor heat treatment (VHT) method to control pest and diseases of papaya and the fruit quality during storage. Papayas were vapor heat treated at medium temperature of 46.5 0C for 0, 15, and 30 minutes. After the treatment, the fruits were waxed using beeswax of 6 % in concentration and then stored at temperature of 10 0C. The results show that the fruitfly of oriental fruitfly (Bactrocera dorsalis) was completely killed by treating in deep water testing at temperature of 46 0C for 10 minutes or at 43 0C for 30 minutes. The VHT of papaya at fruit core temperature of 45.5-46.0 0C for 15-30 minutes following waxing using beeswax of 6% in concentration was found to be effective to control pest and diseases until 21 days of storage without any visible signs of heat injury and without adversely affecting the quality of the fruit. Keywords: Papaya, vapor heat treatment, waxing, quarantine Diterima: 20 Agustus 2007; Disetujui: 24 Nopember 2007

Postharvest quality of Dragon fruit ( Hylocereus undatus) following disinfesting hot air treatments

Dragon fruit ( Hylocereus undatus) are a host of fruit fly ( Bactrocera spp.), and thus export to many markets will require a disinfestation treatment. This work investigated the potential for disinfestation by heat treatment (HT) of cv. Binh Thuan in order to meet the biosecurity requirements of importing countries. Main-season fruit from Viet Nam were subjected to hot air treatments and stored for 2–4 weeks storage at 5 °C in sealed polypropylene bags, and fruit quality examined during subsequent shelf-life at 20 °C. HTs applied were fruit core temperatures (FCT) of 46.5 °C for durations of 20 and 40 min, and 48.5 °C for 50, 70 and 90 min. Assessments included turgor of the bracts and stem, the appearance of the body of the fruit and presence of rots, skin colour, flesh firmness, soluble solids concentration, fruit acidity, taste, and flesh translucence. ‘Binh Thuan’ Dragon fruit proved to be tolerant of hot air treatment and at the lower HT temperature (FCT 46.5 °C for 20 min) fruit quality was not significantly different from non-heated control fruit, either after treatment at harvest, or after storage for up to 4 weeks. However, metrics quantifying the appearance of both control- and HT-fruit generally deteriorated with storage time at 5 °C, although the internal appearance of the flesh, and taste, remained acceptable throughout. Shelf-life effects were restricted to comparison of the lower HT temperature (FCT 46.5 °C for 20 min) and non-heated control fruit. Shelf-life after any of the storage periods was terminated after only 4 d, as fruit available for study had not been sprayed with fungicides during the season, and developed anthracnose rots readily at 20 °C. No differences in shelf-life characteristics were established between HT fruit and control fruit. Our results provide strong evidence that ‘Binh Thuan’ Dragon fruit are a suitable candidate for fruit fly disinfestation by hot air HTs, and that fruit quality during or after storage does not suffer as a consequence.

Chemical and quality traits of ‘Olinda’ and ‘Campbell’ oranges after heat treatment at 44 or 46 °C for fruit fly disinfestation

The chemical and quality characteristics of ‘Olinda’ and ‘Campbell’ oranges (nucellar budlines from Valencia late cultivar) were evaluated after exposure to a fruit core temperature of 44°C and held at 44°C for 100min or 46°C and held at 46°C for 50min, subsequent storage at 6°C for 2 weeks and an additional week of simulated marketing period (SMP) at 20°C. Exposure to either heat treatment caused neither visible damage nor fruit softening. Fruit weight loss rate in ‘Olinda’ oranges was unaffected by treatment but was higher than control fruit in heat exposed ‘Campbell’ oranges after storage, though at the end of SMP differences between treated and untreated fruit were non-significant. While neither heat treatment affected decay incidence in ‘Olinda’ oranges, significantly less decay was found in heat treated ‘Campbell’ fruit compared to control fruit both during storage and SMP.The chemical analyses of flavedo tissue of ‘Olinda’ oranges revealed that there were no treatment differences in neutral sugars, soluble and insoluble pectins and calcium bound to insoluble pectin fraction. The calcium content bound to soluble pectin fractions increased following heat treatments. At the end of SMP there was a significant decrease of soluble pectin and a significant increase of calcium bound to insoluble pectins in flavedo from oranges of the 46 and 44°C treatments.Following treatment at 46°C ‘Olinda’ fruit had a significantly lower content of soluble solids concentration. However, differences in soluble solids concentration between treated and control fruit after storage and SMP were not significant.Post-treatment levels of ethanol in both cultivars were significantly higher than in non-treated fruit. During storage and SMP, significant increases of ethanol were detected in control fruits with respect to their initial levels, whereas a reverse trend occurred in fruit subjected to heat treatment. Upon termination of the heat treatment at 44 or 46°C, mean taste scores of ‘Olinda’ oranges were lower than those of untreated fruit, while the taste of ‘Campbell’ oranges was adversely affected only by the 46°C treatment. After storage and SMP, taste differences between treated and control fruit were not significant. Flavour scores were unaffected by the treatment at 44°C. Following treatment at 46°C flavour rating in ‘Olinda’ fruit was significantly lower than control fruit while after storage and SMP the differences in flavour scores between treated and untreated fruit were non significant. Heat treatment to a fruit core temperature of 44°C for 100min or 46°C for 50min can thus have important commercial applications as an alternative to toxic chemical fumigants or to longer and more expensive disinfestation treatments such as cold quarantine.

ENERGY BALANCE OF APPLES UNDER EVAPORATIVE COOLING

Sunburn (or sun scald) of fruit surfaces exposed to direct sun is a major economic problem of fresh apples and other important horticultural crops. There is a critical need to maximize evaporative efficiency and avoid excessive water use. A process-based energy balance model has been developed and compared with field data for apple skin temperatures during evaporative cooling to reduce sunburn on apples in the Pacific Northwest. The model worked well, although it tended to slightly overpredict during times with high advective heat energy. Automated control of evaporative cooling by cycling based on fruit core temperatures worked well in a controlled test stand and minimized total water use. Model results support the management of overtree evaporative cooling systems based on pulsing water applications at sufficiently high rates so that sufficient free water evaporating from the fruit surface will maintain core temperatures of exposed fruit in the 30°C to 32°C range. Results indicated that the model could potentially be used with sensor (e.g., thermocouples) feedback for the initiation, management, and control of overtree evaporative cooling systems to reduce sunburn and conserve water.

A heated air quarantine disinfestation treatment against Queensland fruit fly (Diptera: Tephritidae) for tomatoes

A circulated heated-air treatment at 92% RH to achieve and maintain a minimum fruit core temperature of 44°C for 2 h is shown to disinfest tomatoes against Queensland fruit fly, Bactrocera tryoni (Froggatt) for market access quarantine purposes. The efficacy of the treatment exceeded 99.99%, tested at the 95% confidence level. An estimated 78 439 eggs were used for large-scale trials, as the stage of the pest most tolerant of heat at the treatment temperature.

Effect of fruit maturity on the response of 'Kensington' mango fruit to heat treatment

The effects of conditioning and hot water treatments on immature and mature ‘Kensington’ mangoes were examined. A hot water treatment of 47°C fruit core temperature held for 15 min increased weight loss (50%), fruit softness (15%), disrupted starch hydrolysis and interacted with maturity to reduce the skin yellowness (40–51%) of early harvested fruit. Immature fruit were more susceptible to hot water treatment-induced skin scalding, starch layer and starch spot injuries and disease. Conditioning fruit at 40°C for up to 16 h before hot water treatment accelerated fruit ripening, as reflected in higher total soluble solids and lower titratable acidity levels. As fruit maturity increased, the tolerance to hot water treatment-induced skin scalding and the retention of starch layers and starch spots increased and susceptibility to lenticel spotting decreased. A conditioning treatment of either 22° or 40°C before hot water treatment could prevent the appearance of cavities at all maturity levels. The 40°C conditioning temperature was found to be more effective in increasing fruit heat tolerance than the 22°C treatment; the longer the time of conditioning at 40°C, the more effective the treatment (16 v. 4 h). For maximum fruit quality, particularly for export markets, it is recommended that mature fruit are selected and conditioned before hot water treatment to reduce the risk of heat damage.

Moist and Vapor Forced Air Treatments of Apples and Pears: Effects on the Mortality of Fifth Instar Codling Moth (Lepidoptera: Tortricidae)

Apples and pears were exposed to forced hot air to generate simulated fruit heating profiles in a computer controlled, graduated temperature water bath system and to evaluate the effects of the heat treatments on 5th-instar codling moth, Cydia pomonella (L.). Three apple and 2 pear varieties were exposed to 3 temperatures (44, 46, and 48°C) of forced air under either moist or vapor conditions. The fruit heating profiles were used to program a computer controlled water bath to simulate fruit heating for treatment of 5th-instar codling moth. Heat treatments in which fruit core temperatures did not exceed 43°C were the least effective in causing mortality, whereas treatments that produced core temperatures ≥46°C were the most effective. Heating rates were slower for the moist forced air heating than vapor forced air; these rates resulted in slightly less effective larval kill. Mortalities of larvae infesting apples exposed to vapor forced air at 44°C approximated those obtained in the computerized water bath system. Whenever the heat treatment was followed by cold storage, larval mortality was enhanced.

Postharvest quality of zucchini (Cucurbita pepo L.) following high humidity hot air disinfestation treatments and cool storage

Abstract Zucchini ( Cucurbita pepo L.) were disinfested by a high humidity hot air treatment (HT) to a fruit core temperature of 45 °C for 30 min, and then stored at 7–8 °C. Skin yellowing (indicated by percentage yellowing and hue angle) generally increased with storage time, and was exacerbated by HT. While zucchini quality can be maintained for up to 11 days following HT, it appears that chilling injury prior to such treatment reduces the ability of the fruit to withstand this method of disinfestation.

Conditioning with hot air reduces heat damage caused to 'Kensington' mango (Mangifera indica Linn.) by hot water disinfestation treatment

Hot water treatment (HWT) offers a cost-effective method for fruit fly disinfestation but may cause injury to 'Kensington' mango (Mangifera indica Linn.). Conditioning fruit with hot air before disinfestation may alleviate these injuries. Fruit from 2 major production regions in Queensland were subjected to conditioning treatments with hot air (38-40�C) for 0, 4,8, 12, and 16 h before HWT (fruit core temperature of 45�C held for 30 min). Injuries to fruit not conditioned before HWT included accentuated lenticel spotting, external and internal cavities, and a starchy layer beneath the skin. Fruit conditioned for 8 or 12 h before HWT had minimal injuries. Conditioning with hot air before HWT has the potential to minimise and/or eliminate heat injuries associated with hot water disinfestation treatment. Further testing, particularly on a commercial scale, will be required to optimise these conditioning treatments for use by the Australian mango industry.

Conditioning `Kensington' Mango with Hot Air Alleviates Hot Water Disinfestation Injuries

In an effort to develop an inexpensive alternative to vapor-heat insect disinfestation of `Kensington' mango (Mangifera indica Linn.), the effect of postharvest hot water treatments (HWT) on fruit quality was determined. Fruit were given 46C HWT for 30 minutes at a fruit core temperature of 45C either 24 hours after harvest or after various conditioning treatments of 4 to 24 hours at 39 ± 1C in air. Fruit were compared to nontreated fruit after a subsequent 7 days at 22C. The HWT increased fruit softening and reduced chlorophyll fluorescence and disease incidence. The longer conditioning times produced softer fruit. Conditioning reduced damage to the fruit caused by HWT. Preconditioning for ≥8 hours resulted in &lt;1% of fruit being damaged as shown by cavities, skin scald, and starch layer formation. The quantitatively measured higher mesocarp starch content paralleled the visible starch layer injury. Skin yellowing increased in response to HWTs that were not damaging to the fruit. Fruit ripening changes were unequally affected by HWT and by conditioning before HWT; thus, the sequence and extent of these changes must be determined to establish a reliable and useful hot water disinfestation treatment.

Effect of fruit maturity on quality and physiology of high-humidity hot air-treated ‘Kensington’ mango (Mangifera indica Linn.)

Abstract Mature and immature ‘Kensington’ mangoes ( Mangifera indica Linn.) were treated with an experimental high humidity hot air treatment (HT) to a fruit core temperature of 46.5 °C for 10 min for disinfestation purposes and to test for fruit injury reportedly associated with fruit immaturity. Two methods of determining fruit maturity were examined with fruit harvested over two different seasons, in order to gain a broad range of maturities. No internal or external injury was caused to fruit at any maturity stage by the treatment. Mature HT fruit softened faster and had increased skin colour development compared to immature HT fruit. HT shows commercial potential since the physiological changes associated with treatment and maturity can be managed with careful postharvest handling practices. We recommend only mature fruit be harvested and treated since quality and market performance will be maximised.

Mechanical Injury during Postharvest Handling of `Solo' Papaya Fruit

`Solo' papaya (Carica papaya L.) fruit removed at different points from a commercial packing house showed that skin injury due to mechanical damage increased as fruit moved through the handling system. The occurrence of “green islands” -areas of skin that remain green and sunken when the fruit was fully ripe-apparently were induced by mechanical injury. Skin injury was seen in fruit samples in contact with the sides of field bins, but not in fruit taken from the center of the bins. Bruise-free fruit at different stages of ripeness (5% to 50% yellow) were dropped from heights of 0 to 100 cm onto a smooth steel plate to simulate drops and injury incurred during commercial handling. No skin injury occurred, although riper fruit showed internal injury when dropped from higher than 75 cm. Fruit (10% to 15% yellow) dropped onto sandpaper from a height of 10 cm had skin injury symptoms similar to those seen on fruit from the commercial handling system. These results suggest that abrasion and puncture injury were more important than impact injury for papaya fruit. Heating fruit at 48C for ≈6 hours or until fruit core temperature (FCT) reached 47.5C aggravated the severity of skin injury. Delays in the application of heat treatment from dropping did not reduce the severity of skin injury significantly, except for fruit heated 24 hours after dropping. Waxing fruit alleviated the severity of skin injury, whether applied before or after the heat treatment. Skin injury to papaya was caused by abrasion and puncture damage-not impact-and increased during postharvest handling of the fruit. The injury was associated mainly with fruit hitting the walls of wooden bins-bin liners may reduce this injury.

MECHANICAL INJURY IN SOLO PAPAYA FRUIT

Ripe yellow papaya fruit in the markets frequently show green sunken areas called “green islands” (GI). This disorder seems to be caused by mechanical injury in a commercial postharvest handling system. Fruit at different stages of ripeness (5 to 50% yellow) were dropped from different heights (0 to 100 cm) onto a smooth steel plate to try to create GI. The injury sustained was not the same as GI seen in fruit from the handling system. Fruit (10 to 15% yellow) dropped on different grades of sandpaper (220 mesh to 36 mesh) from a height of 10 cm had injury symptoms similar to those seen on fruit from the handling system. These results suggest that abrasion damage was more important than impact damage in papaya fruit. Heating fruit at 48°C for -6 hours or until fruit core temperature (FCT) reached 47.5°C aggravated the severity of GI. Delaying the time of heating from the time of dropping did not significantly lower the severity of GI, except for fruit heated 24 hours after dropping. Waxing fruit alleviated the severity of GI. The results indicate that avoidance of abrasive surfaces such as the plywood walls of field bins is the best approach to avoiding the unsightly GI blemishes on papaya peel.

Response of Tropical Horticultural Commodities To Insect Disinfestation Treatments.

There is a need to develop effective, non-damaging, non-polluting, non-carcinogenic procedures for insect disinfestation and disease control in fresh horticultural products. The loss of ethylene dibromide as a fumigant and the uncertainties of other fumigants, has meant that alternatives are needed. The most likely possibilities include irradiation, heat, cold and controlled atmospheres. Irradiation doses required for sterilization of insects cause only minor physiological changes, while controlled atmospheres appear to require longer periods of exposure than the postharvest life of most tropical fruit. The sensitivity of tropical commodities to temperatures less than 10°C makes cold treatments inappropriate for most tropical commodities. Heat treatments seem to be most promising. For papaya, the requirement is that the fruit core temperature reach 47.2°C, this can occasionally disrupt fruit ripening. The sensitivity to heat is modified by seasonal, variety and rate of heating factors. The sensitivity can be related to the heat shock response and the presence of heat shock proteins.