Evaluation of Lippia scaberrima essential oil and some pure terpenoid constituents as postharvest mycobiocides for avocado fruit

Mycobiocides are attracting research interest worldwide as possible postharvest pathogen control measures to replace synthetic fungicides. In this study, the application of two essential oils as fungicides was evaluated. Initially, the in vitro antifungal effects of Lippia scaberrima essential oil and three of the major oil components, (d)-limonene, R-(−)-carvone, and 1,8-cineole, as well as that of S-(+)-carvone, were investigated against Colletotrichum gloeosporioides, Lasiodiplodia theobromae, and an Alternaria isolate. The oil and terpenoids caused significant inhibition of the mycelial growth of all the pathogens when applied at a concentration of 2000 μL L⁻¹. The most potent volatile component of L. scaberrima essential oil, able to inhibit all the pathogens tested, proved to be R-(−)-carvone. The efficacy of the essential oil (1000 and 2000 μL L⁻¹) incorporated into the commercial coating was confirmed on fruit inoculated with two of the pathogens. A simulated export trial was done using Lippia essential oil, in addition to Mentha spicata (spearmint) essential oil, as supplements for fruit coatings. Results indicate that essential oils rich in R-(−)-carvone could be valuable alternatives to synthetic fungicides for the postharvest management of avocado fruit. The combination of essential oils with a commercial coating, acceptable to the organic market, offers additional protection to this vulnerable commodity.     

Effects of gamma and UV-C irradiation on the postharvest control of papaya anthracnose

Anthracnose is the main postharvest disease in papaya fruit. Today, there is considerable interest on alternative methods of control to promote resistance against pathogens and supplement or replace the use of fungicides. The goal of this work was to evaluate the effects of gamma and UV-C irradiation on Colletotrichum gloeosporioides, the causal agent of anthracnose. Mycelial growth, sporulation, and conidial germination were evaluated in vitro after fungal exposition to different irradiation doses. In the in vivo assays, ‘Golden’ papaya fruit were inoculated through subcuticular injections of a conidial suspension or mycelium discs. Next, fruit were submitted to different irradiation doses (0, 0.12, 0.25, 0.5, 0.75, and 1 kGy), using Co⁶⁰ as source, or UV-C (0, 0.2, 0.4, 0.84, 1.3, and 2.4 kJ m⁻²). To check the possibility of resistance induction by irradiation, papayas were also inoculated 24, 48, or 72 h after the treatments. The fruit were stored at 25 °C/80% RH for 7 days and evaluated for incidence and rot severity. The results showed that the 0.75 and 1 kGy doses inhibited conidial germination and mycelial growth in vitro. All doses increased fungal sporulation. The 0.75 and 1 kGy doses reduced anthracnose incidence and severity, but did not reduce them when the fruit were inoculated after irradiation. All UV-C doses inhibited conidial germination and those higher than 0.84 kJ m⁻² inhibited mycelial growth. The 0.4, 0.84, and 1.3 kJ m⁻² UV-C doses reduced fungal sporulation in vitro. There was no effect of UV-C doses and time intervals between treatment and inoculation on anthracnose control and fungal sporulation in fruit lesions. Moreover, all UV-C doses caused scald on the fruit. Thus, gamma irradiation can contribute for the reduction of postharvest losses caused by anthracnose and reduce the use or doses of fungicides on disease control.     

Internal ethylene concentrations in apple fruit at harvest affect persistence of inhibition of ethylene production after 1-methylcyclopropene treatment

Factors that affect the efficacy of 1-methycyclopropene (1-MCP) treatment of apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] include cultivar and maturity. In this study, ‘McIntosh’, ‘Cortland’ and ‘Empire’ apples were categorized by internal ethylene concentrations (IECs) at harvest, treated with 1 μL L⁻¹ 1-MCP, and the IECs of individual fruit followed at 30 d intervals during air storage at 0.5 °C for 90 d. IECs at harvest ranged from <0.5 μL L⁻¹ to ≥100 μL L⁻¹, 51 < 100 μL L⁻¹, and 10 < 50 μL L⁻¹ for ‘McIntosh’, ‘Cortland’ and ‘Empire’, respectively. 1-MCP treatment resulted in a decrease of IECs in fruit of all cultivars by day 30 after harvest. During subsequent storage IECs remained low in fruit with <1 μL L⁻¹ at harvest, but in ‘McIntosh’, ‘Cortland’ increased in proportion to IECs at harvest, but not in ‘Empire’. The importance of initial IECs in fruit on the persistence of 1-MCP inhibition of ethylene production was confirmed in a further experiment, in which IECs in untreated and 1-MCP treated ‘McIntosh’ and ‘Empire’ apples were measured for up to 194 d. 1-MCP also decreased 1-aminocyclopropene-1-carboxylic acid (ACC) concentrations in fruit. The results of our study are consistent with the hypothesis that IEC modulates the sensitivity of climacteric fruit to 1-MCP.     

Thiabendazole residue loading in dip,drench and wax coating applications to control green mould and chilling injury on citrus fruit

Green mould (caused by Penicillium digitatum) is a major cause of postharvest losses in citrus. Residue loading of thiabendazole (TBZ) with application methods typically used in South African packhouses and green mould control was studied. TBZ was applied curatively and protectively in dip, drench and wax coating treatments and fruit were inoculated with a TBZ-sensitive or a TBZ-resistant isolate of P. digitatum. The dip treatments consisted of TBZ concentrations of 0–2000 μg mL⁻¹; fruit were dipped for 60 s at 22 °C at a pH of 7. Residues differed between fruit batches and ranged from 0.5 to 1.7 μg g⁻¹ at 1000 μg mL⁻¹ TBZ. Curative dip treatments almost completely controlled green mould (>96% at 1000 μg mL⁻¹ TBZ). The residue level needed for 75% curative control ranged from 0.06 to 0.22 μg g⁻¹, depending on citrus type. Protective treatments were unreliable and control varied from 17% to 97.9% at 1000 μg mL⁻¹ TBZ between fruit batches. Drench treatments consisted of exposure times of 30, 60 and 90 s with 1000 or 2000 μg mL⁻¹ TBZ. Average TBZ residues were 2.14 μg g⁻¹ for Clementine mandarin fruit and 3.50 μg g⁻¹ for navel orange fruit. Green mould control on navel orange fruit resulted in 66–92%, 34–90% and 9–38% control for curative treatments after 6 and 24 h and protective treatments, respectively, depending on fruit batch. Wax with 4000 μg mL⁻¹ TBZ was applied at 0.6, 1.2 and 1.8 L wax ton⁻¹ fruit. Chilling injury was evaluated after fruit storage at −0.5 °C for 40 days. Average TBZ residues loaded was 1.3, 1.3 and 2.7 μg g⁻¹ at the recommended 1.2 L ton⁻¹ for Satsuma mandarin, Clementine mandarin and Valencia orange fruit, respectively. Protective treatments showed lower infection levels (14–20%) than curative treatments (27–40%) for Valencia orange fruit. The same trend was observed with Satsuma (92–95% curative; 87–90% protective) and Clementine mandarin fruit (82–90% curative; 59–88% protective), but control was relatively poor. TBZ application in wax exceeded 5 μg g⁻¹ at higher wax loads (1.2 and 1.8 L ton⁻¹). Wax treatments showed a significant reduction in chilling injury; TBZ had an additive effect. TBZ resistant isolates could not be controlled.     

Evaluation of the use of chlorine dioxide by fogging for decreasing postharvest decay of fig

Postharvest diseases limit the storage period and marketing life of figs. The efficacy of chlorine dioxide by fogging was tested for the control of postharvest diseases of black fig (Ficus carica L. cv. Bursa Siyahi). Fruit were fogged with various concentrations of chlorine dioxide in a cold storage unit for 60 min at room temperature. Treated fruit were stored either in air or modified atmosphere bags for 7 d at 1 °C followed by 2 d shelf-life at 20 °C. Fogging at 300–1000 μL L⁻¹ significantly reduced natural incidence of decay, most of which was gray mold. The efficacies of fogging at 500 and 1000 μL L⁻¹ were at the same level and fogging at 1000 μL L⁻¹ was superior to that at 300 μL L⁻¹ in fruit stored in air. Modified atmosphere packaging did not improve the efficacy of fogging in reducing decay incidence. The epiphytic population on the fruit surface was similarly reduced by chlorine dioxide fogging. All treatments significantly reduced total microorganisms, fungal and bacterial populations in fruit. In addition, microorganisms in the storage atmosphere were significantly reduced. None of the treatments affected the visual quality and taste of fruit.     

Fungicidal activity of compounds extracted from the pericarp of Areca catechu against Colletotrichum gloeosporioides in vitro and in mango fruit

Areca catechu L., a member of the Palmaceae family, is one of the most commonly used drugs in the world. Compounds obtained from the hexane, ethyl acetate and methanol extracts of the pericarp of A. catechu L. were assessed in vitro and in mango fruit for antifungal activity against Colletotrichum gloeosporioides Penz. In vitro studies also indicated that three triterpenes, namely fernenol (fern-9(11)-en-3α-ol), arundoin (fern-9(11)-en-3α-ol ME), and a mixture of stigmasterol and β-sitosterol, and one fatty acid, lauric acid, could inhibit the mycelial growth of C. gloeosporioides with EC₅₀ values of 36.7, 47.5, 56.7 and 111.5 mg L^?1, respectively. Furthermore, fernenol, arundoin, and the mixture of stigmasterol and β-sitosterol highly inhibited spore germination and germtube elongation. Mango fruit studies suggested that fernenol, arundoin and the mixture of stigmasterol and β-sitosterol were significantly more effective than benomyl for controlling postharvest anthracnose disease when used at 100 and 200 mg L^?1.     

Rapid ingress of gaseous 1-MCP and acute suppression of ripening following short-term application to midclimacteric tomato under hypobaria

Our previous studies demonstrated that tomato fruit (breaker or pink) exposed at the midclimacteric stage to hypobaric hypoxia for 6 h exhibited transient increased sensitivity to subsaturating levels of 1-methylcyclopene (1-MCP). In the present study, we examined the effect of gaseous 1-MCP (500 nL L⁻¹, 20.8 μmol m⁻³) applied to mid-climacteric (>60% peak ethylene production) tomato fruit under hypobaric hypoxia (10 kPa, 2.1 kPa O₂,) for 1 h. Application of 500 nL L⁻¹ 1-MCP under atmospheric conditions had little effect on softening and timing and magnitude of peak ethylene production, and moderate effects on respiration and lycopene and PG accumulation. By contrast, midclimacteric fruit exposed to 500 nL L⁻¹ gaseous 1-MCP under hypobaric hypoxia for 1 h showed acute disturbance of ripening. Firmness and hue angle declines were delayed for ten days and peak ethylene production for eleven days compared with trends for the other treatments. Maximum ethylene production did not exceed 50% of maxima for the other treatments and a definitive respiratory climacteric was not observed. Accumulation of internal gaseous 1-MCP was enhanced under hypobaric hypoxia. Internal 1-MCP in fruit exposed to 20 μL L⁻¹ 1-MCP (831 μmol m⁻³) under hypobaric hypoxia for 2 or 10 min averaged 7.5 ± 0.5 and 8.7 ± 1.4 μL L⁻¹, respectively, compared with 0.8 ± 0.3 and 3.9 ± 0.7 μL L⁻¹ in fruit exposed under atmospheric conditions. After 1 h exposure, internal 1-MCP averaged 10.8 ± 2.2 μL L⁻¹ under hypobaric hypoxia compared with 5.3 ± 1.4 μL L⁻¹ under atmospheric conditions. The results indicate that high efficacy of 1-MCP applied under hypobaric hypoxia is due to rapid ingress and accumulation of internal gaseous 1-MCP.     

Preharvest application of abscisic acid promotes anthocyanins accumulation in pericarp of litchi fruit without adversely affecting postharvest quality

Pericarp colour of litchi fruit is an important quality attribute that determines its market value and consumer acceptance. Plant growth regulators (PGR) such as abscisic acid (ABA) and ethephon are known to play important roles in peel colour development during maturation and ripening of non-climacteric fruits (e.g. grape and litchi). Our aim was to investigate the effects of preharvest application of ABA, ethephon and their combination on pericarp colour and fruit quality of litchi (cv. Calcuttia) and also to assess the potential effects on postharvest performance of fruit. Exogenous application of ABA (150 or 300 mg L⁻¹) at the colour-break stage significantly increased the concentration of total anthocyanins and cyanidin-3-O-rutinoside, the major anthocyanin contributing ∼71–96% of the total anthocyanins, in litchi pericarp compared to ethephon (500 μL L⁻¹). Among different anthocyanins quantified, the relative contribution of cyanidin-3,5-diglucoside to the total anthocyanins was significantly higher in all PGR-treated fruit compared to the control, but the concentration of cyanidin-3-O-glucoside was specifically enhanced by ABA. No significant effect on the concentrations of epicatechin, and quercetin-3-O-rutinoside was observed in response to PGR treatments. Ethephon (500 μL L⁻¹) treatment did not significantly increase the anthocyanin levels in pericarp, but it caused more degradation of chlorophyll pigments than control. Aril quality with regard to firmness, soluble solids and acidity was not significantly affected by PGR treatments, except that ethephon-treated fruit showed significant softening and lower acidity. Postharvest changes in fruit quality attributes including pericarp browning during cold storage at 5 °C for 14 d were mainly related to the storage duration effect, rather than PGR treatment. In conclusion, ABA treatment (150 or 300 mg L⁻¹) at the colour-break stage enhanced anthocyanins accumulation in litchi pericarp without adversely affecting postharvest quality and storage stability for 14 d.     

Effects of cinnamon extract,chitosan coating,hot water treatment and their combinations on crown rot disease and quality of banana fruit

The antifungal activities of cinnamon extract (CE), piper extract (PE) and garlic extract (GE) were evaluated on banana crown rot fungi (Colletotrichum musae, Fusarium spp. and Lasiodiplodia theobromae) in vitro. The assay was conducted with extracts of CE, PE and GE with concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0 and 0.75 g L⁻¹ of carbendazim (CBZ) on potato dextrose agar at room temperature. CE completely inhibited conidial germination and mycelial growth of all fungi at 5.0 g L⁻¹. PE totally suppressed mycelial growth of all fungi at 5.0 g L⁻¹ and conidial germination at 10.0 g L⁻¹ except for Fusarium spp. GE had no significant effects but low concentrations (0.1 and 0.5 g L⁻¹) enhanced germ tube elongation of the three fungi. The ED₅₀ values were higher for mycelial growth than for conidia except for Fusarium spp. Combined treatments were investigated on crown rot development in banana fruit (Musa AAA group ‘Kluai Hom thong’). Treatments included 5.0 g L⁻¹ CE, 1% (w/v) chitosan solution, hot water treatment (HWT, 45 °C for 20 min), CE plus chitosan, CE plus HWT and 0.75 g L⁻¹ of CBZ, applied before and after inoculation of the fruit. Crown rot development was assessed during storage at 13 °C for 7 weeks. Disease development was least (25%) on CE treated fruit after inoculation compared to CBZ but was higher when CE was applied before inoculation. Chitosan significantly delayed ripening as in terms of peel color, firmness, soluble solids and disease severity. CE showed no negative effects on quality of fruit. CE plus HWT caused unacceptable peel browning.     

Determination of optimal sulfur dioxide time and concentration product for postharvest control of gray mold of blueberry fruit

Highbush blueberries (Vaccinum spp.) are a major export fruit crop of Chile which is stored at 0 °C and transported to markets in Asia, Europe, and the USA, using more than 15 d of maritime transportation. Under these conditions, gray mold caused by Botrytis cinerea can produce important economic losses. The effectiveness of sulfur dioxide (SO₂) concentration × time treatments on gray mold control was determined in the laboratory and validated prior to refrigerating the fruit, using pallet scale SO₂ fumigation treatment on the following blueberry cultivars: ‘Brigitta’, ‘Legacy’, ‘Liberty’ and ‘O’Neal’. In inoculated ‘Brigitta’ and ‘Liberty’ blueberries, gray mold prevalence varied from 97.2% to 97.5% in non-treated fruit, and this value was reduced from 7.9% to 6.1% in blueberries that were exposed to a SO₂ concentration × time (Ct) product of 400 (μL L⁻¹) h. The relationship between SO₂ Ct products and gray mold prevalence under laboratory conditions was best explained by exponential models, which had a determination coefficient (R²) that ranged from 0.88 to 0.96. The estimated EC₉₀ values varied between 245 and 400 (μL L⁻¹) h, and the SO₂ Ct between 250 and 350 (μL L⁻¹) h was validated using a pallet scale application treatment to obtain the best control and minimal variation. No visual phytotoxicity symptoms of SO₂ were observed with the Ct that was tested in this study. Therefore, SO₂ fumigation was demonstrated to be an effective and practical technology for reducing the risk of blueberry gray mold decay during storage, and further effort should be given to register the use of this product for blueberries in the main Chilean export markets.     

Hexanal reduces infection of tomatoes by Botrytis cinerea whilst maintaining quality

Hexanal vapour and intact tomatoes were used as models to assess the opportunities for control of Botrytis cinerea rots by controlled release of organic vapours. Hexanal vapour concentrations in the ranges 5–270 μL L⁻¹ were applied continuously or as a single dose at the start of storage. The postharvest microbiological, physiological and quality attributes of control and hexanal treated tomatoes were investigated during storage for 7 days at 20 ± 1 °C and ∼99% RH. Continuous hexanal exposure effectively suppressed grey mould with the minimum inhibitory concentration (MIC) being 40–70 μL L⁻¹; the single-dose treatment showed minimal antifungal activity. During continuous exposure at the MIC the fruit respiration rate was increased ∼50% and reddening was slowed. No clear trend was observed in ethylene production and treated fruit did not differ from the controls in firmness or mass loss. The controlled release of low concentrations of hexanal vapour into a packaging headspace appears a feasible mechanism for prolonging tomato storage life.     

Application of abscisic acid (ABA) at veraison advanced red color development and maintained postharvest quality of ‘Crimson Seedless’ grapes

‘Crimson Seedless’ is a popular table grape cultivar, but in warm-climates, its fruits often fail to develop adequate red color, even after they have been treated with ethephon. Application of abscisic acid (ABA) may improve color more effectively than ethephon, but its potential effects on postharvest quality must be considered before recommending its use on table grapes. Therefore, we compared the postharvest quality attributes of grapes treated preharvest with 250 μL L⁻¹ ethephon, the current industry standard, to that of grapes treated with 150 or 300 μL L⁻¹ ABA, or nontreated. Treatment with either ethephon or 150 μL L⁻¹ ABA allowed grapes to be harvested 10 d before nontreated fruit, and fruits treated with 300 μL L⁻¹ ABA attained marketable quality 30 d before nontreated fruit. Early harvest was possible because the treatments induced more rapid coloring of the grapes, and though total yield was not affected by any plant growth regulator (PGR), all PGRs doubled packable yields by improving the color of the grapes. ABA-treated grapes were characterized by superior appearance both in berries and clusters’ rachises compared to ethephon-treated and control grapes. Other quality attributes such as firmness, berry weight, decay incidence, and shatter remained unaffected among treatments. Therefore, ABA is an effective alternative to ethephon for enhancing the color and maintaining postharvest quality of ‘Crimson Seedless’ grapes.     

Integration of Lactobacillus plantarum A7 with thyme and cumin essential oils as a potential biocontrol tool for gray mold rot on strawberry fruit

Chemical fungicides have been intensively used in the control of postharvest decay in fruit in postharvest conditions; nevertheless, continuous use of these fungicides has faced two major obstacles: development of pathogen resistance to many key fungicides, and public knowledge on the health and environmental hazards of these compounds. This study evaluated the efficacy of Lactobacillus plantarum A7, thyme (Thymus vulgaris L.) and cumin (Cuminum cyminum L.) essential oils and the combination of these three elements as postharvest biocontrol agents against Botrytis spp. on strawberry fruit. Thyme oil had a remarkable antifungal effect against Botrytis spp. in vitro, whereas an inhibitory effect of cumin oil was achieved in higher concentrations. With thyme oil (2 h after artificial inoculation of the fruit), among three tested concentrations, only the 200 μL/L concentration showed an inhibitory effect on strawberries against Botrytis spp. (91.97%), while higher concentrations of cumin oil were required to prevent decay significantly. Both combinations of L. plantarum+ cumin oil and L. plantarum+ thyme oil completely inhibited the mycelia growth of the pathogens in vitro. Results showed that the combined treatments of strawberry fruit with L. plantarum+ cumin oil (50 μL/L) and L. plantarum+ thyme oil (100 μL/L) resulted in remarkably improved control of Botrytis infections, in comparison to the stand-alone application of L. plantarum A7 or essential oils. Quality (i.e. pH, acidity and ascorbic acid content) and sensory attributes of the strawberry fruit were better in the case of using cumin compared to thyme oil, when a combination of L. plantarum A7 and essential oils was used. This study has demonstrated that the integration of L. plantarum A7 with thyme and cumin essential oils is a potential biocontrol tool as a biofungicide in postharvest stage.     

Ripening and sensory analysis of Guatemalan-West Indian hybrid avocado following ethylene pretreatment and/or exposure to gaseous or aqueous 1-methylcyclopropene

Previous reports showed that both gaseous and aqueous 1-methylcyclopropene (1-MCP) delay ripening of avocado (Persea americana Mill.), but there are no reports of the influence of 1-MCP on its sensory attributes. The objective of this study was to evaluate the effects of ethylene pretreatment and/or exposure to gaseous or aqueous 1-MCP on fruit ripening and sensory attributes of ‘Booth 7’ avocado, a Guatemalan-West Indian hybrid. Separate experiments were conducted during two seasons (2008 and 2009) with fruit harvested at preclimacteric stage in October (early season) and in November (late season). Fruit from Season 1 were exposed to ethylene (4.07 μmol L⁻¹) for 12 h at 20 °C, and stored for more 12 h at 20 °C in an ethylene-free (ethylene, <0.1 μL L⁻¹) room prior to treatment with either aqueous (1.39 or 2.77 μmol L⁻¹ a.i.) or gaseous (3.15 or 6.31 nmol L⁻¹ a.i.) 1-MCP. Ripening was monitored and firmness, respiration, ethylene production and weight loss were measured. Texture profile analysis and sensory analysis were performed on ripe fruit only (firmness, 10–15 N). Fruit from Season 2 were not exposed to ethylene pretreatment but treated only with aqueous 1-MCP 24 h after harvest. Fruit were assessed exclusively for sensory analysis when ripe (firmness, 10–15 N). Treatment with either 1-MCP formulation effectively delayed ripening from 4 to 10 d for early-season fruit, and from 4 to 6 d for late-season fruit. Higher concentrations of 1-MCP of either formulation had the greatest effect on selected pulp textural parameters of early-season fruit; the gaseous formulation had greater effect on late-season fruit quality than the aqueous formulation. In general, sensory panelists ratings of overall liking were not affected by 1-MCP treatment. Both aqueous and gaseous 1-MCP formulations delayed ripening of the Guatemalan-West Indian ‘Booth 7’ avocado without significant loss in appearance or in sensory attributes and, therefore, could be considered for use as a postharvest treatment for this hybrid.     

Diffusivity of 1-methylcyclopropene in spinach and bok choi leaf tissue,disks of tomato and avocado fruit tissue,and whole tomato fruit

Gaseous 1-methylcyclopropene (1-MCP) has been widely employed for delaying ripening and senescence of harvested fruit and vegetables; however, details on ingress of gaseous1-MCP in plant tissues, which might contribute to differences in responsiveness of different horticultural commodities to 1-MCP, have not been reported. In this study, we used spinach and bok choi leaves, disks from tomato epidermis, stem-scar and avocado-exocarp tissues, and whole tomato fruit to examine ingress of gaseous 1-MCP. Using a dual-flask system, equilibration of 20 μL L⁻¹ (831 μmol m⁻³) 1-MCP through leaf tissue was reached within 1–2 h, and paralleled 1-MCP transfer through glass-fiber filter paper. For disks derived from fruit tissues, changes in 1-MCP concentrations in the dual-flask system showed anomalous patterns, declining as much as 70% in source flasks with negligible accumulation in sink flasks. The pattern of 1-MCP distribution was markedly different from that of ethylene, which approached equal distribution with tomato stem-scar and avocado exocarp but not tomato epidermis tissues. 1-MCP ingress was further addressed by exposing whole tomato fruit to 20 μL L⁻¹ 1-MCP followed by sampling of internal fruit atmosphere. Tomato fruit accumulated internal gaseous 1-MCP rapidly, reaching approximately 8–9 μL L⁻¹ within 3–6 h at 20 °C. Internal 1-MCP concentration ([1-MCP]) declined around 74 and 94% at 1 and 3 h after exposure, respectively. Ingress was similar at all ripening stages and reduced by 45% in fruit coated with commercial wax. Blocking 1-MCP ingress through stem- and blossom-scar tissues reduced accumulation by around 60%, indicating that ingress also occurs through epidermal tissue. Fruit preloaded with 1-MCP and immersed in water for 2 h retained about 45% of post-exposure gaseous [1-MCP], indicating that 1-MCP is not rapidly sorbed or metabolized by whole tomato fruit. Rapid ingress of gaseous 1-MCP was also observed in tomato fruit exposed to aqueous 1-MCP. Both accumulation and post-exposure decline in internal gaseous [1-MCP] are likely to vary among different fruit and vegetables in accordance with inherent sorption-capacity, surface properties (e.g., waxes, stoma), volume and continuity of gas-filled intercellular spaces, and tissue hydration.     

Physiology of fresh-cut ‘Galia’ (Cucumis melo var. reticulatus) from ripe fruit treated with 1-methylcyclopropene

‘Galia’ (Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit were harvested at the three-quarter slip stage and treated with 1 μL L⁻¹ 1-methylcyclopropene (1-MCP) at 20 °C for 24 h. The fruit were processed and stored as fresh-cut cubes and intact fruit for 10 d at 5 °C. Ethylene production of fresh-cut cubes was approximately 4–5-fold higher than intact fruit at day 1. Afterward, the ethylene production of fresh-cut cubes declined significantly whereas that of intact fruit remained relatively constant at about 0.69–1.04 ng kg⁻¹ s⁻¹. 1-MCP delayed mesocarp softening in both fresh-cut and intact fruit and the symptoms of watersoaking in fresh-cut fruit. Continuously stored fresh-cut cubes and cubes derived from intact fruit not treated with the ethylene antagonist softened 27% and 25.6%, respectively, during 10 d storage at 5 °C while cubes derived from 1-MCP-treated fruit softened 9% and 17%, respectively. Fresh-cut tissue from 1-MCP-treated fruit exhibited slightly reduced populations of both total aerobic organisms and Enterobacterium, although the differences did not appear to be sufficient to explain the differences in keeping quality between 1-MCP-treated and control fruit. Based primarily on firmness retention and reduced watersoaking, 1-MCP treatment deferred loss of physical deterioration of fresh-cut ‘Galia’ cubes at 5 °C by 2–3 d compared with controls.     

Assessment of blue light treatments on citrus postharvest diseases

Exposure of mature ‘Fallglo’ tangerine fruit to blue light with a photon fluence rate 40 μmol m⁻² s⁻¹ reduced symptom development of blue mold (Penicillium italicum), green mold (Penicillium digitatum), and stem end rot (Phomopsis citri) postharvest decays. Direct exposure to blue light was required to reduce decay caused by Penicillium. Blue light (40 μmol m⁻² s⁻¹) reduced in vitro fungal growth of P. italicum and P. citri. The growth of P. digitatum was more tolerant to blue light, however, the activity of fungal polygalacturonase was reduced by blue light at the intensity of 40 μmol m⁻² s⁻¹. Gas chromatography–mass spectrometry analysis identified 29 chemical constituents in flavedo oil; blue light induced only octanal accumulation. Application of octanal suppressed growth of P. italicum, P. digitatum, and P. citri in vitro. Treatment of fruit with octanal at 5 mM or 50 mM suppressed symptom development caused by Penicillium and P. citri, but discolored the peel. Inhibition of postharvest decays by blue light may be due to a combination of inhibition of fungal growth and induction of defensive responses in the host.     

Volatile profiles of ripening West Indian and Guatemalan-West Indian avocado cultivars as affected by aqueous 1-methylcyclopropene

Separate experiments were conducted with three major commercial avocado (Persea americana Mill.) cultivars grown in Florida: ‘Simmonds’ (early-season, West Indian race); ‘Booth 7’ (mid-season, Guatemalan-West Indian hybrid); and ‘Monroe’ (late-season, Guatemalan-West Indian hybrid). Fruit were harvested at preclimacteric stage and left untreated (Control) or treated 24 h after harvest with aqueous 1-methylcyclopropene (1-MCP) at 1.39 (treatment M1) or 2.77 μmol L⁻¹ a.i. (treatment M2) (75 or 150 μg L⁻¹) for 1 min at 20 °C. Whole fruit ripening was monitored at 20 °C/92% ± 3% R.H. and based on whole fruit firmness, respiration and ethylene evolution. Fruit volatiles were assessed at preclimacteric (24 h after harvest), mid-ripe (half of initial fruit firmness) and ripe maturity stages, from 100 g of chopped pulp using a purge and trap system. Untreated, firmer fruit ‘Monroe’ (268 N at harvest) ripened within 12 d of harvest while softer fruit ‘Simmonds’ (118 N) ripened within only 6 d. 1-MCP treatment extended ripening time from 33% (M1) to 83% (M2). All fruit softened normally, indicating the potential benefits of aqueous 1-MCP as a postharvest treatment for avocado when applied at these concentrations. Volatile profiles differed among the three cultivars with several compounds detected in only one cultivar, results that may contribute to a potential identification of the origin of the cultivar based on fruit volatile composition. The West Indian cultivar ‘Simmonds’ had much higher emission of hexanal (preclimacteric fruit) and cis-3-hexenal and cis-3-hexen-1-ol (ripe fruit) than the Guatemalan-West Indian hybrids ‘Booth 7’ and ‘Monroe’. On the other hand, these latter hybrids had much higher levels of alkanes than ‘Simmonds’. Treatment with 1-MCP increased emissions of alkanes during ripening of ‘Booth 7’ and ‘Monroe’. Total volatiles of avocado decreased during ripening mainly due to the significant reduction of sesquiterpenes, the main group of volatiles in all cultivars at harvest (‘Simmonds’, 53%; ‘Booth 7’, 78%; ‘Monroe’, 66%). β-Caryophyllene was the major compound at harvest, but decreased to less than 2% in ripe fruit, at which point most sesquiterpenes were not detected. Among the 10 sesquiterpenes commonly found in the avocado cultivars in this study, only α-Copaene had significantly higher emissions in mid-ripe fruit treated with the higher concentration of 1-MCP (2.77 μmol L⁻¹ a.i.), suggesting that ethylene participates in the regulation of this sesquiterpene.     

Control of Neofabraea alba by plant volatile compounds and hot water

Fumigation by plant volatile compounds and hot water treatment were tested in vitro and in vivo for their activity against Neofabraea alba (anamorph Phlyctema vagabunda), the cause of lenticel rot in apple fruit. In vitro trials with volatile compounds showed a consistent inhibition of pathogen growth by carvacrol, trans-cinnamaldehyde, citral and trans-2-hexenal, while (?)-carvone, hexanal, p-anisaldehyde, 2-nonanone and eugenol showed progressively lower inhibition. The greatest inhibition of mycelial growth was demonstrated by carvacrol (effective doses for 50 and 95 inhibition [ED₅₀ and ED₉₅] = 5.9 and 17.0 μL L^?1, respectively; minimum inhibitory concentration [MIC] = 36.9 μL L^?1) and of conidial germination by trans-2-hexenal (ED₅₀ and ED₉₅ = 4.1 and 6.9 μL L^?1, respectively; MIC = 9.2 μL L^?1). Hot water showed a complete inhibition of conidial germination in vitro after 10, 2 and 1 min of exposure at 40, 45 and 50 °C, respectively, and a complete inhibition of mycelial growth after 20 min of exposure at 75 °C. Among the volatile compounds tested, only 25 μL L^?1 of carvacrol slightly reduced fungal infection on artificially infected apples (11.4% efficacy). Hot water treatment at 45 °C for 10 min showed high efficacy in the control of lenticel rot on apples. Reduction of infection was 80% in artificially inoculated fruit (cv Golden Delicious) and 90% in naturally infected fruit (cv Pink Lady) after 90 and 135 d of storage, respectively.     

Papaya endoxylanase biochemical characterization and isoforms expressed during fruit ripening

Papaya fruit ripening processes involve the coordinated action of several hydrolases that causes cell wall degradation. Endoxylanase participates in xylan or arabinoxylan modifications and its importance has been related to papaya softening. However, endoxylanase has been not fully characterized biochemically and kinetically. Semipurified endoxylanase from ripe ‘Maradol’ papaya fruit had an optimal temperature from 45 °C to 50 °C, a pH optimum of 5.5 against Remazol brilliant blue-xylan (RBB-Xylan) and enzymatic activity remained stable during 36 h at 45 °C. The activation energy of the enzyme was 25.5 kJ mol⁻¹, and the V_max at 32, 37 and 42 °C was 788.9, 888.9 and 1085.6 μg kg⁻¹ s⁻¹, respectively. The K_m did not change as a function of temperature and was measured as 1.8 g L⁻¹ and was within the range reported for other xylanases. Total proteins were extracted from color-break, half-ripe and ripe fruit. A pre-endoxylanase at 63.9 kDa was identified in the color-break fruit and an active endoxylanase at 32.5 kDa that was only found in ripe fruit, when the highest enzymatic activity was obtained. Immunodetection on two-dimensional gel electrophoresis (2DE) protein blots showed three isoforms of the pre-endoxylanase at color-break and ripe stages and, four isoforms in ripe fruit that were absent in color-break fruit. The biochemical and kinetic characteristics of the endoxylanase are crucial to our understanding papaya fruit softening.