Effect of postharvest biofumigation on fungal decay,sensory quality,and antioxidant levels of blueberry fruit

Postharvest decay, caused by various fungal pathogens, is an important concern in commercial blueberry production, but current options for managing postharvest diseases are limited for this crop. Four plant essential oils (cinnamon oil, linalool, p-cymene, and peppermint leaf oil) and the plant oil-derived biofungicides Sporan (rosemary and wintergreen oils) and Sporatec (rosemary, clove, and thyme oils) were evaluated as postharvest biofumigants to manage fungal decay under refrigerated holding conditions. Hand-harvested Tifblue rabbiteye blueberry fruit were inoculated at the stem end with conidial suspensions of Alternaria alternata, Botrytis cinerea, Colletotrichum acutatum, or sterile deionized water (check inoculation) and subjected to biofumigation treatments under refrigeration (7 °C) for 1 wk. Sporatec volatiles reduced disease incidence significantly (P < 0.05) in most cases, whereas other treatments had no consistent effect on postharvest decay. Sensory analysis of uninoculated, biofumigated berries was performed utilizing a trained sensory panel, and biofumigation was found to have significant negative impacts on several sensory attributes such as sourness, astringency, juiciness, bitterness, and blueberry-like flavor. Biofumigated fruit were also analyzed for antioxidant capacity and individual anthocyanins, and no consistent effects on these antioxidant-related variables were found in treated berries. Because of limited efficacy in reducing postharvest decay, negative impacts on sensory qualities, and failure to increase antioxidant levels, the potential for postharvest biofumigation of blueberries under refrigerated holding conditions appears limited.     

Mechanisms of action and efficacy of four isolates of the yeast Metschnikowia pulcherrima active against postharvest pathogens on apples

The mechanisms of action and efficacy of four isolates (GS37, GS88, GA102, and BIO126) of the yeast Metschnikowia pulcherrima against Botrytis cinerea, Penicillium expansum, Alternaria sp., and Monilia sp., all postharvest pathogens of apple fruit, were studied in vitro and on apples, in controlled and semi-commercial conditions. An application of a cell suspension (10⁸ cells per ml) of the antagonists in artificial wounds of apples reduced growth of B. cinerea and P. expansum after storage at 23 °C. A complete suppression of the pathogen was obtained against Monilia sp., stored at 23 °C, and against B. cinerea and P. expansum, stored at 4 °C. The results against Alternaria sp. were more variable. Applications of culture filtrates and autoclaved cells of the isolates were ineffective in reducing the diameter of the lesions on the fruit, supporting the hypothesis that living cells are necessary for biocontrol. In experiments of antagonism in vitro, on different solid substrates, a reduction in the mycelium growth of the pathogens resulted, so that, at least in vitro, the antagonists could produce some diffusible toxic metabolites. In co-cultivation in vitro on a synthetic medium, B. cinerea spore (10⁵ ml⁻¹) germination was completely inhibited by the presence of 10⁸ cells of the antagonists, while culture filtrates and autoclaved suspensions were not able to reduce germination. Dipping boxes of apples cv. Golden delicious in a suspension of 10⁷ antagonist cells per ml and storing for 8 months in controlled atmosphere at 1 °C, showed levels of control against B. cinerea and P. expansum similar to those from thiabendazole.     

The efficacy of ultrasonic fumigation for disinfestation of storage facilities against postharvest pathogens

Inoculum of postharvest pathogens can accumulate inside storage rooms and contaminate new batches of fruit and vegetables, but this chain can be broken by disinfecting storage facilities between storage periods. Quaternary ammonium (QA) has been known for over 50 years as an efficient disinfectant against microorganisms, with wide applications in the food industry. The aim of this study was to determine the efficacy of didecyldimethylammonium chloride (Sporekill, designated here as QA^sk), against development of Botrytis cinerea after direct exposure or by ultrasonic fogging. Following direct exposure to a concentration of QA^sk below 5 mg L^?1, a population of 10⁴ conidia of B. cinerea was inactivated after 2 min; ultrasonic fogging with QA^sk at 500 mg L^?1 took 30 min to achieve consistent inactivation. Fumigation at 20 °C was considerably more effective than fumigation at 5 °C, and similar results were obtained for three other postharvest pathogens, Penicillium expansum, Colletotrichum gloeosporioides and Alternaria alternata. These results show that conidia of B. cinerea are highly sensitive to direct exposure to QA^sk, but that effective sanitation of a storage facility by ultrasonic fumigation requires a QA^sk concentration two orders of magnitude greater.     

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.     

Control of postharvest diseases of fruit with an invert emulsion formulation of Trichoderma harzianum Rifai

Control of primary postharvest diseases caused by Rhizopus stolonifer, Botrytis cinerea, and Penicillium expansum on a variety of fresh fruit was evaluated with an invert emulsion formulation of Trichoderma harzianum. Diseases evaluated were quantified by the period of protection conferred by the antagonist and the diameter of decay lesions. Treatment of the various fruit species with formulated T. harzianum conidia in an invert emulsion significantly (P ≤ 0.05) reduced the mean lesion diameters of R. stolonifer on apple, pear, peach and strawberry, B. cinerea on grape, pear, strawberry, and kiwifruit, and P. expansum on grape, pear, and kiwifruit in comparison with the control treatment. Significant differences (P ≤ 0.05) were obtained in the mean percent reduction in lesion diameter caused by the same postharvest pathogens on the same fruit species due to the treatment with the formulated T. harzianum conidia relative to control treatment. The greatest mean percent reduction (86.7%) was obtained on apple fruit for the infection with R. stolonifer. Significant differences (P ≤ 0.05) were also obtained in the mean durations of the minimum protection period due to treatment with the formulated T. harzianum against the infection with the same postharvest pathogens on the same fruit species. The longest mean duration of the minimum protection period (up to 59 days) was obtained for unwounded apple fruit against the infection with R. stolonifer. Overall, the results indicate that the treatment with the invert emulsion formulation of T. harzianum protected fruit from infection by the primary postharvest pathogens of the fruit tested for up to 2 months and reduced the diameters of decay lesion up to 86% and is a promising treatment to prolong the postharvest shelf-life of fresh fruit.     

Effectiveness of a short hyperbaric treatment to control postharvest decay of sweet cherries and table grapes

The effectiveness of short hyperbaric treatments to control postharvest decay of sweet cherries (Prunus avium L., cv Ferrovia) and table grapes (Vitis vinifera L., cv Italia) was investigated. Sweet cherries and table grape berries were exposed to the pressure of 1140 mmHg (1.5 atm) for 4 and 24 h, respectively, in 64 L gas-proof tanks. Fruit kept at ambient pressure (near 760 mmHg, 1.0 atm) served as a control. Postharvest rots of sweet cherries arose from naturally occurring infections, whereas table grape berries were artificially wounded, exposed to the hyperbaric treatment, then the wounds inoculated with 20 μL of a Botrytis cinerea conidial suspension (5 × 10⁴ spores mL⁻¹). Sweet cherries were stored at 0 ± 1 °C for 14 d, followed by 7 d at 20 ± 1 °C. Table grapes berries were kept at 20 ± 1 °C for 3 d. On sweet cherries, hyperbaric treatment reduced the incidence of brown rot, grey mould, and blue mould, with respect to the control. Similarly, on treated table grapes a significant reduction of lesion diameter and percentage of B. cinerea infected berries was observed. Induced resistance was likely to be responsible for the observed decay reduction. To our knowledge, this is the first report on the effectiveness of short hyperbaric treatments in controlling postharvest decay of sweet cherries and table grapes.     

Essential oil vapours suppress the development of anthracnose and enhance defence related and antioxidant enzyme activities in avocado fruit

Anthracnose caused by Colletotrichum gloeosporioides is a major postharvest disease in avocados that causes significant losses during transportation and storage. Complete inhibition of the radial mycelia growth of C. gloeosporioides in vitro was observed with citronella or peppermint oils at 8 μL plate⁻¹ and thyme oil at 5 μL plate⁻¹. Thyme oil at 66.7 μL L⁻¹ significantly reduced anthracnose from 100% (untreated control) to 8.3% after 4 days, and to 13.9% after 6 days in artificially wounded and inoculated ‘Fuerte’ and ‘Hass’ fruit with C. gloeosporioides. GC/MS analysis revealed thymol (53.19% RA), menthol (41.62% RA) and citronellal (23.54% RA) as the dominant compounds in thyme, peppermint and citronella oils respectively. The activities of defence enzymes including chitinase, 1, 3-β-glucanase, phenylalanine ammonia-lyase and peroxidase were enhanced by thyme oil (66.7 μL L⁻¹) treatment and the level of total phenolics in thyme oil treated fruit was higher than that in untreated (control) fruit. In addition, the thyme oil (66.7 μL L⁻¹) treatment enhanced the antioxidant enzymes such as superoxide dismutase and catalase. These observations suggest that the effects of thyme oil on anthracnose in the avocado fruit are due to the elicitation of biochemical defence responses in the fruit and inducing the activities of antioxidant enzymes. Thus postharvest thyme oil treatment has positive effects on reducing anthracnose in avocados.     

Control of fungal decay of apples and peaches by the biofumigant fungus Muscodor albus

The potential of the volatile-producing fungus Muscodor albus for controlling postharvest diseases of fresh fruit by biological fumigation was investigated. In vitro tests showed that M. albus volatiles inhibited and killed a wide range of storage pathogens belonging to species of Botrytis, Colletotrichum, Geotrichum, Monilinia, Penicillium and Rhizopus. Fumigation of apples for 7 days with culture of M. albus grown on autoclaved grain gave complete control of blue mold (Penicillium expansum) and gray mold (Botrytis cinerea) in wound-inoculated fruits. There was no direct contact between the fruit and the M. albus culture. Shorter fumigation times ranging between 24 and 72 h, applied immediately or 24 h after inoculation, also controlled blue mold and gray mold. In wound-inoculated peaches, 24–72 h fumigation with M. albus provided complete control of brown rot (Monilinia fructicola). The volatile profile of M. albus-colonized grain was measured by gas chromatograph connected to a flame ionization detector (GC-FID) and showed that 2-methyl-1-butanol and isobutyric acid were the major volatile compounds found in the headspace. Since M. albus is a sterile mycelium and does not require direct contact with the crops to be treated, it could be an attractive biological fumigant for controlling postharvest diseases.     

Prestorage application of high carbon dioxide combined with controlled atmosphere storage as a dual approach to control Botrytis cinerea in organic ‘Flame Seedless’ and ‘Crimson Seedless’ table grapes

Pre-storage application of 40% CO₂ at 0 °C for 24 or 48 h and controlled atmosphere (12% O₂ + 12% CO₂) storage at 0 °C for up to eight weeks on decay control and quality of organic ‘Flame Seedless’ and ‘Crimson Seedless’ table grapes were studied as a postharvest disease control alternative. To simulate different potential field conditions, these organic treatments were applied to organic-grown grapes that were naturally infected (without inoculation), surface inoculated (berries inoculated by spraying with a conidia suspension), and nesting inoculated (clusters inoculated by placing in the middle an artificially infected berry) with the pathogen Botrytis cinerea, the cause of grape gray mold. Under these three conditions, a 40% CO₂ for 48 h pre-storage treatment followed by controlled atmosphere reduced the gray mold incidence from 22% to 0.6% and from 100% to 7.4% after four and seven weeks, respectively. High CO₂ pre-storage alone limited botrytis incidence in both naturally and artificially infected grapes, but was more effective when combined with CA. These treatments did not affect visual or sensory fruit quality. Exposure to high CO₂ for 24 or 48 h effectively inhibited mycelial growth of B. cinerea in PDA plates incubated at 22 °C for up to 72 h. Conidia germination in PDA plates was reduced ∼60% after 12 h incubation. In vitro studies demonstrated a fungistatic effect, but further studies on the mechanism of action could improve treatment performance. This novel high CO₂ initial fumigation followed by controlled atmosphere during storage or transportation could be a commercially feasible alternative for postharvest handling of organic and conventional table grapes. Our results encourage validating this combined physical treatment in other cultivars and under commercial conditions.     

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.     

Antifungal protection and antioxidant enhancement of table grapes treated with emulsions,vapors, and coatings of cinnamon leaf oil

Table grapes have high market value in international markets due to their attractive taste and high antioxidant content. However, their market potential is limited by losses due to Botrytis cinerea Pers. Fr. Cinnamon leaf oil (CLO) is a natural fungicidal and antioxidant agent that can be used to avoid postharvest losses due to B. cinerea Pers. Fr. and to increase the antioxidant levels of this produce. CLO was applied to grapes as water emulsions (0, 0.5, 2.5, and 5 g L⁻¹), as vapors (0, 0.196, 0.392, and 0.588 g L⁻¹), or as a chemical incorporated into pectin coatings (0 and 36.1 g L⁻¹). Afterwards, berries were stored at 10 °C for 15 d and were evaluated periodically for the fungal decay index, the total phenolic and flavonoid contents and the antioxidant activity using the Trolox equivalent antioxidant capacity and DPPH radical inhibition methods. The odor acceptability of the treated berries was evaluated after 10 d of storage. The CLO emulsion (5 g L⁻¹) significantly reduced the fungal decay without affecting the antioxidant properties of the berries. The application of CLO as a vapor was more effective according to the evaluated parameters than the emulsions; all tested concentrations inhibited fungal decay and increased the flavonoid content and antioxidant activity. When CLO was incorporated into the pectin, no fungal decay appeared, and the highest antioxidant activity was observed after 15 d of storage. Additionally, all treatments, except the emulsion treatment, increased the odor acceptability of the treated berries compared to the control berries. From this study, it can be concluded that CLO as vapors or coatings can be used to control decay and increase the antioxidant health benefits of grapes due to CLO's antifungal and antioxidant properties.     

Effects of hot water treatment on anthracnose disease in papaya fruit and its possible mechanism

Harvested papaya fruit are perishable due to rapid ripening and softening and susceptibility to biotic or abiotic stresses. Hot water treatment (HWT) can preserve fruit quality by reducing decay. The present study investigated effects of HWT on controlling fungal pathogens of papaya fruit and the possible mechanism by which HWT induced disease resistance. HWT (54 °C, 4 min) of papaya fruit had a pronounced effect on reducing the carrier rate of Colletotrichum gloeosporioides (C. gloeosporioides) in fruit peel, significantly inhibited the incidence of anthracnose and stem-end rot, effectively delayed fruit softening, but slightly promoted the rate of fruit coloring. HWT reduced the anthracnose index and fruit ripeness to a certain extent and induced changes in the wax arrangement on the surface of treated fruit, causing the wax to melt. The cracks and most stomata appeared to be partially or completely plugged by the melted wax, thereby providing a mechanical barrier against wound pathogens. HWT induced the expression of CpPGIP and promptly induced the expression of CpNPR1, and then regulated the expression of the CpPR1 gene, which may enhance the resistance of the fruit to anthracnose disease and reduce the decay rate. Together, these results confirm that HWT could reduce disease incidence and induce resistance, and thus maintain postharvest quality during storage and prolong the shelf-life of papaya fruit.     

Deployment of low-level ozone-enrichment for the preservation of chilled fresh produce

Tomatoes, strawberries, table grapes and plums were inoculated with Botrytis cinerea (grey mould), transferred to chilled storage (13 °C) and exposed to ‘clean air’ or low-level ozone-enrichment (0.1 μmol mol⁻¹). Ozone-enrichment resulted in a substantial decline in spore production as well as visible lesion development in all treated fruit. Exposure-response studies performed specifically on tomato fruit (exposed to concentrations ranging between 0.005 and 5.0 μmol mol⁻¹ ozone) revealed lesion development and spore production/viability to be markedly reduced in produce exposed to ozone prior to, or following, infection with B. cinerea; higher concentrations/duration of exposure yielding greater reductions in lesion development and spore production/viability. Impacts on Botrytis colonies grown on Potato Dextrose Agar (PDA) for 5–6 days at 13 °C and 95% relative humidity (RH) revealed less effects than studies on fruit inoculated with the pathogen in vivo. Taken as a whole, the results imply that ozone-induced suppression of pathogen development is due, to some extent, to impacts on fruit–pathogen interactions. This work suggests that ozone may constitute a desirable and effective residue-free alternative to traditional postharvest fungicide practices. Data presented illustrate that optimal ozone treatment regimes are likely to be commodity-specific and require detailed investigation before such practices can be contemplated commercially.     

Evaluation of the use of sulfur dioxide to reduce postharvest losses on dark and green figs

Postharvest diseases limit the storage period and market life of fresh figs (Ficus carica L.). The objective of this work was to determine the effect of sulfur dioxide (SO₂) applied by fumigation and/or by dual release SO₂ generating pads on postharvest decay and quality retention of ‘Black Mission’ and ‘Brown Turkey’ (dark skin), and ‘Kadota’ and ‘Sierra’ (green skin) figs. A protocol for the computer-controlled application of gaseous SO₂ has been developed which allows the application of very low specific concentration × time products of SO₂ and simultaneous monitoring of the application progress. In vitro tests with important fungal, yeast and bacterial postharvest pathogens plated on Petri dishes and exposed to a SO₂ concentration × time product (C × t) of 100 (μL/L) h at different temperatures showed fewer survived at 20 °C than at 0 °C. Therefore, fumigations were carried out at 20 °C in the rest of the experiments. The evaluation of different SO₂ concentration × time products showed that a product of 25 (μL/L) h provided the best compromise between decay control and fruit injury. The performance of SO₂ fumigations on warm or cold fruit, its combination with SO₂ generating pads, and the use of repeated fumigations during cold storage were also evaluated. All the SO₂ treatments tested reduced the percentage of decay, extending the market life of fresh figs. However, in some cases, the use of SO₂ generating pads increased the incidence of skin bleaching. Fumigation of warm fruit at 25 (μL/L) h of SO₂ reduced populations of Alternaria and Rhizopus spp. growing on the fig surface. The treatment was more effective against Rhizopus spp. than against Alternaria spp. Contamination of fruit by Botrytis spp. and Penicillium spp. was also reduced by SO₂. In conclusion, results showed that SO₂ can be a potential tool to control postharvest rots and therefore increase the market life of fresh figs.     

Control of postharvest grey mould (Botrytis cinerea Per.: Fr.) on strawberries by glucosinolate-derived allyl-isothiocyanate treatments

The vapours of allyl-isothiocyanate (AITC) were evaluated in in vitro and in vivo trials against Botrytis cinerea, a severe pathogen of strawberries. In in vitro trials AITC activity was assayed on conidial germination and mycelial growth of the fungus. The mycelium appeared less sensitive to AITC than conidia (EC₅₀ values of 1.35 mg L⁻¹ and 0.62 mg L⁻¹, respectively). In addition, AITC had a fungistatic effect against the pathogen, since the values of EC₅₀, for both parameters, increased by around 30% after AITC removal. In in vivo trials, ‘Tecla’ and ‘Monterey’ strawberries (spring-bearing and day-neutral cultivars, respectively) obtained from organic production and naturally infected by B. Cinerea, were exposed for 4 h in an atmosphere enriched by pure AITC or derived from defatted seed meals of Brassica carinata (0.1 mg L⁻¹, in a 0.1 m³ treatment cabinet). After 2 days at 0 °C and another 3–4 days at 20 °C, the fruit were evaluated for grey mould infections. The AITC treatment reduced the decay caused by the pathogen by over 47.4% up to 91.5%, significantly different from the untreated fruit. No significant differences were found between synthetic and glucosinolate-derived AITC. Residue analysis performed on fruit at the end of storage (7 d after treatment) showed values lower than 1 mg kg⁻¹. Total phenolic content and antioxidant capacity estimated in treated and untreated strawberries showed no significant difference between control and AITC treated fruit. Our results show it is possible to reduce the incidence of postharvest grey mould on strawberries with a treatment of AITC (0.1 mg L⁻¹) for 4 h, opening a potential application of biofumigation in the postharvest control of B. cinerea in strawberry.     

Blueberry leaf extracts incorporated chitosan coatings for preserving postharvest quality of fresh blueberries

The phenolic compounds in blueberry (Vaccinium spp.) fruit and leaf extracts (BLE) were determined based on HPLC analysis. Antimicrobial assays against Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium and Escherichia coli, as well as fungi isolated from the rotting blueberry fruit were conducted. The effects of chitosan coating incorporating different concentrations of BLE on the quality of fresh fruit during postharvest storage at 2 ± 1 °C and 95 ± 2% relative humidity (RH) for 35 d and then at room conditions for 3 d were also investigated. Five different coating treatments were applied including 2% (w/v) chitosan coating (T1), 2% (w/v) chitosan coating containing 4% (w/v, T2), 8% (w/v, T3), or 12% (w/v, T4) BLE, and 2% (w/v) chitosan coating containing 12% BLE plus modified atmosphere packaging (MAP at 3 kPa O₂ + 12 kPa CO₂) (T5). A sample of blueberries dipped into distilled water was used as control (T0). BLE had a greater variety of phenolic compounds than fruit extracts with syringic acid the highest concentration (0.259 ± 0.003 g kg⁻¹), but the total phenolic content in BLE was lower (P < 0.05) than in fruit extracts. BLE showed good antimicrobial activity against all tested microorganisms, with a minimum inhibition concentration from 25 to 50 g L⁻¹. The 2% chitosan coating that incorporated 8% or 12% BLE showed some degree of decreasing decay rate of fruit compared with the control, and the coating with BLE plus MAP had more effective control of fruit decay. All treated samples maintained higher total phenolic content and radical scavenging activity than the control. This study suggested that chitosan coating incorporating BLE can be employed to extend shelf-life and maintain high nutritional value of fresh blueberries during postharvest storage.     

Application of low concentrations of ozone during the cold storage of table grapes

The control by ozone of postharvest decay of table grapes, caused by Botrytis cinerea and other pathogens, was evaluated in chambers and commercial storage facilities. Ozone at 0.100 μL/L or higher inhibited the spread of gray mold among stored grapes. Ozone diffusion into many types of commercial packaging was measured. Boxes made of uncoated paper corrugate inhibited diffusion more than those composed of coated paper corrugate, plastic corrugate, hard plastic, or expanded polystyrene. Internal packaging of hard plastic clamshell containers inhibited diffusion less than low density polyethylene cluster bags. Atmospheres of 0.100 μL/L ozone in the day and 0.300 μL/L at night reduced the natural incidence of gray mold by approximately 65% after 5–8 weeks of storage. Its effectiveness to control postharvest decay was compared to sulfur dioxide fumigation. After 68 days at 1 °C the incidence of gray mold among grapes stored in air, ozone, or with weekly sulfur dioxide fumigation was 38.8%, 2.1%, and 0.1%, respectively. However, decay by other fungi, such as Alternaria spp. and Penicillium spp., was controlled by sulfur dioxide, but not by ozone. In some tests, rachis appearance was moderately harmed by ozone. The combination of ozone use in storage following a single initial sulfur dioxide fumigation, or its use in between biweekly sulfur dioxide fumigations, controlled both gray mold and other pathogens and matched the commercial practice of initial and weekly sulfur dioxide fumigation. The use of both gases in this way reduced sulfur dioxide use greatly. Differences in flavor of grapes treated with ozone were not detectable compared to those stored in air, and grapes treated with ozone were preferred over those treated with sulfur dioxide.     

Effect of hyperbaric,controlled atmosphere,and UV treatments on peach volatiles

The effect of hyperbaric (HP) and controlled atmosphere (CA) storage and prestorage treatment with ultra violet (UV) radiation on the volatile chemistry of peach [Prunus persica (L.) Batsch] fruit was assessed. Peach volatiles were analyzed using a dynamic headspace system with Tenax trap, automated short path thermal desorption, and GC–MS. The composition of volatile compounds emanating from the fruit varied quantitatively and qualitatively with storage (4 weeks). A total of 65 volatiles were identified, 21 prior to storage and 59 after 4 weeks storage. Six of the prestorage volatiles were not found after storage. The concentration of total volatiles and esters, the highest relative proportion of primary classes increased 32.5- and 36.5-fold, respectively, during storage. Ethyl butanoate, ethyl hexanoate, and ethyl heptanoate contributed to peach aroma due to their low odor thresholds and high concentrations. Using a factorial design (2 × 2 × 2), the main effects [storage pressure (P), storage gas atmosphere (A), and UV pretreatment] and interactions (P × A, P × UV, A × UV, and P × A × UV) were determined. P contributed most to the concentration of total volatile compounds followed by A; HP and HP + CA with or without UV significantly reduced the concentration of total volatiles and esters. Prestorage UV irradiation treatment did not affect the emission of volatile compounds. Principal component analysis (PCA) using 59 volatile compounds emanating from stored fruit indicated a significant effect of P and A on the emission of volatiles that were divided into four treatment groups accounting for 67.5% of the total variance, i.e., AP + Air, AP + CA, HP + Air, and HP + CA. The PCA distribution indicated which compounds contributed most to differences in volatile pattern among treatments: ethyl (Z)-4-octenoate, ethyl heptanoate, ethyl octanoate, and decanal (AP + Air); 3-methylbutyl acetate, ethyl butanoate, ethyl hexanoate, and 2-methylbutanoate (HP + CA); nonanal and hexanal (AP + CA); and hexyl acetate (HP + Air).     

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.     

A method for evaluating fruit abscission potential of grapes and cherry tomato clusters

Abscission is an important postharvest factor for table grapes and cluster cherry tomatoes. There are methods to measure the individual fruit removal force but until now there has been no objective method to study the abscission at a whole cluster level. The working principle of the instrument is that a cluster is attached to a rod which is allowed to fall freely for a pre-determined distance; as the rod stops, the momentum of the berries is converted to detachment force applied to the abscission zone of each berry. The abscission potential can be evaluated as a percentage of fruit detached from cluster under given conditions. The instrument was constructed for robust and adjustable experimental use. It is shown that the abscission percentage for both table grapes and cluster cherry tomatoes was proportional to the free-fall distance. By using the instrument, we showed that the abscission potential of cluster cherry tomatoes was low during the first 2 weeks of storage and that it increased thereafter. Storage of cluster cherry tomatoes at 7 °C resulted in significantly less abscission than at 12 °C, as assessed either by manual shaking or by using the instrument. Treatment of grapes with the cytokinin-like compound forchlorfenthuron at 4 mg L⁻¹ during the early stages of fruit development resulted in significant reduction in abscission potential. These results demonstrate that the method can be used as a reliable experimental tool for objective evaluation of abscission potential.