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.     

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.     

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.     

Gas sensor array for blueberry fruit disease detection and classification

A conducting polymer gas sensor array (electronic nose) was evaluated for detecting and classifying three common postharvest diseases of blueberry fruit: gray mold caused by Botrytis cinerea, anthracnose caused by Colletotrichum gloeosporioides, and Alternaria rot caused by Alternaria sp. Samples of ripe rabbiteye blueberries (Vaccinium virgatum cv. Brightwell) were inoculated individually with one of the three pathogens or left non-inoculated, and volatiles emanating from the fruit were assessed using the gas sensor array 6–10 d after inoculation in two separate experiments. Principal component analysis of volatile profiles revealed four distinct groups corresponding to the four inoculation treatments. MANOVA, conducted on profiles from individual assessment days or from combined data, confirmed that the four treatments were significantly different (P < 0.0001). A hierarchical cluster analysis indicated two super-clusters, i.e., control cluster (non-inoculated fruit) vs. pathogen cluster (inoculated fruit). Within the pathogen cluster, fruit infected by B. cinerea and Alternaria sp. were more similar to each other than to fruit infected by C. gloeosporioides. A linear Bayesian classifier achieved 90% overall correct classification for data from experiment 1. Tenax? trapping of volatiles with short-path thermal desorption and quantification by gas chromatography–mass spectrometry was used to characterize volatile compounds emanated from the four groups of berries. Six compounds [styrene, 1-methyl-2-(1-methylethyl) benzene, eucalyptol, undecane, 5-methyl-2-(1-methylethyl)-2-cyclohexen-1-one, and thujopsene] were identified as contributing most in distinguishing differences in the volatiles emanating from the fruit due to infection. A canonical discriminant analysis model using the relative concentration of each of these compounds was developed and successfully classified the four categories of berries. This study underscores the potential feasibility of using a gas sensor array for blueberry postharvest quality assessment and fungal disease detection.     

Integration of continuous biofumigation with Muscodor albus with pre-cooling fumigation with ozone or sulfur dioxide to control postharvest gray mold of table grapes

An integrated approach was evaluated that combined biological and chemical fumigation of table grapes to control postharvest gray mold caused by Botrytis cinerea. After fumigation of the grapes with ozone or sulfur dioxide during pre-cooling, the fruit were then exposed to continuous biofumigation by the volatile-producing fungus Muscodor albus during storage. Biofumigation was provided by in-package generators containing a live grain culture of the fungus. This grain formulation of M. albus survived the initial ozone or sulfur dioxide fumigation, but sulfur dioxide reduced its production of isobutyric acid, an indicator of the production of antifungal volatiles. Gray mold incidence was reduced among inoculated ‘Autumn Seedless’ grapes from 91.7 to 19.3% by 1 h fumigation with 5000 μL L^?1 ozone, and further reduced to 10.0% when ozone fumigation and M. albus biofumigation were combined. The natural incidence of gray mold among organically grown ‘Thompson Seedless’ grapes after 1 month of storage at 0.5 °C was 31.0%. Ozone fumigation and M. albus biofumigation reduced the incidence of gray mold to 9.7 and 4.4, respectively, while the combined treatment reduced gray mold incidence to 3.4%. The use of commercial sulfur dioxide pads reduced the incidence to 1.1%. The combination of ozone and M. albus controlled decay significantly, but was less effective than the standard sulfur dioxide treatments. Although less effective than sulfur dioxide treatment, ozone and M. albus controlled decay significantly, and could be alternatives to sulfur dioxide, particularly for growers complying with organic production requirements.     

Pre-storage hypobaric treatments delay fungal decay of strawberries

Fungal decay is a major cause of postharvest losses in strawberries. The traditional approach for controlling fungal decay is the use of fungicides. However, the use of fungicides has been questioned as a sustainable and safe method, and is also prohibited in many countries. One potential physical method for reducing fungal decay is application of a short-term hypobaric treatment prior to storage. In this study efficacy of postharvest hypobaric treatments to control natural rot development in strawberries was evaluated. Strawberries were treated with hypobaric pressures (25 kPa_a, 50 kPa_a and 75 kPa_a) for 4 h at 20 °C and subsequently stored at 20 °C or 5 °C. A 50 kPa_a treatment consistently delayed rot development in samples stored at either temperature confirming that the technique has potential as a non-chemical treatment. Moreover 50 kPa_a treatments did not affect weight loss and firmness at either 20 °C or 5 °C. An initial increase in respiration rate was observed in 50 kPa_a treated samples potentially indicating mild stress due to hypobaric treatment. An in vitro fungal study found that 50 kPa_a treatment for 4 h did not affect the rate of radial growth of colonies of Botrytis cinerea and Rhizopus stolonifer, providing further evidence that the potential mechanism of hypobaric treatment is induction of the defence system within the fruit rather than a direct effect on fungal viability. Further molecular and biochemical research is required to evaluate the possible stimulation of resistance in fruit through short-term hypobaric treatments.     

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.     

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.     

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.     

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.     

Some conventional and latent anti-listerial effects of essential oils,herbs, carrot and cabbage in fresh-cut vegetable systems

The anti-listerial effectiveness of selected essential oils (EOs) and shredded fresh herbs (thyme, oregano and rosemary) was examined on a range of modified atmosphere packaged fresh-cut vegetables (lettuce, carrot discs, cabbage and dry coleslaw mix). Anti-listerial effects were in the order: thyme EO > oregano EO > rosemary herb > rosemary EO. While thyme EO demonstrated the best anti-listerial effect, direct application of all the EOs damaged product appearance. Shredded fresh rosemary herb appeared to have a major anti-listerial effect, but shredded fresh thyme and oregano showed no anti-listerial effects. However, fresh rosemary herb was only effective in fresh-cut products when it was stomached with the product prior to microbial analysis. The effectiveness of these antimicrobials varied depending on the product type. Greater anti-listerial effects were recorded on carrot discs and shredded cabbage than on shredded lettuce. Adding shredded carrot to packages enhanced the apparent anti-listerial effects, suggesting a synergistic effect between carrot and rosemary.     

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.     

Combination of hot water,Bacillus amyloliquefaciens HF-01 and sodium bicarbonate treatments to control postharvest decay of mandarin fruit

An antagonistic isolate Bacillus amyloliquefaciens HF-01, sodium bicarbonate (SBC) and hot water treatment (HW) were investigated individually and in combination against green and blue mold and sour rot caused by Penicillium digitatum, P. italicum and Geotrichum citri-aurantii respectively, in mandarin fruit. Populations of antagonists were stable in the presence of 1% or 2% SBC treatment, and spore germination of pathogens in potato dextrose broth was greatly controlled by the hot water treatment of 45 °C for 2 min. Individual application of sodium bicarbonate at low rates and hot water treatment, although reducing disease incidence after 8 weeks or 4 weeks of storage at 6 °C or 25 °C respectively, was not as effective as the fungicide treatment. The treatment comprising B. amyloliquefaciens combined with 2% SBC or/and HW (45 °C for 2 min) was as effective as the fungicide treatment and reduced decay to less than 80% compared to the control. B. amyloliquefaciens HF-01 alone or in combination with 2% SBC or/and HW significantly reduced postharvest decay without impairing fruit quality after storage at 25 °C for 4 weeks or at 6 °C for 8 weeks. These results suggest that the combination of B. amyloliquefaciens HF-01, SBC and HW could be a promising method for the control of postharvest decay on citrus while maintaining fruit quality after harvest.     

Effect of modified atmosphere packaging and storage temperature on volatile composition and postharvest life of minimally-processed pomegranate arils (cvs. ‘Acco’ and ‘Herskawitz’)

This study investigated the effects of passive modified atmosphere packaging (MAP), storage temperature (5, 10 and 15 °C) and duration of 14 days on the postharvest quality attributes, compositional change in flavour attributes and microbiological quality of minimally processed pomegranate arils (Punica granatum L.), cvs ‘Acco’ and ‘Herskawitz’. Volatile compounds were extracted via headspace solid phase micro-extraction (HS-SPME) and analyzed by gas chromatography–mass spectrometry (GC–MS). A total of 17 and 18 volatiles were detected and identified in the headspace of pomegranate juices of ‘Acco’ and ‘Herskawitz’, respectively. Based on the physicochemical attributes and microbial evaluation, the postharvest life of MA-packaged ‘Acco’ and ‘Herskawitz’ was limited to 10 days due to fungal growth ≥2 log CFU g⁻¹ at 5 °C. However, the concentration (%) and compositional changes in volatile compounds indicated that the flavour/aroma life (7 days) was shorter than the postharvest shelf-life based on appearance and other physicochemical (10 days) for both cultivars.     

Evaluation of postharvest treatments with chemical resistance inducers to control green and blue molds on orange fruit

Preventive and curative activities of postharvest treatments with selected chemical resistance inducers to control postharvest green (GM) and blue (BM) molds on oranges (cvs. ‘Valencia’ or ‘Lanelate’) artificially inoculated with Penicillium digitatum and Penicillium italicum, respectively, were evaluated. In vivo primary screenings to select the most effective chemicals and concentrations were performed with benzothiadiazole (BTH), β-aminobutyric acid (BABA), 2,6-dichloroisonicotinic acid (INA), sodium silicate (SSi), salicylic acid (SA), acetylsalicylic acid (ASA) and harpin. INA at 0.03 mM, SA at 0.25 mM, BABA at 0.3 mM and BTH at 0.9 mM were selected and tested afterwards as dips at 20 °C for 60 or 150 s with oranges artificially inoculated before or after the treatment and incubated for 7 d at 20 °C. Although it was an effective treatment, SSi at 1000 mM was discarded because of potential phytotoxicity to the fruit rind. Preventive or curative postharvest dips at room temperature had no effect or only reduced the development of GM and BM very slightly. Therefore, these treatments cannot be recommended for inclusion in postharvest decay management programs for citrus packinghouses.     

Hot water dipping treatments on Tarocco orange fruit and their effects on peel essential oil

The most common and serious diseases which affect citrus fruit after harvest in Italy are induced by Penicillium digitatum Sacc. and Penicillium italicum Weh., responsible respectively for green and blue mold rots. This paper deals with the effectiveness of hot water dipping (HWD) treatments as alternative means to control postharvest decay on Tarocco orange fruit [Citrus sinensis (L.) Osbeck], and their effect on fruit quality with special regard to peel essential oils. Selected treatments were HWD at 52 °C for 180 s and at 56 °C for 20 s. These treatments were compared with an effective fungicide standard treatment (Imazalil) and an untreated control. The results showed that HWD at 56 °C for 20 s was more effective in inhibiting P. digitatum spore germination than HWD at 52 °C for longer exposure time. In addition, HWD treatment at 56 °C significantly increased the level of alcohols, esters and aliphatic (fatty) aldehydes. Therefore, the lowest values of decay incidence recorded in HWD fruit treated at 56 °C may be due to the increase in oxygenated monoterpenes, esters and aldehydes. Finally, HWD treatments did not cause surface damage or color change and did not influence internal quality parameters.     

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 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.     

Combination of postharvest antifungal chemical treatments and controlled atmosphere storage to control gray mold and improve storability of ‘Wonderful’ pomegranates

Common food additives (sodium bicarbonate (SB), sodium carbonate (SC), and potassium sorbate (PS)) were compared to the fungicide fludioxonil for the control of gray mold on California-grown ‘Wonderful’ pomegranates artificially inoculated with Botrytis cinerea and stored at 7.2 °C in either air or controlled atmosphere (CA, 5 kPa O₂ + 15 kPa CO₂) conditions. Fludioxonil was superior to other treatments. PS was the most effective additive. Synergistic effects between antifungal treatments and CA storage were observed. After 15 weeks of storage at 7.2 °C, the combination of PS treatment (3 min dip in 3% solution at 21 °C) and CA storage was as effective as the combination of heated fludioxonil (30 s dip in 0.6 g L⁻¹ of active ingredient at 49 °C) and air storage. Mixtures of PS with SB or SC did not improve the efficacy of either treatment alone. In tests conducted in commercial facilities, decay development and external and internal fruit quality were assessed on naturally infected pomegranates stored in either air or CA after application of a selected postharvest antifungal combined treatment (CTrt) integrating PS, SB + chlorine, and fludioxonil. CTrt was effective in controlling natural gray mold after 6 weeks of storage at 8.9 °C, but lacked persistence and it was not effective after 14 weeks. CA storage greatly enhanced decay control ability of CTrt. Skin red color was better maintained in CA-stored than in air-stored fruit. Juice color and properties (SSC, TA, and pH) were not practically affected by either postharvest treatment or storage condition. The integration of PS treatments with CA storage could provide an alternative to synthetic fungicides for the management of pomegranate postharvest decay.     

Semi-commercial ultralow oxygen treatment for control of western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae), on harvested iceberg lettuce

Pallet-scale ultralow oxygen (ULO) treatment was applied to iceberg lettuce after various lengths of postharvest storage to determine the effects of pre-treatment storage on lettuce tolerance to ULO treatment for control of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Lettuce from seven cultivars was vacuum cooled and stored at 2 °C after harvest for 0, 2, 3, and 5 d before being subjected to 2-d ULO treatment with 0.003% oxygen at 10 °C ambient temperature. Complete control of thrips was achieved in all three tests. Temperature of lettuce increased from about 5 °C at the start of ULO treatment to 9.6 °C at the end of the treatment. Fresh vacuum-cooled lettuce from three of seven cultivars sustained injury to heartleaves by the ULO treatment. Lettuce that had been stored at the low temperature for 2, 3, or 5 d before the ULO treatment tolerated the ULO treatment and there was no significant quality reduction compared with untreated controls. Heavier heads were significantly more susceptible to heartleaf injury than lighter heads. This study demonstrated that 2-d postharvest refrigerated storage followed by 2-d ULO treatment was effective in controlling western flower thrips with minimal adverse effects on lettuce quality. The ULO treatment protocols developed in this study also have potential to be scaled-up for commercial ULO treatment applications.