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.     

Characterization of sensitivity of grove and packing house isolates of Penicillium digitatum to pyrimethanil

In most northeast Argentinean citrus packing houses, postharvest fungicide treatments are based on the use of thiabendazole and imazalil. However, these fungicides have been used in a manner highly conducive to the selection and proliferation of resistant biotypes of Penicillium digitatum, the main fruit decay fungus in the area. Recently, a new fungicide, pyrimethanil (PYR), was introduced to control molds. Aims of this study were to determine the baseline sensitivities for PYR against isolates of P. digitatum considering its use in the region is not yet widespread and to evaluate the control of the fungus in vivo. One hundred and nine (109) P. digitatum isolates were collected from diseased fruit within citrus groves (43 isolates) and packing houses (66 isolates). EC₅₀ was determined for each isolate by measuring colony diameters on different agar dilutions of the fungicide. The mean EC₅₀ value of the green mold isolates collected from the groves was 0.14 ± 0.03 mg L⁻¹ while the mean EC₅₀ of those collected from packing houses was 0.13 ± 0.05 mg L⁻¹. No resistant isolates were found in the field where the fungicide is not used, while one isolate originated from a packing house showed an EC₅₀ of 3.40 mg L⁻¹, 26-fold higher than the mean level. This isolate was collected from lemons stored in cool rooms of a packing house where PYR had not been used. Fruit decay by sensitive isolates was reduced approximately 80% by PYR applied at 500–600 mg L⁻¹ by immersion for 60 s at room temperature to inoculated oranges and mandarins. In contrast, the resistant isolate was not controlled by PYR applied at 1000 mg L⁻¹. Thus, the introduction of PYR applied into packing houses should be done carefully and control strategies should be implemented in order to minimize the development of resistant isolates.     

Interactive effects of ozone and 1-methylcyclopropene on decay resistance and quality of stored carrots

Fresh carrots were treated with or without 1.0 μL L⁻¹ 1-methylcyclopropene (1-MCP) at 10 °C for 16 h, and then exposed to 300 or 1000 nL L⁻¹ ozone at 10 °C for 0, 1, 2, or 4 days. The carrots were stored at 0 °C for up to 24 weeks and evaluated every 4 weeks for resistance to challenge inoculations of Botrytis cinerea and Sclerotinia sclerotiorum. Quality attributes and stress and flavor volatiles were also quantified. Decay resistance to B. cinerea was induced by treatments with 1000 nL L⁻¹ ozone for 2 or 4 days, however no lasting resistance to S. sclerotiorum was induced. Firmness was reduced in carrots treated with either 300 or 1000 nL L⁻¹ ozone for 4 days. Treatment with ozone for 1, 2, or 4 days resulted in 60–90% greater respiration rates than controls, but this effect diminished within 4 weeks of storage. Ozone treatments stimulated the production of the stress volatiles ethanol and hexanal, which were, respectively, 43- and 11-times greater than the controls immediately after a 4-day exposure to 1000 nL L⁻¹, but this effect diminished with storage time. Sucrose concentrations were reduced, but terpene concentrations were increased. Treatment with 1-MCP reduced B. cinerea resistance induced by the ozone treatments. Respiration rates, loss of sucrose, and increase in glucose and fructose during storage were also reduced by 1-MCP treatment. Treatment with 1-MCP had no effect on weight loss or firmness. In general, the concentrations of pre-storage ozone that induced resistance to B. cinerea also reduced carrot quality and therefore are not likely of commercial value.     

Impact of a decontamination step with peroxyacetic acid on the shelf-life,sensory quality and nutrient content of grated carrots packed under equilibrium modified atmosphere and stored at 7 °C

Peroxyacetic acid (PAA) is a strong oxidizer and exerts antimicrobial properties. The effect of a decontamination step with 80 and 250 mg L⁻¹ PAA on shelf-life of grated carrots stored under equilibrium modified atmospheric packaging at 7 °C was determined and compared with the shelf-life of unwashed and water-washed carrots. Microbial parameters, including total aerobic plate count, numbers of lactic acid bacteria, Lactobacillae and yeasts, and sensory quality were evaluated. Next to these parameters, atmospheric gas composition, pH and nutrient content were also monitored. The suggested packaging configuration prevented CO₂ accumulation, but at the end of the study anoxic conditions were reached for unwashed carrots and carrots washed with 80 mg L⁻¹ PAA. The microbial shelf-life of water-washed carrots was 4 d based on the yeast count, whereas the flavour was not acceptable after 5 d. The total aerobic plate count and the yeast count determined the shelf-life of carrots treated with 80 mg L⁻¹ PAA on 5 d, whereas the flavour was unacceptable after 7 d. None of the microbial parameters determined the shelf-life of carrots washed with 250 mg L⁻¹ PAA. However, this treatment had already a pronounced adverse effect on the initial sensory quality. Water washing already decreased the content of all individually studied nutrients (−16 to −28%), except for lutein content and the antioxidant capacity. Additional losses after adding PAA on day 0 were found for α-tocopherol and phenols. Regardless of the applied treatment, α- and β-carotene remained stable during storage, whereas ζ-carotene, lutein and α-tocopherol were unstable. The phenol content and the antioxidant capacity of unwashed, water-washed and 80 mg L⁻¹ PAA-treated carrots increased significantly at the end of the storage period, whereas no changes were found in carrots treated with 250 mg L⁻¹ PAA.On the condition that carrots were packed under an adequate EMA, the 80 mg L⁻¹ PAA treatment showed possibilities for extending shelf-life without pronounced effects on nutrient content.     

Essential oils and silver nanoparticles (SNP) as novel agents to extend vase-life of gerbera (Gerbera jamesonii cv. ‘Dune’) flowers

The aim of this study was to evaluate the efficacy of silver nanoparticles (SNP) and essential oils as novel antimicrobial agents in extending the vase-life of gerbera (Gerbera jamesonii cv. ‘Dune’) flowers. The vase-life of flowers held in a solution containing 5 mg L⁻¹ SNP plus 6% sucrose was found to be significantly higher than with 8-HQC (8-hydroxyquinoline citrate) or control treatments. However, the vase-life was not different to that of flowers held in similar concentrations of silver nitrate. All gerbera flowers held in SNP solutions showed significantly higher relative fresh weight than the control. Vase-life of gerbera flowers was extended by addition of either 50 or 100 mg L⁻¹ carvacrol and either 1 or 2 mg L⁻¹ SNP from 8.3 to 16 d. In addition, the relative fresh weight and solution uptake of gerbera flowers were increased by addition of 100 mg L⁻¹ essential oils and 1 or 2 mg L⁻¹ SNP as compared to that of control flowers. Our results suggest the potential application of essential oils or SNP as novel alternatives to common chemicals used in preservative solutions for gerbera flowers.     

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.     

Combination of peracetic acid and hot water treatment to control postharvest brown rot on peaches and nectarines

Brown rot caused by Monilinia spp. is the most important postharvest disease of stone fruit. From preliminary studies, the combination of 0.25% hydrogen peroxide, 0.02% peracetic acid (PAA) and 0.075% acetic acid, corresponding to 300 mg L⁻¹ of PAA, was selected to control Monilinia fructicola. Brown rot control was similarly controlled when the same concentration of PAA was applied with a PAA-based commercial product. In order to reduce PAA concentration, combinations of different concentrations and temperatures were evaluated. A treatment of 200 mg L⁻¹ of PAA at 40 °C for 40 s was selected to control pre-existing and future infections, different inoculum concentrations of M. fructicola and to control brown rot on naturally infected fruit. Brown rot was completely controlled with the selected treatment when peaches and nectarines were inoculated 0 h before the treatment but it was not controlled when infection time was increased to 24, 48 and 72 h. Also, the treatment significantly controlled brown rot at all inoculum concentrations evaluated (10³, 10⁴, 10⁵ and 10⁶ conidia mL⁻¹) in both peaches and nectarines, but no protection against future infections was observed. In naturally infected fruit, brown rot incidence was slightly but significantly reduced to 61 and 36% in ‘Roig d’Albesa’ and ‘Placido’ peaches, respectively, but not in nectarines. Immersion for 40 s in 200 mg L⁻¹ of PAA at 40 °C provides an alternative treatment to control only recent infections of Monilinia spp. whatever their concentration without generally affecting fruit quality.     

Development of SCAR markers and a semi-selective medium for the quantification of strains Ach 1-1 and 1113-5, two Aureobasidium pullulans potential biocontrol agents

Aureobasidium pullulans strains Ach 1-1 and 1113-5 are two effective biocontrol agents against Botrytis cinerea and Penicillium expansum on stored apples. In the present work, a monitoring system allowing their identification and quantification was developed. The methodology used consisted of the development of both molecular markers and a semi-selective medium. The random amplified polymorphic DNA (RAPD) technique was applied to a collection of 15 strains of A. pullulans, including Ach 1-1 and 1113-5. Five specific RAPD fragments were amplified for strain Ach 1-1 and three others for strain 1113-5. Among them, a fragment of 528 bp specific to strain Ach 1-1 (generated with the OPR-13 RAPD primer) and another one of 431 bp specific to strain 1113-5 (amplified with the OPQ-03 RAPD primer) were selected, cloned, sequenced, and used to design sequence-characterized amplified region (SCAR) primers. Three different SCAR markers were amplified: two specific to strain Ach 1-1 (189 bp and 387 bp) and one specific to strain 1113-5 (431 bp). These SCAR primers can clearly identify strains Ach 1-1 and 1113-5 among 14 strains of A. pullulans and among eight yeast strains commonly present on apple fruit surfaces. Their selectivity was also tested using DNA extracted from epiphytic microflora of the apple surface. As a semi-selective medium, PDA medium supplemented with 0.5 mg L⁻¹ euparen, 1 mg L⁻¹ sumico, 2.5 mg L⁻¹ hygromycin B, 30 mg L⁻¹ streptomycin sulphate, and 1 mg L⁻¹ cycloheximide was selected. It inhibited the development of the air microflora and appeared highly toxic for the epiphytic microflora of apple surface without altering the growth of the targeted strains Ach 1-1 and 1113-5. The combination of the semi-selective medium and SCAR markers provides a valuable monitoring tool to specifically identify and quantify A. pullulans strain Ach 1-1 and strain 1113-5 and could be used in future studies to evaluate their population dynamics under various laboratory and practical conditions.     

Effects of phosphine fumigation on postharvest quality of four Chinese cut flower species

Chrysanthemum (White, Yellow, and Daisy), carnation (Master and Barbara), rose (Carola, Black magic, Diana, Champagne, and Avalanche), and Chinese rose (Golden Medallion, Diplomat, Marina, and Athena) are the main Chinese cut flower species produced for exportation. Cut flowers infested with quarantine pests need methyl bromide (MB) fumigation to satisfy phytosanitary requirements of importing countries. Phosphine (PH₃) is a potential alternative to methyl bromide. Development of phosphine as a phytosanitary treatment requires information regarding its phytotoxicity to cut flowers. Therefore phosphine fumigation at 24 °C and 2 °C was investigated to evaluate its effects on the postharvest quality of cut flowers. Phosphine fumigation for 6 h with dosages as high as 12.2 mg L⁻¹ at 24 °C produced no adverse effects on flower color, diameter, vase life, and other damage indices (DI) for all cultivars. However, different adverse effects on some cultivars were observed after 12 d fumigation at 2 °C. There were significant changes for color values of Carola, Black magic, Diana, Champagne, Avalanche, and Diplomat; significant decrease in flower diameter and vase life of Diana, Champagne, and Avalanche at 3.04 mg L⁻¹, white Chrysanthemum and Diploma at 1.52 and 3.04 mg L⁻¹; significant increase in DI of Champagne and Avalanche at 3.04 mg L⁻¹, and White chrysanthemum, Diana, and Diploma at 1.52 and 3.04 mg L⁻¹. In combination with information on phosphine toxicity to insect pests at ambient and low temperatures in the literature, it is suggested that phosphine fumigation could be a viable replacement of MB fumigation for quarantine treatment of these four cut flower species.     

Energy efficiency of potato production practices for bioethanol feedstock in northern Japan

In 2007–2009, field experiments were conducted to identify agronomic practices affording the lowest energy inputs (i.e. total energy inputs from fuels and other agricultural material inputs required to produce 1 L of ethanol) under potato-based bioethanol feedstock production in northern Japan. On a hectare basis, for a standard 4.4 m⁻² planting density, conventional practices [two inter-row cultivations (weeding and preparation for ridging) and final ridging] yielded an estimate of 4.85 kL ha⁻¹, representing an energy input of 5.86 MJ L⁻¹. The energy input savings arising from the lesser fuel consumption associated with fewer tractor operations under no- and low-ridge cropping practices were outweighed by a reduction in ethanol yields, resulting in slightly greater energy inputs (6.09 ± 0.65 and 5.89 ± 0.30 MJ L⁻¹, respectively). Similarly, poorer ethanol yields outweighed the reduction in energy inputs arising from lessened seed potato production-associated energy inputs under lowered planting densities of 3.8 and 3.3 m⁻², resulting in ethanol yield-based energy inputs of 5.98 ± 0.33 and 6.01 ± 0.41 MJ L⁻¹, respectively. Omitting fungicide applications significantly lowered biocide-related energy inputs, but yielded 20 and 63% lower ethanol yields for Phytophthora-resistant and -susceptible genotypes, respectively, substantially worsening energy efficiencies (6.24 ± 0.42 and 12.2 ± 6.3 MJ L⁻¹). In northern Japan, use of high starch-yielding genotypes served as the only way to increase ethanol yields and improve energy efficiency for potatoes used in bioethanol feedstock production. A 29% greater ethanol yield (6.26 ± 0.46 kL ha⁻¹) and 21% better energy efficiency (4.63 ± 0.23 MJ L⁻¹) were achieved by replacing the standard potato cultivar with a high starch-yielding variety. The yield-based energy inputs with a high starch-yielding potato variety were significantly lower than those with conventional sugar beet in northern Japan (5.82 MJ L⁻¹).     

Gamma irradiation increases storability and shelf life of minimally processed ready-to-cook (RTC) ash gourd (Benincasa hispida) cubes

Radiation treatment in a dose range of 0.5–2.5 kGy in combination with low temperature storage (4–15 °C) was attempted for improvement in shelf life of ready-to-cook (RTC) ash gourd (Benincasa hispida). Parameters such as microbial load, color, firmness and sensory attributes were monitored during storage. Optimum processing conditions (2 kGy; 10 °C) resulted in improved shelf life of seven days compared to the non-irradiated controls. Total bacterial count of 1.57 × 10³ CFU/g was recorded at the end of storage period (12 d). Higher total phenolic content and total antioxidant activity was observed in irradiated samples as compared to control. Irradiated samples had total phenolic content of 103.3 ± 5.2 mg kg⁻¹ and total antioxidant activity of 384.2 ± 9.7 mg kg⁻¹ while corresponding values for control samples were 67.8 ± 5.4 and 115.5 ± 7.0 mg kg⁻¹ at the end of storage period. Irradiated samples (2 kGy) showed excellent sensory and visual qualities during entire storage period.     

Low temperature phosphine fumigation for postharvest control of Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) on carnation

Phosphine (PH₃) fumigation with different concentrations and exposure durations at low temperature was studied to determine its effects on Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) on carnations, and on postharvest quality. Laboratory tests showed that tolerance of L. huidobrensis to phosphine fumigation at 5 °C varied with different life stages. 1 d-old eggs and adults showed the highest susceptibility, and 3 d-old eggs was the most tolerant stage. In the fumigation tests of 3 d-old eggs with a range of phosphine concentrations from 0.46 to 2.73 mg L⁻¹ and exposure durations from 6 to 144 h at 5 °C, 85.96–282.08 h fumigation durations were required to achieve 99% mortality with different phosphine concentrations. The expression of C^0.77T = k was obtained, which indicated that exposure duration other than phosphine concentration was the critical factor in the toxicity of phosphine against the 3 d-old eggs of L. huidobrensis. Controlled atmosphere (CA) treatment with increased CO₂ and reduced O₂ had synergistic effects on phosphine toxicity. Phosphine fumigation could achieve 100% mortality for insects of L. huidobrensis on carnation, and had no significant adverse effects on vase life and damage indices of carnation at 1.92 mg L⁻¹ PH₃ and 8% CO₂ for 32 h, and at 3.44 mg L⁻¹ for 3 d at 5 °C. All results suggested that phosphine fumigation at low temperature could be used as an alternative for postharvest control of L. huidobrensis on carnations.     

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.     

Effects of ozone on sugar beet grown in open-top chambers

Sugar beet (Beta vulgaris cv. Patriot) plants were grown on field plots and in open-top chambers (OTCs) in two successive years. In the OTC treatments, plants were exposed to charcoal filtered air, unfiltered air or unfiltered air enriched with additional ozone (O₃). Ozone exposure continued for almost 5 months and the 8-h average concentration was raised from 34 to 39 nL L⁻¹ in the ambient air chambers to 62 nL L⁻¹ in the ozone enriched chambers. In both years, the AOT40 exposure index in the ozone enriched chambers exceeded 30 μL L⁻¹ h during the 5-month exposure period compared to 6.5 and 2.9 μL L⁻¹ h in ambient air in 2003 and 2004, respectively. Visible symptoms in the form of small white necrotic flecks appeared in both seasons in the ozone enriched chambers. When the data for both years were analysed statistically, a significant reduction of root yield of 6% and a slight reduction of sugar content were detected. These changes resulted in an overall reduced sugar yield ha⁻¹ of about 9%. Although the sensitivity of sugar beet to ozone is highly variety-dependent, in general this biennial crop appears less sensitive than annual crops such as wheat and potato. Ozone has limited effects on quality parameters in sugar beet, although an increase in α-amino-N content was observed, in agreement with the increased nitrogen content resulting from ozone exposure of wheat and potato.Enclosure within the OTCs increased aboveground biomass but decreased root yield (fresh biomass) and sugar content. These effects were most likely caused by a reduction of radiation by the chamber walls and annulus. The increased temperature in the chambers reduced yield quality by increasing mineral content.     

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.     

The combined effects of aqueous chlorine dioxide,fumaric acid,and ultraviolet-C with modified atmosphere packaging enriched in CO2 for inactivating preexisting microorganisms and Escherichia coli O157:H7 and Salmonella typhimurium inoculated on buckwheat sprouts

The combined effects of a sanitizer mixture, ultraviolet-C (UV-C), and modified atmosphere packaging (MAP) on the quality of non-inoculated and inoculated (Escherichia coli O157:H7 and Salmonella typhimurium) buckwheat sprouts were examined. Buckwheat sprouts were treated with a sanitizer mixture (comprising 100 mg L⁻¹ aqueous ClO₂ and 0.3% fumaric acid) and 2 kJ m⁻² UV-C, packaged under two different conditions (air and CO₂ gas) and storage for 8 d at 4 °C. The combination of the sanitizer mixture and UV-C treatment reduced the initial counts of preexisting microorganisms in the buckwheat sprouts by 1.9 log CFU g⁻¹ and reduced the initial inoculated counts of E. coli O157:H7 and S. typhimurium on buckwheat sprouts by 3.0 and 2.3 log CFU g⁻¹, respectively. The preexisting microorganisms and inoculated pathogens in buckwheat sprouts packaged under CO₂ gas were significantly reduced during storage following the combined treatment compared to those of the control by above 95%. Differences in Hunter L^*, a^*, and b^* values among the treatments were negligible. The combined sanitizer mixture and UV-C treatment increased the sprout rutin content by 147%, but there was no significant difference in 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity between treatments during storage. Therefore, the combination of sanitizer mixture made from aqueous ClO₂ and fumaric acid, UV-C irradiation, and MAP can improve the microbial safety and quality of buckwheat sprouts.     

Influence of fumigation with high concentrations of ozone gas on postharvest gray mold and fungicide residues on table grapes

To control postharvest decay, table grapes are commercially fumigated with sulfur dioxide. We evaluated ozone (O₃) fumigation with up to 10,000 μL L^?1 of ozone for up to 2 h to control postharvest gray mold of table grapes caused by Botrytis cinerea. Fumigation for 1 h with 2500 or 5000 μL L^?1 of ozone were equal in effectiveness. Both treatments reduced postharvest gray mold among inoculated ‘Thompson Seedless’ grapes by approximately 50% when the grapes were examined after storage for 7 d at 15 °C following fumigation. In a similar experiment, ‘Redglobe’ grapes were stored for 28 d at 0.5 °C following fumigation for 1 h with 2500 or 5000 μL L^?1 of ozone. Both treatments were equal in effectiveness, but inferior to fumigation with 10,000 μL L^?1. Ozone was effective when grapes were inoculated and incubated at 15 °C up to 24 h before fumigation. The cluster rachis sustained minor injuries in some tests, but berries were never harmed. Ozone was applied in three combinations of time and ozone concentration (10,000 μL L^?1 for 30 min, 5000 μL L^?1 for 1 h, and 2500 μL L^?1 for 2 h) where each had a constant concentration × time product (c × t) of 5000 μL L^?1 × h. The effectiveness of each combination was similar. The incidence of gray mold was reduced by approximately 50% among naturally inoculated, organically grown ‘Autumn Seedless’ and ‘Black Seedless’ table grapes, and by 65% among ‘Redglobe’ table grapes, when they were fumigated with 5000 μL L^?1 ozone for 60 min in a commercial ozone chamber and stored for 6 weeks at 0.5 °C. Residues of fenhexamid, cyprodinil, pyrimethanil, and pyraclostrobin were reduced by 68.5, 75.4, 83.7, and 100.0%, respectively, after a single fumigation of table grapes with 10,000 μL L^?1 ozone for 1 h. Residues of iprodione and boscalid were not significantly reduced. Ozone is unlikely to replace sulfur dioxide treatments in conventional grape production unless its efficacy is improved, but it could be an acceptable technology to use with grapes marketed under “organic” classification, where the use of SO₂ is prohibited, or if SO₂ use were to be discontinued.     

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.     

Respiration rate response of four baby leaf Brassica species to cutting at harvest and fresh-cut washing

The influence of the first and second cutting at harvest on the physiological response of four baby leaf Brassica species was studied. The species were salad rocket (Eruca vesicaria), wild rocket (Diplotaxis tenuifolia), mizuna (Brassica rapa L. ssp. nipposinica) and watercress (Nasturtium officinale) stored at 1, 4, 8 and 12 °C. In addition, the microbial and metabolic behaviours of baby leaves were evaluated after different washing treatments including water, ozonated water (10 mg L⁻¹ total dose), ozonated water activated with ultraviolet C light (UV-C) and heat shock wash (50 °C, 1 min). Temperature had a significant effect on both respiration rate and post-cutting life. The production of CO₂ increased between 2- and 4-fold when temperature increased from 1 to 12 °C. Minor differences in leaf respiration rate between the first and second leaf cutting were observed for salad rocket and wild rocket, while leaves from the second cutting of mizuna and watercress leaves had a higher respiration rate than from the first cutting. Ozone, and ozone combined with UV-C, were the most efficient washing treatments in reducing total mesophilic counts, while heat shock treatment did not affect them. Additionally, naturally occurring Listeria spp. were controlled well in wild rocket and mizuna (<1 log cfu g⁻¹) when the ozone treatments were applied. On the other hand, respiration rates of the Brassica species were not substantially affected by the washing treatments when stored at 4 °C. Maximum CO₂ production was observed immediately after washing but decreased during the first 24 h of storage. Baby leaves washed with cold water consistently showed a lower respiration rate than the other washing treatments. Heat shock was the washing treatment that most influenced the increase in the respiration rate of baby leaves during storage at 8 °C.     

Postharvest nitric oxide fumigation delays fruit ripening and alleviates chilling injury during cold storage of Japanese plums (Prunus salicina Lindell)

We investigated the effects of nitric oxide (NO) fumigation on fruit ripening, chilling injury, and quality of Japanese plums cv. ‘Amber Jewel’. Commercially mature fruit were fumigated with 0, 5, 10, and 20 μL L⁻¹ NO gas at 20 °C for 2 h. Post-fumigation, fruit were either allowed to ripen at 21 ± 1 °C or were stored at 0 °C for 5, 6, and 7 weeks followed by ripening for 5 d at 21 ± 1 °C. NO-fumigation, irrespective of concentration applied, significantly (P ≤ 0.5) suppressed respiration and ethylene production rates during ripening at 21 ± 1 °C. At 21 ± 1 °C, the delay in ripening caused by NO-fumigation was evident from the restricted skin colour changes and retarded softening in fumigated fruit. NO treatments (10 and 20 μL L⁻¹) delayed the decrease in titratable acidity (TA) without a significant (P ≤ 0.5) effect on soluble solids concentration (SSC) during ripening. During 5, 6, and 7 weeks of storage at 0 °C, NO-fumigation was effective towards restricting changes in the ripening related parameters, skin colour, firmness, and TA. The individual sugar (fructose, glucose, sucrose, and sorbitol) profiles of NO-fumigated fruit were significantly different from those of non-fumigated fruit after cold storage and ripening at 21 ± 1 °C. CI symptoms, manifest in the form of flesh browning and translucency, were significantly lower in NO-fumigated fruit than in non-fumigated fruit after 5, 6, and 7 weeks storage followed by ripening for 5 d at 21 ± 1 °C. NO-fumigation was effective in reducing decay incidence in plums during ripening without storage and after cold storage at 0 °C for 5, 6, and 7 weeks. In conclusion, the postharvest exposure of ‘Amber Jewel’ plums to NO gas (10 μL L⁻¹) delayed ripening by 3–4 d at 21 ± 1 °C, and also alleviated chilling injury symptoms during cold storage at 0 °C for 6 weeks.