Hydroxypropyl Methylcellulose and Gum Arabic Composite Edible Coatings Amended with Geraniol to Control Postharvest Brown Rot and Maintain Quality of Cold-Stored Plums.

In this study, the effect of hydroxypropyl methylcellulose (HPMC) and gum Arabic (GA) edible coatings amended with 0.2% geraniol (GE) were evaluated for the control of brown rot, caused by Monilinia fructicola, on artificially inoculated plums (Prunus salicina Lindl., cv. Angeleno) stored for 5 weeks at 1 °C. Brown rot is the most important pre- and postharvest fungal disease of stone fruits, causing severe economic losses worldwide. Geraniol is an important constituent of many essential oils that can be obtained as a byproduct from different industrial procedures, such as those of the juice industry. Fruit postharvest quality was also evaluated after 5 and 8 weeks of storage at 1 °C, followed by 3 days at 7 °C plus 5 days at 20 °C, simulating packinghouse, transport, and retail shelf-life conditions, respectively. HPMC coatings containing 0.2% GE reduced the incidence and severity of brown rot by 37.5 and 64.8%, respectively, compared to uncoated fruit after 5 weeks of storage at 1 °C. HPMC-coated plums, with and without GE, showed the highest level of firmness, the lowest change in external peel color parameters (L*, a*, b*, C*, hue), and the lowest flesh bleeding compared to uncoated control and GA-coated samples throughout the entire storage period, which correlated with a higher gas barrier of these coatings without negatively affecting sensory quality. Furthermore, the HPMC-0.2% GE coating provided the highest gloss to coated plums, showing the potential of this coating as a safe and environmentally friendly alternative to conventional fungicides and waxes for brown rot control and quality maintenance of cold-stored plums.

Natural Pectin-Based Edible Composite Coatings with Antifungal Properties to Control Green Mold and Reduce Losses of 'Valencia' Oranges.

Novel pectin-based, antifungal, edible coatings (ECs) were formulated by the addition of natural extracts or essential oils (EOs), and their ability to control green mold (GM), caused by Penicillium digitatum, and preserve postharvest quality of 'Valencia' oranges was evaluated. Satureja montana, Cinnamomum zeylanicum (CN), Commiphora myrrha (MY) EOs, eugenol (EU), geraniol (GE), vanillin, and propolis extract were selected as the most effective antifungal agents against P. digitatum in in vitro assays. Pectin-beeswax edible coatings amended with these antifungals were applied to artificially inoculated oranges to evaluate GM control. ECs containing GE (2 g/kg), EU (4 and 8 g/kg), and MY EO (15 g/kg) reduced disease incidence by up to 58% after 8 days of incubation at 20 °C, while CN (8 g/kg) effectively reduced disease severity. Moreover, ECs formulated with EU (8 g/kg) and GE (2 g/kg) were the most effective on artificially inoculated cold-stored oranges, with GM incidence reductions of 56 and 48% after 4 weeks at 5 °C. Furthermore, ECs containing EU and MY reduced weight loss and maintained sensory and physicochemical quality after 8 weeks at 5 °C followed by 7 days at 20 °C. Overall, ECs with EU were the most promising and could be a good natural, safe, and eco-friendly commercial treatment for preserving orange postharvest quality.

Postharvest Treatments with Sulfur-Containing Food Additives to Control Major Fungal Pathogens of Stone Fruits.

The sulfur-containing salts, classified as food additives, sodium metabisulfite (SMBS), potassium metabisulfite (PMBS), aluminum sulfate (AlS), and aluminum potassium sulfate (AlPS), were evaluated for their activity against Monilinia fructicola, Rhizopus stolonifer, and Geotrichum candidum, the most economically important fungal pathogens causing postharvest disease of stone fruit. In in vitro tests with potato dextrose agar (PDA) Petri dishes amended with different concentrations of the salts (0, 10, 20, 30, 50, and 100 mM), SMBS and PMBS at all concentrations, AlS above 20 mM, and AlPS above 30 mM, completely inhibited the mycelial growth of the three fungi after incubation at 25 °C for up to 10 days. In in vivo primary screenings with artificially inoculated nectarines, aqueous solutions of the four salts reduced the incidence and severity of brown rot (BR) at concentrations of 10 and 50 mM, whereas only AlS and AlPS reduced Rhizopus rot (RR), and none of the salts was effective against sour rot (SR). Solutions at 100 mM were phytotoxic and injured the fruit peel. In small-scale trials, 1 min dip treatments at 20 °C in SMBS or PMBS at 10 mM significantly reduced the incidence and severity of BR after incubation at 20 °C for up to 8 days. Conversely, dips in AlS and AlPS reduced neither BR nor RR. Results highlight the potential of SMBS and PMBS as new nonpolluting tools for the integrated control of BR, but not RR and SR, on stone fruit.

Curative activity of postharvest GRAS salt treatments to control citrus sour rot caused by Geotrichum citri-aurantii.

The effectiveness of the "generally recognized as safe" (GRAS) salts potassium sorbate (PS), sodium benzoate (SB), sodium ethylparaben (SEP) and sodium methylparaben (SMP) to control sour rot, caused by Geotrichum citri-aurantii, was assessed by dipping economically important citrus species and cultivars in aqueous solutions for 30, 60 or 150 s at 20 °C, followed by examination after 8 d of storage at 28 °C. Curative activity was determined because the fruit were inoculated 24 h prior to treatment. Dipping fruit for 60 s in SMP (200 mM), SEP (200 mM) or SB (3% w/v) were very effective and reduced sour rot incidence and severity by up to 90%. Their effectiveness was similar or superior to that of the conventional fungicide propiconazole (PCZ). In contrast, PS (200 mM) did not control sour rot on 'Oronules' or 'Ortanique' mandarins, but it reduced sour rot incidence on 'Barnfield' oranges by 50% compared to inoculated, water-treated control fruit. Sour rot was better controlled on oranges than on mandarins. Furthermore, heating the solutions to 50 °C enhanced their effectiveness, while post-treatment rinsing of the fruit with tap water reduced their effectiveness. Dipping 'Valencia Late' oranges in SB (3% w/v) or SMP (200 mM) for 60 s followed by long storage for up to 8 weeks at 5 °C and 90% RH, reduced sour rot incidence from 55% among water-treated control fruit to 2 to 6%, and matched the effectiveness of PCZ. No fruit in any test were visibly harmed. Both SB and SMP salts could be potential alternatives to conventional fungicides, such as PCZ or guazatine, for the integrated postharvest management of citrus sour rot.

Control of major citrus postharvest diseases by sulfur-containing food additives.

Sodium metabisulfite (SMBS), potassium metabisulfite (PMBS), aluminum sulfate (AlS) and aluminum potassium sulfate (AlPS), common sulfur-containing salts used as food additives, were evaluated for their antifungal activity against Penicillium digitatum, Penicillium italicum and Geotrichum citri-aurantii, the most economically important pathogens causing postharvest diseases of citrus fruits. In vitro radial mycelial growth was measured on potato dextrose agar (PDA) Petri dishes amended with five different concentrations of the salts (10, 20, 30, 50, 100 mM) after 7 d of incubation at 25 °C. SMBS and PMBS at all concentrations, and AIS and AIPS above 20 mM, completely inhibited the growth of these fungi. The curative antifungal activity of the four salts to control citrus green (GM) and blue (BM) molds and sour rot (SR) was evaluated on 'Valencia' oranges artificially inoculated in rind wounds with P. digitatum, P. italicum and G. citri-aurantii, respectively. In vivo primary screenings showed no significant antifungal activity of AlS and AlPS to control the three diseases at any dose tested, but SMBS and PMBS reduced the incidence and severity of GM, BM and SR at various concentrations. Effective salts and concentrations were selected for in vivo dip treatments in small-scale trials. Dips at room temperature (20 °C) in SMBS and PMBS at 20 and 50 mM for 60 or 120 s significantly reduced the incidence and severity of GM and BM, with PMBS at 50 mM for 120 s the most effective treatment. Conversely, dips in SMBS and PMBS at 50 mM for 60 or 120 s did not reduce SR incidence and severity. SMBS and PMBS treatments are potentially new tools to be included in reduced-risk non-polluting strategies to control Penicillium diseases, but not SR, on citrus fruits.

Short-Term Exposure to High CO2 and O2 Atmospheres to Inhibit Postharvest Gray Mold of Pomegranate Fruit.

The effect of short-term exposure to high CO2 or O2 atmospheres, alone or in combination with heat (35°C), for the control of postharvest gray mold was evaluated on 'Mollar de Elche' pomegranate fruit artificially inoculated with Botrytis cinerea and stored at 20 or 5°C. Exposure to high CO2 for 48 h at 20°C effectively reduced gray mold on pomegranate fruit incubated at 20°C for 5 days in a concentration-based manner. Furthermore, gaseous treatments with partial pressures of 95 kPa CO2 or 30 kPa O2 + 70 kPa CO2 for 48 h significantly reduced gray mold incidence and severity on fruit regardless of storage temperature. Moreover, for fruit receiving gaseous treatments at 20°C then cold stored for 12 weeks, there were no apparent negative effects of the treatments on their quality (weight loss, skin color, maturity index, pH, and sensory quality). In general, compared with those applied at 20°C, treatments at 35°C did not improve gray mold inhibition and adversely affected some quality parameters. In conclusion, 48-h exposures to specific atmospheres at 20°C may be a suitable treatment to extend pomegranate storage life and could be part of integrated control programs to control postharvest decay.

Incidence and Etiology of Postharvest Fungal Diseases of Persimmon (Diospyros kaki Thunb. cv. Rojo Brillante) in Spain.

'Rojo Brillante' is currently the most important persimmon cultivar in Spain. The incidence and etiology of postharvest diseases affecting this cultivar were determined under local conditions. Latent and wound pathogens were assessed for two consecutive seasons on commercially grown persimmons from two orchards. Healthy persimmons were either surface-disinfested or artificially wounded on the rind and placed in humid chambers at 20 or 25°C for up to 9 weeks. Additionally, decay was assessed on commercially handled persimmons stored at 1°C for up to 20 weeks. In all cases, the most frequent disease was alternaria black spot (ABS) caused by Alternaria alternata and an ABS severity index specific for 'Rojo Brillante' persimmons was established. Other minor pathogens causing latent infections, mostly stem-end rots, included Botrytis cinerea, Lasiodiplodia theobromae, Neofusicoccum spp., Pestalotiopsis clavispora, and Colletotrichum gloeosporioides. Penicillium expansum and, to much a lesser extent, Cladosporium cladosporioides were other pathogens causing wound infections. These two fungi and A. alternata and B. cinerea were also isolated from cold-stored fruit. Common isolates were identified by macroscopic and microscopic morphology and/or DNA amplification and sequencing. Pathogenicity of selected isolates was demonstrated by fulfilling Koch's postulates. Disease development at 20 and 5°C was characterized on artificially inoculated persimmons.

Evaluating food additives as antifungal agents against Monilinia fructicola in vitro and in hydroxypropyl methylcellulose-lipid composite edible coatings for plums.

Common food preservative agents were evaluated in in vitro tests for their antifungal activity against Monilinia fructicola, the most economically important pathogen causing postharvest disease of stone fruits. Radial mycelial growth was measured in Petri dishes of PDA amended with three different concentrations of the agents (0.01-0.2%, v/v) after 7 days of incubation at 25 °C. Thirteen out of fifteen agents tested completely inhibited the radial growth of the fungus at various concentrations. Among them, ammonium carbonate, ammonium bicarbonate and sodium bicarbonate were the most effective while sodium acetate and sodium formate were the least effective. The effective agents and concentrations were tested as ingredients of hydroxypropyl methylcellulose (HPMC)-lipid edible coatings against brown rot disease on plums previously inoculated with M. fructicola (curative activity). 'Friar' and 'Larry Ann' plums were inoculated with the pathogen, coated with stable edible coatings about 24h later, and incubated at 20 °C and 90% RH. Disease incidence (%) and severity (lesion diameter) were determined after 4, 6, and 8 days of incubation and the 'area under the disease progress stairs' (AUDPS) was calculated. Coatings containing bicarbonates and parabens significantly reduced brown rot incidence in plums, but potassium sorbate, used at 1.0% in the coating formulation, was the most effective agent with a reduction rate of 28.6%. All the tested coatings reduced disease severity to some extent, but coatings containing 0.1% sodium methylparaben or sodium ethylparaben or 0.2% ammonium carbonate or ammonium bicarbonate were superior to the rest, with reduction rates of 45-50%. Overall, the results showed that most of the agents tested in this study had significant antimicrobial activity against M. fructicola and the application of selected antifungal edible coatings is a promising alternative for the control of postharvest brown rot in plums.