RESUMO

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.

RESUMO

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.

Assuntos

RESUMO

A large amount of GRAS (generally recognized as safe) salts and concentrations were evaluated in in vitro tests (inhibition of mycelial growth on PDA dishes) against Lasiodiplodia theobromae, the causal agent of citrus Diplodia stem-end rot. Ammonium carbonate (AC, 0.2%), potassium sorbate (PS, 2.0%), potassium carbonate (PC, 0.2%), sodium methylparaben (SMP, 0.1%), sodium ethylparaben (SEP, 0.1%), sodium benzoate (SB, 2.0%), and potassium silicate (PSi, 2.0%) were selected as the most effective. Disease control ability of edible composite coatings formulated with hydroxypropyl methylcellulose (HPMC), beeswax (BW), and these selected antifungal GRAS salts was assessed in in vivo experiments with 'Ortanique' mandarins and 'Barnfield' oranges artificially inoculated with L. theobromae. Coatings containing 2% PS, 0.1% SEP, or 2% SB were the most effective reducing disease severity (up to 50% reduction) and were also applied to non-inoculated and cold-stored 'Barnfield' oranges to determine their effect on postharvest fruit quality. After periods of 21 and 42 d at 5 °C followed by 7 d of shelf life at 20 °C, coatings containing SEP and SB significantly reduced weight loss and did not adversely affect the physicochemical quality attributes (firmness, soluble solid content, titratable acidity, and ethanol and acetaldehyde content) and sensory flavor with respect to uncoated control fruit. Although the internal gas concentration (CO2 level) of coated fruit increased, the coatings did not induce off-flavors.

Assuntos

RESUMO

Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores.

Assuntos

RESUMO

The antifungal activity of food additives or 'generally recognized as safe' (GRAS) compounds was tested in vitro against Botrytis cinerea and Alternaria alternata. Radial mycelial growth of each pathogen was measured in PDA Petri dishes amended with food preservatives at 0.2, 1.0, or 2.0% (v/v) after 3, 5, and 7 days of incubation at 25 °C. Selected additives and concentrations were tested as antifungal ingredients of hydroxypropyl methylcellulose (HPMC)-lipid edible coatings. The curative activity of stable coatings was tested in in vivo experiments. Cherry tomatoes were artificially inoculated with the pathogens, coated by immersion about 24 h later, and incubated at 20 °C and 90% RH. Disease incidence and severity (lesion diameter) were determined after 6, 10, and 15 days of incubation and the 'area under the disease progress stairs' (AUDPS) was calculated. In general, HPMC-lipid antifungal coatings controlled black spot caused by A. alternata more effectively than gray mold caused by B. cinerea. Overall, the best results for reduction of gray mold on cherry tomato fruit were obtained with coatings containing 2.0% of potassium carbonate, ammonium phosphate, potassium bicarbonate, or ammonium carbonate, while 2.0% sodium methylparaben, sodium ethylparaben, and sodium propylparaben were the best ingredients for coatings against black rot.

Assuntos