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.

Short Exposure to High CO2 and O2 at Curing Temperature to Control Postharvest Diseases of Citrus Fruit.

Curing of citrus fruit at 30 to 37°C and 90 to 98% relative humidity for 65 to 72 h is an effective alternative to fungicides to control postharvest green and blue molds caused by Penicillium digitatum and P. italicum, respectively. However, commercial adoption is limited because treatment is long and it may harm fruit quality. In order to improve the feasibility of curing, short CO2 or O2 exposures at curing temperature were evaluated on 'Nadorcott', 'Clemenules', and 'Ortanique' mandarin fruit and 'Valencia' orange. Fruit were artificially inoculated, exposed 24 h later to air (control); CO2 at 15, 30, 50, or 95 kPa; or O2 at 30 or 45 kPa at 20 or 33°C for 8, 24, or 48 h and incubated at 20°C for 4, 7, or 15 days. Exposure at 33°C with CO2 at 15 kPa for 24 h or O2 at 30 kPa for 48 h effectively controlled both green and blue molds after 7 days of incubation at 20°C; however, control of both diseases was minimal after 15 days. To assess potential induction of disease resistance, fruit were treated as described above, then inoculated after 1, 2, or 5 days at 20°C and evaluated after 3 and 6 more days at 20°C. All of the treatments were ineffective in inducing fruit resistance. Short exposures of citrus fruit to high CO2 or O2 at curing temperatures may be part of a control program alternative to synthetic fungicides, especially for organic fruit markets.

Potassium sorbate residue levels and persistence in citrus fruit as detected by a simple colorimetric method.

A colorimetric method that employed extraction of the macerated fruit, followed by a reaction with 2-thiobarbituric acid, was used to quantify potassium sorbate residues in citrus fruit. A recovery of more than 90% in oranges and lemons was obtained. Potassium sorbate residues determined by this method and a standard high-performance liquid chromatography (HPLC) method were similar. Residues were proportionate to the potassium sorbate concentration in the treatment solution. In oranges stored at 15 degrees C, following the potassium sorbate treatments, residues declined initially rapidly and later more slowly, until residues stopped declining after 6 days. A brief double-dip rinse in tap water applied immediately after immersion of lemons in a 2% (wt/vol) potassium sorbate removed more than 90% of the potassium sorbate residue. The influence of high-pressure water washing (HPWW) on potassium sorbate residues in potassium-sorbate-treated fruit was determined. Potassium sorbate residues were more effectively reduced by rinsing oranges than lemons.