Commercial Packinghouse Research Articles

Onion bulb size differentially affects bulb quality attributes by mediating mineral nutrients and targeted major metabolites during long-term cold storage in commercial packinghouse

Onion bulb size differentially affects bulb quality attributes by mediating mineral nutrients and targeted major metabolites during long-term cold storage in commercial packinghouse

Effects of packinghouse operations on the flavor of ‘Orri’ mandarins

Mandarins have a delicate flavor and are easy to peel and easy to consume. However, they are relatively perishable and suffer from flavor deterioration after harvest. The goal of the current study was to examine the effects of commercial packinghouse operations on the flavor of ‘Orri’ mandarins. For that purpose, we collected fruit from four different points along a commercial citrus packing line: (1) directly from the harvest bin, (2) after application of a hot (53°C) fungicide treatment for 30 s, (3) after waxing, and (4) after waxing and after the fruit had passed through a hot‐air drying tunnel (37°C) for 2 min. The collected fruit were stored for 3 or 6 weeks at 5°C and then kept for five more days under shelf‐life conditions at 22°C. The observed results indicate that the hot fungicide treatment had no effect on flavor quality. However, the waxing and waxing +drying treatments resulted in significant increases in ethanol accumulation, lower flavor‐acceptability scores, and increased off‐flavors. Gas‐chromatography mass‐spectrometry (GC–MS) analysis revealed that the waxing and waxing +drying treatments resulted in particular increases in the levels of alcohol and ethyl ester volatiles; whereas levels of other aroma volatiles (i.e., esters, aldehydes, monoterpenes, and sesquiterpenes) decreased after storage in all fruit samples. Overall, the waxing process in commercial citrus packinghouses increased ethanol and ethyl ester volatile levels and harmed flavor acceptability. These findings demonstrate the need to identify new wax formulations that do not hamper fruit‐flavor quality.

Determining Bacterial Load and Water Quality Parameters of Chlorinated Tomato Flume Tanks in Florida Packinghouses

Monitoring and maintenance of water quality in dump tanks or flume systems is crucial to maintaining proper sanitizer levels to prevent pathogen cross-contamination during postharvest washing of tomatoes, but there is limited information on how organic matter influences sanitizer efficacy in the water. The main objective of this study was to monitor water quality in flume tanks and evaluate the efficacy of postharvest washing of tomatoes in commercial packinghouses. Flume tank water samples (n = 3) were collected on an hourly basis from three packinghouses in Florida and analyzed for pH, total dissolved solids (TDS), free chlorine, chemical oxygen demand (COD), oxidation-reduction potential, and turbidity. Additionally, three flume-water samples were collected and tested for total aerobic plate count (APC), total coliforms (TC), and Escherichia coli. Fresh tomatoes (n = 3), both before and after washing, were collected and analyzed for the same bacterial counts. Turbidity, COD, and TDS levels in flume water increased over time in all packinghouses. Correlations observed include COD and turbidity (r = 0.631), turbidity and TDS (r = 0.810), and oxidation-reduction potential and chlorine (r = 0.660). APC for water samples had an average range of 0.0 to 4.7 log CFU/mL and TC average range of 0.0 to 4.7 log CFU/mL. All water samples were negative for E. coli. The average APC for pre- and postflume tomatoes from the three packinghouses was 6.0 log CFU per tomato and ranged from 2.2 to 7.4 log CFU per tomato. The average TC count was <1.5 and 7.0 log CFU per tomato for pre- and postwash tomatoes, respectively. There was no significant effect (P > 0.05) of postharvest washing on the microbiological qualities of tomatoes. Water quality in flume tanks deteriorated over time in all packinghouses during a typical operational day of 4 to 8 h.

Listeria monocytogenes Survival on Peaches and Nectarines under Conditions Simulating Commercial Stone-Fruit Packinghouse Operations.

Recent recalls of stone fruit due to potential Listeria contamination and associated foodborne outbreaks highlight the risk for pathogen transmission through stone-fruit consumption. Particularly, surface contamination of fruits increases the risk for cross-contamination of produce during processing and storage. This highlights the need for quality control in stone fruits intended for consumption. To develop effective food safety practices, it is essential to determine the critical factors during stone-fruit processing that influence Listeria survival. Therefore, this study evaluated the ability of Listeria to survive on peaches and nectarines under simulated stone-fruit loading and staging, waxing and fungicide application and storage conditions. The results of our study indicate that current stone-fruit handling conditions do not favor Listeria growth. However, once fruit is contaminated, Listeria can survive on the fruit surface in significant numbers under current processing conditions. Therefore, there is a need to develop and implement preventive controls at the stone-fruit packinghouse to prevent Listeria contamination and deter pathogen persistence.

Canine Olfactory Detection of a Non-Systemic Phytobacterial Citrus Pathogen of International Quarantine Significance.

For millennia humans have benefitted from application of the acute canine sense of smell to hunt, track and find targets of importance. In this report, canines were evaluated for their ability to detect the severe exotic phytobacterial arboreal pathogen Xanthomonas citri pv. citri (Xcc), which is the causal agent of Asiatic citrus canker (Acc). Since Xcc causes only local lesions, infections are non-systemic, limiting the use of serological and molecular diagnostic tools for field-level detection. This necessitates reliance on human visual surveys for Acc symptoms, which is highly inefficient at low disease incidence, and thus for early detection. In simulated orchards the overall combined performance metrics for a pair of canines were 0.9856, 0.9974, 0.9257 and 0.9970, for sensitivity, specificity, precision, and accuracy, respectively, with 1–2 s/tree detection time. Detection of trace Xcc infections on commercial packinghouse fruit resulted in 0.7313, 0.9947, 0.8750, and 0.9821 for the same performance metrics across a range of cartons with 0–10% Xcc-infected fruit despite the noisy, hot and potentially distracting environment. In orchards, the sensitivity of canines increased with lesion incidence, whereas the specificity and overall accuracy was >0.99 across all incidence levels; i.e., false positive rates were uniformly low. Canines also alerted to a range of 1–12-week-old infections with equal accuracy. When trained to either Xcc-infected trees or Xcc axenic cultures, canines inherently detected the homologous and heterologous targets, suggesting they can detect Xcc directly rather than only volatiles produced by the host following infection. Canines were able to detect the Xcc scent signature at very low concentrations (10,000× less than 1 bacterial cell per sample), which implies that the scent signature is composed of bacterial cell volatile organic compound constituents or exudates that occur at concentrations many fold that of the bacterial cells. The results imply that canines can be trained as viable early detectors of Xcc and deployed across citrus orchards, packinghouses, and nurseries.

Use of Chlorine Dioxide to Treat Recirculated Process Water in a Commercial Tomato Packinghouse: Microbiological and Chemical Risks

Antimicrobial treatment of fresh produce wash water can enable water reuse by avoiding microbial cross-contamination. In this study, the efficacy of chlorine dioxide (ClO2; 2-3 mg/L) to maintain the microbiological quality of process wash water in a tomato packinghouse was assessed. Different parameters were measured, including the physicochemical characteristics of the wash water (pH, oxidation-reduction potential (ORP), chemical oxygen demand (COD), absorbance at 254 nm (UVA254), temperature, electrical conductivity (EC)), the levels of different microorganisms present in water and in the product (aerobic mesophilic bacteria (AMB), total coliforms, yeasts and molds, E. coli), and the presence of chlorate as disinfection by-product. The treatment with ClO2 had a significant effect on the microbial populations present in the recirculated wash water and the tomatoes compared with the use of untreated recirculated water. The microbial load in tomatoes washed with tap water, and ClO2-treated recirculated water was similar. The transfer of chlorate from wash water to the fruits was very low under the conditions tested. The results obtained indicate that ClO2 could be a suitable option for the reuse of wash water in commercial packinghouses, as it reduces the microbial populations in wash water while not leading to the presence of disinfection by-products, such as chlorate, in the final product. This study shows that the monitorization and control of the microbiological quality of process wash water should be managed together with good practices able to guarantee hygienic conditions of the equipment by implementing efficient cleaning and disinfection systems.

Critical points affecting the microbiological safety of bell peppers washed with peroxyacetic acid in a commercial packinghouse

The washing stage from a bell pepper commercial packinghouse was assessed to study some of the critical control points related to bacterial cross-contamination. The washing line comprised two overhead spray bars applications: a pre-wash step without peroxyacetic acid (PAA), and a wash step with PAA. The physicochemical characteristics of the wash water and the bacterial quality and safety of the wash water and bell peppers (including aerobic mesophilic bacteria (AMB), Salmonella spp., and Shiga-toxigenic E. coli (STEC)) were studied. Additionally, the performance of commercial test methods (reflectometry, amperometric probe, chronoamperometric sensor) for measuring the residual concentration of PAA was examined. The bacterial load of the pre-wash water (8.7 ± 1.3 log cfu/100 mL AMB) was very high and thus peppers after the pre-wash showed a significantly higher bacterial load (4.9 ± 0.9 log cfu/g AMB) than the unwashed (3.8 ± 0.7 log cfu/g AMB) or the washed peppers (3.3 ± 0.8 log cfu/g AMB) (p < 0.05). However, no pathogenic bacteria were detected in bell pepper samples (n = 40), and only one water sample was confirmed positive for STEC (n = 64, 1.6% prevalence). The chronoamperometric sensor (PAASense) and the online amperometric probe showed similar results, while the reflectometry (Quantofix) significantly sub estimated (p < 0.05) PAA concentration. The results obtained highlight the need for interventions to improve hygiene in the washing line to ensure the microbiological quality and safety of bell peppers. The maintenance of optimal PAA concentrations in all the washing steps is critical for reducing the chance of water-mediated cross-contamination.

Influence of sulfur dioxide-emitting polyethylene packaging on blueberry decay and quality during extended storage

Abstract Blueberries are highly susceptible to decay after harvest and application of sulfur dioxide (SO2) has been shown to effectively control decay during extended storage. Box liners are in commonly used with other commodities to reduce water loss. In 2017 three varieties, ‘Emerald’, Jewel’ and ‘Misty’, were obtained from commercial packing houses. They were contained in plastic clamshells with 12 clamshells per box. We examined: 1) two liners that continuously emitted SO2 from sodium metabisulfite incorporated into the liner film. These ventilated with holes that comprised 0.3 % or 0.9 % of the liner surface area; 2) two solid, non-ventilated liners designed to develop a modified atmosphere (MA) during storage, either alone or with SO2 emitting sheets inside the packages within the liners; 3) control packages without liners. After packaging the fruit were placed into storage for either 3 or 6 weeks and then evaluated for decay and fruit quality. The effect on decay was determined both by assessing natural decay and by determining the spread of decay from berries inoculated with Botrytis cinerea. In 2018 two varieties, ‘Draper’ and ‘Duke’ were tested in a similar manner, except a 0.1 % vented liner replaced the 0.9 % liner, which performed poorly in 2017, and the SO2-emitting sheets were not included as a treatment. In 2018 we measured concentrations of SO2 and atmospheric gases were monitored within the packages. Results from both years indicated that the SO2-emitting liners were effective in reducing natural decay and the spread of aerial mycelial growth of B. cinerea from inoculated berries compared to treatments without SO2. Treatments that combined SO2 and MA (SO2/MA) were the most effective. MA alone did not consistently control decay. The high level of effectiveness of the SO2/MA treatment in controlling decay may be due to higher humidity levels within the packages that would enhance SO2 activity, because SO2 concentrations did not differ among the liner types and concentrations of CO2 in the MA packaging were too low to have had much effect. Weight loss was significantly less in packaging with liners with less vent area, with the least being in the MA packaging, regardless of the presence of SO2. Less weight loss was associated with reduced shrivel, although firmness was not always greater. SO2 concentrations measured in 2018 did not exceed 10 μL L-1 and bleaching of the berries did not occur in either year. SO2-emitting liners are an effective means of preserving blueberry quality during extended storage, particularly when combined with MA. The simplicity of assembling a package with a single liner versus using a conventional liner followed by a SO2-emitting sheet could be of benefit to blueberry packers.

Occurrence of Botrytis prunorum Causing Calyx-End Rot in European Pear Fruits During Cold Storage in Chile

The European pear tree (Pyrus communis L.) is an important fruit species, with 8,217 ha concentrated in central Chile. Previously, only Botrytis cinerea has been described causing calyx-end rot in pears in Chile. During the 2016 to 2017 postharvest season, pears with symptoms of calyx-end rot were observed from a commercial packinghouse in Curico, Maule Region, after 60 days at 0°C. The rot prevalence registered during cold storage was 3, 2, and 7% for cultivars Beurre Bosc, Forelle, and Packham’s Triumph, respectively. The symptoms started in the pear calyx end as a light brown to dark brown lesion with soft watery decay toward the endocarp. To isolate the causal agent, symptomatic pear fruits (n = 72) were surface disinfected with 75% ethanol, and then small fragments (5-mm length) from rotten internal tissue were placed on Petri dishes containing PDA acidified with 0.5 ml/liter of 92% lactic acid (APDA) and incubated for 7 days at 20°C. Fifty-one isolates of Botrytis were obtained and classified according to conidia production as high sporulating (HS) and low sporulating (LS) on pea agar medium (PAM) containing per liter 160 g of pea (liquefied for 2 min in 1 liter of distilled water, adjusted to pH 6.0 using HCl), 5 g of sucrose, and 25 g of agar. The HS isolates (n = 38) were morphologically and molecularly identified as Botrytis cinerea Pers. The LS isolates (n = 13) produced white to yellowish colonies, floccose, tufted, and scarce sporulation, with a mean of 0.6 and 7.0 conidia/cm² after 7 days at 20°C on APDA and PAM media, respectively. Conidia were ovoid, hyaline, smooth, and (5.9) 11.2 ± 2.0 (14.7) × (5.3) 6.3 ± 0.6 (8.1) µm (n = 40). Conidiophores were septate, dark, and constricted at the base, hyaline and branched at the apex, and shorter than would correspond to B. cinerea. The molecular identification of six representative isolates was made by analysis of glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), and DNA-dependent RNA polymerase subunit II (RPB2) genes (Staats et al. 2005). BLAST search showed 99 to 100% identity with isolate type Bpru8 of GenBank accessions KP339979 (G3PDH), KP339993 (HSP60), and KP339986 (RPB2) of Botrytis prunorum (Ferrada et al. 2016). Sequences of isolates BEP-10-1 to BEP-10-6 were deposited in GenBank (MN136239 to MN136244, MN136245 to MN136250, and MN136251 to MN136256 for G3PDH, HSP60, and RPB2, respectively). Pathogenicity testing was performed using three isolates (BEP-10-1 to BEP-10-3) in ripe pears (n = 75 fruits), cultivar Beurre Bosc. An isolate of B. cinerea (BAP-4) was included in this test. Fruits were surface disinfected (75% ethanol, 2 min), wounded with a sterile hypodermic syringe in the calyx-end area, and inoculated with 50 µl of a conidial suspension (10⁶ conidia/ml). The control fruits were inoculated with distilled water. After 10 days at 20°C in a humid chamber (>85% relative humidity), all inoculated fruits with B. prunorum developed brown, watery soft rot in the calyx-end area with lesions from 15.7 to 38.6 mm. Fruits inoculated with B. cinerea showed a lesion from 37.8 to 41.9 mm. B. prunorum isolates had a significantly lower virulence than B. cinerea (P < 0.05). Control fruit remained healthy. The pathogen was reisolated from diseased fruit and molecularly identified as B prunorum. To our knowledge, this is the first report of B. prunorum causing pear calyx-end rot in Chile and worldwide. Recently, B. prunorum was described causing kiwifruit rot in Chile (Elfar et al. 2017). These results confirm the occurrence of B. prunorum, with an isolation frequency of 25% of the total Botrytis isolates obtained during cold storage in Chile.

Selection Pressure Pathways and Mechanisms of Resistance to the Demethylation Inhibitor-Difenoconazole in Penicillium expansum.

Penicillium expansum causes blue mold, the most economically important postharvest disease of pome fruit worldwide. Beside sanitation practices, the disease is managed through fungicide applications at harvest. Difenoconazole (DIF) is a new demethylation inhibitor (DMI) fungicide registered recently to manage postharvest diseases of pome fruit. Herein, we evaluated the sensitivity of 130 P. expansum baseline isolates never exposed to DIF and determined the effective concentration (EC50) necessary to inhibit 50% germination, germ tube length, and mycelial growth. The respective mean EC50 values of 0.32, 0.26, and 0.18 μg/ml indicate a high sensitivity of P. expansum baseline isolates to DIF. We also found full and extended control efficacy in vivo after 6 months of storage at 1°C. We conducted a risk assessment for DIF-resistance development using ultraviolet excitation combined with or without DIF-selection pressure to generate and characterize lab mutants. Fifteen DIF-resistant mutants were selected and showed EC50 values of 0.92 to 1.4 μg/ml and 1.7 to 3.8 μg/ml without and with a DIF selection pressure, respectively. Resistance to DIF was stable in vitro over a 10-week period without selection pressure. Alignment of the full CYP51 gene sequences from the three wild-type and 15 mutant isolates revealed a tyrosine to phenylalanine mutation at codon 126 (Y126F) in all of the 15 mutants but not in the wild-type parental isolates. Resistance factors increased 5 to 15-fold in the mutants compared to the wild-type-isolates. DIF-resistant mutants also displayed enhanced CYP51 expression by 2 to 14-fold and was positively correlated with the EC50 values (R2 = 0.8264). Cross resistance between DIF and fludioxonil, the mixing-partner in the commercial product, was not observed. Our findings suggest P. expansum resistance to DIF is likely to emerge in commercial packinghouse when used frequently. Future studies will determine whether resistance to DIF is qualitative or quantitative which will be determinant in the speed at which resistance will develop and spread in commercial packinghouses and to develop appropriate strategies to extend the lifespan of this new fungicide.

A three-year survey of Florida packinghouses to determine microbial loads on pre- and post-processed tomatoes

Prevention of microbial cross-contamination during postharvest handling is an important step to minimize microbial food safety hazards of produce. Dump tanks and flume systems are widely used in many states (e.g., Florida) to transfer/wash tomatoes, and are one of the most critical points where cross-contamination may occur. This study presents data gathered over three years (2013, 2014, and 2015) on tomatoes collected from five growing regions in Florida to evaluate the risk associated with postharvest processing of tomatoes in commercial packinghouses. A total of 840 and 839 composite samples, from pre- and post-processed tomatoes, respectively, were analyzed for aerobic plate count (APC), and total coliforms (TC) and generic E. coli (EC). The least square mean (LSM) value of APC for all samples (both pre- and post-processed) was 6.0 log CFU/tomato (n = 840), whereas the LSM for TC counts was 4.1 log CFU/tomato (n = 839). Ninety-one (10.8%) and 820 (97.7%) out of 839 samples of post-processed samples had TC and generic EC counts below the detection limit of 1.3 log CFU/tomato, respectively. APC and TC counts in post-processed samples were significantly lower (p < 0.0001) than those in the pre-processed samples. There was no significant difference (p = 0.1011) in the occurrence of generic EC pre- and post-process. APC and TC were significantly higher (p < 0.0001) on samples collected in 2014 than 2013 and 2015, while the generic EC levels were not significantly different between 2013 and 2014. All samples collected in 2015 were negative for generic EC. TC counts varied significantly (p < 0.0001) by season, with highest counts in summer and lowest in the winter, over the three-year period. APC were significantly (p < 0.0001) higher in summer and fall seasons as compare to winter and spring. Microbial loads were significantly higher in the northern sites compared to the southern sites. Tomatoes from site 5 (southernmost) had significantly lower APC and TC (p < 0.0001) than recorded from other four sites. Data from this research demonstrated that the postharvest wash treatments used at the packinghouse surveyed in this study effectively reduced the overall microbial load and prevented cross-contamination.

Critical points and magnitude of impacts on the packing line: effect on ripening and quality of 'Packham's Triumph' pears

Pears have a very sensitive epidermis and are prone to signal mechanical blemishes, which result in reduced visual quality and low consumer acceptance. The objective of this work was to identify critical points and the magnitude of impact forces on a packing line at a commercial packinghouse. The effect of injuries on ripening and quality of ´Packham´s Triumph´ pears was also evaluated after cold storage. The packing line was scrutinized on its transfer points, fruit drop heights and cushioning overlays, which allowed to acquire the maximum accelerations on each spot. The maximum acceleration forces were reproduced in the lab with ‘Packham’s Triumph’ pears to evaluate the effects on fruit quality after cold storage. Four critical points were noticed on the packing line: at the transfer from the conveyor belt to the lifting rollers, at the transfer from the lifting rollers to the washing ramp with rotatory brushes, at the entrance to the singulator at the end of the conveyor belt and at the drop from the sizer to the packing stalls. Ripening of ‘Packham’s Triumph’ pears invariably came about during cold storage, and independently of the imposed impacts. The impacts under the circumstances of the test did not affect the quality of ´Packham´s Triumph´ pears kept for up to 120 days at cold storage followed by five days at room temperature.

The Effects of a Modified Hot Water Treatment on Anastrepha ludens (Diptera: Tephritidae)-Infested Mango.

The Mexican fruit fly, Anastrepha ludens (Loew), is a quarantine pest in mango (Mangifera indica L.) that can be controlled by using a hot water treatment (HWT). This treatment is normally followed by a 30-min hydrocooling (HYC) process that reduces the negative effects that the treatment has on fruit quality. However, if hot water-treated fruits are immediately immersed in water at 21 °C, the survival rate of third-instar A. ludens may be increased. The current approved treatment protocol states that if HYC is used, then treated fruit should undergo an additional 10-min HWT or on platform for 30 min before HYC. We aimed to determine the efficacy of HWT without an additional 10-min treatment before being subjected to HYC, while taking into consideration that the most important conditions are the temperature of the fruit core throughout treatment and the type of infestation, either oviposition or inoculation. Two experimental tests were conducted. Our first aim was to determine the effectiveness of HWT followed by HYC using three varieties and different size classes of mangoes ('Ataulfo' 200-375 and 401-570 g; 'Tommy Atkins' 401-500 and 501-700 g; 'Kent' 401-500 g). The four treatment combinations used to test HWT and immediate HYC at 21 °C were 1) HWT, 2) HWT/HYC, 3) HWT + 10 min/HYC, and 4) HWT/30 min on platform/HYC; an independent experiment was used for each variety. The second aim was to validate the HWT/HYC combination by performing confirmatory tests in commercial packing houses. The results showed that as long as the mango core temperature reached 45 °C during the HWT, it was not necessary to add the 10-min treatment to the HWT before HYC at 21 °C was applied. To ensure that the larvae are subjected to the HWT treatment for sufficient time to be lethal, the temperature of the fruit core throughout the treatment must be recorded.

POSTHARVEST OF IRRADIATED TAHITI LIME FRUITS

ABSTRACT This study aimed to evaluate the postharvest quality evolution of gamma-irradiated ‘Tahiti’ limes. Shiny, olivegreen fruits with coarse skin (56 cm equatorial diameter) harvested in commercial orchars and processed in commercial packing house line were used. In a preliminary assay, fruits harvested in April 2011 were exposed to a gamma radiation range from 0 to 750 Gy. The 250 and 750 Gy doses negatively affected skin quality and pulp of exposed fruits. For this reason, new assays were carried out using lower doses to irradiate fruits harvested in July 2011 (off-season) and January 2012 (regular harvest period). Fruit harvested in both periods were selected and exposed to radiation doses of 0, 50, 100, 150, and 200 Gy. All irradiations occurred at a rate of 0.46 Gy/h. After fruit irradiation, physical and chemical analyses were performed along a 20-day storage period at room temperature (24 ± 1ºC and 80 ± 5% RH). Irradiation of fruits harvested in July 2011 and January 2012 and treated with doses of up to 200 Gy did not affect the ascorbic acid content, but doses &gt; 100 Gy caused skin yellowing of fruits harvested on both periods. Gamma radiation at doses = 50 Gy reduced the total soluble solids content in off-season fruits. Exposure of fruits harvested in the main harvest period to radiation doses = 150 Gy increased weight loss. Irradiation of ‘Tahiti’ limes at doses between 50 Gy and 700 Gy did not preserve postharvest quality during storage at room temperature.

Effect of modified atmosphere packaging on sensory quality, chemical parameters and shelf life of carrot roots (Daucus carota L.) stored at chilled and abusive temperatures

The influence of short-term storage in air atmosphere and modified atmosphere (MA) conditions obtained by different film perforations and storage conditions on carrot root quality was studied. The carrots were stored at temperature conditions simulating the commercial distribution chain. The quality was evaluated using chemical analyses, descriptive sensory analyses and evaluation of decay at the end of storage. One kilogram of carrots were packaged at a commercial packing house in pouches with (1) 13 laser perforations, (2) 11 warm needle perforations and 3) approximately 560 warm needle perforations per 10×10cm (“bread pouch”). The packages were stored at optimal (chill) storage conditions of 4°C for 6d followed by 6°C for 9d, or at an abusive temperatures (common retail storage) conditions of 4°C for 3d, 20°C for 3d and 6°C for 9d. The highest weight loss during storage was observed for the “bread” perforated packages stored at retail conditions (2.3%) and at chill conditions (1.4%). The weight loss was below 0.34% for all the other packages with different perforation and storage combinations. The gas concentration in the needle perforated packages was close to air both at chill and retail storage conditions. In laser perforated packages at chill conditions, the O2-concentration stabilised at 12–13kPa and the CO2-concentration at 9–10kPa, whereas at abused temperature the O2 concentration decreased to 4kPa the last day of storage at 20°C (day 6) and CO2 concentration approximately at 32kPa at day 6. The low O2 concentration and high CO2 concentration in laser perforated packages stored at retail conditions and the high ethanol content measured in these carrots could indicate anaerobic respiration. These carrots also had significantly higher scores for ethanol odour and flavour. The carrots in laser and needle perforated packages stored at chill conditions had the highest scores for terpene odour and flavour. Percentage diseased carrots were highest in the laser perforated packages stored at retail conditions. The experiment showed that the overall carrot quality was best maintained in needle perforated packages with a gas atmosphere close to air, giving no major weight loss, no ethanol formation and the lowest incidences of storage diseases at both chill and retail conditions.

Occurrence of Fludioxonil Resistance in Penicillium digitatum from Citrus in California

Penicillium digitatum is the causal agent of green mold, one of the most important postharvest diseases of citrus (Citrus spp.). Fludioxonil can be used alone or in combination with azoxystrobin for the control of green mold and other postharvest diseases on citrus. Baseline sensitivity to fludioxonil in P. digitatum populations from California citrus packinghouses has been previously established (Kanetis et al. 2008). To monitor resistance to fludioxonil in P. digitatum, 20 Penicillium spp. isolates were obtained from decayed oranges by isolation from decayed tissue and 22 isolates were recovered from potato dextrose agar plates amended with 0.5 mg/liter fludioxonil (Kanetis et al. 2006) and exposed to packinghouse air for 5 min each sampling time during March to July 2013 in two California citrus packinghouses. All isolates were single-spore cultured and identified as P. digitatum based on morphological characters (Pitt 1979). The sequence analysis of the internal transcribed spacer (ITS) region, using the primers ITS1/ITS4, was conducted to confirm the species-level identification. A MegaBLAST search showed that the sequences of all isolates had 99% homology (E-value = 0.0) with that of P. digitatum deposited at GenBank (Accession No. AF033471.1). In a mycelial growth assay, 15 of the 42 P. digitatum isolates were able to grow at 0.5 μg/ml, a previously established discriminatory concentration (Kanetic et al. 2006). EC50 values (the effective concentration that inhibits fungal growth by 50% relative to the control) of fludioxonil for the resistant isolates were >100 mg/liter following a method described by Li and Xiao (2008). To assess whether fludioxonil at the label rate was able to control fludioxonilresistant isolates, ‘Eureka’ lemons were wounded with a stainless steel rod (1 × 2 mm) and inoculated with 10 μl of conidial suspensions (6 × 10 conidia/ml) of a representative sensitive or a resistant isolate. After 4 h, inoculated fruit were dipped for 30 s in either a formulated product of fludioxonil, Graduate (50% active ingredient; Syngenta Crop Protection, Research Triangle Park, Raleigh, NC) at 1,198 mg/liter, or water as a control, and then stored at 20°C in air for 7 days. There were four 20-fruit replicates for each treatment and the experiment was performed twice. All inoculated water-dipped fruit were decayed, while fludioxonil completely controlled green mold on fruit inoculated with the fludioxonil-sensitive isolate. However, 100% fruit inoculated with the fludioxonil-resistant isolate and treated with fludioxonil were decayed. Fludioxonil-insensitive isolates have been reported to occur in natural populations of P. digitatum before its commercial use, but at very low frequency (1.4 to 2.5 × 10) (Kanetis et al. 2006). This is the first report of fludioxonil resistance in P. digitatum collected from commercial citrus packinghouses after the introduction of the fungicide on the market. These fludioxonil-resistant isolates were obtained from packinghouses where the fungicide had been used during citrus packing for 2 consecutive years, approximately for a 3-month period in each year, indicating that fludioxonil-resistant individuals emerged quickly in P. digitatum populations. Our results show that fludioxonil failed to control green mold incited by the fludioxonil-resistant isolate, suggesting that appropriate fungicide resistance management practices need to be implemented to ensure adequate control.

Postharvest Strategies for Managing Phytophthora Brown Rot of Citrus using Potassium Phosphite in Combination with Heat Treatments.

Phytophthora brown rot, caused by several species of Phytophthora, is an economically important disease of citrus in areas with rainfall during the late stages of fruit development. Recent export restrictions of California orange fruit to China due to the presence of brown rot caused by the quarantine pathogen Phytophthora syringae have mandated more rigorous disease management. We evaluated postharvest applications with the phosphonate fungicide potassium phosphite in combination with heat treatments. In timing studies, potassium phosphite at 1,500 μg/ml was most effective when applied within 18 h after inoculation of orange fruit with P. citrophthora, reducing the incidence of decay by >96% as compared with the control. Potassium phosphite was also highly effective in inoculations with P. syringae. Heated water treatments at 60°C were consistently and highly effective in reducing the incidence of brown rot after inoculation with P. citrophthora, whereas treatments at 55 or 50°C were more variable and generally less effective. Two-stage treatments of fruit were conducted in the laboratory to simulate current packinghouse practices and to evaluate any interaction of the efficacy of potassium phosphite with treatments of two commonly used postharvest fungicides (i.e., imazalil and thiabendazole [TBZ]) or a postharvest carnauba-based fruit coating. In these studies, an aqueous imazalil-potassium phosphite (2,000 μg/ml) dip at ambient temperature that was followed by a spray treatment of imazalil and TBZ prepared in fruit coating significantly reduced the incidence of brown rot from the control. When the aqueous dip was applied at 54°C, brown rot developed in only 1% of the fruit as compared with 76% in the water control. The efficacy of potassium phosphite was also demonstrated in commercial packinghouse treatments. Based on our research, this fungicide was registered for postharvest use against brown rot of citrus and is exempt from tolerance in the United States and many other countries.

First Report of Penicillium expansum Isolates With Reduced Sensitivity to Fludioxonil From a Commercial Packinghouse in Pennsylvania

HomePlant DiseaseVol. 99, No. 8First Report of Penicillium expansum Isolates With Reduced Sensitivity to Fludioxonil From a Commercial Packinghouse in Pennsylvania PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Penicillium expansum Isolates With Reduced Sensitivity to Fludioxonil From a Commercial Packinghouse in PennsylvaniaV. L. Gaskins, I. Vico, J. Yu, and W. M. Jurick IIV. L. GaskinsSearch for more papers by this author, I. VicoSearch for more papers by this author, J. YuSearch for more papers by this author, and W. M. Jurick IISearch for more papers by this authorAffiliationsAuthors and Affiliations V. L. Gaskins , Food Quality Laboratory, USDA-ARS, Beltsville, MD I. Vico , Department of Phytomedicine, University of Belgrade, Serbia J. Yu W. M. Jurick II , Food Quality Laboratory, USDA-ARS, Beltsville, MD Published Online:23 Jun 2015https://doi.org/10.1094/PDIS-11-14-1161-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Blue mold, caused by Penicillium expansum, is among the most economically significant disease of stored apples worldwide (Li and Xiao 2008). All commercial apples are susceptible to blue mold, leaving producers to rely on cultural practices and fungicides for control. Scholar (Syngenta Crop Protection, Greensboro, NC) was registered for control of Penicillium spp. on pome fruits. Scholar is a protectant, contact postharvest fungicide (active ingredient, fludioxonil). In February 2012, water samples were obtained from a presizing flume at a commercial facility in Pennsylvania with five isolates identified as P. expansum according to Pitt (2002). Conidial suspensions from each isolate were grown in triplicate on potato dextrose agar amended with 0.5 μg/ml technical grade fludioxonil and repeated according to Li and Xiao (2008). Four isolates with reduced sensitivity (R) grew, while one sensitive (S) isolate did not. Species-level identity was conducted for a representative R and S isolate via genomic DNA extraction followed by conventional PCR using β-tubulin specific primers according to Sholberg et al. (2005). MegaBLAST analysis of the 2× consensus amplicon sequences for the S isolate was 100% identical to P. expansum GenBank accession FJ012853.1 (E value = 0.0), while the R isolate was 100% identical to P. expansum accession JN872743.1 (E value 0.0). To evaluate if Scholar applied to apple fruits at the labeled rate before or after inoculation with either an R or S P. expansum isolate could control decay, ‘Golden Delicious’ apples were dipped in Scholar SC or sterile water, wounded, and inoculated with 20 µl of a 1 × 104 conidia ml−1 suspension of either isolate, and stored at 25°C for 9 days. Twenty apples were inoculated for each treatment per experiment, which was repeated. Water-only treated and uninoculated fungicide-treated fruit served as negative controls and were symptomless. Water-dipped P. expansum-inoculated fruit had 100% decay, while P. expansum-inoculated fruit treated with Scholar SC were asymptomatic. In contrast, when fruit were wounded, inoculated with either the R or S isolate, and then dipped in the labeled rate of the Scholar SC fungicide, 78% decay incidence was observed for both isolates 8 days post inoculation. This is the first report of P. expansum with reduced sensitivity to fludioxonil obtained from presizing water at a commercial facility in Pennsylvania with a history of Scholar fungicide use. Repeated exposure to Scholar by P. expansum isolates with reduced sensitivity to fludioxonil may facilitate the development of resistant isolates able to cause decay on fruit during storage. Findings from this research impact current disease control management strategies for pome fruits in the Pennsylvania area given the limited (3) number of control options coupled with documented resistance to thiabendazole and pyrimethanil in the literature.

Relationship of Typical Core Temperatures After Hydrocooling on Retention of Different Quality Components in Sweet Cherry

The research was conducted to first determine the commercial reality in regards to effectiveness of hydrocooling of sweet cherries (Prunus avium) at commercial packing houses. Temperature data obtained from the commercial studies were then used as a guide to evaluate the effect of small differences (0.5, 3, and 5 °C) in sweet cherry core temperature on the quality retention of ‘Sweetheart’ sweet cherries over 6 weeks of storage to simulate container shipment. Sweet cherry core temperatures after in-line hydrocooling and at the time of packing were generally around 3 or 5 °C. Once palletized and placed in commercial cold rooms, the internal boxes of a pallet did not cool any further. Only when a pallet was exposed to direct airflow from cooling coils did the exterior boxes in an assembled pallet show any further reduction in core temperature of packed sweet cherries. Experiments to evaluate the differences in quality retention at close to ideal core temperature (0.5 °C) vs. at more typical 3 or 5 °C core temperatures demonstrated significant decline when the two higher temperatures were maintained over 6 weeks of storage. Sweet cherry firmness, titratable acidity, and stem removal force value declines in storage were significantly affected by these small differences in core temperature, showing the best retention at 0.5 °C. Stem browning increased significantly with 3 or 5 °C storage by 6 weeks of storage. Decay was also significantly increased with warmer temperatures, but the results were variable likely due to differences in fruit infection at the time of harvest. Soluble solids were unaffected by storage temperature, and weight loss and pitting severity were somewhat affected. These results support the need for post packing cooling of sweet cherries as the core temperatures achieved by in-line hydrocoolers during packing do not reduce temperatures sufficiently to ensure good quality retention over longer periods of time that are required for container shipping to export markets. Therefore, forced-air cooling is recommended to further reduce sweet cherry temperatures in the box, before shipping.

First Report of Pyrimethanil Resistance in Botrytis cinerea from Stored Apples in Pennsylvania.

Botrytis cinerea Pers.: Fr. (teleomorph Botryotinia fuckeliana [de Bary] Whetzel) causes gray mold on apple fruit. A survey of commercial packinghouses in Washington State revealed that it accounted for 28% of the decay in storage (1). Fungicide application coupled with cultural practices are the primary method of control as all commercial apple cultivars are susceptible to gray mold. In February 2013, gray mold was observed at ~5% incidence for commercially packed 'Gala' apple fruit that had been treated with Penbotec (active ingredient: pyrimethanil, Shield-Bright, Pace International) prior to controlled atmosphere storage in Pennsylvania. Eight infected apple fruit were collected, placed in 80 count boxes on cardboard trays, and stored at 4°C. One isolate was obtained from each decayed apple, placed on potato dextrose agar (PDA) petri plates, and incubated at 20°C with natural light. Eight single-spore isolates were identified as B. cinerea based on cultural characteristics. Species level identification was executed by obtaining mycelial genomic DNA, amplifying the ITS rDNA, and sequencing the ~550-bp amplicon directly (2). MegaBLAST analysis of the 2X consensus for the 8 isolates revealed 100% identity to B. cinerea ITS sequences in GenBank (KF156296.1 and JX867227.1) with E values of 0.0, thus confirming the morphological identification. Minimum inhibitory concentration (MIC) was determined using conidial suspensions obtained from ~14-day-old plates (104 spores/ml) and a range (0 to 500 μg/ml) of technical grade pyrimethanil on three replicated 96-well microtiter plates containing a defined medium for each experiment. Conidial proliferation was inhibited at 250 μg/ml for all eight isolates and the experiment was conducted four times. To further define the resistance levels between the isolates, mycelial growth analysis using a plug of actively growing mycelium from the margin of ~3-day-old plates was conducted with a defined medium three times with technical grade pyrimethanil with three plates per experiment. Five isolates grew at 250 μg/ml (highly resistant), while three did not (moderately resistant). To assess resistance in vivo, organic 'Gala' apples were rinsed with soap and water, sprayed with 70% ethanol, placed on trays, and allowed to air dry. Apples were wounded with a sterile finishing nail, inoculated with 20 μl of a conidial suspension (104 spores/ml) of either a moderately or a highly resistant isolate, and dipped in the labeled application rate of Penbotec at 500 μg/ml or sterile water for 30 s. Fruit were stored in 100 count boxes at 22°C for 5 days and decay incidence and severity were recorded. Ten fruit composed a replicate per treatment and the experiment was repeated. Water inoculated controls were symptomless and water-dipped inoculated fruit had 100% decay. Penbotec-treated fruit had 100% decay incidence and mean lesion diameters of 37.6 (±13.1 mm) for the highly, and 35.7 (±9.0 mm) for the moderately resistant isolate. This is the first report of pyrimethanil resistance in B. cinerea from decayed apples collected from a commercial packinghouse in Pennsylvania. The results indicate that pyrimethanil resistance has developed in B. cinerea, which can result in control failures on Penbotec-treated fruit during storage. Furthermore, it emphasizes the need for additional tools to manage gray mold on apple fruit and may pose issues for export concerning the spread of fungicide-resistant inoculum.