Chilling temperatures and controlled atmospheres alter key volatile compounds implicated in basil aroma and flavor.

Use of basil in its fresh form is increasingly popular due to its unique aromatic and sensory properties. However, fresh basil has a short shelf life and high chilling sensitivity resulting in leaf browning and loss of characteristic aroma. Moderate CO2 atmospheres have shown potential in alleviating symptoms of chilling injury in basil during short-term storage but its effect on the flavor volatiles is unclear. Moreover, studies on basil volatile profile as impacted by chilling temperatures are limited. We investigated the response of two basil genotypes to low temperatures and atmosphere modification, with emphasis on the volatile organic compounds responsible for basil aroma and flavor. Leaves were stored for 6 days at 5, 10, or 15°C combined with three different CO2 atmospheres (0.04%, 5% or 10%). Basil volatile profile was assessed using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Leaves suffered severe chilling injury and greater loss of aroma volatiles at 5°C compared to 10°C and 15°C. More than 70 volatiles were identified for each genotype, while supervised multivariate analysis revealed 26 and 10 differentially-accumulated volatiles for 'Genovese' and 'Lemon' basil, respectively, stored at different temperatures. Storage in 5% CO2 ameliorated the symptoms of chilling injury for up to 3 days in 'Genovese', but not in 'Lemon' basil. Both chilling temperatures and controlled atmospheres altered key volatile compounds implicated in basil aroma and flavor, but temperature had a bigger influence on the observed changes in volatile profile.

Non-destructive method to classify walnut kernel freshness from volatile organic compound (VOC) emissions using gas chromatography-differential mobility spectrometry (GC-DMS) and machine learning analysis.

Analysis of volatile organic compounds (VOCs) can be an effective strategy to inspect the quality of horticultural commodities and following their degradation. In this work, we report that VOCs emitted by walnuts can be studied using gas chromatography-differential mobility spectrometry (GC-DMS), and those GC-DMS data can be analyzed to predict the rancidity of walnuts, i.e., classify walnuts into grades of freshness. Walnut kernels were assigned a class n depending on their level of freshness as determined by a peroxide assay. VOC samples were analyzed using GC-DMS. From these VOC data, a partial least square regression (PLSR) model provided a freshness prediction value m, which corresponded to the rancid class n when m=n±0.5. The PLSR model had an accuracy of 80% to predict walnut grade and demonstrated a minimal root mean squared error of 0.42 for the m response variables (representative of walnut grade) with the GC-DMS data. We also conducted gas chromatography-mass spectrometry (GC-MS) experiments to identify volatiles that emerged or were enhanced with more rancid walnuts. The findings of the GC-MS study of walnut VOCs align excellently with the GC-DMS study. Based on our results, we conclude that a GC-DMS device deployed with a pre-trained machine learning model can be a very effective device for classifying walnut grades in the industry.

Validation and demonstration of a pericarp disc system for studying blossom-end rot of tomatoes.

BACKGROUND: Blossom-end rot in tomatoes is often used as a model system to study fruit calcium deficiency. The study of blossom-end rot development in tomatoes has been greatly impeded by the difficulty of directly studying and applying treatments to the affected cells. This manuscript presents a novel method for studying blossom-end rot development after harvest in immature whole fruit and in pericarp discs. RESULTS: Pericarp discs removed from the bottom pericarp of immature healthy fruit developed blossom-end rot like symptoms, corresponding to a decrease in L* value and an increase in a* value. Symptoms also developed in columella tissue, but not in stem-end pericarp tissue, similar to patterns observed during blossom-end rot development on the plant. Ascorbate oxidase and peroxidase activity, which are elevated in blossom-end rot affected fruit compared to healthy fruit, were both correlated with colorimetric measures of tissue darkening in discs. Respiration rate was higher in discs that later developed blossom-end rot symptoms, with increased respiration in asymptomatic discs on day 1 of storage being associated with symptom development on day 2. Calcium chloride and ascorbic acid treatments inhibited symptom development, demonstrating the potential of this method to provide causal evidence. CONCLUSIONS: Results indicate that symptom development in this system is consistent with blossom-end rot development with regards to location, color change, and the activity of key enzymes. This system has the potential to be used to elucidate the cause of fruit calcium deficiency and improve knowledge of the biological basis for calcium's diverse effects on fruit.

Effect of Canning and Freezing on the Nutritional Content of Apricots.

The effect of commercial canning and freezing on the nutritional content of fresh apricots was investigated. Processed samples were analyzed post-processing and after 3 months of storage and compared directly to fresh apricots from the same source. Vitamin C, beta-carotene, total phenols, and antioxidants were quantified. Compared to fresh, canned apricots initially exhibited similar levels of antioxidants, a 17% increase in beta-carotene, and a 48% increase in phenols, while vitamin C was reduced by 37%. After 3 months of storage, antioxidant levels were 47% higher than fresh. Vitamin C did not change significantly following storage and beta-carotene decreased by 15%. The canned apricot fruit packed in light syrup did not have higher total soluble solids (TSS) levels indicating no increase in fruit sugar content. Frozen apricots exhibited large increases in antioxidants (529%), beta-carotene (35%), vitamin C (3,370%), and phenols (406%) compared to fresh. After 3 months of storage, frozen apricots decreased in vitamin C (29%) and phenols (17%), but remained 2,375% and 318% higher than fresh, respectively. Beta-carotene increased during storage, reaching levels 56% higher than fresh while antioxidant activity was unchanged. This study demonstrates that key nutrients in canned and frozen apricots are retained or amplified upon processing, with the exception of vitamin C in canned apricots. The routine addition of citric and ascorbic acid to fruit prior to freezing resulted in significantly higher antioxidants, vitamin C, and phenols. Consumers eating canned or frozen apricots can feel confident of similar or superior nutritional content as compared to fresh apricots. PRACTICAL APPLICATION: The apricot industry is limited by the short shelf life of the fruit and consumer belief that processed produce is not as nutritious as fresh. Assessing the nutritional content of canned and frozen apricots and determining that processed apricots can deliver nearly comparable nutrient levels to fresh apricots provides the evidence needed to dispel these misconceptions and potentially increase demand for processed apricots among consumers.

Effect of Passive Drying on Ascorbic Acid, α-Tocopherol, and ß-Carotene in Tomato and Mango.

The effect of two passive drying methods on the degradation of ascorbic acid (vitamin C),  α-tocopherol (vitamin E), and ß-carotene (provitamin A) in ripe mango and tomato was determined. Samples of both commodities were dried outdoors in a solar drying cabinet or indoors in sealed plastic boxes containing ceramic zeolite drying beads in a bead-to-fruit ratio of 1:10. Nutrient content of the dried samples was compared to fresh samples (undried control) obtained from the same batch of fruit. Mango samples tended to reach an equilibrium weight of approximately 18% of their initial weight after 28 to 30 hr of drying in both drying methods, while tomatoes equilibrated at 5% to 6% of their initial weight after 8 to 10 hr of drying in the solar drying cabinet and after approximately 30 hr using drying beads. The content of all three nutrients in solar dried tomato, and of ß-carotene in mango were significantly (P < 0.05) lower than the control. α-Tocopherol and ß-carotene content in tomato and ß-carotene content in mango were significantly lower than the control in samples dried using drying beads. Drying method had a significant (P < 0.05) effect on nutrient content; ascorbic acid and ß-carotene content were lower in solar dried tomato than in tomato dried with drying beads. For mango, ß-carotene content was lower after solar drying as compared to drying with drying beads. Drying fruit at lower temperatures using drying beads resulted in higher overall nutrient content of the dried fruit. PRACTICAL APPLICATION: Agriculturalists in developing countries still depend largely on solar drying methods as a means of extending the shelf life and increasing the value of fruit and vegetable products. Zeolite drying beads are reusable and are capable of drying fruit relatively quickly in a controlled environment, and may reduce the degradation of certain nutrients due to heat during solar drying.

'Bartlett' pear fruit (Pyrus communis L.) ripening regulation by low temperatures involves genes associated with jasmonic acid, cold response, and transcription factors.

Low temperature (LT) treatments enhance ethylene production and ripening rate in the European pear (Pyrus communis L.). However, the underlying molecular mechanisms are not well understood. This study aims to identify genes responsible for ripening enhancement by LT. To this end, the transcriptome of 'Bartlett' pears treated with LT (0°C or 10°C for up to 14 d), which results in faster ripening, and control pears without conditioning treatment was analyzed. LT conditioned pears reached eating firmness (18N) in 6 d while control pears took about 12 d when left to ripen at 20°C. We identified 8,536 differentially expressed (DE) genes between the 0°C-treated and control fruit, and 7,938 DE genes between the 10°C-treated and control fruit. In an attempt to differentiate temperature-induced vs. ethylene-responsive pathways, we also monitored gene expression in fruit sequentially treated with 1-MCP then exposed to low temperature. This analysis revealed that genes associated with jasmonic acid biosynthesis and signaling, as well as the transcription factors TCP9a, TCP9b, CBF1, CBF4, AGL24, MYB1R1, and HsfB2b could be involved in the LT-mediated enhancement of ripening independently or upstream of ethylene.

Spatial variance of physicochemical properties within mangos and the effect of initial ripeness stage on the quality of fresh-cut mangos.

BACKGROUND: This study aimed to assess the spatial variation in physicochemical properties within individual mangos, as well as to investigate the influence of initial ripeness level on physicochemical characteristics of fresh-cut mangos. Individual mangos were evaluated at 12 specific flesh positions in the inner and outer sides. Mango cubes of 1.5 cm prepared from three firmness stages were monitored for changes during 9 days of storage at 5 °C. RESULTS: Mango fruit varied significantly in firmness and color based on spatial position, with the ripening direction from the inner flesh outward and from the stem end to blossom end. Limitations to fresh-cut mango quality were 'desiccation' (dried cut surface) and 'edge or tissue damage' (cut edge damage or brown and bruise-like appearance). Firmer texture and paler yellow of inner flesh were found in less mature mango fruit (P < 0.001). The optimal ripeness stage for fresh-cut mango products was 45 N, based on ease of handling, fresh appearance at the time of purchase and intermediate physicochemical properties (firmness, color and SSC/TA ratio). CONCLUSION: Spatial variance and initial ripeness stage affect fresh-cut mango quality. Therefore, they must be considered by fresh-cut mango processors in order to attain optimal product quality. © 2015 Society of Chemical Industry.

Ethyl Formate Fumigation of Dry and Semidry Date Fruits: Experimental Kinetics, Modeling, and Lethal Effect on Carob Moth.

Ethyl formate (EF) was studied as a fumigant agent with the objective to replace methyl bromide (MB) for date fruit disinfestations. Date fruits Phoenix dactylifera 'Deglet Nour' with different initial moisture content (16% for dry dates, 20% for semidry dates, and a mixture of the two types) were separately fumigated with EF at different concentrations: 28.6, 57.3, 85.9, and 114.6 g/m3 for 2 h. Experimental data of EF sorption during fumigation was successfully fitted to Peleg's model. This model allows the prediction of the effects of date moisture content and EF concentration on sorption behavior. Samples with different moisture content showed similar EF sorption behavior. Dates were artificially infested with carob moth (Ectomyelois ceratoniae (Zeller)) at different life stages. Eggs, third- and fifth-instars, and pupae were exposed to 28.6, 57.3, 85.9, and 114.6 g/m3 EF for 2 h. Among these life stages, fifth-instars were the most resistant to EF fumigation. A 2-h fumigation with 114.6 g/m3 EF provided complete control of eggs, third-instars, and pupae of carob moth, and generated 91.6% mortality of fifth-instars. A longer fumigation time or higher EF concentration may provide complete control of all life stages of carob moth.

A transcriptome approach towards understanding the development of ripening capacity in 'Bartlett' pears (Pyrus communis L.).

BACKGROUND: The capacity of European pear fruit (Pyrus communis L.) to ripen after harvest develops during the final stages of growth on the tree. The objective of this study was to characterize changes in 'Bartlett' pear fruit physico-chemical properties and transcription profiles during fruit maturation leading to attainment of ripening capacity. RESULTS: The softening response of pear fruit held for 14 days at 20 °C after harvest depended on their maturity. We identified four maturity stages: S1-failed to soften and S2- displayed partial softening (with or without ET-ethylene treatment); S3 - able to soften following ET; and S4 - able to soften without ET. Illumina sequencing and Trinity assembly generated 68,010 unigenes (mean length of 911 bp), of which 32.8 % were annotated to the RefSeq plant database. Higher numbers of differentially expressed transcripts were recorded in the S3-S4 and S1-S2 transitions (2805 and 2505 unigenes, respectively) than in the S2-S3 transition (2037 unigenes). High expression of genes putatively encoding pectin degradation enzymes in the S1-S2 transition suggests pectic oligomers may be involved as early signals triggering the transition to responsiveness to ethylene in pear fruit. Moreover, the co-expression of these genes with Exps (Expansins) suggests their collaboration in modifying cell wall polysaccharide networks that are required for fruit growth. K-means cluster analysis revealed that auxin signaling associated transcripts were enriched in cluster K6 that showed the highest gene expression at S3. AP2/EREBP (APETALA 2/ethylene response element binding protein) and bHLH (basic helix-loop-helix) transcripts were enriched in all three transition S1-S2, S2-S3, and S3-S4. Several members of Aux/IAA (Auxin/indole-3-acetic acid), ARF (Auxin response factors), and WRKY appeared to play an important role in orchestrating the S2-S3 transition. CONCLUSIONS: We identified maturity stages associated with the development of ripening capacity in 'Bartlett' pear, and described the transcription profile of fruit at these stages. Our findings suggest that auxin is essential in regulating the transition of pear fruit from being ethylene-unresponsive (S2) to ethylene-responsive (S3), resulting in fruit softening. The transcriptome will be helpful for future studies about specific developmental pathways regulating the transition to ripening.

Growth and survival of Enterobacteriaceae and inoculated Salmonella on walnut hulls and maturing walnut fruit.

Postharvest contamination of in-shell walnuts may occur when the fruit is dropped to or harvested from the orchard floor or as the outer hull is removed with mechanical abrasion and water. To evaluate the effect of maturity on the potential for microbial contamination, 'Howard' walnut fruits were collected weekly from the tree canopy, from 6 to 7 weeks before to 1 week after typical commercial harvest. The numbers of microorganisms able to form colonies on plate count agar, MacConkey agar (presumptive Enterobacteriaceae), or violet red bile lactose agar (presumptive coliforms) were compared on whole walnut fruits collected by hand directly from the tree or after exposure to the orchard floor for 10 min or 24 h. Salmonella Enteritidis PT 30 was inoculated at <1 to 8 log CFU/g onto 5-g hull pieces (from walnut fruit of different maturities) and stored at ambient temperature (23 to 26°C) in unsealed bags (38 to 90% relative humidity [RH] within bag) or in low humidity (20 to 45% RH) or high humidity (68 to 89% RH) for up to 14 days. Salmonella at 2 or 5 log CFU/ml was inoculated onto hulls before or up to 14 days after blending with water. As the walnut fruit matured, the indigenous bacterial levels on the surface increased, irrespective of whether fruit was collected from the tree or the ground. The RH influenced the growth of inoculated bacteria on hull pieces: Salmonella declined to <0.3 log CFU/g within 24 h at low RH but multiplied from 2 to 6 log CFU/g over 14 days of storage at >40% RH. Salmonella populations declined to <1 CFU/ml within 24 h in freshly blended green hulls but survived or multiplied in blended brown hulls or in blended green hulls that had been stored for 24 h or more before being inoculated.

Effect of ethylene and temperature conditioning on sensory attributes and chemical composition of 'Comice' pears.

'Comice' is among the pear varieties most difficult to ripen after harvest. Ethylene, cold temperature, and intermediate (10 °C) temperature conditioning have been successfully used to stimulate the ability of 'Comice' pears to ripen. However, the sensory quality of pears stimulated to ripen by different conditioning treatments has not been evaluated. In this study, a descriptive sensory analysis of 'Comice' pears conditioned to soften to 27, 18, and 9 N firmness with ethylene exposure for 3 or 1 days, storage at 0 °C for 25 or 15 days, or storage at 10 °C for 10 days was performed. Sensory attributes were then related to changes in chemical composition, including volatile components, water-soluble polyuronides, soluble solids content (SSC), and titratable acidity (TA). The sensory profile of fruit conditioned with ethylene was predominant in fibrous texture and low in fruity and pear aroma. Fruit conditioned at 0 °C was described as crunchy at 27 and 18 N firmness and became juicy at 9 N firmness. Fruit conditioned at 0 °C produced the highest quantity of alcohols and fewer esters than fruit conditioned at 10 °C, and they had higher fruity and pear aroma than fruit conditioned with ethylene, but lower than fruit conditioned at 10 °C. Fruit held at 10 °C were predominant in fruity and pear aroma and had the highest concentration of esters. Water-soluble polyuronides were strongly, positively correlated (r > 0.9) with sensory attributes generally associated with ripeness, including juiciness, butteriness, and sweetness and negatively correlated (r > -0.9) with sensory attributes generally associated with the unripe stage, such as firmness and crunchiness. However, water-soluble polyuronides were not significantly different among conditioning treatments. Sensory sweetness was not significantly correlated with SSC, but TA and SSC/TA were significantly correlated with sensory tartness. However, there were no significant differences among the conditioning treatments in sweet or sour taste perception when the fruit fully softened. The results indicate that the various methods of conditioning 'Comice' pear fruits for ripening had different effects on their sensory and chemical properties that may influence their sensory quality.

Effectiveness of calcium chloride and calcium lactate on maintenance of textural and sensory qualities of fresh-cut mangos.

UNLABELLED: The effects of calcium chloride (CaCl2 ) and calcium lactate on maintaining textural and sensory quality of fresh-cut "Kent" and "Tommy Atkins" mangos and determination of treatments preferred by consumers were investigated. Mango cubes (1.5 × 1.5 × 1.5 cm) were subjected to different CaCl2 and calcium lactate concentrations (0 M, 0.068 M, 0.136 M, 0.204 M) and dip times (0, 1, 2.5, 5 min). Instrumental quality parameters (firmness, color, soluble solids, titratable acidity) were analyzed periodically during 9 d of storage at 5 °C. Tommy Atkins mango cubes became more orange, but also had more browning than Kent mango cubes during storage at 5 °C. Firmness retention during storage was greater with mangos cubes treated with CaCl2 than with calcium lactate, therefore we focused our instrumental analysis only on CaCl2 -treated cubes. The firmness of Tommy Atkins mango cubes was higher than Kent. Soluble solids content (SSC), titratable acidity (TA), and SSC/TA were higher in fresh-cut Kent mango cubes. Mangos treated with CaCl2 showed retarded softening during storage, and the retardation was greater at higher calcium concentrations. A consumer test was conducted to cluster consumers based on mango preference in order to correlate consumer liking and calcium treatments, as well as to uncover consumer intentions for in-store fresh-cut mango purchases. Treatment at 10 °C with 0.136 M CaCl2 for 2.5 min for Tommy Atkins mangos and 1 min for Kent mangos was effective in retaining firmness during storage at 5 °C and was also not disliked by consumers. A cluster analysis divided consumers into 2 preference groups, with Kent mangos significantly preferred over Tommy Atkins. PRACTICAL APPLICATION: Fresh-cut mangos often develop tissue softening and discoloration during storage. Short dips (1 to 3 min) in either CaCl2 or calcium lactate effectively improve fresh-cut mango firmness and color retention after cutting. Mango samples treated with CaCl2 had higher liking scores compared to those treated with calcium lactate. "Kent" mango variety is more suitable than "Tommy Atkins" for fresh-cut processing in terms of less tissue browning and higher consumer liking.

Effects of 1-methylcyclopropene and hot water quarantine treatment on quality of "Keitt" mangos.

The optimal 1-methylcyclopropene (1-MCP) treatment to slow ripening of whole "Keitt" mangos, either alone or in combination with hot water treatment (HWT) (prior to or post 1-MCP) was identified. USDA-APHIS mandates that HWT can be used for control of fruit flies, but this may affect fruit response to 1-MCP. Mangos were evaluated by repeated measurement of nondestructive firmness, peel color, and ethylene production on the same mango fruits during 2 wk of ripening at 20 °C after treatment. The magnitude of ethylene production increased as a result of both 1-MCP and HWT. With softer mangos (65 N), treatment with 1-MCP alone delayed fruit softening and extended the number of days to full-ripeness (25 N) from 5 d in untreated fruit to 11 d. For these riper fruit, application of 1-MCP prior to HWT extended the days to full-ripeness to 9 d compared with 7 d when 1-MCP was applied after HWT. With firmer mangos (80 N), 1-MCP treatments alone prolonged the days to full-ripeness to 13 d as compared to 11 d for the untreated fruit. There was no significant concentration effect on firmness retention among 1-MCP treatments (0.5, 1.0, or 10.0 µL/L). HWT resulted in a faster rate of fruit softening, taking only 7 d to reach full-ripeness. Combining 1-MCP with HWT reduced the rate of softening compared to HWT alone, resulting in 9 to 11 d to full-ripeness. Application of 1-MCP before HWT showed a greater ability to reduce the rate of fruit softening compared with 1-MCP treatment after HWT.

Calcium partitioning and allocation and blossom-end rot development in tomato plants in response to whole-plant and fruit-specific abscisic acid treatments.

The mechanisms regulating Ca(2+) partitioning and allocation in plants and fruit remain poorly understood. The objectives of this study were to determine Ca(2+) partitioning and allocation in tomato plants and fruit in response to whole-plant and fruit-specific abscisic acid (ABA) treatments, as well as to analyse the effect of changes in Ca(2+) partitioning and allocation on fruit susceptibility to the Ca(2+) deficiency disorder blossom-end rot (BER) under water stress conditions. Tomato plants of the cultivar Ace 55 (Vf) were grown in a greenhouse and exposed to low Ca(2+) conditions during fruit growth and development. Starting 1 day after pollination (DAP), the following treatments were initiated: (i) whole plants were sprayed weekly with deionized water (control) or (ii) with 500mg l(-1) ABA; or fruit on each plant were dipped weekly (iii) in deionized water (control) or (iv) in 500mg l(-1) ABA. At 15 DAP, BER was completely prevented by whole-plant or fruit-specific ABA treatments, whereas plants or fruit treated with water had 16-19% BER incidence. At 30 DAP, BER was prevented by the whole-plant ABA treatment, whereas fruit dipped in ABA had a 16% and water-treated plants or fruit had a 36-40% incidence of BER. The results showed that spraying the whole plant with ABA increases xylem sap flow and Ca(2+) movement into the fruit, resulting in higher fruit tissue and water-soluble apoplastic Ca(2+) concentrations that prevent BER development. Although fruit-specific ABA treatment had no effect on xylem sap flow rates or Ca(2+) movement into the fruit, it increased fruit tissue water-soluble apoplastic Ca(2+) concentrations and reduced fruit susceptibility to BER to a lesser extent.

Survival of foodborne pathogens on inshell walnuts.

The survival of Salmonella enterica Enteritidis PT 30 or five-strain cocktails of S. enterica, Escherichia coli O157:H7, and Listeria monocytogenes was evaluated on inshell walnuts during storage. Inshell walnuts were separately inoculated with an aqueous preparation of the pathogens at levels of 10 to 4 log CFU/nut, dried for 24 h, and then stored at either 4 °C or ambient conditions (23-25 °C, 25-35% relative humidity) for 3 weeks to more than 1 year. During the initial 24-h drying period, bacterial levels declined by 0.7 to 2.4 log CFU/nut. After the inoculum dried, further declines of approximately 0.1 log CFU/nut per month of Salmonella Enteritidis PT 30 levels were observed on inshell walnuts stored at 4 °C; at ambient conditions the rates of decline ranged from 0.55 to 2.5 log CFU/nut per month. Rates of decline were generally greater during the first few weeks of storage, particularly at lower inoculum levels. The survival of the five-strain cocktails inoculated at very low levels (under 400 CFU/nut) was determined during storage at ambient conditions. The pathogens could be recovered by either enumeration or enrichment from most samples throughout the 3-month storage period; reductions in bacterial levels from the beginning to end of storage were 0.7, 0.2, and 2.3 log CFU/nut for Salmonella, E. coli O157:H7, and L. monocytogenes, respectively. For 6% of all nut samples (14 of 234 samples), pathogens were isolated from the second but not first 24-h enrichment, suggesting that bacterial cells were viable but not easily culturable. Salmonella-inoculated walnuts were exposed for 2 min to water or a 3% solution of sodium hypochlorite (to mimic commercial brightening) either 24 h or 7 days after inoculation; treated nuts were dried for 24h and held at ambient conditions. Salmonella levels were reduced by less than 0.5 log or 2.4 to 2.6 log CFU/nut on water- or chlorine- treated walnuts, respectively, regardless of postinoculation treatment time. Additional reductions of 2.6 and 2.1 log CFU/nut were observed for water- and chlorine-treated walnuts, respectively, after storage for 2 weeks at ambient conditions. Bacterial foodborne pathogens are capable of long-term survival on the surface of inshell walnuts even when initial levels are low.

An integrated approach for flavour quality evaluation in muskmelon (Cucumis melo L. reticulatus group) during ripening.

Numerous and diverse physiological changes occur during fruit ripening and maturity at harvest is one of the key factors influencing the flavour quality of fruits. The effect of ripening on chemical composition, physical parameters and sensory perception of three muskmelon (Cucumis melo L. reticulatus group) cultivars was evaluated. Significant correlations emerging from this extensive data set are discussed in the context of identifying potential targets for melon sensory quality improvement. A portable ultra-fast gas-chromatograph coupled with a surface acoustic wave sensor (UFGC-SAW) was also used to monitor aroma volatile concentrations during fruit ripening and evaluated for its ability to predict the sensory perception of melon flavour. UFGC-SAW analysis allowed the discrimination of melon maturity stage based on six measured peaks, whose abundance was positively correlated to maturity-specific sensory attributes. Our findings suggest that this technology shows promise for future applications in rapid flavour quality evaluation.

Postharvest control of western flower thrips (Thysanoptera: Thripidae) and California red scale (Hemiptera: Diaspididae) with ethyl formate and its impact on citrus fruit quality.

The postharvest control of arthropod pests is a challenge that the California citrus industry must overcome when exporting fruit overseas. Currently, methyl bromide fumigation is used to control postharvest pests on exported citrus, but it may soon be unavailable because of use restrictions and cost of this health-hazard ozone-depleting chemical. Ethyl formate is a natural plant volatile and possible alternative to methyl bromide in postharvest insect control. The objectives of this study were 1) to evaluate the mortality of third instar California red scale [Aonidiella aurantii (Maskell)] (Hemiptera: Diaspididae) and adult western flower thrips [Frankliniella occidentalis (Pergande)] (Thysanoptera: Thripidae) under a wide range of ethyl formate concentrations, 2) to determine the ethyl formate concentration required to reach a Probit 9 level of control for both pests, and 3) to test the effects of ethyl formate fumigation on the quality of navel oranges [Citrus sinensis (L.) Osbeck] and lemons [Citrus limon (L.) Burman f.] at 24 h after fumigation, and at different time periods to simulate shipping plus storage (5 wk at 5 degrees C), and shipping, storage, handling, and shelf-life (5 wk at 5 degrees C, plus 5 d at 15 degrees C, and 2 d at 20 degrees C). The results indicate that ethyl formate is a promising alternative to methyl bromide for the California citrus industry, because of successful control of adult western flower thips and third instar California red scale and no deleterious effect on fruit quality at any of the evaluated periods and quality parameters.

Role of pectin methylesterases in cellular calcium distribution and blossom-end rot development in tomato fruit.

Blossom-end rot (BER) in tomato fruit (Solanum lycopersicum) is believed to be a calcium (Ca²âº) deficiency disorder, but the mechanisms involved in its development are poorly understood. Our hypothesis is that high expression of pectin methylesterases (PMEs) increases Ca²âº bound to the cell wall, subsequently decreasing Ca²âº available for other cellular functions and thereby increasing fruit susceptibility to BER. The objectives of this study were to evaluate the effect of PME expression, and amount of esterified pectins and Ca²âº bound to the cell wall on BER development in tomato fruit. Wild-type and PME-silenced tomato plants were grown in a greenhouse. At full bloom, flowers were pollinated and Ca²âº was no longer provided to the plants to induce BER. Our results show that suppressing expression of PMEs in tomato fruit reduced the amount of Ca²âº bound to the cell wall, and also reduced fruit susceptibility to BER. Both the wild-type and PME-silenced fruit had similar total tissue, cytosolic and vacuolar Ca²âº concentrations, but wild-type fruit had lower water-soluble apoplastic Ca²âº content and higher membrane leakage, one of the first symptoms of BER. Our results suggest that apoplastic water-soluble Ca²âº concentration influences fruit susceptibility to Ca²âº deficiency disorders.

Survival of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes on inoculated walnut kernels during storage.

The survival of single strains or cocktails of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes was evaluated on walnut kernels. Kernels were separately inoculated with an aqueous preparation of the pathogens at 3 to 10 log CFU/g, dried for 7 days, and then stored at 23°C for 3 weeks to more than 1 year. A rapid decrease of 1 to greater than 4 log CFU/g was observed as the inoculum dried. In some cases, the time of storage at 23°C did not influence bacterial levels, and in other cases the calculated rates of decline for Salmonella (0.05 to 0.35 log CFU/g per month) and E. coli O157:H7 (0.21 to 0.86 log CFU/g per month) overlapped and were both lower than the range of calculated declines for L. monocytogenes (1.1 to 1.3 log CFU/g per month). In a separate study, kernels were inoculated with Salmonella Enteritidis PT 30 at 4.2 log CFU/g, dried (final level, 1.9 log CFU/g), and stored at -20, 4, and 23°C for 1 year. Salmonella Enteritidis PT 30 declined at a rate of 0.10 log CFU/g per month at 23°C; storage time did not significantly affect levels on kernels stored at -20 or 4°C. These results indicate the long-term viability of Salmonella, E. coli O157:H7, and L. monocytogenes on walnut kernels and support inclusion of these organisms in hazard assessments.

Dynamic alternations in cellular and molecular components during blossom-end rot development in tomatoes expressing sCAX1, a constitutively active Ca2+/H+ antiporter from Arabidopsis.

Although calcium (Ca) concentration in cellular compartments has been suggested to be tightly regulated, Ca deficiency disorders such as blossom-end rot (BER) in tomato (Solanum lycopersicum) fruit may be induced by abnormal regulation of Ca partitioning and distribution in the cell. The objectives of this work were to analyze the effects of high expression of the constitutively functional Arabidopsis (Arabidopsis thaliana) Ca(2+)/H(+) exchanger (sCAX1) tonoplast protein in tomato fruit on cellular Ca partitioning and distribution, membrane integrity, and the transcriptional profile of genes potentially involved in BER development. Wild-type and sCAX1-expressing tomato plants were grown in a greenhouse. Wild-type plants did not develop BER, whereas sCAX1-expressing plants reached 100% BER incidence at 15 d after pollination. The sCAX1-expressing fruit pericarp had higher total tissue and water-soluble Ca concentrations, lower apoplastic and cytosolic Ca concentrations, higher membrane leakage, and Ca accumulation in the vacuole of sCAX1-expressing cells. Microarray analysis of healthy sCAX1-expressing fruit tissue indicated down-regulation of genes potentially involved in BER development, such as genes involved in membrane structure and repair and cytoskeleton metabolism, as well as up-regulation of genes that may have limited BER damage expansion, such as genes coding for heat shock proteins, glutathione S-transferases, and peroxidases. The results indicate that the high expression of the sCAX1 gene reduces cytosolic and apoplastic Ca concentrations, affecting plasma membrane structure and leading to BER symptom development in the fruit tissue.