Robert A. Saftner

University of the District of Columbia, Washington, Washington, D.C., United States

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Publications (28)13.13 Total impact

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    ABSTRACT: With 3 figures and 4 tablesAbstractPenicillium expansum and Colletotrichum acutatum cause blue mould and bitter rot of apples during storage which results in significant economic losses. Resistance to these pathogens in commercial apple cultivars has not been documented in the literature. An apple germplasm collection, from the centre of origin in Kazakhstan, is maintained in Geneva, New York. This collection represents a more diverse apple gene pool than commercial cultivars and was evaluated for resistance to the pathogens that cause blue mould and bitter rot. Resistance reactions were skewed towards susceptibility for both fungi and comprised the majority of accessions examined. However, resistance to P. expansum was confirmed in select accessions over multiple years. Maturation patterns and quality indices for soluble solids and acidity, which may also affect susceptibility, were highly variable and represent the genetic diversity of the germplasm collection. Resistance in four accessions to C. acutatum and two accessions resistant to both P. expansum and C. acutatum are reported here for the first time. Data from this study will serve as a foundation for conventional apple breeding programmes and molecular genetics investigations to provide resistance against blue mould and bitter rot in commercial apple varieties.
    Plant Breeding 07/2011; 130(4):481 - 486. · 1.18 Impact Factor
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    ABSTRACT: A mixture of two yeast antagonists, Metschnikowia pulcherrima and Cryptococcus laurentii, originally isolated from apples and exhibiting greater biocontrol activity against blue mold of apple than either yeast applied alone, were used in combination with sodium bicarbonate (SBC) in a pilot test in which treated fruit were stored under commercial controlled atmosphere (CA) storage conditions. Conidia of Penicillium expansum, antagonists cells and SBC were added to the drench solution. The treatments were applied to apples by drenching entire bins filled with apples containing 100 wounded fruit evenly distributed among five positions in each bin. The treated fruit were stored in commercial CA storages for approximately six months in the 2005-2006 and 2006-2007 storage seasons and then evaluated for incidence of decay. In both years, the treatments with the antagonist alone or in combination with SBC were equally effective and reduced blue mold incidence by 84-97% in 2005-2006 and 73-82% in 2006-2007. SBC alone significantly reduced blue mold incidence compared to the non-treated control but was less effective than the antagonist alone or in combination with SBC. This pilot test showed that the combination of these two antagonists and SBC can be an effective decay control method under commercial CA conditions, confirming results from our earlier laboratory studies using similarly treated fruit stored under CA conditions.
    01/2008;
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    ABSTRACT: We compared the instrumental and sensory quality characteristics of blueberry fruit from ten highbush (Vaccinium corymbosum L.) cultivars, Chanticleer, Weymouth, Hannah's Choice, Duke, Bluecrop, Coville, Berkeley, Bluegold, Elliott and Lateblue and two rabbiteye (Vaccinium virgatum Aiton) cultivars, Coastal and Montgomery, grown in New Jersey. Cultivars varied in sensory intensity and acceptability scores. Highbush cultivars, Coville and Hannah's Choice, scored highest among the cultivars in sensory scores for intensity of blue color, juiciness, sweetness and blueberry-like flavor and for acceptability of appearance, color, fruit size, sweet/tart balance, flavor and overall eating quality. In contrast, rabbiteye cultivars, Coastal and Montgomery, and the highbush cultivars, Elliott and Weymouth, scored lowest among the cultivars in sensory scores for intensity of bursting energy, skin toughness, texture during chewing, juiciness, and blueberry-like flavor and for acceptability of appearance, color, fruit size, flavor and overall eating quality. Analytical quality characteristics of surface color, size, compression firmness, soluble solids content (SSC), pH, titratable acidity (TA), SSC/TA ratio, and aromatic volatile concentration also varied among cultivars, but no instrumental measurement adequately predicted consumer acceptability scores. The overall eating quality of blueberry fruit was best correlated with flavor scores followed by sensory scores for intensity of juiciness, bursting energy and sweetness and for acceptability of appearance.
    Postharvest Biology and Technology. 01/2008;
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    J.H. Bai, R.A. Saftner, A.E. Watada, Y.S. Lee
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    ABSTRACT: Fresh-cut cantaloupe cubes were placed in film-sealed containers in which the internal gas mixture was attained naturally (nMAP), was flushed with 4 kPa O2 plus 10 kPa CO2 (fMAP), or was maintained near atmospheric levels by perforating the film (PFP). While both nMAP and fMAP maintained the salable quality of melon cubes for 9 d at 5 degrees C, fMAP maintained quality better than nMAP. The benefit of fMAP was indicated by better color retention, and by reduced translucency, respiration rate, and microbial population compared with nMAP. Shelf life of cubes in PFP was only 5 to 7 d at 5 degrees C, and its rapid decline was due to tissue translucency and/or off-odor development.
    01/2008;
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    ABSTRACT: ‘Golden Delicious’ apples were wound-inoculated with Penicillium expansum and treated with various combinations of sodium bicarbonate and two antagonists (Metschnikowia pulcherrima, Cryptococcus laurentii), and then stored in air or controlled atmosphere (CA = 1.4 kPa O2 and 3 kPa CO2) for 2 or 4 months at 1 °C. The antagonists survived and their populations increased during both air and CA storage. The antagonists alone reduced blue mold but were more effective when combined. Sodium bicarbonate tended to reduce lesion size when used with these antagonist, either when they were used alone or combined. Storage under CA conditions also increased the effectiveness of both antagonist, when used alone or in combination. The only treatment that completely eliminated P. expansum-incited decay was the combination of the two antagonists and sodium bicarbonate on fruit stored under CA conditions. The proper combination of alternative control measures can provide commercially acceptable long-term control of fruit decay and could help reduce our dependency on fungicides.
    Postharvest Biology and Technology. 09/2007;
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    ABSTRACT: Maintaining the postharvest quality of fresh-cut fruit after processing and throughout distribution and marketing is a major challenge facing the fresh-cut fruit industry. Analytical quality characteristics of packaged fresh-cut watermelon slices from non-treated and 1-methylcyclopropene (1-MCP)- and/or ethylene-treated whole fruit were investigated. Freshly harvested seedless watermelon (‘Sugar Heart’) were stored 7–14 days in air before exposure to 0, 0.5 or 1.0 μL L−1 1-MCP for 18 h followed by 5 days exposure to 0 or 10 μL L−1 ethylene, all at 20 °C. Following treatment, fruit were processed into wedge-shaped slices, packaged into rigid trays sealed with a high oxygen transmission rate film overlap and stored 1, 6 or 12 days at 5 °C. During storage, fresh-cut watermelon slices from non-treated and 1-MCP- and 1-MCP + ethylene-treated whole fruit maintained similar respiration rates and internal atmospheres of CO2 and O2 and were of similar quality with total aromatic volatile concentrations decreasing and puncture firmness, soluble solids content (SSC), cut surface pH and color remaining relatively stable. In contrast, fresh-cut slices from fruit treated with ethylene alone had higher respiration rates and modified package atmospheres containing more CO2 and O2; lower firmness, SSC and chromaticity values; higher pH and an altered volatile profile compared to those of slices from non-treated and 1-MCP- and 1-MCP + ethylene-treated fruit. The 22 most abundant volatiles were various aldehydes, alcohols and ketones. During storage, many individual volatiles decreased in concentration but some increased including (Z)-6-nonen-1-ol, a volatile having a pumpkin-like aroma. The results indicated that low dosage 1-MCP treatments prior to ethylene exposure of whole watermelons prevented ethylene-mediated quality deterioration in fresh-cut slices stored under modified atmosphere conditions at 5 °C.
    Postharvest Biology and Technology. 01/2007;
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    ABSTRACT:   The effects of exogenous ethylene, 1-methylcyclopropene (1-MCP), or both on microbial growth on watermelon fruit and watermelon slices were investigated. Freshly harvested seedless watermelons (Citrullus lanatus, cv. Sugar Heart) were treated with 0.5 or 1.0 ppm 1-MCP, 10 ppm ethylene, 1-MCP + ethylene, or left untreated as controls. Fruits were processed into wedge-shaped slices, packaged into rigid trays sealed with a polyethylene film with a 29.2 pmol s−1 m−2 Pa−1 oxygen transmission rate. The slices were evaluated after 0-, 6-, and 12-d storage at 5 °C. Ethylene treatment alone increased the populations of aerobic bacteria, lactic acid bacteria, and yeasts and molds on the packaged slices during storage compared to those on corresponding control slices and resulted in extensive juice leakage from the slices. The ethylene treatment also resulted in high aerobic bacterial counts throughout the flesh of whole melons compared to the controls. Treating watermelons with 0.5 or 1.0 ppm 1-MCP prior to ethylene exposure counteracted the deleterious effects of ethylene. Extending the time from harvest to 1-MCP treatment increased the population of aerobic bacteria, but had no detectable effect on the growth of lactic acid bacteria or yeasts and molds. The results indicate that low concentrations (0.5 or 1.0 ppm) of 1-MCP can be used on whole watermelon to avoid deleterious effects of exogenous ethylene to which the melons could be exposed during shipping or storage.
    Journal of Food Science 07/2006; 71(6):M180 - M184. · 1.78 Impact Factor
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    ABSTRACT: Maintaining the sensory, microbial and postharvest quality of fresh-cut fruit after processing and throughout distribution and marketing is a major challenge facing the fresh-cut fruit industry. Fresh-cut chunks of orange-fleshed honeydew (‘Honey Gold’, ‘Orange Dew’, ‘Temptation’ and three breeding lines) and green-fleshed honeydew (‘Honey Brew’) and an orange-fleshed cantaloupe (‘Cruiser’) harvested at commercial and full-slip maturities were compared after storage for 0–11 days in air at 5 °C. Fresh-cut cantaloupe had higher respiration and ethylene production rates, aromatic volatile concentrations, and β-carotene/chroma and orange hue (except ‘Orange Dew’) than those of honeydew whereas honeydew chunks generally had higher soluble solids content (SSC), Kramer firmness and lower microbial counts than cantaloupe chunks. All genotypes had similar ascorbic acid levels. During storage, analytical quality characteristics of fresh-cut chunks from all genotypes were well maintained even though microbial populations increased especially on cantaloupe chunks. Consumers liked the flavor, texture, sweetness and overall eating quality of the orange-fleshed honeydew genotypes as well as or better than those of cantaloupe and green-fleshed honeydew. ‘Orange Dew’ scored highest in appearance and had the highest β-carotene concentration, chroma and orange hue among orange-fleshed honeydew genotypes whereas ‘Temptation’ generally scored highest for flavor intensity and acceptability and overall eating quality; and it had the highest aromatic volatile concentrations among the orange-fleshed honeydews. Many individual volatiles were identical in cantaloupe and honeydews; however, honeydew genotypes, particularly ‘Temptation’, were distinctive from cantaloupe and green-fleshed honeydew in having relatively high levels of various nonenyl and nonadienyl acetates having honeydew-like or uncharacterized aromas. Fresh-cut chunks from full-slip melons generally had higher analytical and sensory quality characteristics but higher microbial counts and lower shelf stability compared to those from commercially mature fruit. The results indicate that orange-fleshed honeydews are a promising new melon type for fresh-cut processing.
    Postharvest Biology and Technology. 01/2006;
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    ABSTRACT: Modified atmosphere packaging (MAP) is widely used to maintain the quality of fresh-cut produce by matching the oxygen transmission rate (OTR) of the packaging film to the respiration rate of the packaged product. The effect of the interaction between film OTR and the initial headspace O2 on quality of fresh-cut vegetables has not previously been reported. Romaine lettuce leaves were sliced, washed, dried and packaged with film OTRs of 8.0 and 16.6 pmol s−1 m−2 Pa−1, and with initial headspace O2 of 0, 1, 2.5, 10 and 21 kPa. Packages were hermetically sealed and stored at 5 °C for up to 14 days. For samples packaged in 16.6 OTR film, increasing the initial headspace O2 concentration delayed O2 depletion within the packages, hastened the onset and increased the intensity of discoloration, and inhibited the development of CO2 injury, acetaldehyde and ethanol accumulation, off-odors and electrolyte leakage. With 8.0 OTR-packaged lettuce pieces, ≤1 kPa initial headspace O2 treatments induced an essentially anaerobic environment within the packages and increased acetaldehyde and ethanol accumulation and off-odor development. Increasing the initial O2 concentration above 1 kPa in 8.0 OTR packages transiently increased O2 concentrations and reduced fermentative volatile production, off-odors, electrolyte leakage and CO2 injury. Regardless of initial headspace O2 concentration, all 16.6 OTR-packaged samples had severe discoloration after 14 days of storage. Quality was better maintained in 8.0 OTR-packaged lettuce pieces as the initial headspace O2 concentration was increased. A 21 kPa initial O2 treatment of 8.0 OTR-packaged lettuce maintained good quality throughout storage and had the best overall quality score. Copyright © 2005 Society of Chemical Industry
    Journal of the Science of Food and Agriculture 08/2005; 85(10):1622 - 1630. · 1.76 Impact Factor
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    ABSTRACT: Development of fresh-cut apple products requires consideration of cultivars that store well as both intact and fresh-cut fruit. We compared the instrumental and sensory quality of 2 apple cultivars, Granny Smith and Fuji, that are used for fresh cutting with 2 new cultivars, Pink Lady and GoldRush, which were considered to have quality characteristics suitable for fresh cutting. Firmness, titratable acidity (TA), soluble solids content (SSC), and aromatic volatile concentration were measured in intact fruit of the 4 cultivars during 12 mo storage in air at 0 °C and during 3 wk storage at 5 °C as fresh-cut slices. After 1 wk storage as fresh-cut slices, sensory evaluations for acceptability of flesh and peel appearance, flavor, texture, and overall eating quality were performed. During storage, GoldRush apples maintained > 80 N firmness, approximately 17% SSC, > 0.5% TA, and had high aromatic volatile production, that is, maintained quality better than the other cultivars. The quality and shelf stability of GoldRush slices were also as good as or better than slices from the other cultivars, whereas Granny Smith slices generally rated lower than the other cultivars. The acceptability of flavor, texture, and overall eating quality of GoldRush slices was as good as that for Pink Lady and Fuji. The quality of GoldRush apples can be maintained throughout the year in refrigerated air storage and still remain suitable for fresh-cut processing. The results indicate that GoldRush and Pink Lady are 2 promising new, high-quality apple cultivars for fresh cutting. Keywords: fresh-cut fruit, Malus × domestica, postharvest quality, respiration rate, shelf life
    Journal of Food Science 05/2005; 70(5):S317 - S324. · 1.78 Impact Factor
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    Ji Gang, Yaguang Luo, Robert A Saftner, Kenneth C Gross
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    ABSTRACT: ADDITIONAL INDEX WORDS. CO 2 injury, electrolyte leakage, oxygen transmission rate, postharvest technology ABSTRACT. Fresh-cut tissues are subjected to severe injury during preparation that leads to increased respiratory activ-ity and quality deterioration. Modifi ed atmosphere packaging (MAP) has been used to maintain quality of fresh-cut produce, but O 2 depletion and excessive CO 2 accumulation can be injurious. This study was conducted to evaluate the effect of delayed packaging and MAP using two different oxygen transmission rate (OTR) fi lms on quality maintenance and shelf stability of fresh-cut romaine lettuce (Lactuca sativa L.). Romaine lettuce leaves were cut, washed, dried, and placed for 0, 4, 8, and 12 hours at 5 °C in ambient air before packaging. Fresh-cut samples were placed into packages prepared from fi lms having OTRs of 8.0 and 16.6 pmol·s –1 ·m –2 ·Pa –1 , fl ushed with N 2 to reach an initial headspace O 2 level of 1.5 kPa O 2 , and stored at 5 °C for up to 14 days. Delayed packaging affected gas composition, fermentative volatile production, off-odor development, color, CO 2 injury, and tissue electrolyte leakage. With increasing delay be-fore packaging, fermentative volatile production, off-odor development, and CO 2 injury progressively decreased and discoloration increased. The modifi ed atmospheres obtained with 16.6 OTR fi lm increased discoloration when present, and generally had less off-odor development and CO 2 injury compared to MAP with 8.0 OTR fi lm. Delayed packaging affected overall quality of fresh-cut romaine lettuce packaged with both fi lms. A 12-hour delayed packaging into packages prepared from 8.0 OTR fi lm maintained quality by inhibiting CO 2 injury, off-odor development, and tissue electrolyte leakage. However, an 8-hour delayed packaging into packages prepared from 16.6 OTR fi lm was better at maintaining the quality of fresh-cut romaine lettuce at 5 °C for 14 days. The results indicated that delayed packaging could be an alternative method to optimize or balance package O 2 during suboptimal OTR fi lm packaging conditions. Packaged fresh-cut vegetables are becoming more and more popular because they are convenient and ready-to-eat. The fresh-cut produce industry has been on a double-digit growth rate in response to an increased demand by consumers. However, fresh-cut produce has limited shelf stability due to rapid quality deterioration (Huxsoll et al., 1989; Jacxsens et al., 2002). The major technical issues associated with packaged fresh-cut romaine lettuce are discoloration and decay. Modifi ed atmosphere packag-ing (MAP) technology has been successfully used to control both discoloration and decay. It is essential to maintain an optimum balance of O 2 and CO 2 in the packages to minimize discoloration and decay. The balanced atmospheres are afforded by the selec-tion of suitable fi lm oxygen transmission rate (OTR), respiring surface area, product weight, and respiration rate (Lakakul et al., 1999). Packages are often fl ushed with N 2 to reach a desired initial O 2 level to increase the O 2 equilibration rate and to control browning immediately after processing. However, this practice faces several challenges due to the large variations in respira-tion rate from different varieties, large seasonal variation, and postharvest storage duration prior to processing. In particular, the large variation in respiration rate often results in O 2 being either too high or too low in the package, resulting in the development of tissue discoloration when O 2 is higher than optimal or tissue The authors wish to thank Willard Douglas for adjusting an automatic system to rapidly measure respiration and ethylene production rates of fresh-cut lettuce. Use of a company name or product by the USDA does not imply approval or recom-mendation of the product to the exclusion of others that also may be suitable.
    J. AMER. SOC. HORT. SCI. 01/2005; 130(130):116-123116.
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    ABSTRACT: ‘Golden Delicious’ apples were wound-inoculated with either Colletotrichum acutatum or Penicillium expansum and then treated with various combinations of heat (38 °C) for 4 days, 2% sodium bicarbonate, and two biocontrol agents alone or combined. The fruit were stored for 4 months at 1 °C and then at 20 °C for 2 weeks. Either heat or the antagonists reduced decay caused by C. acutatum, but a combination of the two was required to completely eliminate decay caused by this pathogen in most cases. Sodium bicarbonate alone or in combination with the antagonists had little effect on C. acutatum. The antagonists alone reduced decay caused by P. expansum but tended to be more effective when combined. Sodium bicarbonate increased the effectiveness of decay control by each antagonist alone or in combination. All of the treatments that included heat virtually eliminated decay caused by this pathogen. The proper combination of alternative control measures can provide an effective strategy to reduce postharvest decay of apple fruit.
    Postharvest Biology and Technology. 01/2005;
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    ABSTRACT: ‘Golden Delicious’ apples were wound inoculated with conidial suspensions of either Colletotrichum acutatum or Penicillium expansum, then treated with heat (38 °C) for 4 days, sodium bicarbonate, and/or one of two heat tolerant biocontrol agents (yeasts). Following four months storage at 0 °C, the apples were left at room temperature for two weeks. Populations of antagonists were stable throughout the experiment and were higher on the heated than the non-heated fruit. Both antagonists reduced decay caused by P. expansum, whereas heat or heat in combination with either antagonist eliminated decay. Either heat or the antagonists alone reduced decay caused by C. acutatum, but a combination of the two was required to completely eliminate decay caused by this pathogen. Adding sodium bicarbonate to the heated or antagonist-treated fruit had little effect on decay caused by either pathogen but when used on non-heated fruit, it significantly reduced decay severity caused by P. expansum after four months at 0 °C. The goal of this research is to combine alternative methods of control to provide an effective substitute for synthetic pesticides.
    Postharvest Biology and Technology. 10/2004;
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    ABSTRACT: ABSTRACT Penicillium expansum, P. digitatum, and P. italicum acidify the ambient environments of apple and citrus fruit during decay development. They use two mechanisms for this: the production of organic acids, mainly citric and gluconic, and NH(4)(+) utilization associated with H(+) efflux. Exposure of P. expansum and P. digitatum hyphae to pH 5.0 increased their citric acid production, compared with the production of organic acids at acidic ambient pH. In decayed fruit, both pathogens produced significant amounts of citric and gluconic acids in the decayed tissue and reduced the host pH by 0.5 to 1.0 units. Ammonium depletion from the growth medium or from the fruit tissue was directly related to ambient pH reduction. Analysis of transcripts encoding the endopolygalacturonase gene, pepg1, from P. expansum accumulated under acidic culture conditions from pH 3.5 to 5.0, suggesting that the acidification process is a pathogenicity enhancing factor of Penicillium spp. This hypothesis was supported by the finding that cultivars with lower pH and citric acid treatments to reduce tissue pH increased P. expansum development, presumably by increasing local pH. However, organic acid treatment could not enhance decay development in naturally acidic apples. Conversely, local alkalinization with NaHCO(3) reduced decay development. The present results further suggest that ambient pH is a regulatory cue for processes linked to pathogenicity of postharvest pathogens, and that specific genes are expressed as a result of the modified host pH created by the pathogens.
    Phytopathology 02/2004; 94(1):44-51. · 2.97 Impact Factor
  • Arvind A Bhagwat, Robert A Saftner, Judith A Abbott
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    ABSTRACT: A commercial and three experimental wash treatments for fresh-cut apple slices were evaluated for their ability to affect survival of foodborne pathogens and to maintain quality characteristics measured instrumentally and by sensory analysis. For each apple variety (Fuji and Granny Smith), instrumental firmness, cut surface color, and sensory scores for firmness and flavor of fresh-cut apple slices treated with the commercial and experimental wash solutions were similarly maintained during storage (6 days at 5°C). Prior to their use with apple slices, all three experimental wash solutions reduced the survival of Salmonella serovar Typhimurium and Vibrio cholera by 5 logs or more and the experimental solution at pH 2.0 also reduced survival of Escherichia coli O157:H7, Listeria monocytogenes and Shigella flexneri by at least 5 logs, whereas the commercial wash solution had antibacterial activity only against V. cholera. During treatment of apple slices, the wash solutions changed compositionally over time as indicated by a decrease in conductivity, increases in soluble solids content and osmolality, and changes in pH; and they lost their antibacterial activity. Keeping microbial safety in view, wash solutions should not be reused on multiple batches of sliced apples. Instead, alternative washing strategies that maintain the antimicrobial properties of the wash solutions need to be developed for fresh-cut apple slices.
    Food Microbiology. 01/2004;
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    ABSTRACT: We compared the eating quality of a new apple cultivar, ‘GoldRush,’ with ‘Golden Delicious’ (one of its parents), ‘Fuji,’ and ‘Granny Smith’ (the latter two often used for fresh-cut apple slices). We also compared a commercial with an in-house processing treatment, NatureSeal for apples and Produce Quality and Safety Laboratory (PQSL), respectively. Intact apples that had been stored for about 6 months were washed, processed into fresh-cut slices, stored, and then served to consumers. Both NatureSeal and PQSL treatments maintained cut-surface color values similar to values at the time of cutting. NatureSeal-treated slices were rated slightly better for texture than those receiving the PQSL treatment, but there was no significant difference in acceptability of appearance or flavor. Acceptability scores for the texture and flavor of ‘GoldRush,’ and of ‘Fuji’ when included, were higher than those of ‘Granny Smith’ and ‘Golden Delicious.’ There were small age and gender biases, with older women liking ‘GoldRush’ less and older men liking ‘Granny Smith’ less than other age groups and cultivars in one study. No instrumental measurement was a satisfactory predictor of sensory acceptability scores. ‘GoldRush’ proved to be a promising new cultivar for fresh-cut apple slices and the in-house processing solution maintained the quality of apple slices similar to that of a commercial processing treatment.
    Postharvest Biology and Technology. 01/2004;
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    ABSTRACT: The fresh-cut produce industry has been the fastest-growing portion of the food retail market during the past 10 years, providing consumers with convenient and nutritious food. However, fresh-cut fruits and vegetables raise food safety concerns, because exposed tissue may be colonized more easily by pathogenic bacteria than intact produce. This is due to the higher availability of nutrients on cut surfaces and the greater potential for contamination because of the increased amount of handling. We found that applied Listeria monocytogenes populations survived and increased only slightly on fresh-cut Red Delicious apples stored at 10 degrees C but increased significantly on fresh-cut honeydew melons stored at 10 degrees C over 7 days. In addition, we examined the effect of lytic, L. monocytogenes-specific phages via two phage application methods, spraying and pipetting, on L. monocytogenes populations in artificially contaminated fresh-cut melons and apples. The phage mixture reduced L. monocytogenes populations by 2.0 to 4.6 log units over the control on honeydew melons. On apples, the reduction was below 0.4 log units. In combination with nisin (a bacteriocin), the phage mixture reduced L. monocytogenes populations by up to 5.7 log units on honeydew melon slices and by up to 2.3 log units on apple slices compared to the control. Nisin alone reduced L. monocytogenes populations by up to 3.2 log units on honeydew melon slices and by up to 2.0 log units on apple slices compared to the control. The phage titer was stable on melon slices, but declined rapidly on apple slices. The spray application of the phage and phage plus nisin reduced the bacterial numbers at least as much as the pipette application. The effectiveness of the phage treatment also depended on the initial concentration of L. monocytogenes.
    Applied and Environmental Microbiology 09/2003; 69(8):4519-26. · 3.68 Impact Factor
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    ABSTRACT: ‘Golden Delicious’ apples were treated with 1-methylcyclopropene (MCP) or kept at room temperature for the duration of the MCP treatment. After the MCP treatment, they were wounded and inoculated with the pathogen Penicillium expansum or with P. expansum and a heat tolerant yeast (antagonist). After incubation at room temperature for up to 48 h, the apples were treated with heat at 38 °C for 4 days, and/or moved to cold storage for up to 5 months. Heat had an eradicative effect, when the pathogen was allowed to incubate in the apple wounds for 6 or 12 h after inoculation, resulting in less decay than at any other incubation time. The highest decay incidence occurred on the control that was inoculated with the pathogen and placed in cold storage. The least decay incidence and the smallest lesion diameter occurred on apples treated with a combination of the antagonist plus heat or heat alone. In general, MCP-treated apples had a higher lesion incidence, but similar lesion severity compared with non-MCP-treated apples. Only in the combination treatment of heat plus the antagonist, when the incubation time of the pathogen was between 6 and 24 h, was the lesion diameter slightly larger on MCP-treated fruit than on fruit not treated with MCP. This difference between the MCP-treated apples and non-MCP-treated apples decreased during storage. Antagonist populations in the apple wounds were stable or increased for all treatments. They were higher on MCP-treated apples than on non-MCP-treated apples and they increased with increasing incubation periods at room temperature after inoculation. Antagonist populations on apples heat treated after inoculation were higher than those kept at room temperature immediately after the heat treatment and after 3 months storage. The heat treatment had an eradicative effect, whereas the antagonist had a protective effect. The combination of heat and antagonist was more effective than either treatment alone, even when there was a delay of the heat treatment for up to 24 h. The combination of these two control measures, therefore, was complementary and resulted in better decay control than either treatment alone.
    Postharvest Biology and Technology. 01/2003;
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    Jinhe Bai, Robert A. Saftner, Alley E. Watada
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    ABSTRACT: Quality characteristics and physiology of fresh-cut honeydew cubes harvested in summer and winter were evaluated. Sanitized melon cubes were packaged and held at three different atmospheres; passively formed atmosphere (passive modified atmosphere packaging (MAP)), active flushing of package with 5 kPa O2+5 kPa CO2 at packaging (active MAP), and perforated film package (PFP) and at three different temperature treatments; continuously at 5 or 10 °C or 2 days at 5 °C and transferred to 10 °C for a total of 11 days. Cubes of summer fruit had higher soluble solids content (SSC), respiration rate, and translucency than that of winter fruit. Translucency and off-odor were the main factors in deterioration of cubes. Cubes in active MAP had better color retention, reduced respiration rate and microbial population, and longer shelf-life than those in passive MAP, which was of better quality and had a longer shelf-life than cubes in PFP. The active MAP and 5 °C continuous was the best combination and the PFP and 10 °C continuous was the worst combination among the treatments for retaining quality and shelf-life of honeydew cubes. Quality attributes differed between cubes of fruit available in winter and summer, but the shelf-life was similar for both winter and summer cubes.
    Postharvest Biology and Technology. 01/2003;
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    ABSTRACT: To maximize control of fruit decay by alternatives to synthetic fungicides after harvest, various control strategies can be integrated. Treatment of fruit with antagonists is one of the most promising alternatives. This treatment, however, has little or no eradicative activity, which limits its use. Fruit treatment with hot air (at 38 °C) for 4 d has eradicative but no residual activity against blue mold (caused by Penicillium expansum) on apple, and 1-methylcyclopropene (1-MCP) is an ethylene receptor inhibitor which slows apple maturation and, presumably, extends action of natural defense mechanisms. An antagonist, Metchnikowia pulcherrima T5-A2, was used in combination with heat and 1-MCP treatments to control bitter rot (caused by Colletotrichum acutatum) and blue mold (caused by P. expansum) on ‘Golden Delicious’ apples under controlled atmosphere (CA) conditions. 1-MCP treatment increased bitter rot and blue mold decays, but both of these decays were effectively controlled on 1-MCP treated apples by a combination of the antagonist and heat treatments. C. acutatum is a weaker pathogen than P. expansum, and bitter rot, even on the control treatments, developed only after 4 months in CA storage followed by 2 weeks incubation at 24 °C. In contrast, non-treated fruit inoculated with P. expansum were completely decayed after 2 months in CA. The antagonist controlled bitter rot more effectively than blue mold, while blue mold was more effectively controlled by heat treatment. The use of 1-MCP on harvested fruit to inhibit maturation can predispose fruit to decay, but the alternatives to synthetic fungicides are capable of preventing this increase in decay.
    Postharvest Biology and Technology. 01/2003;