Rind Surfaces Research Articles

Abrasive brushing reduces pathogen biofilms at cantaloupe rind surface

Foodborne pathogens constitute a major food safety risk for cantaloupe, and pathogen biofilms formed are particularly difficult to remove. The goal of this study was to evaluate abrasive brushing in removing biofilms from cantaloupe surface using Listeria monocytogenes V7 and Salmonella enterica serovar Typhimurium ATCC 13311 as models. Cantaloupe rind pieces were inoculated and then subjected to 30 min or 24 h incubations. The incubated rind pieces were subject to different washing and/or brushing procedures and then the bacterial cells were enumerated. Cryo-SEM showed planktonic cells after 30 min incubation, whereas biofilms formed at rind surfaces after 24 h incubation. For L. monocytogenes 30 min incubation group, the log reductions were 1.4 for brushing, 2.1 for brushing with diatomaceous earth (DE), 2.8 for peroxyacetic acid (PAA) washing, 4.2 for brushing with PAA, and 4.0 for brushing with DE and PAA. In contrast, for the 24 h incubation group, the log reductions were 0.4 for brushing, 1.5 for brushing with DE, 1.1 for PAA washing, 1.6 for brushing with PAA, and 3.0 for brushing with DE and PAA. Similar results were observed for the S. Typhimurium group. These outcomes showed the pathogen-removal efficacy of brushing with DE (abrasive brushing) in the presence of biofilms, suggesting the potential application of abrasive brushing in cleaning cantaloupe for improved food safety.

Utilizing kitchen steamers to inactivate Listeria monocytogenes and Salmonella enterica on whole cantaloupe melons

AbstractCantaloupes contaminated with Listeria and Salmonella have caused large scale of foodborne illness outbreaks in recent years. Prior research has shown that heat treatment can be used to reduce microbial contaminates on fruit surfaces. However, no study has evaluated the use of kitchen steamers for inactivating foodborne pathogens on cantaloupes. The purpose of this study was to test the sanitization efficacy of three models of electrical kitchen steamers (steamer‐A, ‐B, and ‐C) for eliminating foodborne pathogens on cantaloupe surfaces. Fresh cantaloupes were spot‐inoculated with Listeria monocytogens or Salmonella enterica and kept at 4 or 22 °C for a day before steam treatment for ≤100 s. Test results show that the surface of nonrefrigerated cantaloupes can be decontaminated (with ≥5.0 log reduction) within 60 s using any of the tested steamers. For refrigerated fruits (4 °C), however, only two steamers (steamer‐B and ‐C) decontaminated the cantaloupes within 60 s and they were unable to render the pathogens undetected in enriched samples. Salmonella was more susceptible than Listeria to steam treatment. In conclusion, electrical kitchen steamers can be utilized by consumers to sanitize whole cantaloupes prior to consumption. However, fruit temperature and steamer selection can influence the heating time required for surface sanitization.Practical applicationsMelons with netted rind surfaces, such as cantaloupes, likely have caused more outbreaks because their surface shelters pathogens from being eliminated by conventional washing and sanitization. As whole melons marketed at retail stores typically are not treated due to shelf‐life considerations, the safety of untreated melons can be of concern to consumers, especially among at‐risk populations. This study focused on the evaluation of the use of commercially available kitchen steamers in eliminating foodborne pathogens on cantaloupe surfaces. This study showed that kitchen steamers can be utilized to sanitize whole cantaloupes and also at household level, be a highly beneficial for the average concerned consumer to reduce the risk of pathogens on produce before consumption.

Effect of cold storage on survivors and recovery of injuredSalmonellabacteria on fresh‐cut pieces prepared from whole melons treated with heat and hydrogen peroxide

Cantaloupes and honeydew melons inoculated with 107 CFU/ml Salmonella bacteria were treated with 1.5% of hydrogen peroxide (H2O2) at 20°C and minimally treated at 70°C for 3 min before storage at 5, 10, and 20°C. Salmonella bacteria recovered from the cantaloupe and honeydew melon rind surfaces averaged 4.5 and 3.9 log CFU/cm2, respectively, before antimicrobial treatments. Fresh-cut pieces prepared at each day of storage were immediately placed inside the refrigerator (5°C) while some pieces were left at room temperature (20°C) for 30 and 60 min before refrigeration. After minimal thermal hydrogen peroxide treatments, injured Salmonella on whole cantaloupes was significantly (p > 0.05) different than honeydew melons. Cold storage of treated melons at 5°C led to significant (p > 0.05) reduction of the injured bacteria and below detection in fresh-cut pieces even after enrichment process suggesting that minimal thermal antimicrobial processing will reduce transfer of bacteria to fresh-cut pieces during fresh-cut preparation. Practical applications The results of this study indicate that minimal thermal treatment with 1.5% of hydrogen peroxide at 70°C for 3 min and immediate cold storage of treated whole melons designated for fresh-cut preparation will reduce transfer of microbial populations from melons rind surfaces to fresh-cut pieces during fresh-cut preparation.

Shellac, gelatin and Persian gum as alternative coating for orange fruit

Postharvest fruit coatings are an effective method to replace natural waxes lost during washing and handling. The coatings can reduce water loss and impart gloss to the fruit. Edible coatings, instead of synthetic waxes, are perceived to offer advantages with respect to human health concerns and environmental protection. In this research, edible coatings made from relatively inexpensive, easy to dissolve components that are suitable for increasing fruit gloss were studied on ‘Valencia’ oranges during storage. The coating materials included 5, 6 and 7% gelatin, 3.5, 4 and 4.5% Persian gum, 9, 10 and 11% shellac were compared to un-coated control, and fruit coated with a commercial wax. After coating, the fruit were stored for up to 60days at 5°C. Every 20days fruit were removed from storage and evaluated. Scanning electron microscopy images of coated rind surfaces were also obtained. The results indicated that weight loss, fruit firmness, total soluble solids (TSS), titratable acidity (TA), pH, ascorbic acid content, total phenolic content (TPC), total antioxidant capacity (TAC) and respiration rate were affected by the coatings. Shellac coatings reduced weight and firmness loss. As the storage time was increased fruit TA and ascorbic acid content decreased, and pH, TPC and TAC increased. Glossiness was observed in all coatings, however, with increasing storage time, fruit coated by gelatin and Persian gum coatings, showed visible cracks. Shellac was the best coating as it dried quickly, forming a not sticky and odorless coating, and gave highest fruit gloss.

Appearance and overall acceptability of fresh-cut cantaloupe pieces from whole melon treated with wet steam process

Minimally processed fresh-cut fruits have a limited shelf-life because of deterioration caused by spoilage microflora and changes in physiological processes. Whole melons was inoculated with 107 CFU/ml of Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes to achieve 4.8, 4.5 and 4.1 log CFU/cm2, respectively on melon surfaces. The inoculated melons were treated with a wet steam processing unit for 180 s before fresh-cut preparation. Microbial safety was studied and the overall appearance and acceptability of the fresh-cut pieces were investigated by trained panelists. There were no visual signs of physical damage on all treated cantaloupe surfaces immediately after treatments and during storage. All fresh-cut pieces from treated cantaloupes were negative for bacterial pathogens while aerobic mesophilic bacteria were recovered. Appearance and overall acceptability of fresh-cut pieces from treated melons during 6 days at 5 °C were not significantly (p < 0.05) different from control pieces prepared from fresh melons but were significantly (p < 0.05) different from untreated pieces from day 0 under the same storage conditions for 14 days. The results of this study suggests that wet steam treatment of cantaloupes rind surfaces designated for fresh-cut preparation will enhance the microbial safety of fresh-cut pieces, and the overall acceptability of cut pieces.

Pathogen biofilm formation on cantaloupe surface and its impact on the antibacterial effect of lauroyl arginate ethyl

Pathogen biofilm at fruit surface may pose a particular risk to food safety. In this study, the biofilms of Listeria monocytogenes V7 and Salmonella enterica serovar Typhimurium ATCC 13311 on cantaloupe fruit surface were visualized, and the resistance of biofilms against lauroyl arginate ethyl (LAE, an antibacterial compound) was evaluated. Each bacterium was inoculated on isolated cantaloupe rind surfaces at 105–106 CFU/cm2 and after incubation for 2, 12, 24, and 48 h, the surfaces were imaged using cryo-scanning electron microscopy (Cryo-SEM). The images showed that both pathogens formed biofilms on rind surfaces, with S. Typhimurium forming biofilm in 12 h and L. monocytogenes cells starting to aggregate in 2 h. For the inoculated rind surfaces treated with LAE, the cell counts were affected by both the incubation time and LAE concentration. For rind surface with 2 h incubation of S. Typhimurium, 400 and 800 μg/mL LAE was able to achieve >2.00 log reduction; however, 12 h incubation required 1600 and 2000 μg/mL LAE for >2.00 log reduction. In contrast, even the highest LAE concentration (2000 μg/mL) was unable to cause 1.00 log reduction for L. monocytogenes regardless the incubation time applied. The results showed that the biofilms of both bacteria substantially reduced LAE efficacy, and that the biofilm of L. monocytogenes was more resistant than that of S. Typhimurium.

Effect of Hydrogen Peroxide in Combination with Minimal Thermal Treatment for Reducing Bacterial Populations on Cantaloupe Rind Surfaces and Transfer to Fresh-Cut Pieces

Surface structure and biochemical characteristics of bacteria and produce play a major role in how and where bacteria attach, complicating decontamination treatments. Whole cantaloupe rind surfaces were inoculated with Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes at 10(7) CFU/ml. Average population size of Salmonella, Escherichia coli O157:H7, and L. monocytogenes recovered after surface inoculation was 4.8 ± 0.12, 5.1 ± 0.14, and 3.6 ± 0.13 log CFU/cm(2), respectively. Inoculated melons were stored at 5 and 22°C for 7 days before washing treatment interventions. Intervention treatments used were (i) water (H2O) at 22°C, (ii) H2O at 80°C, (iii) 3% hydrogen peroxide (H2O2) at 22°C, and (iv) a combination of 3% H2O2 and H2O at 80°C for 300 s. The strength of pathogen attachment (SR value) at days 0, 3, and 7 of storage was determined, and then the efficacy of the intervention treatments to detach, kill, and reduce transfer of bacteria to fresh-cut pieces during fresh-cut preparation was investigated. Populations of E. coli O157:H7 attached to the rind surface at significantly higher levels (P < 0.05) than Salmonella and L. monocytogenes, but Salmonella exhibited the strongest attachment (SR value) at all days tested. Washing with 3% H2O2 alone led to significant reduction (P < 0.05) of bacteria and caused some changes in bacterial cell morphology. A combination treatment with H2O and 3% H2O2 at 8°C led to an average 4-log reduction of bacterial pathogens, and no bacterial pathogens were detected in fresh-cut pieces prepared from this combination treatment, including enriched fresh-cut samples. The results of this study indicate that the microbial safety of fresh-cut pieces from treated cantaloupes was improved at day 6 of storage at 5°C and day 3 of storage at 10°C.

Microbial safety and overall quality of cantaloupe fresh-cut pieces prepared from whole fruit after wet steam treatment

Fresh-cut cantaloupes have been associated with outbreaks of Salmonellosis. Minimally processed fresh-cut fruits have a limited shelf life because of deterioration caused by spoilage microflora and physiological processes. The objectives of this study were to use a wet steam process to 1) reduce indigenous spoilage microflora and inoculated populations of Salmonella, Escherichia coli O157:H7 and Listeria monocytogenes on the surface of cantaloupes, and 2) reduce the populations counts in cantaloupe fresh-cut pieces after rind removal and cutting. The average inocula of Salmonella, E. coli O157:H7 and Listeria monocytogenes was 107CFU/ml and the populations recovered on the cantaloupe rind surfaces after inoculation averaged 4.5, 4.8 and 4.1logCFU/cm2, respectively. Whole cantaloupes were treated with a wet steam processing unit for 180s, and the treated melons were stored at 5°C for 29days. Bacterial populations in fresh-cut pieces prepared from treated and control samples stored at 5 and 10°C for up to 12days were determined and changes in color (CIE L*, a*, and b*) due to treatments were measured during storage. Presence and growth of aerobic mesophilic bacteria and Salmonella, E. coli O157:H7 and L. monocytogenes were determined in fresh-cut cantaloupe samples. There were no visual signs of physical damage on all treated cantaloupe surfaces immediately after treatments and during storage. All fresh-cut pieces from treated cantaloupes rind surfaces were negative for bacterial pathogens even after an enrichment process. Steam treatment significantly (p<0.05) changed the color of the fresh-cut pieces. Minimal wet steam treatment of cantaloupes rind surfaces designated for fresh-cut preparation will enhance the microbial safety of fresh-cut pieces, by reducing total bacterial populations. This process holds the potential to significantly reduce the incidence of foodborne illness associated with fresh-cut fruits.

Efficacy of Sanitizer Treatments on Survival and Growth Parameters of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes on Fresh-Cut Pieces of Cantaloupe during Storage

For health reasons, people are consuming fresh-cut fruits with or without minimal processing and, thereby, exposing themselves to the risk of foodborne illness if such fruits are contaminated with bacterial pathogens. This study investigated survival and growth parameters of Escherichia coli O157:H7, Salmonella, Listeria monocytogenes, and aerobic mesophilic bacteria transferred from cantaloupe rind surfaces to fresh-cut pieces during fresh-cut preparation. All human bacterial pathogens inoculated on cantaloupe rind surfaces averaged ~4.8 log CFU/cm2, and the populations transferred to fresh-cut pieces before washing treatments ranged from 3 to 3.5 log CFU/g for all pathogens. A nisin-based sanitizer developed in our laboratory and chlorinated water at 1,000 mg/liter were evaluated for effectiveness in minimizing transfer of bacterial populations from cantaloupe rind surface to fresh-cut pieces. Inoculated and uninoculated cantaloupes were washed for 5 min before fresh-cut preparation and storage of fresh-cut pieces at 5 and 10°C for 15 days and at 22°C for 24 h. In fresh-cut pieces from cantaloupe washed with chlorinated water, only Salmonella was found (0.9 log CFU/g), whereas E. coli O157:H7 and L. monocytogenes were positive only by enrichment. The nisin-based sanitizer prevented transfer of human bacteria from melon rind surfaces to fresh-cut pieces, and the populations in fresh-cut pieces were below detection even by enrichment. Storage temperature affected survival and the growth rate for each type of bacteria on fresh-cut cantaloupe. Specific growth rates of E. coli O157:H7, Salmonella, and L. monocytogenes in fresh-cut pieces were similar, whereas the aerobic mesophilic bacteria grew 60 to 80% faster and had shorter lag phases.

Effect of native microflora, waiting period, and storage temperature on Listeria monocytogenes serovars transferred from cantaloupe rind to fresh-cut pieces during preparation.

The most recent outbreak of listeriosis linked to consumption of fresh-cut cantaloupes indicates the need to investigate the behavior of Listeria monocytogenes in the presence of native microflora of cantaloupe pieces during storage. Whole cantaloupes were inoculated with L. monocytogenes (10(8)-CFU/ml suspension) for 10 min and air dried in a biosafety cabinet for 1 h and then treated (unwashed, water washed, and 2.5% hydrogen peroxide washed). Fresh-cut pieces (∼3 cm) prepared from these melons were left at 5 and 10°C for 72 h and room temperature (20°C) for 48 h. Some fresh-cut pieces were left at 20°C for 2 and 4 h and then refrigerated at 5°C. Microbial populations of fresh-cut pieces were determined by the plate count method or enrichment method immediately after preparation. Aerobic mesophilic bacteria, yeast and mold of whole melon, and inoculated populations of L. monocytogenes on cantaloupe rind surfaces averaged 6.4, 3.3, and 4.6 log CFU/cm(2), respectively. Only H(2)O(2) (2.5%) treatment reduced the aerobic mesophilic bacteria, yeast and mold, and L. monocytogenes populations to 3.8, 0.9, and 1.8 log CFU/cm(2), respectively. The populations of L. monocytogenes transferred from melon rinds to fresh-cut pieces were below detection but were present by enrichment. Increased storage temperatures enhanced the lag phases and growth of L. monocytogenes. The results of this study confirmed the need to store fresh-cut cantaloupes at 5°C immediately after preparation to enhance the microbial safety of the fruit.

Incidence, internalization and behavior of Salmonella in mangoes, var. Tommy Atkins

Mangoes imported from South America were responsible for two Salmonella multistate outbreaks in the USA. The hot water immersion treatment utilized for fly larvae control was pointed out as the probably responsible for bacterial internalization in these fruits. The objective of this study was to evaluate: the presence of Salmonella in mangoes, the occurrence of internalization of these bacteria during a laboratory-simulated hydrothermal treatment and the bacterial behavior in mangoes in the rind surfaces and in different portions: stem end, middle side and blossom-end after storage at 8 and 22 °C, for 24 and 144 h. One hundred samples were analyzed; Salmonella was not found in any of the 33 samples destined for the export market, but in two of the remaining samples, destined for the internal market, the presence of that bacterium was detected. The results from the laboratory-simulated experiments proved that bacterial internalization occurred in the intact fruit. In the stem portion the log of MPN/g of bacteria was statistically higher than in the remaining parts of the fruit ( p < 0.05), demonstrating that the stem is the route for bacterial entrance. At 22 °C bacterial multiplication was observed in all portions (the rind surface, stem end, middle side and blossom-end) analyzed. However, at 8 °C the growth was lower, and in the rind surface there was a decrease in the number of bacteria. Thus, microorganisms present in the water used for hydrothermal treatments can migrate to the interior of mangoes, survive and grow in all fruit portions.

Production of copper matrix materials with silicon carbide and alumina reinforcements : Z.Abdel-Hamid et al. (Central Metallurgical R. and D. Inst., Cairo, Egypt.) Mater. Letters, Vol 53, 2002, 244–249

Postharvest fruit coatings are an effective method to replace natural waxes lost during washing and handling. The coatings can reduce water loss and impart gloss to the fruit. Edible coatings, instead of synthetic waxes, are perceived to offer advantages with respect to human health concerns and environmental protection. In this research, edible coatings made from relatively inexpensive, easy to dissolve components that are suitable for increasing fruit gloss were studied on ‘Valencia’ oranges during storage. The coating materials included 5, 6 and 7% gelatin, 3.5, 4 and 4.5% Persian gum, 9, 10 and 11% shellac were compared to un-coated control, and fruit coated with a commercial wax. After coating, the fruit were stored for up to 60 days at 5 °C. Every 20 days fruit were removed from storage and evaluated. Scanning electron microscopy images of coated rind surfaces were also obtained. The results indicated that weight loss, fruit firmness, total soluble solids (TSS), titratable acidity (TA), pH, ascorbic acid content, total phenolic content (TPC), total antioxidant capacity (TAC) and respiration rate were affected by the coatings. Shellac coatings reduced weight and firmness loss. As the storage time was increased fruit TA and ascorbic acid content decreased, and pH, TPC and TAC increased. Glossiness was observed in all coatings, however, with increasing storage time, fruit coated by gelatin and Persian gum coatings, showed visible cracks. Shellac was the best coating as it dried quickly, forming a not sticky and odorless coating, and gave highest fruit gloss.

ウンシュウミカンのいわゆる黄色果について

These investigations were carried out from 1973 to 1977 in order to clarify the conditions of occurrence and the quality of “yellowish fruit” in crops of satsumamandarins, because of the problems raised by their occurrence in recent years in Nagasaki.1. The “L” and “b” values for the rind surfaces of yellowish fruit as measured on Color-Difference Meter were higher than for those of “reddish”, but the “a” values were lower. The ranges of “L”, “a” and “b” values were 60-63, 17-20 and 34-38, respectively for yellowish fruit, and for reddish fruit, 56-60, 22-27 and 32-37, respectively.2. The juice of the yellowish fruits was lower in sugar content and higher in acid content than that of the reddish ones, and the proportion of small yellowish fruit below “S” size was greater than that of small reddish fruit. The rind surface of the yellowish fruit was smooth, less susceptible to injury, and showed a lower occurrence of puffing and wilting during storage.3. The ratio of yellowish fruit in the packing house ranged from 10% to 30%, varying according to the year and the regions.4. The occurrence of yellowish fruit in the lower part of the bearing area of the tree crown was greatest, especially that on the hill side of the tree. A relationship was found to exist between the occurrence of yellowish fruit and light intensity.5. There was a quantity of yellowish fruit in light-deficient orchards facing north-east.6. It was concluded that yellowish fruit was less colored, smaller fruit produced in the inner or lower parts of the tree crown, and that its occurrence depends largely on light conditions in the bearing part of the tree crown.