Stem Scar Research Articles

Effects of Combined Cold Plasma and Organic Acid‐Based Sanitizer Treatments Against Salmonella enterica on Tomato Surfaces

ABSTRACTIncidence of foodborne illness due to bacterial contamination of fresh produce continue to exist despite continuous research on processing interventions to mitigate the problem. In this study, we combined atmospheric cold plasma treatments with an antimicrobial solution containing specific organic acids generally recognized as safe (GRAS) by the FDA and tested its antimicrobial efficacy against Salmonella enterica inoculated on tomato surfaces. Tomato surfaces were inoculated with at 5.6 log CFU/g of Salmonella by spotting 0.1 mL of 7 log CFU/ml Salmonella onto the tomato stem scars, and by dipping whole tomatoes into a solution of 7 log CFU/ml Salmonella for 3 min to achieve 4.1 log CFU/g. Antimicrobial efficacy of the organic acid‐based sanitizer + cold plasma treatments for 30, 60, 120, 180, and 360 s, were investigated, and significant bacterial inactivation was achieved above 120 s treatments. At 120 s, surviving populations of aerobic mesophilic bacteria recovered on the tomatoes surfaces averaged < 2 logs/g while yeast and mold survival averaged < 1 CFU/g. Treatment combination with this organic acid‐based sanitizer + cold plasma for 120 s resulted in a 4.9 log reduction of Salmonella on the stem scar area and a 3.9 log reduction on the smooth peel surface. Similarly, populations of aerobic mesophilic bacteria recovered on treated tomato surfaces averaged < 0.3 log CFU/g. The results of this study indicate that combining an organic acid‐based sanitizer with cold plasma treatments for ≥ 120 s can inactivates significant populations of Salmonella to enhance the microbial safety of tomato surfaces designated for fresh‐cut salad.

Dangler for Accelerated Dehydration: A Novel System for Assessing the Impacts of Relative Humidity on Fruit Water Loss During Cold Storage of Blueberries

Blueberries are prone to dehydration during storage. Firmness is one of the most critical quality attributes associated with this period, with the loss of water from the fruit representing the most significant limitation for the fresh market. Therefore, one of the great challenges is maintaining the quality characteristics of the fruit in shipments by sea, which can take up to 60 days when sent from the southern hemisphere to the northern hemisphere. The random arrangement of each fruit within a packaging unit (different proportions of the stem scar and cuticular surface exposed to the environment) represents an essential source of variation in the prediction of softening during the storage period. A special device, referred to as a dangler for accelerated dehydration (DAD), was designed to expose nearly the entire fruit surface to the environment and determine the impact of factors such as relative humidity and the role of the stem scar and cuticle on fruit water loss. Consequently, to evaluate the ability of DADs to find differences in fruit dehydration, blueberries sampled at early, peak, and late harvest dates were placed in DADs and exposed to three controlled levels of relative humidity (30%, 65%, and 96% relative humidity; 1.2 ± 0.7 °C) for 10 days. Berries within the DADs were untreated, immersed in hexane for 5 seconds to remove bloom, painted with quick-drying nail polish on the pedicel end to seal the stem scar or immersed in hexane for 5 seconds, and painted with quick-drying nail polish on the pedicel end. At each harvest, fruit weight loss was significantly affected by the fruit and RH treatments, as well as the interaction between them. A regression analysis of the control treatment indicated that water loss at lower relative humidities occurred faster in fruit from the first harvest. The results reveal that DADs can be used to characterize preharvest and postharvest stimuli at an individual level and within a short time (10 days).

Evaluation of pulsed light treatment for inactivation of Salmonella in packaged cherry tomato and impact on background microbiota and quality

AbstractThe microbial safety of produce continues to be a real concern. The objective of this study was to investigate the efficacy of high intensity short time pulsed light (PL) application on survival of Salmonella in packaged cherry tomato. Treatment effects on reduction of native microbiota and quality were also evaluated. Stem scars of cherry tomatoes, inoculated with a three serotypes cocktail of Salmonella enterica, was treated with PL for up to 60 s. Polyethylene (PE) films of 25.4, 50.8 and 76.2 μm thickness were used for packaging treatment. A10 s treatment equivalent to a fluence dose of 10.5 J/cm2 was considered optimum. Both packaged and direct PL treatments provided >1 log reduction of the pathogen in 10 s (10.5 J/cm2). Direct treatment for 10 s resulted in 1.9 ± 0.17 log CFU/g reduction of Salmonella. For packaged tomatoes, log reductions decreased with increasing film thickness but not significantly (p < .05). Also, no significant difference in PL decontamination efficacy between packaged and unpackaged tomatoes was observed. Treatment significantly reduced the initial populations of aerobic mesophilic bacteria (3.6 ± 0.31 log), molds and yeast (2.43 ± 0.22 log) by >1 log, respectively. Packaged tomatoes were softer after treatment but not significantly. Storage time did not affect fruit firmness. No significant change in the visual appearance of fruits were observed after treatment and during 14 days of storage. Overall, the results of this study demonstrate that high intensity short time PL treatment may be used to enhance microbial safety and reduce postprocessing contamination of packaged cherry tomato.

Role of cuticular wax composition and stem scar size in the transpirational water loss of blueberries

Role of cuticular wax composition and stem scar size in the transpirational water loss of blueberries

Cold plasma-activated hydrogen peroxide aerosols inactivate Salmonella Typhimurium and Listeria innocua on smooth surfaces and stem scars of tomatoes: Modeling effects of hydrogen peroxide concentration, treatment time and dwell time

This study was conducted to evaluate the effects of hydrogen peroxide (H 2 O 2 ) concentration, treatment time, and dwell time on the efficacy of cold plasma-activated hydrogen peroxide aerosols against bacteria on stem scar and smooth surfaces of tomatoes. Cherry tomatoes inoculated with cocktails of Salmonella Typhimurium and Listeria innocua on the smooth surface and stem scar area were treated for 10, 20 and 30 s followed by 15 and 30 min dwell times in a treatment chamber with cold plasma-activated aerosols generated from 0, 1, 2, 3, 4 and 6% and 7.8% H 2 O 2 . Results showed that the efficacy of the treatments was mostly influenced by the H 2 O 2 concentration and treatment time. The reductions of the two bacteria were modeled as sigmoidal or exponential functions of H 2 O 2 . The models indicated that at H 2 O 2 concentrations ≥4.2%, the treatments reduced populations of L. innocua to non-detectable levels (detection level: 0.70 log CFU/piece) achieving an average 5 log reduction on the smooth surface of tomatoes for all tested treatment times and dwell times. To achieve an average 5-log reduction of Salmonella populations on the smooth surface, H 2 O 2 at concentrations ≥5.7% H 2 O 2 was required. On the stem scar area of tomatoes, populations of Listeria and Salmonella were reduced by less than 2 logs. Our results demonstrated that the efficacy of cold plasma-activated hydrogen peroxide aerosol mainly depended on the concentration of H 2 O 2 , and type and location of inoculated bacteria. • Three main parameters for cold plasma-activated H 2 O 2 process were evaluated. • Non-linear regression models were developed for estimating the efficacy of H 2 O 2 . • Listeria was more sensitive to the activated H 2 O 2 aerosol than Salmonella on tomatoes. • At ≥5.7% H 2 O 2 , both bacteria on the surface of tomatoes were reduced by 5 logs. • Bacteria on stem scar area were more difficult to inactivate than those on surface.

Efficacy of gaseous chlorine dioxide generated by sodium chlorite - carbon dioxide reaction on safety and quality of blueberries, cherry tomatoes, and grapes

This research evaluated the inactivation of Salmonella spp. and Listeria monocytogenes inoculated onto the calyces of blueberries, stem scars of cherry tomatoes, and surfaces of grapes using gaseous chlorine dioxide (ClO2) produced by the reaction between sodium chlorite (NaClO2) and carbon dioxide (CO2). The inoculated samples were treated with ClO2 gas in a treatment chamber for 3 h. The results suggested that the exposures of 366–477 ppm-h achieved 2.8 to 3.8, 2.4 to 4.3, and 3.8 to 6.4 log CFU/g in inactivation of both pathogens on blueberries, cherry tomatoes, and grapes, respectively. The inactivation of pathogens on grapes were significantly greater (p < 0.05) than those on blueberries and cherry tomatoes, likely due to the difference in the inoculation sites. During an 8-day post-treatment storage at 25 °C, the color attributes (L*, a*, and b*) of the fruit samples were not or little affected by either storage time or ClO2 treatment. The weight loss of treated and untreated samples during the storage was more affected by and increased with storage time, but it was higher in the untreated samples. The hardness was significantly affected by and decreased with storage time. It was higher in ClO2-treated blueberry and grape samples, but not in cherry tomato samples. The residual ClO2 on treated fruits, ranging from 0.08 to 0.35 mg/kg, was not affected by the storage time, but it was the highest in blueberry and the lowest in cherry tomato samples. These results clearly demonstrated that this method of gaseous ClO2 generation can be used to reduce pathogens on the fruit samples during postharvest intervention and storage, while improving product safety and quality.

Anatomy of Pinus mugo var. mugo as a fundament for annual-ring-based dating of debris flows in the alpine zone

Dendrogemorphic methods are a very accurate tool for dating past debris flows. Chronological data are very valuable, especially in the alpine zone, because climate change has a very intense impact on the frequency of debris flows here. However, at the same time, the applicability of dendrogeomorphic methods in this environment is limited by the lack of suitable trees. Shrub-like mountain pine (Pinus mugo var. mugo) is often the only tree species in this environment, however, dating using a classical macroscopic approach including the analysis of annual-ring series is frequently challenging due to difficulties with detection of increment growth disturbances. Thus, this study focuses on the possibility of detecting growth responses of P. mugo to debris flow exposure at the anatomical level.A total of 14 P. mugo specimens were sampled using discs through stem scars. Anatomical analysis was performed on microsections realized in two radial segments on each stem disc (one as a control). In each segment, five consecutive annual rings (two before damage, one damaged and two after damage) were analyzed each divided into early and late wood zones. The results showed a significant reduction in tracheid parameters (cross-sectional area, radial width, and tangential width) in the early wood zone. Another significant anatomical response was found as an increase in the number of radial rays. Possible effects of scar size and shrub age on the intensity of the anatomical response are also discussed. Thus, this study demonstrated the potential applications of anatomical analyses of P. mugo and suggested new possibilities for dating debris flows within the limit zone of applicability of dendrogeomorphological methods.

Jasmonic Acid Activates the Fruit-Pedicel Abscission Zone of 'Thompson Seedless' Grapes, Especially with Co-Application of 1-Aminocyclopropane-1-carboxylic Acid.

Two studies were conducted to determine how methyl jasmonate (MeJA), jasmonic acid (JA), and 1-aminocyclopropane-1-carboxylic acid (ACC) affect grape berry abscission in the initial days after treatment. The overarching goal was to determine whether JA, with or without ACC, may hold the potential to sufficiently reduce fruit detachment force (FDF) and increase the proportion of berries with dry stem scars while minimizing preharvest abscission, effects that could be useful in the production of stemless table grapes. On Thompson Seedless grapes, JA was at least as effective as MeJA for stimulating berry abscission based on reduced fruit detachment force (FDF) and yielding detached berries with dry stem scars. Further, since previous studies showed that ACC improved MeJA-induced grape abscission, we tested ACC effects on JA activity. We found that JA rapidly induced preharvest berry abscission, confirming previous results. ACC alone did not induce preharvest berry abscission, but ACC improved the effectiveness of JA on reducing FDF and increasing dry stem scar development. These studies also demonstrated that JA-induced abscission occurs within the first day after treatment. Commercial use of JA plus ACC as an abscission agent requires that FDF sufficiently declines, and the incidence of dry stem scars increases, prior to a significant increase in fruit abscission. However, the rapid progression of fruit abscission may require harvest either within 24 and 48 h after treatment or the use of a passive catch system.

Blueberry water loss is related to both cuticular wax composition and stem scar size

The contributions of the cuticle and stem scar to blueberry water loss were evaluated in four cultivars. Among the cultivars, 55–69% of the water loss occurred through the cuticle, indicating the key role of the cuticle and cuticular waxes in restricting water loss. Cuticular wax content at harvest ranged from 38.12 to 67.00 μg cm−2 across the four cultivars and increased during four-week postharvest storage by an average of 49.5%. Oleanolic and ursolic acid were the most abundant wax compounds. The amount and proportion of oleanolic acid were negatively related to water loss. Wax esters were at low levels in all cultivars, but their content and proportion were directly related to water loss. The stem scar size was directly related to water loss, but only within a given cultivar and not across cultivars. This study provided new knowledge on the role of the cuticular waxes and stem scar in determining water loss in blueberries.

Combination of aerosolized acetic acid and chlorine dioxide‐releasing film to inactivate Salmonella enterica and its effect on quality of tomatoes and Romaine lettuce

AbstractNovel intervention technologies are needed to minimize pathogen contamination of fresh produce. The present study was undertaken to develop an in‐package treatment system that combined aerosolized acetic acid (AA) and chlorine dioxide (ClO2)‐releasing film in which the acid triggered the release of ClO2 from its precursor. A four‐strain cocktail of Salmonella enterica (S. Montevideo, S. Typhimurium, S. Newport, and S. Saint‐paul) was inoculated onto the surfaces of cut Romaine lettuce and the stem scars of cherry tomatoes. The inoculated samples were placed into clamshell containers containing one ClO2‐releasing film (2.5 × 2.5 cm). After the packages were sealed, AA (2 and 4%) was aerosolized for 60 s into the packages through perforated openings. Results demonstrated that the combination of AA with the ClO2‐releasing film significantly reduced Salmonella populations with reductions of &gt;4 log and &gt;2 log CFU/piece on lettuce and tomato stem scars, respectively. The ClO2‐releasing film or aerosolized AA alone did not result in any significant reductions of Salmonella populations except aerosolized 4% AA, which achieved 2.21 log CFU/piece reductions on lettuce. The combinations and 4% AA treatment caused damage to fresh‐cut lettuce during 14 days of storage as evidenced by the deterioration in appearance, softening, and decreased ascorbic acid and antioxidant levels. The treatments did not significantly affect most of the quality attributes of cherry tomatoes during 21 days of storage at 10°C. Overall, our results demonstrate that the novel combination of AA and ClO2‐releasing film may be used to enhance microbial safety and quality of cherry tomatoes.

Cu-chitosan nano-net improves keeping quality of tomato by modulating physio-biochemical responses

Minimizing the post-harvest losses in fruits and vegetables is one of the challenging tasks in agriculture. To address this issue, we report nano-net of Cu-chitosan nanoparticles (Cu-chitosan NPs) which has the ability to extend the shelf-life of stored tomato. The application of Cu-chitosan NPs (0.01–0.04%) significantly curtailed microbial decay (< 5 versus > 50% in control), physiological loss in weight (14.36 versus 28.13% in control), respiration rate (0.01173 versus 0.01879 g CO2 kg−1 h−1) and maintained fruit firmness (34.0 versus 17.33 N in control) during storage. Further, these NPs significantly retarded loss of titratable acidity, retained total soluble solids, total and reducing sugars, lycopene, ascorbic acid and inhibited polyphenol oxidase. Likewise, NPs effectively preserved L* (lightness), a* (red/green) and b* (blue/yellow) values and maintained organoleptic score. Scanning electron microscopy study confirmed that Cu-chitosan NPs orchestrate into an invisible-intangible nano-net over tomato surface which may plausibly act as a potential barrier at all possible openings (stem scar, cuticle wax, lenticels, and aquaporins) to control microbial infection, moisture loss, gas exchanges and respiration rate. Overall, nano-net extended keeping quality of tomatoes up to 21 days at room temperature (27 ± 2 °C, 55 ± 2% relative humidity).

Cold plasma-activated hydrogen peroxide aerosol on populations of Salmonella Typhimurium and Listeria innocua and quality changes of apple, tomato and cantaloupe during storage - A pilot scale study

The occurrence of foodborne illness outbreaks associated with fresh fruits and vegetables continues to be a major concern. Effective technologies that can be applied commercially are urgently needed. A pilot scale study was carried out to investigate the efficacy of ionized hydrogen peroxide (iHP) treatment for the inactivation of Salmonella Typhimurium and Listeria innocua inoculated on apple and tomato smooth surfaces, tomato stem scars and cantaloupe rinds, and to evaluate changes in quality parameters during simulated shelf life study. iHP is the process of activating low concentration of aerosolized hydrogen peroxide with cold plasma. After treatments with 17.62 mL/m3 iHP in a large chamber (4.27 × 2.44 × 2.14 m), the inoculated bacteria were significantly reduced to a level below the detection limit (0.70 log CFU/piece) on the smooth surfaces of apples and tomatoes placed as a single layer in crates. Reductions of more than 3 log CFU/piece and approximately 1 log CFU/piece were obtained for cantaloupe rinds and tomato stem scars, respectively. When apples were placed in crates with multiple layers, 22% of fruits exhibited detectable Salmonella and 11% of fruits had detectable Listeria. Treated fruits from the pilot scale study were stored at 17 °C for 14 days and analyzed for quality every week. Results showed that iHP did not significantly affect appearance, color, texture, pH, soluble solids content, ascorbic acid, and antioxidants of the fresh produce items. The study demonstrates that the technology can be applied to fresh fruits to enhance microbial safety while maintaining quality. Challenges remain as to how to facilitate iHP exposure to all fruit surfaces in commercial settings.

Cold plasma enhances the efficacy of aerosolized hydrogen peroxide in reducing populations of Salmonella Typhimurium and Listeria innocua on grape tomatoes, apples, cantaloupe and romaine lettuce

In the present study, we investigated whether cold plasma activation affected the efficacy of aerosolized hydrogen peroxide against S. Typhimurium and L. innocua. Stem scars and smooth surfaces of grape tomatoes, surfaces of Granny Smith apples and Romaine lettuce (both midrib and upper leaves) and cantaloupe rinds were inoculated with two-strain cocktails of S. Typhimurium and 3-strain cocktails of L. innocua. The inoculated samples were treated with 7.8% aerosolized H2O2 with and without cold plasma for various times. For all fresh produce items and surfaces, cold plasma significantly (P < 0.05) improved the efficacy of aerosolized H2O2 against Salmonella and L. innocua. Without cold plasma activation, H2O2 aerosols only reduced populations of Salmonella by 1.54–3.17 log CFU/piece while H2O2 with cold plasma achieved 2.35–5.50 log CFU/piece reductions of Salmonella. L. innocua was more sensitive to the cold plasma-activated H2O2 than Salmonella. Cold plasma activated H2O2 aerosols reduced Listeria populations by more than 5 log CFU/piece on all types and surfaces of fresh produce except for the tomato stem scar area. Without cold plasma, the reductions by H2O2 were only 1.35–3.77 log CFU/piece. Overall, our results demonstrated that cold plasma activation significantly enhanced the efficacy of H2O2 mist against bacteria on fresh produce.

Inactivation of Salmonella in cherry tomato stem scars and quality preservation by pulsed light treatment and antimicrobial wash

The objective of this study was to evaluate the effectiveness of pulsed light (PL) treatment, a novel antimicrobial (LAPEN) wash and combinations thereof in inactivating Salmonella on stem scars of cherry tomato. The treatment effects on background microbiota and sensory quality was also investigated while in storage for 21 days at 10 °C. Three serotypes of Salmonella enterica were chosen to prepare inoculum for the current investigation for their link with tomato and produce outbreaks. Stem scars of tomato were spot inoculated before being treated with PL (1–63 J/cm2), LAPEN sanitizer (2 min) or combinations of PL with LAPEN Sanitizer. Significant inactivation was observed at low doses of PL. A 30 s treatment equivalent to a dose of 31.5 J/cm2, was found optimal. The optimal dose provided 2.3 log reduction of Salmonella while a 2 min wash in LAPEN sanitizer provided 2.1 log CFU/g reduction on stem scars. Two possible sequences of PL and LAPEN combinations were explored. For PL-LAPEN combination, inoculated tomatoes were initially exposed to optimum PL dose (31.5 J/cm2) and then washed 2 min in LAPEN sanitizer whereas for LAPEN-PL combination, tomatoes were initially immersed 2 min in LAPEN prior to PL treatment. Treatment of PL-LAPEN demonstrated a strong synergistic inactivation as no Salmonella survivor were detectable after treatment indicating greater than 5 log reduction, whereas LAPEN-PL combination revealed a compound inactivation providing 4.5 logs reduction of the pathogen. The PL-LAPEN treatment not only reduced native microbiota of tomato but also hindered their growth while in storage for three weeks. The firmness and visual appearance quality of tomato were not significantly influenced due to PL-LAPEN combination treatment until day 21, when the texture of treated tomato was significantly influenced. Overall, the results reveal that PL-LAPEN combination treatment can be implemented as a novel approach to enhance microbial safety and quality of cherry tomato.

Advanced oxidation process for the inactivation of Salmonella typhimurium on tomatoes by combination of gaseous ozone and aerosolized hydrogen peroxide

Fresh produce-associated outbreaks of foodborne illnesses continue to occur every year in the U.S., suggesting limitations of current practices and the need for effective intervention technologies. Advanced oxidation process involves production of hydrogen radicals, which are the strongest oxidant. The objective of the present study was to evaluate the effectiveness of advanced oxidation process by combining gaseous ozone and aerosolized hydrogen peroxide. Grape tomatoes were inoculated with a 2-strain cocktail of Salmonella typhimurium on both stem scar and smooth surface. Gaseous ozone (800 and 1600 ppm) and aerosolized hydrogen peroxide (2.5, 5 and 10%) were separately or simultaneously introduced into a treatment chamber where the inoculated tomatoes were placed. During the 30 min treatments, hydrogen peroxide was aerosolized using an atomizer operated in two modes: continuously or 15 s on/50 s off. After the treatments, surviving Salmonella on the smooth surface and stem scar were enumerated. Results showed that ozone alone reduced Salmonella populations by <0.6 log CFU/fruit on both the smooth surface and the stem scar area, and aerosolized hydrogen peroxide alone reduced the populations by up to 2.1 log CFU/fruit on the smooth surface and 0.8 log CFU/fruit on stem scar area. However, the combination treatments reduced the populations by up to 5.2 log CFU/fruit on smooth surface and 4.2 log CFU/fruit on the stem scar. Overall, our results demonstrate that gaseous ozone and aerosolized hydrogen peroxide have synergistic effects on the reduction of Salmonella populations on tomatoes.

Quality deterioration of grape tomato fruit during storage after treatments with gaseous ozone at conditions that significantly reduced populations of Salmonella on stem scar and smooth surface

Gaseous ozone was evaluated for its effectiveness in reducing populations of Salmonella and native microorganisms on grape tomatoes and its impact on sensory and nutritional quality of the fruit. Grape tomatoes with Salmonella enterica serovar Typhimurium inoculated onto stem scar and smooth surface were treated with 1.71, 3.43 and 6.85 mg L−1 gaseous ozone for 2 or 4 h. For quality studies, non-inoculated tomatoes were treated with gaseous ozone under the same concentrations and durations and stored at 10 °C for 21 d. Sensory properties (appearance and off-odor), total plate count (TPC), mold and yeast count, instrumental color, firmness, and lycopene and vitamin C content were measured on d 1, 7, 14, and 21 of storage. Results showed that 6.85 mg L−1 ozone for 2 and 4 h treatments reduced Salmonella populations by approximately 2 log CFU fruit−1 on both smooth surface and stem scar area of tomatoes. Other treatments did not significantly reduce the populations of Salmonella. Significant reductions on TPC were observed on fruit treated with 6.85 mg L−1 ozone for 2 and 4 h and 3.43 mg L−1 for 2 h on d 1 and 7 of storage. However, mold and yeast counts were not consistently affected by the gaseous ozone treatments. Ozone at 3.43 and 6.85 mg L−1 for 4 h negatively impacted the ratings of appearance and off-odor. In addition, the same treatments significantly reduced firmness and decreased lycopene and vitamin C contents. Overall, our results indicated that gaseous ozone that achieved significant reductions of Salmonella populations caused deteriorations in the quality of grape tomatoes.

The on field differentiation of snow avalanche- and debris flow-induced scars in trees as a fundament for improving dendrogeomorphic sampling strategy (case study from the Great Cold Valley in High Tatra Mountains)

Snow avalanches (SA) and debris flows (DF) are among the widespread geomorphic processes in high mountains. One of the most reliable method for determining their historical occurrence is related to dendrogeomorphical analyses. Sampling focused only on one process suffers from the noise caused by disturbances induced by the other process. Thus, the aim of this paper is to find specific parameters of stem scars that significantly differ when they are caused by different processes. For this purpose, six parameters of 102 sampled scars on mountain pine (Pinus mugo var. mugo) individuals growing on the polygenic debris fan in the High Tatra Mountains were recorded. For the verification of origin of scars from historically known DF and SA events, the intra-seasonal dating of callus tissue using microcuts was performed. 50 DF scars and 52 SA scars were identified and analysed. Several significant differences were identified, which serve as recommendations for a future sampling strategy. DF scars were significantly longer, wider, and occurred at lower distances above the ground in comparison with SA scars. DF scars expressed a significant negative relationship between scar length and its distance above the ground. The selection of scars with described parameters for a pointed analysis of SA or DF could help with sampling of scars caused by the analysed process.

Salmonella enterica Contamination of Market Fresh Tomatoes: A Review

Salmonella contamination associated with market fresh tomatoes has been problematic for the industry and consumers. A number of outbreaks have occurred, and dollar losses for the industry, including indirect collateral impact to agriculturally connected communities, have run into the hundreds of millions of dollars. This review covers these issues and an array of problems and potential solutions surrounding Salmonella contamination in tomatoes. Some other areas discussed include (i) the use of case-control studies and DNA fingerprinting to identify sources of contamination, (ii) the predilection for contamination based on Salmonella serovar and tomato cultivar, (iii) internalization, survival, and growth of Salmonella in or on tomatoes and the tomato plant, in biofilms, and in niches ancillary to tomato production and processing, (iv) the prevalence of Salmonella in tomatoes, especially in endogenous regions, and potential sources of contamination, and (v) effective and experimental means of decontaminating Salmonella from the surface and stem scar regions of the tomato. Future research should be directed in many of the areas discussed in this review, including determining and eliminating sources of contamination and targeting regions of the country where Salmonella is endemic and contamination is most likely to occur. Agriculturalists, horticulturalists, microbiologists, and epidemiologists may make the largest impact by working together to solve other unanswered questions regarding tomatoes and Salmonella contamination.

Tomato type and post-treatment water rinse affect efficacy of acid washes against Salmonella enterica inoculated on stem scars of tomatoes and product quality

A study was conducted to evaluate the effects of post-treatment rinsing with water on the inactivation efficacy of acid treatments against Salmonella inoculated onto stem scar areas of two types of tomatoes. In addition, impact on fruit quality was investigated during 21 days post-treatment storage at 10 °C. A four-strain cocktail of Salmonella enterica (S. Montevideo, S. Newport, S. Saintpaul, and S. Typhimurium) was inoculated onto stem scar areas of grape and large round tomatoes. The inoculated fruits were then treated for 2 min with the following solutions: water, 2% lactic acid +2% acetic acid +2% levulinic acid, 1.7% lactic acid +1.7% acetic acid +1.7% levulinic acid, and 3% lactic acid +3% acetic acid. After treatments, half of the fruits were rinsed with water while another half were not rinsed. Non-inoculated grape tomatoes for quality analysis were treated with the same solutions with and without subsequent water rinse. Results demonstrated that the acid combinations reduced populations of Salmonella enterica on the stem scar area of grape tomatoes by 1.52–1.90 log CFU/fruit, compared with the non-treated control while water wash and rinse removed the bacterium by only 0.23–0.30 log CFU/fruit. On the stem scar of large round tomatoes, the same acid treatments achieved 3.54 log CFU/fruit reduction of the pathogen. The varying response to the acid washes between grape and large round tomatoes seems to be related to the differences in surface characteristics of stem scar areas observed with SEM. Rinsing with water after acid combination treatments did not significantly affect the efficacy of the treatments in either grape or large round tomatoes. Acidic off-odor was detected on fruits treated with acid combination without water rinse 1 day after treatment while water rinse eliminated the off-odor. The acid treatments with and without water rinse did not consistently affect appearance, color, firmness, or lycopene or ascorbic acid contents of tomatoes during 21-days storage at 10 °C. Considering the similarity in antimicrobial efficacy between the fruits with and without water rinse following acid treatments, and the elimination of acidic odor by water rinse, fruits should be rinsed with water after acid treatments. Overall, our results demonstrated that the acids were more effective in inactivating Salmonella on large round tomatoes than on grape tomatoes, and water rinses following acid treatments eliminated the acidic odor without affecting the efficacy of the acids against Salmonella.

Using antimicrobials as a food safety measure during phytosanitary treatments in mangoes

Prevention of plant-borne pest infestation necessitates use of phytosanitary procedures, as in the case of U.S.-imported mangoes. Supplementation of hydrothermal disinfestation and/or post-process cooling waters with chemical sanitizers could provide mango packers with antimicrobial interventions reduce or prevent microbial pathogen transmission on mangoes. The current study determined: i) the effectiveness of chlorine (CL) or lactic acid (LA) addition to water used for hydrothermal and cooling treatments to reduce Salmonella survival on mangoes during disinfestation treatment, and; ii) Salmonella internalization into stem scars following hydrothermal and cooling treatments in sanitizer-supplemented water. Salmonella survival during post-treatment storage and effects of treatments on mango color and firmness were also determined. A 2.0 log-cycle reduction was obtained on stem scars subjected to hydrothermal treatment; reductions of 2.2 and 1.3 log-cycles were obtained on stem scars with LA and OCl− treatment, respectively. An additional 1.0 log-cycle reduction during cooling was observed for OCl−-treated mangos; Salmonella were not detected (<2.0 log CFU/10 cm2) on LA-treated mangos. On hydrothermal-treated rinds, a 0.5 log cycle reduction was obtained for control fruit; a reduction of 1.7 log cycles was obtained for both LA- and OCl−-treated fruit. Internalized Salmonella were detected in stem scar tissues obtained following hydrothermal treatment and cooling by enrichment, and survived storage at 10 °C for 12 days. In general, there were no differences in the reduction of Salmonella between CL and LA, although in two occasions CL was less effective. However, mango color was compromised by use of LA. Chlorine use both in hot and cool dips is recommended for minimizing Salmonella transmission on mango surfaces.