Efficacy of Ozone Against Escherichia coli O157:H7 on Apples

Apples were inoculated with Escherichia coli O157:H7 and treated with ozone. Sanitization treatments were more effective when ozone was bubbled during apple washing than by dipping apples in pre‐ozonated water. The corresponding decreases in counts of E. coli O157:H7 during 3‐min treatments were 3.7 and 2.6 log₁₀ CFU on apple surface, respectively, compared to < 1 log₁₀ CFU decrease in the stem‐calyx region in both delivery methods. Optimum conditions for decontamination of whole apples with ozone included a pretreatment with a wetting agent, followed by bubbling ozone for 3 min in the wash water, which decreased the count of E. coli O157:H7 by 3.3 log₁₀CFU/g.     

Potential sources of microbial contamination in unpasteurized apple cider

A study was conducted to identify possible sources of microbial contamination and to assess the effect of good cleaning and sanitation practices on the microbial quality and safety of unpasteurized apple cider. Raw unwashed apples, washed apples, cleaning water, fresh cider, and finished cider samples were collected from five Ontario producers over 4 months and microbiologically tested. Total coliforms were found in 31, 71 and 38% of the unwashed apple, water, and washed apple samples, respectively. Escherichia coli was found in 40% of the water samples from one producer alone. The washing step was identified as a potential source of contamination, possibly due to water in the dump tanks seldom being refreshed, and because scrubbers, spray nozzles, and conveyors were not properly cleaned and sanitized. Higher total coliform counts (P < 0.0001) and prevalence (P < 0.0001) in fresh cider compared with those in unwashed apples and washed apples indicated considerable microbial buildup along the process, possibly explained by the lack of appropriate equipment sanitation procedures. Results showed that producers who had better sanitary practices in place had lower (P < 0.001) total coliform prevalence than the rest of the producers. Overall results show that good sanitation procedures are associated with improved microbial quality of fresh cider in terms of total coliforms and that operators who pasteurize and/or UV treat their product should still be required to have a sound good manufacturing practices program in place to prevent recontamination. Cryptosporidium parvum, an important pathogen for this industry, was found in different sample types, including washed apples, water, and fresh and finished cider.     

Antibrowning and Antimicrobial Properties of Sodium Acid Sulfate in Apple Slices

ABSTRACT: There are few available compounds that can both control browning and enhance microbial safety of fresh‐cut fruits. In the present study, the antibrowning ability of sodium acid sulfate (SAS) on “Granny Smith” apple slices was first investigated in terms of optimum concentration and treatment time. In a separate experiment, the apple slices were treated with water or 3% of SAS, calcium ascorbate, citric acid, or acidified calcium sulfate for 5 min. Total plate count, color, firmness, and tissue damage were assessed during a 21‐d storage at 4 °C. Results showed that the efficacy of SAS in inhibiting browning of apple slices increased with increasing concentration. A minimum 3% of SAS was needed to achieve 14 d of shelf life. Firmness was not significantly affected by SAS at 3% or lower concentrations. Antibrowning potential of SAS was similar for all treatment times ranging from 2 to 10 min. However, SAS caused some skin discoloration of apple slices. When cut surface of apple slices were stained with a fluorescein diacetate solution, tissue damage could be observed under a microscope even though visual damage was not evident. Among the antibrowning agents tested, SAS was the most effective in inhibiting browning and microbial growth for the first 14 d. Total plate count of samples treated with 3% SAS was significantly lower than those treated with calcium ascorbate, a commonly used antibrowning agent. Our results suggested that it is possible to use SAS to control browning while inhibiting the growth of microorganisms on the apple slices if the skin damage can be minimized. Practical Application: Fresh‐cut apples have emerged as one of the popular products in restaurants, schools, and food service establishments as more consumers demand fresh, convenient, and nutritious foods. Processing of fresh‐cut apples induces mechanical damage to the fruit and exposes apple tissue to air, resulting in the development of undesirable tissue browning. The fresh‐cut industry currently uses antibrowning agents to prevent discoloration. However, the antibrowning solutions can become contaminated with human pathogens such as Listeria monocytogenes, and washing of apple slices with the contaminated solutions can result in the transfer of pathogens to the product. It would be ideal if an antibrowning compound prevented the proliferation of human pathogens in solutions and minimized the growth of pathogens during storage. The study was conducted to investigate antibrowning and antimicrobial properties of sodium acid sulfate (SAS) in comparison with other common antibrowning agents on Granny Smith apples. Results showed that among the antimicrobial agents we tested, SAS was the most effective in inhibiting browning and microbial growth for 14 d at 4 °C. However, SAS caused some skin discoloration of apple slices. Overall, SAS can potentially be used to inhibit tissue browning while reducing the microbial growth on apple slices. The information is useful for the fresh‐cut produce industry to enhance microbial safety of fresh‐cut apples while minimizing browning, thus increasing the consumption of the health benefiting fresh fruit.     

Influence of fruit variety, harvest technique, quality sorting, and storage on the native microflora of unpasteurized apple cider

Apple variety, harvest, quality sorting, and storage practices were assessed to determine their impact on the microflora of unpasteurized cider. Seven apple varieties were harvested from the tree or the ground. The apples were used fresh or were stored at 0 to 4 degrees C for < or = 5 months and were pressed with or without quality selection. Cider yield, pH, Brix value, and titratable acidity were measured. Apples, postpressing apple pomace, and cider samples were analyzed for aerobic bacteria, yeasts, and molds. Aerobic bacterial plate counts (APCs) of ciders from fresh ground-picked apples (4.89 log CFU/ml) were higher than those of ciders made from fresh, tree-picked apples (3.45 log CFU/ml). Quality sorting further reduced the average APC to 2.88 log CFU/ml. Differences among all three treatment groups were significant (P < 0.0001). Apple and pomace microbial concentrations revealed harvest and postharvest treatment-dependent differences similar to those found in cider. There were significant differences in APC among apple varieties (P = 0.0001). Lower counts were associated with varieties exhibiting higher Brix values and higher titratable acidity. Differences in APC for stored and fresh apples used for cider production were not significant (P > 0.05). Yeast and mold counts revealed relationships similar to those for APCs. The relationship between initial microbial load found on incoming fruit and final cider microbial population was curvilinear, with the weakest correlations for the lowest apple microflora concentrations. The lack of linearity suggests that processing equipment contributed to cider contamination. Tree-picked quality fruit should be used for unpasteurized cider production, and careful manufacturing practices at cider plants can impact both safety and quality of the final product.     

INFLUENCE OF 1-METHYLCYCLOPROPENE AND NATURESEAL ON THE QUALITY OF FRESH-CUT "EMPIRE" AND "CRISPIN" APPLES

Wounding during processing triggers physiological reactions that limits shelf life of fresh‐cut apples. Exposure of “Empire” and “Crispin” apples at harvest to the ethylene antagonist, 1‐methylcyclopropene (1‐MCP), on the maintenance of fresh‐cut quality was evaluated in combination with post‐cut dipping of NatureSeal^TM Efficacy of 1‐MCP on fresh‐cut physiology and quality depended on the storage duration and apple cultivar. Ethylene production of apple slices was inhibited by 1‐MCP but not by NatureSeal. Total volatiles produced by fresh‐cut apples were not affected by NatureSeal but by 1‐MCP when 1‐month stored “Crispin” apples were used. 1‐MCP influenced the quality attributes of fresh‐cut slices prepared from apples stored either 4 months in cold storage or 6 months in controlled atmosphere. Enzymatic browning and softening of the cut‐surface, TSS and total microbial growth were suppressed by 1‐MCP in “Empire” apples. The influence of 1‐MCP on quality attributes in “Crispin” apple slices was marginal.     

Detection of Listeria monocytogenes in Fresh Produce Using Molecular Beacon—Real‐time PCR Technology

ABSTRACT: The capability of an assay to detect Listeria monocytogenes from artificially inoculated fresh‐cut produce such as cantaloupe and mixed salad was demonstrated. An oligonucleotide probe that becomes fluorescent upon hybridization to the target DNA (Molecular Beacon, MB) was used in a real‐time polymerase chain reaction (PCR) assay. As few as 4 to 7 colony‐forming units (CFU) of L. monocytogenes per 25 g of artificially contaminated produce could be detected. A comparison of 2 commercially available kits using MB‐PCR (iQ‐Check, Bio‐Rad Laboratories) and conventional PCR (BAX, Dupont Qualicon) was performed on artificially inoculated produce. The time required to detect L. monocytogenes (from produce to PCR) was considerably shorter for the iQ‐Check protocol (approximately 26 h) compared with the BAX‐PCR (approximately 52 h). The iQ‐Check protocol was also used to confirm the identity of the L. monocytogenes isolates obtained during a microbiological screen of conventional and organic leaf lettuce and alfalfa sprout samples from local supermarkets. The iQ check protocol was successful in differentiating L. monocytogenes isolates from other Listeria spp. such as L. welshimeri, L. innocua, and L. ivanovii. This is the 1st report of the application of the MB probe being used for real‐time detection of L. monocytogenes in whole and fresh‐cut produce.     

Outbreaks and factors influencing microbiological contamination of fresh produce

Fresh fruits and vegetables are nutritionally well‐recognised as healthy components in diets. The microbiological foodborne outbreaks associated with the consumption of fresh produce have been increasing. Salmonella spp., Escherichia coli O157:H7, Staphylococcus aureus, Campylobacter spp. and Listeria monocytogenes are the most common pathogens that contaminate fresh produce. This review discusses recent foodborne outbreaks linked to fresh produce, factors that affect microbiological contamination and measures that could be adopted to reduce the foodborne illnesses. © 2016 Society of Chemical Industry     

Control of Listeria monocytogenes Contamination in Ready‐to‐Eat Meat Products

The ubiquitous nature of Listeria monocytogenes and its ability to grow at refrigerated temperature makes L. monocytogenes a significant threat to the safety of ready‐to‐eat (RTE) meat products. The contamination by L. monocytogenes in RTE meat primarily occurs during slicing and packaging after cooking. The effectiveness of post‐package decontamination technology such as in‐package thermal pasteurization, irradiation, and high‐pressure processing are discussed. Formulating meat products with antimicrobial additives is another common approach to control L. monocytogenes in RTE meat. Irradiation is an effective technology to eliminate L. monocytogenes but can influence the quality of RTE meat products significantly. The effect of irradiation or the combination of irradiation and antimicrobials on the survival of L. monocytogenes and the quality of RTE meat is discussed.     

The occurrence,growth, and biocontrol of Listeria monocytogenes in fresh and surface-ripened soft and semisoft cheeses

Listeria monocytogenes continues to pose a food safety risk in ready-to-eat foods, including fresh and soft/semisoft cheeses. Despite L. monocytogenes being detected regularly along the cheese production continuum, variations in cheese style and intrinsic/extrinsic factors throughout the production process (e.g., pH, water activity, and temperature) affect the potential for L. monocytogenes survival and growth. As novel preservation strategies against the growth of L. monocytogenes in susceptible cheeses, researchers have investigated the use of various biocontrol strategies, including bacteriocins and bacteriocin-producing cultures, bacteriophages, and competition with native microbiota. Bacteriocins produced by lactic acid bacteria (LAB) are of particular interest to the dairy industry since they are often effective against Gram-positive organisms such as L. monocytogenes, and because many LAB are granted Generally Regarded as Safe (GRAS) status by global food safety authorities. Similarly, bacteriophages are also considered a safe form of biocontrol since they have high specificity for their target bacterium. Both bacteriocins and bacteriophages have shown success in reducing L. monocytogenes populations in cheeses in the short term, but regrowth of surviving cells can commonly occur in the finished cheeses. Competition with native microbiota, not mediated by bacteriocin production, has also shown potential to inhibit the growth of L. monocytogenes in cheeses, but the mechanisms are still unclear. Here, we have reviewed the current knowledge on the growth of L. monocytogenes in fresh and surface-ripened soft and semisoft cheeses, as well as the various methods used for biocontrol of this common foodborne pathogen.     

Incidence of Land and Physicochemical Composition of Apples on the Qualitative and Quantitative Development of Microbial Flora During Cider Fermentations

Lactic acid bacteria and yeasts were numerated, isolated and identified from ciders prepared with the same variety of apple from apple trees grown on three different lands: silt, siliceous clay and green clay. The land has an incidence on the time (earliness) of ripeness of the apples and on their sugar content and, therefore, on the development of the microbial flora in the ciders obtained from these fruits. The same genera of yeasts and lactic acid bacteria were isolated from the three ciders, except the yeast Candida famata exclusively found in the must obtained from apples grown on silt. At the quantitative level, the highest development of yeasts was observed in the must from the land green clay whereas lactic acid bacteria growth was enhanced in the must from the land siliceous clay.     

Fate of Escherichia coli in apple and reduction of its growth using the postharvest biocontrol agent Candida sake CPA‐1

BACKGROUND: Generally, acidic fruits and fruit juices are considered ‘safe’ from a microbiological point of view. However, some outbreaks of foodborne illnesses have been linked to the consumption of unpasteurised cider. The aim of this work was to study the survival of Escherichia coli in apple juice, wounds and flesh and on apple surfaces at different temperatures and to determine the effect of the fungal biocontrol agent Candida sake CPA‐1 against the colonisation of apple by E. coli. RESULTS: Trials were conducted with a mixture of five strains of E. coli isolated from apples. E. coli was unable to grow in apple juice at 5, 15 and 25 °C but survived. At 10 °C and above, E. coli thrived in fresh‐cut apple and wounds. At 5 °C it survived in apple wounds after 27 days of storage and after 21 days in fresh‐cut apples. When E. coli was inoculated in apple wounds together with the yeast antagonist C. sake, its growth was reduced by approximately 1 log cfu wound^?1 at 25 °C. At 5 °C no effect of the biocontrol agent was observed. CONCLUSION: Despite the low pH of apple, a rapid increase in the bacterial population is possible if the temperature is not kept low enough. The biocontrol agent C. sake, developed to prevent fruit decay during storage, could also reduce E. coli growth in wounded apples at abusive temperatures. This would represent an additional benefit of using this biocontrol agent when applied to control postharvest diseases. Copyright © 2009 Society of Chemical Industry     

Effect of pomegranate (Punica granatum) pomace extract as a washing agent on the inactivation of Listeria monocytogenes inoculated on fresh produce

Pomegranate pomace extract (PPE) was used as a substitute to chlorinated water for washing of fresh produce. PPE contained punicalagins and ellagic acids, and it had a good inhibitory effect against Listeria monocytogenes based on the results of disc diffusion test and time‐kill assay. Red chard, beet, chicon and red mustard leaves were treated with 7 mg mL^?1 PPE as a washing solution to inactivate L. monocytogenes inoculated on fresh produce and compared with 0.05 mg mL^?1 NaOCl treatment. After the treatment, L. monocytogenes population on the four leafy vegetables was reduced by 1.96–2.97 log CFU g^?1 compared to that on nontreated samples. The reductions in L. monocytogenes after PPE treatment were higher than those observed after NaOCl treatment. Further, the PPE treatment did not affect the surface colour of all fresh produce applied in this study. Thus, PPE can be used as an effective antimicrobial washing agent of fresh produce.     

Modelling the cross‐contamination of Listeria monocytogenes in pork during bowl chopping

This study has developed a predictive model for the cross‐contamination of pork by Listeria monocytogenes during bowl chopping. The transfer rates of L. monocytogenes were measured in sixteen chopping scenarios based on practical work. Meanwhile, contaminated bowl chopper was cleaned with either a dry rag (DR), warm water (WW) or 70% ethanol + water (EW), respectively. It was showed that significant differences (P < 0.05) were observed among the three cleaning methods on the reduction of L. monocytogenes, the greatest log reduction being achieved by EW. Moreover, the model introduced by a previous study, predicting cross‐contamination of L. monocytogenes during meat slicing, was improved and validated in this study. Verification results showed that the improved model was acceptable for predicting L. monocytogenes cross‐contamination during pork chopping with coefficients of determination (R² > 0.82), accuracy factors (A_f < 1.44), bias factors (B_f < 1.42), and root mean square error (RMSE < 0.99). Furthermore, the modified model might provide an effective tool for assessing the risk of the cross‐contamination of meat products.     

Quality Change of Apple Slices Coated with Aloe vera Gel during Storage

Fresh‐cut apples are easily susceptible to browning and microbial spoilage. In this study, an edible coating prepared from Aloe vera gel containing antibrowning solution was applied to preserve the quality of fresh‐cut apples during storage. Fresh‐cut apples were treated with both an Aloe vera gel and an Aloe vera gel containing 0.5% cysteine and then stored at 4 °C for 16 d. The color, firmness, weight loss, soluble solid content, titratable acidity, microbial analysis, and sensory evaluation were analyzed during storage. Fresh‐cut apples coated with the Aloe vera gel showed delayed browning and reduced weight loss and softening compared to the control. The Aloe vera gel coating was also effective in reducing the populations of the total aerobic bacteria and yeast and molds. In particular, Aloe vera gel containing 0.5% cysteine was most effective in delaying browning and the reduction of microbial populations among the treatments. These results suggest that an Aloe vera gel coating can be used for maintaining the quality of fresh‐cut apples.     

Microbial populations on animal hides and beef carcasses at different stages of slaughter in plants employing multiple-sequential interventions for decontamination

Multiple-sequential interventions were applied commercially to reduce beef carcass contamination in eight packing plants. The study evaluated microbial populations on animal hides and changes in carcass microbial populations at various stages in the slaughtering process. Sponge swab samples yielded mean (log CFU/100 cm2) total plate counts (TPC), total coliform counts (TCC), and Escherichia coli counts (ECC) on the exterior hide in the ranges of 8.2 to 12.5, 6.0 to 7.9, and 5.5 to 7.5, respectively, while corresponding contamination levels on carcass surfaces, after hide removal but before application of any decontamination intervention, were in the ranges of 6.1 to 9.1, 3.0 to 6.0, and 2.6 to 5.3, respectively. Following the slaughtering process and application of multiple-sequential decontamination interventions that included steam vacuuming, pre-evisceration carcass washing, pre-evisceration organic acid solution rinsing, hot water carcass washing, postevisceration final carcass washing, and postevisceration organic acid solution rinsing, mean TPC, TCC, and ECC on carcass surfaces were 3.8 to 7.1, 1.5 to 3.7, and 1.0 to 3.0, respectively, while corresponding populations following a 24 to 36 h chilling period were 2.3 to 5.3, 0.9 to 1.3, and 0.9, respectively. The results support the concept of using sequential decontamination processes in beef packing plants as a means of improving the microbiological quality of beef carcasses.     

Irrigation water quality and microbial safety of leafy greens in different vegetable production systems: A review

Access to large sources of quality water for irrigation is fundamental to the hygienic cultivation of fresh produce. However, due to factors such as contamination of water bodies, access to clean uncontaminated water is fast becoming an ever increasing global challenge. The unavailability of quality source water increases the risk of contamination of fresh produce with human pathogenic microorganisms, which may compromise public health. Over the past few years, there has been a decline in the microbiological quality of surface water and other sources used for irrigation. This is mainly due to upstream fecal contamination. Therefore, the assessment and subsequent suitability of alternative water sources for irrigation such as roof-harvested rainwater should be considered. Contrasting views regarding the quality of roof-harvested rainwater (RHRW) have been published. Pathogens such as Salmonella and Campylobacter species and Listeria monocytogenes have been reported in RHRW. Leafy green vegetables such as cabbage, spinach, and lettuce are produced across a wide range of farming systems from regulated formal (commercial farms) to informal (small-scale and homestead gardens) setups. This review will discuss global water challenges associated with irrigation water, microbial quality of source water for irrigation, crop contamination, and pathogen detection and characterization methodologies.     

Effect of short‐term air storage after removal from controlled‐atmosphere storage on apple and fresh‐cut apple quality

BACKGROUND: One of the realities of apple distribution for long‐term stored fruit is that a controlled‐atmosphere (CA) storage room will be unsealed and fruit held in air storage and marketed over several weeks. This work was conducted to determine the effect of post‐CA air storage of whole fruit on potential shelf life for fresh‐cut apple slices. RESULTS: Fresh‐cut slices of ‘Spartan’ and ‘Delicious’ apples held in post‐CA air storage for 2 or 4 weeks showed the least changes in cut surface color as compared with those made from apples immediately on removal from CA. Shelf life was most improved by post‐CA air storage in the ‘Spartan’ apples, which were more advanced in maturity as compared with the ‘Delicious’ apples. Internal ethylene concentration, firmness, and respiration changed significantly with post‐CA air storage, suggesting a relationship between physiological status of the whole fruit and shelf life of slices made from that fruit. CONCLUSION: The results support the hypothesis that apples had suppressed physiological activity in CA storage and are susceptible to accelerated deterioration upon cutting. Holding fruit for 2 weeks in air storage allowed recovery of physiological activity, which resulted in greater resistance to deterioration in response to fresh‐cut processing. Copyright © 2010 Crown in the right of Canada. Published by JohnWiley & Sons, Ltd     

Effect of Surface Properties on Colloid Retention on Natural and Surrogate Produce Surfaces

Bacterial contamination of fresh produce is a growing concern in food industry. Pathogenic bacteria can attach to and colonize the surfaces of fresh produce and cause disease outbreaks among consumers. Surface properties of both bacteria and produce affect bacterial contamination; however, the effects of produce roughness, topography, and hydrophobicity on bacterial retention are still poorly understood. In this work, we used spherical polystyrene colloids as bacterial surrogates to investigate colloid retention on and removal (by rinsing) from fresh produce surfaces including tomato, orange, apple, lettuce, spinach, and cantaloupe, and from surrogate produce surface Sharklet (a micro‐patterned polymer). All investigated surfaces were characterized in terms of surface roughness and hydrophobicity (including contact angle and water retention area measurements). The results showed that there was no single parameter that dominated colloid retention on fresh produce, yet strong connection was found between colloid retention and water retention and distribution on all the surfaces investigated except apple. Rinsing was generally not efficient in removing colloids from produce surfaces, which suggests the need to modify current cleaning procedures and to develop novel contamination prevention strategies. This work offers a physicochemical approach to a food safety problem and improves understanding of mechanisms leading to produce contamination.     

Antibacterial activity of egg yolk antibody (IgY) against Listeria monocytogenes and preliminary evaluation of its potential for food preservation

BACKGROUND: Egg yolk antibody (IgY) is a unique type of immunoglobulin found in egg yolks, and many reports have described its ability to inhibit corresponding antigen bacteria. The objective of this study was to evaluate the antibacterial activity of IgY specific to Listeria monocytogenes, an important food pathogen to both humans and animals, as well as its potential use for food preservation. RESULTS: Specific IgY was generated by immunising Leghorn chickens with whole cells of L. monocytogenes, and its inhibitory effect on bacterial growth was tested in liquid medium and food samples. After 8 h of incubation with specific IgY, there was a significant decrease in the growth (absorbance at 600 nm) of L. monocytogenes in comparison with controls. IgY also inhibited the growth of L. monocytogenes inoculated onto fresh or smoked salmon samples. Compared with those of blanks, numbers of L. monocytogenes were reduced by more than 2 log units after 15 days of storage at 6 ± 1 °C in the presence of specific IgY. CONCLUSION: The results suggest the potential application of specific IgY as a natural antimicrobial agent for food preservation. Copyright © 2011 Society of Chemical Industry