Apple,Carrot, and Hibiscus Edible Films Containing the Plant Antimicrobials Carvacrol and Cinnamaldehyde Inactivate Salmonella Newport on Organic Leafy Greens in Sealed Plastic Bags

The objective of this study was to investigate the antimicrobial effects of carvacrol and cinnamaldehyde incorporated into apple, carrot, and hibiscus‐based edible films against Salmonella Newport in bagged organic leafy greens. The leafy greens tested included organic Romaine and Iceberg lettuce, and mature and baby spinach. Each leafy green sample was washed, dip inoculated with S. Newport (10⁷ CFU/mL), and dried. Each sample was put into a Ziploc® bag. Edible films pieces were put into the Ziploc bag and mixed well. The bags were sealed and stored at 4 °C. Samples were taken at days 0, 3, and 7 for enumeration of survivors. On all leafy greens, 3% carvacrol films showed the best bactericidal effects against Salmonella. All 3 types of 3% carvacrol films reduced the Salmonella population by 5 log₁₀ CFU/g at day 0 and 1.5% carvacrol films reduced Salmonella by 1 to 4 log₁₀ CFU/g at day 7. The films with 3% cinnamaldehyde showed 0.5 to 3 log reductions on different leafy greens at day 7. The films with 0.5% and 1.5% cinnamaldehyde and 0.5% carvacrol also showed varied reductions on different types of leafy greens. Edible films were the most effective against Salmonella on Iceberg lettuce. This study demonstrates the potential of edible films incorporated with carvacrol and cinnamaldehyde to inactivate S. Newport on organic leafy greens.     

Effects of Allspice, Cinnamon, and Clove Bud Essential Oils in Edible Apple Films on Physical Properties and Antimicrobial Activities

ABSTRACT:  Essential oils (EOs) derived from plants are rich sources of volatile terpenoids and phenolic compounds. Such compounds have the potential to inactivate pathogenic bacteria on contact and in the vapor phase. Edible films made from fruits or vegetables containing EOs can be used commercially to protect food against contamination by pathogenic bacteria. EOs from cinnamon, allspice, and clove bud plants are compatible with the sensory characteristics of apple-based edible films. These films could extend product shelf life and reduce risk of pathogen growth on food surfaces. This study evaluated physical properties (water vapor permeability, color, tensile properties) and antimicrobial activities against  Escherichia coli  O157:H7,  Salmonella enterica,  and  Listeria monocytogenes  of allspice, cinnamon, and clove bud oils in apple puree film-forming solutions formulated into edible films at 0.5% to 3% (w/w) concentrations. Antimicrobial activities were determined by 2 independent methods: overlay of the film on top of the bacteria and vapor phase diffusion of the antimicrobial from the film to the bacteria. The antimicrobial activities against the 3 pathogens were in the following order: cinnamon oil > clove bud oil > allspice oil. The antimicrobial films were more effective against  L. monocytogenes  than against the  S. enterica . The oils reduced the viscosity of the apple solutions and increased elongation and darkened the colors of the films. They did not affect water vapor permeability. The results show that apple-based films with allspice, cinnamon, or clove bud oils were active against 3 foodborne pathogens by both direct contact with the bacteria and indirectly by vapors emanating from the films.     

Antibacterial Effects of Allspice, Garlic, and Oregano Essential Oils in Tomato Films Determined by Overlay and Vapor-Phase Methods

ABSTRACT:  Physical properties as well as antimicrobial activities against  Escherichia coli  O157:H7,  Salmonella enterica , and  Listeria monocytogenes  of allspice, garlic, and oregano essential oils (EOs) in tomato puree film-forming solutions (TPFFS) formulated into edible films at 0.5% to 3% (w/w) concentrations were investigated in this study. Antimicrobial activities were determined by 2 independent methods: overlay of the film on top of the bacteria and vapor-phase diffusion of the antimicrobial from the film to the bacteria. The results indicate that the antimicrobial activities against the 3 pathogens were in the following order: oregano oil > allspice oil > garlic oil.  Listeria monocytogenes  was less resistant to EO vapors, while  E. coli  O157:H7 was more resistant to EOs as determined by both overlay and vapor-phase diffusion tests. The presence of plant EO antimicrobials reduced the viscosity of TPFFS at the higher shear rates, but did not affect water vapor permeability of films. EOs increased elongation and darkened the color of films. The results of the present study show that the 3 plant-derived EOs can be used to prepare tomato-based antimicrobial edible films with good physical properties for food applications by both direct contact and indirectly by vapors emanating from the films.     

Inhibition of Three Pathogens on Bologna and Summer Sausage Using Antimicrobial Edible Films

Whey protein isolate (WPI) films (pH 5.2) containing 0.5 to 1.0% p‐aminobenzoic acid (PABA) and/or sorbic acid (SA) were assessed for antimicrobial and mechanical properties while in contact with sliced bologna and summer sausage that were inoculated with Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica subsp. enterica serovar Typhimurium DT104. WPI films containing SA or PABA decreased L. monocytogenes, E. coli, and S. Typhimurium populations by 3.4 to 4.1,3.1 to 3.6, and 3.1 to 4.1 logs, respectively, on both products after 21 d at 4 °C. Background flora was inhibited compared with controls. Film tensile strength decreased while % elongation remained unchanged following 72 h of product contact.     

主要食源性致病菌的PCR检测方法优化及在冷鲜猪肉病原污染调查中的应用

为优化针对主要食源性致病菌的PCR鉴定体系,以及了解猪肉制品中主要食源性致病菌的污染状况,对文献中报道的沙门氏菌属(鼠伤寒沙门氏菌及肠炎沙门氏菌)的5套PCR体系及大肠杆菌O157:H7的6套PCR体系进行比较分析,结果筛选出2套最优体系。基于这两套体系以及本实验室研究人员建立的单增李斯特菌的特异性检测方法,对从杭州市场上采集的50份常温鲜猪肉及150份冷鲜猪肉中单增李斯特菌、沙门氏菌及大肠杆菌O157:H7的污染状况进行调查。调查结果显示,200份样品中致病菌总检出率为21%。冷鲜猪肉中的致病菌检出率(24.7%)明显高于常温鲜猪肉(10%)。单增李斯特菌在常温鲜猪肉中的检出率为2%,而在冷鲜猪肉中检出率达14.7%;沙门氏菌在冷鲜猪肉中的检出率(11.3%)亦高于常温鲜猪肉(8.0%);大肠杆菌O157:H7均未检出。在检出的沙门氏菌中,有4株为鼠伤寒沙门氏菌,均来自冷鲜猪肉。本研究结果提示,市场上冷鲜猪肉存在微生物性安全隐患,这可能是由于其较为复杂的生产流通环节受到污染所致。     

Incorporation of Essential Oils and Nanoparticles in Pullulan Films to Control Foodborne Pathogens on Meat and Poultry Products

The incorporation of essential oils and nanotechnology into edible films has the potential to improve the microbiological safety of foods. The aim of this study was to evaluate the effectiveness of pullulan films containing essential oils and nanoparticles against 4 foodborne pathogens. Initial experiments using plate overlay assays demonstrated that 2% oregano essential oil was active against Staphylococcus aureus and Salmonella Typhimurium, whereas Listeria monocytogenes and Escherichia coli O157:H7 were not inhibited. Two percent rosemary essential oil was active against S. aureus, L. monocytogenes, E. coli O157:H7, and S. Typhimurium, when compared with 1%. Zinc oxide nanoparticles at 110 nm were active against S. aureus, L. monocytogenes, E. coli O157:H7, and S. Typhimurium, when compared with 100 or 130 nm. Conversely, 100 nm silver (Ag) nanoparticles were more active against S. aureus than L. monocytogenes. Using the results from these experiments, the compounds exhibiting the greatest activity were incorporated into pullulan films and found to inhibit all or some of the 4 pathogens in plate overlay assays. In challenge studies, pullulan films containing the compounds effectively inhibited the pathogens associated with vacuum packaged meat and poultry products stored at 4 °C for up to 3 wk, as compared to control films. Additionally, the structure and cross‐section of the films were evaluated using electron microscopy. The results from this study demonstrate that edible films made from pullulan and incorporated with essential oils or nanoparticles may improve the safety of refrigerated, fresh or further processed meat and poultry products.     

Heat Resistance of Salmonella spp., Listeria monocytogenes, Escherichia coli 0157:H7, and Listeria innocua M1, a Potential Surrogate for Listeria monocytogenes, in Meat and Poultry: A Review

ABSTRACT: The heat-resistance data in meat and poultry for various strains of Salmonella, Listeria monocytogenes , and Escherichia coli O157:H7 as well as Listeria innocua M1 are summarized. Heat resistance of these organisms is affected by many factors. Different strains of the same organism have different responses to heat. Heat resistance can also be influenced by the age of the culture, growth conditions, pH, and numerous other factors. Data from this review may prove useful to processors in validating their times and temperatures for thermal processing of meat and poultry. The obvious gaps in the data will provide researchers opportunities to fill those gaps. In addition, it will encourage the development of surrogates, whether biological or otherwise, that will be able to be used in an actual processing environment.     

Inactivation of Listeria monocytogenes on ham and bologna using pectin-based apple, carrot, and hibiscus edible films containing carvacrol and cinnamaldehyde

Edible films can be used as wrapping material on food products to reduce surface contamination. The incorporation of antimicrobials into edible films could serve as an additional barrier against pathogenic and spoilage microorganisms that contaminate food surfaces. The objective of this study was to investigate the antimicrobial effects of carvacrol and cinnamaldehyde, incorporated into apple, carrot, and hibiscus-based edible films against Listeria monocytogenes on contaminated ham and bologna. Ham or bologna samples were inoculated with L. monocytogenes and dried for 30 min, then surface wrapped with edible films containing the antimicrobials at various concentrations. The inoculated, film-wrapped samples were stored at 4 °C. Samples were taken at day 0, 3, and 7 for enumeration of surviving L. monocytogenes by plating on appropriate media. Carvacrol films showed better antimicrobial activity than cinnamaldehyde films. Compared to control films without antimicrobials, films with 3% carvacrol induced 1 to 3, 2 to 3, and 2 to 3 log CFU/g reductions on ham and bologna at day 0, 3, and 7, respectively. Corresponding reductions with 1.5% carvacrol were 0.5 to 1, 1 to 1.5, and 1 to 2 logs, respectively. At day 7, films with 3% cinnamaldehyde reduced L. monocytogenes population by 0.5 to 1.5 and 0.5 to 1.0 logs on ham and bologna, respectively. Inactivation by apple films was greater than that by carrot or hibiscus films. Apple films containing 3% carvacrol reduced L. monocytogenes population on ham by 3 logs CFU/g on day 0 which was 1 to 2 logs greater than that by carrot and hibiscus films. Films were more effective on ham than on bologna. The food industry and consumers could use these films to control surface contamination by pathogenic microorganisms. PRACTICAL APPLICATION: Antimicrobial edible, food-compatible film wraps prepared from apples, carrots, and hibiscus calyces can be used by the food industry to inactivate Listeria monocytogenes on widely consumed ready to eat meat products such as bologna and ham. This study provides a scientific basis for large-scale application of edible fruit- and vegetable-based antimicrobial films on foods to improve microbial food safety.     

Antimicrobial, Mechanical, and Moisture Barrier Properties of Low pH Whey Protein-based Edible Films Containing p-Aminobenzoic or Sorbic Acids

ABSTRACT: Low pH (5.2) whey protein isolate-based edible films containing p-aminobenzoic acid (PABA) or sorbic acid (SA) were developed and assessed for inhibition of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Typhimurium DT104 in a disc diffusion assay. Water vapor permeability (WVP), tensile strength (TS), and percent elongation (%E) were also determined. Using 1.5% PABA and SA, average inhibition zone diameters were 21.8, 14.6, 13.9, and 26.7, 10.5, 9.7 mm for L. monocytogenes, E. coli O157:H7, and S. Typhimurium DT104, respectively. Three strains of S. Typhimurium DT104 were resistant to 0.5% SA. Addition of PABA and SA increased %E, but decreased TS. WVP was not affected by 0.5% and 0.75% SA; however, PABA increased WVP.     

Statistical Modeling of D- and z-value of E. coli O157:H7 and pH in Apple Cider Containing Preservatives

ABSTRACT: The objective of this study was to model the heat resistance of E. coli O157:H7 in apple cider as a function of added sorbate, benzoate, and malic acid. Inactivation experiments were done at 47, 50, and 53 °C, and D and z values were calculated. Models for D₄₇, D₅₀, and D₅₃ showed that all 3 additives significantly decreased heat resistance. Furthermore, z-values increased with addition of preservatives and low pH. Model predictions showed that at 50 °C, 5-log reduction is attainable in a few minutes when the cider contains additives, while preliminary test results showed that at 20 °C, a 5-log reduction could be obtained in about 90 min in cider with 0.1% sorbate, 0.1% benzoate, and 1% malic acid.     

气体二氧化氯对苹果表面细菌杀菌规律研究

本实验研究了气体二氧化氯杀灭金黄色葡萄球菌、大肠杆菌、单核细胞增生李斯特氏菌以及腐生酵母菌四种苹果表面的危险致病菌的杀菌规律.在杀菌时间5min、杀菌温度25℃条件下,金黄色葡萄球菌、大肠杆菌、单核细胞增生李斯特氏菌和腐生酵母菌杀菌达到99.99%的杀菌率,所需的气体二氧化氯的浓度分别为23、21、6和11mg/L.在杀菌气体二氧化氯浓度10mg/L、杀菌温度25℃时,四种菌杀菌时间分别达到7、8、2和6.5min时,杀菌率均超过99.99%.在实验范围内,作用温度对杀菌效果影响不大.     

杀灭鲜切洋葱上食源性致病菌消毒剂的筛选及杀菌条件的优化

研究了几种消毒剂对鲜切洋葱表面食源性致病菌的杀灭效果,为提高洋葱等鲜切蔬菜的食用安全提供依据。用清水、次氯酸钠(200mg/L)、二氧化氯(10mg/L)、过氧化氢(20.0g/L)、酸化亚氯酸钠(1.0g/L)、过氧乙酸(80mg/L)、柠檬酸(10.0g/L)、乳酸(10.0g/L)以及乳酸(10.0g/L)结合55℃处理染菌的鲜切洋葱3min,以酸化亚氯酸钠效果最好,可分别减少3.19log CFU/g大肠杆菌O157∶H7,3.11log CFU/g单增李斯特菌和2.60logCFU/g鼠伤寒沙门氏菌。以李斯特菌为研究对象应用响应面优化酸化亚氯酸钠杀菌参数,优化结果为1.0g/L,处理2min。对酸化亚氯酸钠产生的药伤进行评价,发现处理后再经清水漂洗可避免药伤,保持理想的感官品质。      

Thermal inactivation of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in breaded pork patties

ABSTRACT:  Decimal reduction times ( D -values) and thermal resistance constants ( z -values) for 3 foodborne pathogenic bacteria in formulated ready-to-eat breaded pork patties were determined with thermal inactivation studies. Meat samples, inoculated with Escherichia coli O157:H7, Salmonella , and Listeria monocytogenes cultures or uninoculated controls, were packaged in sterile bags, immersed in circulated water bath, and held at 55, 57.5, 60, 62.5, 65, 67.5, and 70 °C for different durations of time. The D - and z -values were determined by using a linear regression model. Average calculated D -values for E. coli O157:H7, Salmonella , and L . monocytogenes at a temperature range of 55 to 70 °C were 32.11 to 0.08 min, 69.48 to 0.29 min, and 150.46 to 0.43 min, respectively. Calculated z -values for E. coli O157:H7, Salmonella , and L. monocytogenes were 5.4, 6.2, and 5.9 °C, respectively. The results of this study will be useful to food processors to validate thermal lethality of the studied foodborne pathogens in ready-to-eat breaded pork patties.     

Reduction of Listeria monocytogenes, Salmonella spp., and Escherichia coli O157:H7 During Processing of Country-cured Hams

ABSTRACT: The country-cured ham process, including curing, equalization, cold-smoked or nonsmoked, and aging up to 6 mo, was validated and showed its effectiveness in achieving a 6-log reduction of Listeria monocytogenes, Salmonella spp., and Escherichia coli O157:H7. The viable counts of L. monocytogenes populations decreased to below detection levels after 206 d, Salmonella populations required 122 d, and E. coli O157:H7 required 66 d. However, L. monocytogenes -inoculated hams were positive and Salmonella spp-inoculated and E. coli O157:H7-inoculated hams were negative following enrichment procedures at the end of the aging process. Therefore, the survival of L. monocytogenes on country-cured ham represents a risk.     

Antimicrobial Wine Formulations Active Against the Foodborne Pathogens Escherichia coli O157: H7 and Salmonella enterica

ABSTRACT:  We developed wine formulations containing plant essential oils and oil compounds effective against foodborne pathogenic bacteria Escherichia coli O157:H7 and Salmonella enterica. HPLC was used to determine maximum solubility of antimicrobials in wines as well as amounts of antimicrobials extracted by wines from commercial oregano and thyme leaves. Activity of essential oils (cinnamon, lemongrass, oregano, and thyme) and oil compounds (carvacrol, cinnamaldehyde, citral, and thymol) in wines were evaluated in terms of the percentage of the sample that resulted in a 50% decrease in the number of bacteria (BA₅₀). The ranges of activities in wines (30 min BA₅₀ values) against S. enterica/E. coli were carvacrol, 0.0059 to 0.010/0.011 to 0.021; oregano oils, 0.0079 to 0.014/0.022 to 0.031; cinnamaldehyde, 0.030 to 0.051/0.098 to 0.13; citral, 0.033 to 0.038/0.060 to 0.070; lemongrass oil, 0.053 to 0.066/0.059 to 0.071; cinnamon oil 0.038 to 0.057/0.066 to 0.098; thymol, 0.0086 to 0.010/0.016 to 0.022; and thyme oil, 0.0097 to 0.011/0.033 to 0.039. Detailed studies with carvacrol, the main component of oregano oil, showed that antibacterial activity was greater against S. enterica than against E. coli and that wine formulations exhibited high activities at low concentrations of added antimicrobials. The results suggest that wines containing essential oils/oil compounds, added or extracted from oregano or thyme leaves, could be used to reduce pathogens in food and other environments.     

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.     

Combination of Carbon Dioxide and Cinnamon to Inactivate Escherichia coli O157:H7 in Apple Juice

ABSTRACT: Pasteurized apple juice with CO2 (0, 1, and 4%) and cinnamon (0 and 0.3%) was inoculated with Escherichia coli O157:H7 at 104 CFU/mL, and stored at 5 and 20 °C. Counts on nonselective and selective media, and thin agar layer (TAL; selective medium overlaid with nonselective medium) were determined at 1 h and 1, 3, 7, and 14 d. Inactivation was greater at 20 °C. Samples with 1 and 4% CO₂, alone and combined with cinnamon, presented < 0.7 log CFU/mL in 3 d. Counts in apple juice inoculated at 10² CFU/mL, a low-level E. coli O157:H7 contamination, were nondetectable at 3 d. The TAL method was as effective as nonselective medium to recover injured cells.     

Survival of acid-adapted or non-adapted Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli O157:H7, in traditional Greek salads

The fate of three pathogens Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli O157:H7 that were inoculated in fish roe salad and aubergine salad with or without preservatives after being adapted in acid environment or not, was determined. The salads were stored at 10  ° C and the pathogens population was counted at regular intervals. Parameters (lag time, death rates calculated with Baranyi equation) were used to compare the behaviour of the pathogens. In the absence of preservatives the pathogens survived during the 15 days of storage. A 1 log reduction was observed for Listeria and 2 logs reduction for Salmonella and E. coli in both salads. In most cases, acid adaptation decreased the death rate even in the presence of preservatives. The addition of sorbic and benzoic acid in the salads increased the death rate of the pathogens during storage significantly and they were not detected at 7–10 days for Salmonella , 8–12 days for Listeria and 5 days for E. coli . It is concluded that a well-studied combination of hurdles is appropriate to ensure safety of home-made traditional salads free of preservatives.     

Decontamination of Salmonella,Shigella, and Escherichia coli O157:H7 from Leafy Green Vegetables Using Edible Plant Extracts

Fresh cilantro, parsley, and spinach are products that are regularly consumed fresh, but are difficult to decontaminate, as a result, they are common vehicles of transmission of enteropathogenic bacteria. In this study, the efficacy of plant extracts as alternatives for disinfection of cilantro, parsley, and spinach that were artificially contaminated with Salmonella, Escherichia coli O157:H7, and Shigella sonnei was determined. Edible plant extracts obtained using ethanol as the extraction solvent were tested to determine the minimum bactericidal concentration (MBC) and those that exhibited the lowest MBC were selected for further studies. Leaves of fresh greens were washed with sterile water and dried. For seeding, leaves were submerged in suspensions of 2 different concentrations of bacteria (1.5 × 10⁸ and 1 × 10⁵), dried, and then stored at 4 °C until use. To determine the effects of the extracts, inoculated leafy greens were submerged in a container and subjected to treatments with chlorine, Citrol®, or selected plant extracts. Each treatment type was stored at 4 °C for 0, 1, 5, and 7 d, and the bacterial counts were determined. From the 41 plant extracts tested, the extracts from oregano leaves and from the peel and pulp of limes were found to be as effective as chlorine or Citrol® in reducing by > 2 logs, the population of pathogenic bacteria on leafy greens and therefore, may be a natural and edible alternative to chemicals to reduce the risk of Salmonella, E. coli O157:H7 and S. sonnei contamination on leafy vegetables. Practical Application: The antimicrobial efficacy of the extracts of Mexican lime and oregano was clearly demonstrated on cilantro, parsley, and spinach. The extracts of Mexican lime and oregano provide alternatives to chlorine to significantly reduce bacterial pathogens that have been associated with outbreaks from contaminated leafy green vegetables. A simple, low cost, and labor‐saving extraction system for production of the extracts was used.     

Activity of ε–Polylysine Against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes

ABSTRACT: ε–polylysine is a homopolymer of L-lysine, an essential amino acid, with a reportedly wide antimicrobial spectrum. This study evaluated the antimicrobial activity of ε–polylysine, as compared with known preservatives and organic acids, against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes , in culture broth. The compounds tested included ε–polylysine (0.0025% to 0.05%), sodium diacetate (0.25%), sodium lactate (3.0%), lactic acid (0.1%), and acetic acid (0.1%), alone, as well as in combination with ε– polylysine (0.0025% to 0.03%); all treatments were evaluated in tryptic soy broth supplemented with 0.6% yeast extract. Treatments were inoculated (approximately 2 log colony-forming units [CFU]/mL) with 5-strain ( E. coli O157:H7, S. Typhimurium) or 10-strain ( L. monocytogenes ) mixtures of the pathogens. Survival/growth of the inoculated bacteria was periodically monitored during incubation at 4 °C (30 d) and 24 °C (48 h). Bactericidal effects of ε–polylysine were obtained against E. coli O157:H7 and S. Typhimurium at 4 °C. At the same temperature (4 °C), ε–polylysine alone or in combination with other compounds tested inhibited growth or was bactericidal against L. monocytogenes. All 3 pathogens were inhibited by ε–polylysine at 24 °C; however, L. monocytogenes was the most sensitive and S. Typhimurium the most resistant. The antimicrobial activity of ε–polylysine against E. coli O157:H7 and S. Typhimurium was enhanced ( P < 0.05) when tested in combination with sodium diacetate or acetic acid. Combination treatments with sodium lactate resulted in loss of ε–polylysine activity by the end of the incubation period. Overall, under the conditions of this study, ε–polylysine exhibited antimicrobial effects against the 3 pathogens tested.