Antimicrobial edible apple films inactivate antibiotic resistant and susceptible Campylobacter jejuni strains on chicken breast

Abstract: Campylobacter jejuni is the leading cause of bacterial diarrheal illness worldwide. Many strains are now becoming multidrug resistant. Apple‐based edible films containing carvacrol and cinnamaldehyde were evaluated for bactericidal activity against antibiotic resistant and susceptible C. jejuni strains on chicken. Retail chicken breast samples inoculated with D28a and H2a (resistant strains) and A24a (a sensitive strain) were wrapped in apple films containing cinnamaldehyde or carvacrol at 0.5%, 1.5%, and 3% concentrations, and then incubated at 4 or 23 °C for 72 h. Immediately after wrapping and at 72 h, samples were plated for enumeration of viable C. jejuni. The antimicrobial films exhibited dose‐ and temperature‐dependent bactericidal activity against all strains. Films with ≥1.5% cinnamaldehyde reduced populations of all strains to below detection at 23 °C at 72 h. At 4 °C with cinnamaldehyde, reductions were variable for all strains, ranging from 0.2 to 2.5 logs and 1.8 to 6.0 logs at 1.5% and 3.0%, respectively. Films with 3% carvacrol reduced populations of A24a and H2a to below detection, and D28a by 2.4 logs at 23 °C and 72 h. A 0.5‐log reduction was observed for both A24a and D28a, and 0.9 logs for H2a at 4 °C at 3% carvacrol. Reductions ranged from 1.1 to 1.9 logs and 0.4 to 1.2 logs with 1.5% and 0.5% carvacrol at 23 °C, respectively. The films with cinnamaldehyde were more effective than carvacrol films. Reductions at 23 °C were greater than those at 4 °C. Our results showed that antimicrobial apple films have the potential to reduce C. jejuni on chicken and therefore, the risk of campylobacteriosis. Possible mechanisms of antimicrobial effects are discussed. Practical Application: Apple antimicrobial films could potentially be used in retail food packaging to reduce C. jejuni commonly present on food.     

食品中空肠弯曲菌荧光重组酶聚合酶扩增检测方法的建立

本研究为了实现空肠弯曲菌的快速和便捷检测,建立了一种基于荧光重组酶聚合酶扩增技术(exo-RPA)快速检测空肠弯曲菌的方法。通过对空肠弯曲菌和对照菌株的exo-RPA检测来判断该方法的特异性。用梯度稀释的空肠弯曲菌作为模板进行检测来分析exo-RPA方法的灵敏度。通过对模拟污染样品检测来分析exo-RPA的应用效果。分别以exo-RPA和荧光PCR检测实际食品样品来分析二者的检测效果。空肠弯曲菌exo-RPA方法可特异检出空肠弯曲菌,检测灵敏度达到6.0×102CFU/m L。在模拟污染试验中,含2.5×101 CFU/m L空肠弯曲菌的增菌液在培养24 h后可以被exo-RPA检测出阳性信号。exo-RPA和荧光PCR对于40份样品的检测结果相同。本研究建立的空肠弯曲菌exo-RPA具有特异、灵敏和抗干扰性强的特点,方法操作简便快速,具有较好的应用前景。     

Effect of refrigerated and frozen storage on the survival of Campylobacter jejuni in cooked chicken meat breast

This experimental work aimed to examine the survivability of Campylobacter jejuni in cooked chicken breast under several conditions: storage for 1, 3, and 7 d at refrigerated temperatures (4 °C) and for 20 d at frozen temperatures (-18 °C). In addition, storage at ambient temperature (26 to 28 °C) was involved. Chicken samples were inoculated with a mixed culture of C. jejuni strains (ATCC: 29428 and 33219) of known concentrations (50 and 500 CFU/g). Bacterial cells were recovered and enumerated using standard procedure (Preston method). Bacteria were not detected in the majority of samples stored at ambient temperature. Refrigeration reduced survivals in 95, 90, and 77.5% for samples inoculated with 500 CFU/g and kept for 1, 3, and 7 d, respectively. The maximum reduction reached 1 log(10) cycle for all refrigeration durations. It was observed that bacteria died in 17.5% of samples kept for 7 d at 4 °C. However, survivors in samples inoculated with 50 CFU/g were not detected in 50, 65, and 55% of samples kept for 1, 3, and 7 d, respectively. Freezing rendered survivors not detectable in 70% of samples inoculated with 50 CFU/g, while survived viable counts were reduced in 92.5% of samples inoculated with 500 CFU/g. These findings suggested that C. jejuni could be killed or just sublethally injured with or without reduction in viable counts under the investigated storage temperatures, which may indicate the ability of this bacterium to survive in chicken meat stored under refrigerated and frozen conditions.     

空肠弯曲菌在环境压力条件下的生存机制和可培养性研究进展

空肠弯曲菌是一种重要的革兰氏阴性致病菌,可以产生几种肠毒素能侵袭小肠和大肠黏膜引起急性肠炎,据统计其导致肠炎比例是沙门氏菌的3倍。该菌污染肉类食品后,经冷冻等环境的变化会进入活的非可培养状态(viable but non-culturable state,VBNC),不能用常规方法检测到。空肠弯曲菌在pH值、湿度、温度、营养成分等条件发生极端改变的情况下可以进入VBNC状态。本研究更深入地了解空肠弯曲菌是如何抵御外力影响的,防范食品安全的潜在危害。     

不同杀菌条件对软包装肉鸡鸡翅感官品质的影响

对比分析了相同杀菌值F=6 min下,不同杀菌温度(115、121、127℃)对软包装肉鸡鸡翅品质及感官的影响。试验结果表明,相同的环境升温时间6 min,达到相同的杀菌值F=6 min时,115、121、127℃的恒温时间分别为35、15、11 min,降温时间分别为12.5、13.5、15.5 min。杀菌温度对鸡翅色泽、质构TPA、剪切力的影响显著(P<0.05);杀菌温度越高,L*、b*值越大,而a*越小;不同杀菌温度处理后鸡翅的TPA与剪切力的变化具有协同性,127℃处理后的鸡翅剪切力值及硬度、弹性、咀嚼性等指标值最大。感官分析比较得出,不同杀菌温度处理后的鸡翅之间气味和滋味差异不大,而高温短时鸡翅外观更好,咀嚼性、弹性更高,总体口感更佳。因此,鸡翅的高温短时杀菌,不仅效率高,且色泽好,剪切力高,对鸡翅品质破坏小。     

Efficacies of Garlic and L. sakei in Wine‐Based Marinades for Controlling Listeria monocytogenes and Salmonella spp. in Chouriço de Vinho,a Dry Sausage Made from Wine‐Marinated Pork

Chouriço de vinho is made from roughly minced (10 to 30 mm) pork and fat, seasoned with a marinade made from wine, salt, garlic, and other facultative seasonings used according to the recipe of each producer. The batter is maintained at 4 to 7 ºC for 24 to 48 h. It is then stuffed into natural thin pork gut, cold smoked and matured at a low temperature for 1 to 4 wk. The effect of garlic used in wine‐based marinade and a starter culture of indigenous Lactobacillus sakei on the behavior of Listeria monocytogenes and Salmonella spp. in the processing of chouriço was investigated. The garlic (as powder and fresh juice) was found to contribute (P < 0.05) to the control of both pathogens in broth. Garlic dose, as tested within the usual limits used for seasoning, did not impact the reduction of pathogens. Garlic‐wine‐based marinade and a starter culture of indigenous L. sakei contribute to controlling L. monocytogenes and Salmonella spp. in the processing of chouriço. Their presence was responsible for the loss of viability of L. monocytogenes and Salmonella spp. following 5 d of drying, even sooner than situations where no garlic was used. The results of the present work show that the use of a wine‐based marinade with garlic has an important role in ensuring the safety of the product.     

外源核苷酸对肉鸡生产性能的影响

研究了天然日粮中补充外源核苷酸对肉仔鸡胃肠道等消化器官及生产性能的影响 .0～ 14日龄爱维因肉仔鸡按体重随机分成 4组 ,每组 4个重复 ,分别饲喂玉米豆饼无鱼粉基础日粮 ( 1组 ) ,基础日粮中添加 0 .0 5%核酸 ( 2组 )、0 .1%核酸 ( 3组 )以及基础日粮中含 2 %鱼粉 ( 4组 ) .结果表明 ,第 2 ,3,4组的肉仔鸡 14日龄生长速度比对照组提高 14%～ 17% ,饲料利用率提高 4 %～6% .2、3组鸡 4日龄十二指肠质量、3组鸡空肠质量、胰腺质量显著高于对照组 (P <0 .0 5) ;7日龄小肠粘膜的蛋白酶活性也极显著高于对照组 (P <0 .0 1) .研究表明 ,日粮中添加外源核苷酸对提高肉仔鸡生长速度、胃肠道、胰脏质量、肠粘膜蛋白酶活性均有重要的影响 .     

Improvement of Karmali Agar by Addition of Polymyxin B for the Detection of Campylobacter jejuni and C. coli in Whole‐Chicken Carcass Rinse

The Karmali agar was modified by supplementation with a high concentration of polymyxin B. The goal of the study was to evaluate the effect of a high concentration of polymyxin B on the ability and selectivity of the modified Karmali agar to isolate Campylobacter jejuni and Campylobacter coli from whole chicken carcass rinse. A total of 80 whole chickens were rinsed with 400 mL of buffer peptone water. The rinsed samples were incubated with 2× blood‐free modified Bolton enrichment broth for 48 h, and then streaked onto unmodified Karmali agar and modified Karmali agar supplemented with 100000 IU/L polymixin B (P‐Karmali agar). The suspected colonies were finally confirmed by colony PCR. The P‐Karmali agar exhibited a significantly better (P < 0.05) isolation rate than the unmodified Karmali agar (P‐Karmali agar, 73.8%; unmodified Karmali agar, 33.8%). Moreover, the selectivity of the P‐Karmali agar was also better (P < 0.05) than that of the other selective agar when comparing the number of contaminated plates (P‐Karmali agar, 68.8%; unmodified Karmali agar, 87.5%) and growth index of competing flora (P‐Karmali agar, 1.4; unmodified Karmali agar, 2.7). The improved selective agar excluded competing flora resistant to antibiotic agents in unmodified Karmali agar, increasing isolation rate and selectivity for C. jejuni and C. coli.     

蛹拟青霉发酵菌丝体对青脚土杂肉鸡屠宰性能和肌肉品质的影响

以青脚土杂肉鸡为试验对象,研究了蛹拟青霉液体发酵菌丝体作为饲料添加剂对肉鸡屠宰性能和肌肉品质的影响。结果表明:肉鸡日粮中添加0.25%和0.50%的蛹拟青霉菌丝体时,能显著提高肉鸡的活体重、肌肉中氨基酸、呈味氨基酸的含量,同时也显著提高了肉鸡胸肌肌间脂肪的含量(P<0.05),降低了肌肉的失水率(P<0.05)。但是日粮中添加蛹拟青霉菌丝体对肉鸡的屠宰性能未构成显著性影响。日粮添加蛹拟青霉菌丝体不影响肉鸡的屠宰性能,但可显著改善肉鸡的肌肉品质。     

Effect of thyme essential oil and packaging treatments on fresh Mediterranean swordfish fillets during storage at 4 °C

The present study evaluated the effect of thyme essential oil and packaging on fresh Mediterranean swordfish fillets during storage at 4 °C. Treatments in the present study included the following: air (A), modified atmosphere packaging (M), air with thyme oil (AT) and MAP with thyme oil (MT). Of the physicochemical parameters examined, TBA values for A and M swordfish samples were variable, indicative of no specific oxidative rancidity trend, whereas MT treatment inhibited lipid oxidation in swordfish samples during storage. On the basis of microbiological and sensory data, TMA-N and TVB-N limit values of acceptability for Mediterranean swordfish, of ca. 3.72 and 24.5 mg N/100 g, for the initiation of fresh Mediterranean swordfish spoilage, may be proposed. Of the treatments used in the present study, MT and M were the most effective for the inhibition of pseudomonads and H₂S-producing bacteria in swordfish. Lactic acid bacteria and Enterobacteriaceae (to a lesser extent) were also found to be part of the natural microbial flora of swordfish, irrespective of packaging treatment. Based primarily on sensory data, the shelf-lives of fresh refrigerated Mediterranean swordfish were 8 and 13 days under aerobic and MAP conditions, respectively. Addition of 0.1% thyme essential oil extended the product’s shelf-life under aerobic conditions by 5 days, whereas the combination of MAP and thyme oil resulted in a significant shelf-life extension of the swordfish fillets, i.e. by approximately 7½ days, according to sensory data, as compared to the control sample.     

Antimicrobial Efficacy of Poly (DL‐lactide‐co‐glycolide) (PLGA) Nanoparticles with Entrapped Cinnamon Bark Extract against Listeria monocytogenes and Salmonella typhimurium

Nanoencapsulation of active compounds using poly‐(d,l ‐lactide‐co‐glycolide) (PLGA) is commonly used in the pharmaceutical industry for drug delivery and may have important applications in the food industry. Control of growth of foodborne bacteria with the goals of reducing the number of foodborne illness outbreaks, assuring consumers a safer food supply remains a priority in the food industry. Natural antimicrobials are an excellent way to eliminate pathogens without introducing chemical preservatives that consumers may find undesirable. Cinnamon bark extract (CBE) is an effective pathogen inhibitor isolated from cinnamon spice. PLGA nanoparticles containing CBE were produced using an emulsion‐solvent evaporation method and characterized for size, polydispersity, morphology, entrapment efficiency, in vitro release and pathogen inhibition. PLGA with 2 different ratios of lactide to glycolide (65:35 and 50:50) were used to determine how polymer composition affected nanoparticle characteristics and antimicrobial potency. The size of the nanoparticles ranged from 144.77 to 166.65 nm and the entrapment efficiencies of CBE in 65:35 PLGA and 50:50 PLGA were 38.90% and 47.60%, respectively. The in vitro release profile at 35 °C showed an initial burst effect for both types of PLGA followed by a more gradual release of CBE from the polymer matrix. Both types of PLGA nanoparticles loaded with CBE were effective inhibitors of Salmonella enterica serovar Typhimurium and Listeria monocytogenes after 24 and 72 h at concentrations ranging from 224.42 to 549.23 μg/mL. The PLGA encapsulation improved delivery of hydrophobic antimicrobial to the pathogens in aqueous media.     

The Effect of pH and Chloride Concentration on the Stability and Antimicrobial Activity of Chlorine‐Based Sanitizers

Chlorinated water and electrolyzed oxidizing (EO) water solutions were made to compare the free chlorine stability and microbicidal efficacy of chlorine‐containing solutions with different properties. Reduction of Escherichia coli O157:H7 was greatest in fresh samples (approximately 9.0 log CFU/mL reduction). Chlorine loss in “aged” samples (samples left in open bottles) was greatest (approximately 40 mg/L free chlorine loss in 24 h) in low pH (approximately 2.5) and high chloride (Cl^?) concentrations (greater than 150 mg/L). Reduction of E. coli O157:H7 was also negatively impacted (<1.0 log CFU/mL reduction) in aged samples with a low pH and high Cl^?. Higher pH values (approximately 6.0) did not appear to have a significant effect on free chlorine loss or numbers of surviving microbial cells when fresh and aged samples were compared. This study found chloride levels in the chlorinated and EO water solutions had a reduced effect on both free chlorine stability and its microbicidal efficacy in the low pH solutions. Greater concentrations of chloride in pH 2.5 samples resulted in decreased free chlorine stability and lower microbicidal efficacy.     

Efficacy of Plant‐Derived Antimicrobials as Antimicrobial Wash Treatments for Reducing Enterohemorrhagic Escherichia Coli O157:H7 on Apples

This study investigated the efficacy of 3 GRAS‐status, plant‐derived antimicrobials (PDAs), trans‐cinnamaldehyde (TC), carvacrol (CR), and β‐resorcylic acid (BR) applied as an antimicrobial wash for killing Escherichia coli O157:H7 on apples. “Red delicious” apples inoculated with a 5 strain mixture of E. coli O157:H7 were subjected to washing in sterile deionized water containing 0% PDA (control), 0.15% TC, 0.35% TC, 0.15% CR, 0.30% CR, 0.5% BR, or 1% BR for 1, 3, and 5 min at 23 °C in the presence and absence of 1% soil, and surviving pathogen populations on apples were enumerated at each specified time. All PDAs were more effective in reducing E. coli O157:H7 compared to the water wash treatment (P < 0.05) and reduced the pathogen by 4‐ to 5‐log CFU/apple in 5 min. Chlorine (1%) was the most effective treatment reducing the pathogen on apples to undetectable levels in 1 min (P < 0.05). Moreover, the antimicrobial effect of CR and BR was not affected by the presence of soil, whereas the efficacy of TC and BR was decreased in the presence of soil. Further, no bacteria were detected in the wash solution containing CR and BR; however, E. coli O157:H7 was recovered in the control wash water and treatment solutions containing TC and chlorine, in the presence of 1% soil (P < 0.05). Results suggest that the aforementioned PDAs, especially CR and BR could be used effectively to kill E. coli O157:H7 on apples when used as a wash treatment. Studies on the sensory and quality characteristics of apples treated with PDAs are needed before recommending their usage.     

Trout‐Skin Gelatin‐Based Edible Films Containing Phenolic Antioxidants: Effect on Physical Properties and Oxidative Stability of Cod‐Liver Oil Model Food

Abstract: Trout‐skin (Oncorhynchus mykiss) gelatin‐based films containing antioxidants (epigallocatechin gallate (EGCG), 50 and 250 ppm w/w) and green tea powder (1% and 20% w/w of gelatin) were tested for tensile strength, elastic modulus, and elongation, and oxygen and water vapor transmission rates, in vitro antioxidant activity using the DPPH (2,2‐diphenyl‐1‐picrylhydrazyl) assay and effect on stabilizing cod‐liver oil held under mild thermal abuse conditions. Cod‐liver oil overlaid with films was stored at 40 °C for 20 d and analyzed for peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). Antioxidant activity was retained in films containing green tea powder, but was reduced (P < 0.05) in EGCG films (20 d, 23 °C). Water vapor transmission rate of the films incorporated with antioxidants did not change significantly (P > 0.05), but the oxygen transmission rate for films with 50 ppm EGCG and 20% green tea powder was significant (P < 0.05). Other physical properties varied with antioxidant incorporation. The TBARS and PV of control oil increased from 0.05 ± 0.01 to 4.71 ± 0.30 g MDA/kg oil and from 3.6 ± 0.2 to 178.3 ± 24.5 millieq peroxides/kg oil, respectively, after 20 d. For cod‐liver oil covered with control or antioxidant‐containing films, TBARS remained below 0.37 g MDA/kg oil and PV below 7 millieq peroxides/kg oil. Incorporation of antioxidants to the films did not reduce oil oxidation (P > 0.05) at the levels tested and this was confirmed by activation energy calculations. The rate of oil oxidation was more dependent upon the inherent oxygen barrier property of the films than the presence of antioxidants. Practical Application: This research has the potential to enhance the utilization of fish skins, a valuable food processing by‐product, as edible films with natural antioxidants to extend the shelf life of foods. The film physical properties and barrier to oxygen and water are investigated.