Efficacy of a peroxyacetic acid formulation as an antimicrobial intervention to reduce levels of inoculated Escherichia coli O157:H7 on external carcass surfaces of hot-boned beef and veal

The efficacy of a peroxyacetic acid formulation (POAA) at reducing Escherichia coli O157:H7 contamination on external carcass surfaces of hot-boned beef and veal with a commercial spray apparatus was determined. Hot-boned external carcass surfaces were inoculated with either a high dose (10(6) CFU/cm2) in fresh bovine feces or with a low dose (10(3) CFU/cm2) in diluent of laboratory-cultured E. coli O157:H7. Treatments included a water wash, a POAA (180 ppm) wash, or a water plus POAA wash. Samples were extracted from the external carcass surface with a cork borer to determine the numbers of viable E. coli O157:H7 remaining on the carcass surface after treatment. Although a water wash alone resulted in a 1.25 (94.4%) and a 1.31 (95.1%) mean log reduction on veal and beef inoculated with a high dose of E. coli O157:H7, the POAA treatment resulted in a substantially greater mean log reduction of 3.56 and 3.59 (>99.9%). The water wash only resulted in a 33.9% reduction on veal and 62.8% on beef inoculated with a low dose of E. coli O157:H7, whereas POAA treatment greatly improved pathogen reduction to 98.9 and 97.4% on veal and beef, respectively. The combination of a water wash followed by a POAA treatment resulted in a similar E. coli O157:H7 reduction to that achieved by POAA treatment alone. In conclusion, POAA treatment significantly reduced viable E. coli O157:H7 numbers on experimentally contaminated beef and veal carcasses, which justifies its use as a chemical intervention for the removal of this human pathogen.     

Survey of antimicrobial effects of beef carcass intervention treatments in very small state-inspected slaughter plants

ABSTRACT:  U.S. beef slaughter facilities are required to use a carcass intervention treatment to reduce contamination by Escherichia coli O157:H7. Very small beef slaughter operators generally are unable to carry out challenge studies to validate intervention treatment effectiveness, and in-plant pathogen challenge studies are not permitted. The objective of this study was to evaluate the effectiveness, measured by decreases in generic E. coli , coliforms, Enterobacteriaceae, and aerobic plate count, of intervention treatments used at very small beef slaughter facilities in Wisconsin. Over a 9-mo period, 265 head of beef were sampled at 22 very small beef slaughter facilities before and after the intervention treatment. The interventions studied were dry-aging, low-pressure hot-water spray, high-pressure hot-water spray, 2.5% acetic acid spray, and Fresh Bloom™ (a mix of citric acid, ascorbic acid, and erythorbic acid) spray. Sprays were applied using a hand-held nozzle (hot water) or a pump-type sprayer (acid). There was no significant difference ( P > 0.10) between intervention treatments and all treatments caused significant reductions ( P < 0.10) in indicator organisms. Ranges in average reductions for generic E. coli , coliforms, and Enterobacteriaceae among the treatments were 0.6 to 2.0 log CFU/cm², 0.7 to 2.2 log CFU/cm², and 0.4 to 2.2 log CFU/cm², respectively. For all treatments, rapid decreases in cooler temperature and relative humidity significantly affected indicator reduction, and for hot-water washing, increasing spray time led to significantly greater reductions. Further studies using actual or simulated very-small-plant intervention treatments directly against E. coli O157:H7 would provide additional validation of treatment efficacy.     

Evaluation of peroxyacetic acid as a post-chilling intervention for control of Escherichia coli O157:H7 and Salmonella Typhimurium on beef carcass surfaces

Four experiments were conducted to test the efficacy of peroxyacetic acid as a microbial intervention on beef carcass surfaces. In these experiments, beef carcass surfaces were inoculated with fecal material (no pathogens) or fecal material containing rifampicin-resistant Escherichia coli O157:H7 and Salmonella Typhimurium. Inoculated surfaces were subjected to a simulated carcass wash with and without 2% l-lactic acid treatment before chilling. In Experiments 1 and 2, the chilled carcass surfaces were sprayed with peroxyacetic acid (200 ppm; 43°) for 15 s. Peroxyacetic acid had no effect on microbial counts of any organism measured on these carcass surfaces. However, lactic acid reduced counts of E. coli Type I (1.9log(10) CFU/cm(2)), coliforms (3.0log(10) CFU/cm(2)), E. coli O157:H7 (2.7log(10) CFU/cm(2)), and S. Typhimurium (2.8log(10) CFU/cm(2)) entering the chilling cooler and prevented growth during the chilling period. In Experiment 3, peroxyacetic acid at different concentrations (200, 600, and 1000 ppm) and application temperatures (45 and 55 °C) were used to investigate its effectiveness in killing E. coli O157:H7 and S. Typhimurium compared to 4% l-lactic acid (55 °C). Application temperature did not affect the counts of either microorganism. Peroxyacetic acid concentrations up to 600 ppm had no effect on these microorganisms. Concentrations of 1000 ppm reduced E. coli O157:H7 and S. Typhimurium by up to 1.7 and 1.3log(10) CFU/cm(2), respectively. However, 4% lactic acid reduced these organisms by 2.7 and 3.4log(10) CFU/cm(2), respectively. In Experiment 4, peroxyacetic acid (200 ppm; 43 °C) was applied to hot carcass surfaces. This treatment caused a 0.7log(10) CFU/cm(2) reduction in both E. coli O157:H7 and S. Typhimurium. The collective results from these experiments indicate that peroxyacetic acid was not an effective intervention when applied to chilled inoculated carcass piece surfaces.     

Efficacy of aerosolized peroxyacetic acid as a sanitizer of lettuce leaves

Aerosolized sanitizer was investigated as a potential alternative to aqueous and gaseous sanitizers for produce. Peroxyacetic acid was aerosolized (5.42 to 11.42 microm particle diameter) by a commercially available nebulizer into a model cabinet. Iceberg lettuce leaves were inoculated with three strains each of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium and then treated with aerosolized peroxyacetic acid for 10, 30, or 60 min in a model aerosol cabinet at room temperature (22 +/- 2 degrees C). After treatment, surviving healthy and injured bacterial cells were enumerated on appropriate selective agars or using the overlay agar method. Inoculated iceberg lettuce leaves exposed to aerosolized peroxyacetic acid for 10 min exhibited a 0.8-log reduction in E. coli O157:H7, a 0.3-log reduction in Salmonella Typhimurium, and a 2.5-log reduction in L. monocytogenes when compared with the control. After 30 min of treatment, the three pathogens were reduced by 2.2, 3.3, and 2.7 log, and after 60 min, the reductions were 3.4, 4.5, and 3.8 log, respectively. Aerosolization may be a new and convenient method for sanitizing produce for storage or shipping.     

Bactericidal effects of lettuce after subsequent washing with hypobromous acid and sodium hypochlorite

Sodium hypochlorite (NaClO) is widely used as a sanitizer to maintain microbial safety of lettuce; however, NaClO treatment is insufficient on pathogen reduction due to its high instability for an extended storage time. Hypobromous acid (HOBr) as another sanitizer, relatively stable in processing conditions, was applied to lettuce. The numbers of total aerobic bacteria, Escherichia coli, Salmonella Typhimurium, and Staphylococcus aureus were evaluated on lettuce treated with NaClO and HOBr. The population of 4 selected bacteria on lettuce reduced more than 2.5 log CFU/g. Bactericidal effect maintained for 10 days in combined treatment with 100 mg/L NaClO followed by 200 mg/L HOBr, while the population of the bacteria without HOBr treatment increased. Combined treatment on lettuce can give synergistic effect on reducing microbial population. Residual bromine was not detected on the lettuce treated with HOBr after washed with water for 30 s, indicating that bromine was effectively washed away.     

Efficacy of plant essential oils as antimicrobial agents against Listeria monocytogenes in hotdogs

The purpose of this study was to evaluate the antimicrobial activity of different plant essential oils against Listeria monocytogenes, both in vitro and in a food system. Essential oils of thyme, clove, and pimenta were found to be most effective, based on disc diffusion experiments. Thyme and clove proved to be highly effective against L. monocytogenes in peptone water (1 g/l) and reduced the bacterial population below detection limits at concentrations of 1 ml/l. Experiments were also carried out in hotdogs of different fat content (zero-, low-, and full-fat) to evaluate the antimicrobial activity of essential oils against L. monocytogenes. Thyme essential oil reduced bacterial populations significantly (P⩽0.05) at 1 ml/l level in zero- and low-fat hotdogs, but not in full-fat hotdogs. At 10 ml/l level it reduced the bacterial population >1.3 log₁₀ cfu/g in zero-fat hotdogs, but was less effective in low- and full-fat hotdogs. Clove essential oil also exhibited antimicrobial activity at 1 ml/l in all hotdogs, and was more effective than thyme at 5 ml/l. However, increasing concentration to 10 ml/l did not result in significant (P⩽0.05) reduction of bacterial population. It is concluded that efficacy of essential oils was reduced in a food system due to interaction with food components.     

USDA yield grades and various carcass traits as predictors of carcass composition

Twenty-five carcasses from each of three breedtypes (Brahman, Angus and Brahman × Angus) were physically separated into fat, lean and bone. Several muscles from the round and the femur were used to derive equations to predict carcass composition and muscle-to-bone ratio. The femur (as a percentage of the carcass) was shown to predict percentage carcass bone with 90% accuracy. All of the muscles studied were highly related to total carcass lean but the percentage of carcass as M. biceps femoris was the best single muscle indicator of carcass lean of the muscles studied. More variation in carcass lean could be accounted for by a multiple regression equation, involving all four muscles studied, than by any single muscle. M. biceps femoris-to-femur ratio was found to predict carcass muscle-to-bone ratio with a high degree of accuracy. The USDA yield grades were found to be reliable indicators of carcass composition. A two-variable equation involving adjusted fat thickness and biceps femoris accounted for 88·6% of the variation (RSD = 1/·64) in percentage of carcass as separable lean.     

Novel silver-based nanoclay as an antimicrobial in polylactic acid food packaging coatings

This paper presents a comprehensive performance study of polylactic acid (PLA) biocomposites, obtained by solvent casting, containing a novel silver-based antimicrobial layered silicate additive for use in active food packaging applications. The silver-based nanoclay showed strong antimicrobial activity against Gram-negative Salmonella spp. Despite the fact that no exfoliation of the silver-based nanoclay in PLA was observed, as suggested by transmission electron microscopy (TEM) and wide angle X-ray scattering (WAXS) experiments, the additive dispersed nicely throughout the PLA matrix to a nanoscale, yielding nanobiocomposites. The films were highly transparent with enhanced water barrier and strong biocidal properties. Silver migration from the films to a slightly acidified water medium, considered an aggressive food simulant, was measured by stripping voltammetry. Silver migration accelerated after 6 days of exposure. Nevertheless, the study suggests that migration levels of silver, within the specific migration levels referenced by the European Food Safety Agency (EFSA), exhibit antimicrobial activity, supporting the potential application of this biocidal additive in active food-packaging applications to improve food quality and safety.     

Validating the efficacy of peracetic acid mixture as an antimicrobial in poultry chillers

Peracetic acid mixture (PAHP), which is a combination of peracetic acid and hydrogen peroxide, has been approved as an antimicrobial for use in poultry chillers. To validate its effectiveness, 85 ppm of PAHP was compared with the 30-ppm chlorine treatment in a commercial setting. In this trial, 100 carcasses were sampled for Salmonella and Campylobacter spp. prior to chilling and 100 carcasses were sampled after chilling. In all, 400 carcasses were sampled using 85 ppm of PAHP in the chiller and 400 carcasses were sampled using the chlorine treatment. PAHP at 85 ppm reduced Salmonella-positive carcasses by 92% exiting the chiller, whereas treatment with 30 ppm of chlorine reduced Salmonella by 57%. Additionally, PAHP reduced Campylobacter species-positive carcasses exiting the chiller by 43% while chlorine resulted in a 13% reduction. These results suggest that peracetic acid in combination with hydrogen peroxide may be an effective antimicrobial in poultry chiller applications.     

Beef carcass contamination in a slaughterhouse and prevalence of resistance to antimicrobial drugs in isolates of selected microbial species

Meat contaminating bacteria may be the direct cause of foodborne diseases and represent a potential cause for the drug resistance of human pathogenic agents. The prevalence and resistance to 17 antimicrobial drugs of isolates of selected bacterial species were investigated in 70 swabs of beef carcasses and 70 subsequent samples of beef meat. Molecular techniques (coagulase gene typing Staphylococcus aureus and original gene typing Escherichia coli) were used in the differentiation of isolates. Carcasses were already contaminated after evisceration, least frequently with S. aureus strains (7.5% of samples), most frequently with coagulase-negative staphylococci strains (52.2% of samples). During carcass processing, contamination with resistant or polyresistant strains of S. aureus and E. coli significantly increased (P<0.01). Gene typing isolates of S. aureus and E. coli indicated that the strains probably originated in the processing plant.     

尼泊金十四、十六酯的制备及其抑菌性能研究

以对羟基苯甲酸和正十四醇、正十六醇为原料,对甲苯磺酸作为催化剂,催化合成尼泊金十四、十六酯(分子通式p-HOC6H4CO2R),并测定系列尼泊金酯的抑菌性。通过测定熔点、红外以及质谱,确定合成产物为尼泊金十四、十六酯。优化得到最佳合成条件:催化剂对甲苯磺酸质量为对羟基苯甲酸质量的8.00%;醇酸摩尔比3∶1;反应时间4 h;反应温度120~130℃,十四、十六酯的酯化率为96.57%和96.88%。抑菌实验结果表明,十四酯、十六酯对金黄色葡萄球菌、粪肠球菌、沙门氏菌、志贺氏菌均有抑菌性,且效果强于苯甲酸钠及山梨酸钾。     

Fatty acid composition of Celta pig breed as influenced by sex and location of fat in the carcass

BACKGROUND: The influence of sex and location of fat in the carcass on the fatty acid profile of Celta pigs was studied. Twenty pigs (10 castrated males and 10 females) from the Carballina line were used. RESULTS: The fatty acids composition was predominated by monounsaturated fatty acids (MUFA; approximately 48% of total methyl esters), followed by saturated fatty acids (SFA; approximately 40% of total methyl esters) and, finally, polyunsaturated fatty acids (PUFA; approximately 12% of total methyl esters). The sex and location of fat in the carcass showed significant differences in PUFA and SFA content while both factors were not significantly different with respect to MUFA content. Linoleic, linolenic, eicosatrienoic and arachidonic fatty acids showed the largest difference among the three locations (intramuscular, subcutaneous ventral and subcutaneous dorsal) of the fat in the carcass. CONCLUSION: The fatty acid profile that we observed in the fat of the Celta pigs does not differ greatly from those described by other authors in other autochthonous pig breeds. Principal component analysis offered a good separation of the mean samples according to the sex and location of fat of the pigs. Copyright © 2011 Society of Chemical Industry     

Efficacy of polyethylene-based antimicrobial films containing principal constituents of basil

The feasibility of low-density polyethylene (LDPE)-based films containing linalool or methylchavicol as antimicrobial (AM) packages to retard microbial growth on food surfaces was investigated. The AM LDPE-based films were tested for inhibition against selected microorganisms. Both compounds retained their AM activity, after an extrusion film-blowing process, against Escherichia coli in solid medium. Cheddar cheese was wrapped with the AM films and the packaged cheese samples were stored at 4 °C. The changes in the mesophilic aerobic bacteria and coliform, as well as yeast and mould counts were monitored. In addition, cheese samples inoculated with E. coli or Listeria innocua were wrapped with the AM films, stored at refrigerated (4 °C) or at abuse (12 °C) temperatures and the count of these microorganisms was monitored as a function of time. The results showed an inhibitory effect of these AM films against microbial growth in naturally contaminated cheese and in inoculated samples. The effect on suppression of E. coli and L. innocua growth was more pronounced at the abuse temperature. Methylchavicol-LDPE-based film exhibited a higher efficacy of inhibition than that of linalool-LDPE-based film. In addition, a sensory evaluation was performed with regards to possible taint in the flavour of the cheese. Taint in flavour as affected by linalool or methylchavicol was not significantly detectable by the panelists at the end of the storage period of 6 weeks. This study shows the potential use of polymeric films containing the principal constituents of basil as the AM components for enhancing quality and safety of cheeses.     

Characterization of antimicrobial polylactic acid based films

Olive leaf extract (OLE) (Olea europaea L.), which has antimicrobial effect on many food pathogens, was incorporated as antimicrobial agent into polylactic acid (PLA) films. Antimicrobial activities of films were tested against Staphylococcus aureus. Increasing amount of the OLE in the film discs from 0.9 mg to 5.4 mg caused a significant increase in inhibitory zones from 9.10 mm to 16.20 mm, respectively. Moreover, incorporation of OLE and/or increasing the amount in the film formulation significantly enhanced the water vapor permeability (WVP). The water solubility and the degradation rates of films increased up to 19.3% and 22.4%, respectively. Thus, OLE incorporated PLA films have a prospectively potential in antimicrobial food packaging to reduce post-process growth of S. aureus with improved properties.     

Efficacy of Artabotrys odoratissimus oil as a plant based antimicrobial against storage fungi and aflatoxin B1 secretion

The essential oil of Artabotrys odoratissimus R.Br. was evaluated for antifungal activity against some storage fungi causing contamination of food stuffs. Minimum inhibitory concentration of the oil was found to be 750 μL L⁻¹ against Aspergillus flavus Link. It was found superior over different prevalent synthetic fungicides which inhibited the growth of A. flavus between 1000–5000 μL L⁻¹. The oil exhibited broad fungitoxic spectrum against fourteen different storage fungi. Aspergillus fumigatus was inhibited at 1000 μL L⁻¹ whereas Cladosporium cladosporioides , Curvularia lunata , Fusarium oxysporum , Helminthosporium oryzae , Macrophomina phaseolina , Microsporum gypseum , Mucor racemosus , Penicillium italicum , Pythium debaryanum , Rhizoctonia solani , Sclerotium rolfsii and Trichoderma viride at 500 μL L⁻¹. Aspergillus niger was found to be inhibited only 84.9% at 1000 μL L⁻¹. In addition, the oil showed significant efficacy in arresting aflatoxin B₁ secretion by the toxigenic strain (Navjot 4NSt) of A. flavus at 750 μL L⁻¹. The efficacy of A. odoratissimus oil as aflatoxin suppressor is being reported for the first time.     

Beef hide antimicrobial interventions as a means of reducing bacterial contamination

This project was designed to evaluate interventions capable of reducing bacterial counts on the hide prior to opening. In Trial I, fresh beef hides (n=12) were cut into sections and assigned to serve as either clipped (hair trimmed) or non-clipped sections. Sections were inoculated with a bovine fecal slurry and sampled following a water wash. Treatments (distilled water, isopropyl alcohol, 3% hydrogen peroxide, 2% l-lactic acid, 10% povidone-iodine, and 1% cetylpyridinium chloride (CPC)) were then applied to each section and the sections were sampled for enumeration of aerobic plate counts (APCs), coliforms, and Escherichia coli. Within clipped samples, 1% CPC and 3% hydrogen peroxide caused the greatest reductions in APCs (4.6 and 4.4 log(10)CFU/100-cm(2), respectively), and 1% CPC, 2% l-lactic acid, and 3% hydrogen peroxide caused the greatest reductions in coliform counts (4.5, 4.1, and 3.9 log(10)CFU/100-cm(2), respectively). In Trial II, beef carcasses with hides on were sampled initially and clipped, and then 2% l-lactic acid, 3% hydrogen peroxide, or 1% CPC were applied before sampling. For APCs, 1% CPC produced the greatest reduction on the hide surface (3.8 log(10)CFU/100-cm(2)). Selective application of these antimicrobials to clipped hide opening sites reduced bacterial counts on hide surfaces, and therefore could reduce final carcass counts in these areas by decreasing the bacterial load before opening.     

Decontamination of beef carcass tissue with nisin using a pilot scale model carcass washer

Nisin spray treatments were tested for controlling Gram-positive bacteria attached to beef carcass surface tissue using a pilot scale model carcass washer. Section of lean and adipose tissues were inoculated with approximately 4 log₁₀ cfu cm^-2 of Brochothrix thermosphacta, Carnobacterium divergens or Listeria innocua. Following 28°C water or nisin sprays, bacterial populations were enumerated immediately and after incubation for 24 h at 4°C. Spray treatments with water did not significantly alter the bacterial populations at day 0 or 1 (< 1 log₁₀ reduction). However, nisin spray treatments (5000 AU ml^-1) reduced populations by 1·79 to 3·54 log₁₀ cfu cm^-2 at day 0 and by 1·97 to 3·60 log₁₀ cfu cm^-2 at day 1. This study demonstrates that spray washing is an effective means of applying bacteriocins and that these compounds may be useful as sanitizers of red meat carcasses.     

产抗菌肽乳源乳酸菌的筛选及定向培养

为了获得乳酸菌高效表达抗菌肽的代谢调控方法,对德氏乳杆菌保加利亚亚种等7种乳酸菌进行了产抗菌肽能力的筛选和定向培养。筛选出具有较高抑菌活性的菌株嗜酸乳杆菌和干酪乳杆菌,它们产生的抑菌物质经排除酸、过氧化氢后,仍具有抑菌活性,然而经蛋白酶处理后其抑菌活性明显下降。结果表明,两种菌发酵上清液对金黄色葡萄球菌和大肠杆菌均有抑制作用。经一系列定向培养嗜酸乳杆菌抑菌直径达到(23.53±0.06)mm,与未经定向培养的抑菌直径(11.63±0.15)mm相比抑菌活性提高了102%;经定向培养的干酪乳杆菌抑菌直径达到(21.27±0.25)mm,与未经定向培养的抑菌直径(12.50±0.10)mm相比抑菌活性提高了70.2%。     

柠檬酸和壳聚糖对棉织物抗菌整理的研究

针对柠檬酸和壳聚糖在棉织物抗菌整理中的应用,研究了壳聚糖的浓度对棉织物抗菌性的影响,多元羧酸的含量对壳聚糖固着率的影响及焙烘温度对壳聚糖固着率和白度的影响;并对整理后棉织物的性能进行了测试分析。结果表明,用柠檬酸和壳聚糖的混合液对棉织物进行抗菌整理的效果是明显的,整理后棉织物的耐久定型和折皱回复率都有提高,而且经反复洗涤后,其抗菌性仍达到80%以上。