Hsin-Bai Yin

Potentiating the Heat Inactivation of Escherichia coli O157:H7 in Ground Beef Patties by Natural Antimicrobials.

Escherichia coli O157: H7 (EHEC) is a major foodborne pathogen largely transmitted to humans through the consumption of undercooked ground beef. This study investigated the efficacy of two food-grade, plant-derived antimicrobials, namely rutin (RT), and resveratrol (RV) with or without chitosan (CH) in enhancing EHEC inactivation in undercooked hamburger patties. Further, the effect of aforementioned treatments on beef color and lipid oxidation was analyzed. Additionally, the deleterious effects of these antimicrobial treatments on EHEC was determined using scanning electron microscopy (SEM). Ground beef was inoculated with a five-strain mixture of EHEC (7.0 log CFU/g), followed by the addition of RT (0.05%, 0.1% w/w) or RV (0.1, 0.2% w/w) with or without CH (0.01% w/w). The meat was formed into patties (25 g) and stored at 4°C for 5 days. On days 1, 3, and 5, the patties were cooked (65°C, medium rare) and surviving EHEC was enumerated. The effect of these treatments on meat color and lipid oxidation during storage was also determined as per American Meat Science Association guidelines. The study was repeated three times with duplicate samples of each treatment. Both RT and RV enhanced the thermal destruction of EHEC, and reduced the pathogen load by at least 3 log CFU/g compared to control (P < 0.05). The combination of RT or RV with CH was found to be more effective, and reduced EHEC by 5 log CFU/g (P < 0.05). EHEC counts in uncooked patties did not decline during storage for 5 days (P > 0.05). Moreover, patties treated with RV plus CH were more color stable with higher a∗ values (P < 0.05). SEM results revealed that heat treatment with antimicrobials (CH + RV 0.2%) resulted in complete destruction of EHEC cells and extrusion of intracellular contents. Results suggest that the aforementioned antimicrobials could be used for enhancing the thermal inactivation of EHEC in undercooked patties; however, detailed sensory studies are warranted.

Efficacy of fumigation with Trans-cinnamaldehyde and eugenol in reducing Salmonella enterica serovar Enteritidis on embryonated egg shells

This study investigated the efficacy of two GRAS (generally regarded as safe)-status, plant-derived antimicrobials (PDAs), namely trans-cinnamaldehyde (TC) and eugenol (EUG) applied as a fumigation treatment in reducing SE on embryonated egg shells. Egg shells of day-old embryonated eggs were spot inoculated with a 4-strain mixture of SE (∼6.5 log CFU/egg) and subjected to fumigation with the aforementioned PDAs (0 or 1% concentration) for 20 minutes in a hatching incubator. SE on the shell and embryo was enumerated on days 1, 3, 6, 9, 13, 16 and 18. On day 13, the eggs were re-inoculated, followed by fumigation treatment for 20 minutes. Since the two PDAs were dissolved in ethanol (final concentration 0.04%), eggs fumigated with ethanol were included as a control.Approximately 6 log CFU/egg of SE were recovered from the shell of untreated, inoculated eggs on days 1 and 13. The fumigation of embryonated egg shells with the two PDAs was more effective in reducing SE on the shell and embryo compared to controls (P < 0.05). On day 18, the eggs fumigated with ethanol were SE positive on the shell, whereas no pathogen was detected on eggs subjected to fumigation with TC and EUG. Similarly, although the embryos of eggs subjected to fumigation with ethanol yielded 1 log CFU/egg of SE on day 18, the embryos of TC and EUG treated eggs were devoid of the pathogen. This study demonstrated that TC and EUG dissolved in 0.04% ethanol could potentially be used as a fumigation treatment for reducing SE on embryonated egg shell, however, quality traits of eggs, including the hatchability need to be ascertained.

Natural Approaches for Improving Postharvest Safety of Egg and Egg Products

Abstract Eggs constitute a vital part of the human diet globally. Due to increasing concerns of food-borne outbreaks caused by consumption of contaminated egg and egg products, controlling egg-borne pathogens at the farm level and during processing is warranted. Postharvest treatment of eggs is essential to minimize product contamination from poultry house and processing plants, and reduce residual antibiotics, disinfectants, or synthetic chemicals on eggs. The common practices to enhance egg safety include effective eggshell decontamination by wash/spray and storage at refrigeration to prevent growth of food-borne pathogens, especially Salmonella . Despite the aforementioned practices, egg and egg products contaminated with Salmonella have been frequently implicated in outbreaks worldwide. Thus there is an interest to identify novel strategies for improving postharvest egg safety, especially those involving natural and environment friendly approaches. Extensive research in the last few decades has identified many plant- and animal-derived natural molecules exhibiting antimicrobial properties against an array of food-borne pathogens. This chapter discusses the efficacy of various traditional and natural approaches, including phytochemicals, organic compounds, probiotics, and bacteriophages in improving the microbiological safety of eggs.

Phytochemicals reduce aflatoxin-induced toxicity in chicken embryos

&NA; Aflatoxins (AF) are toxic metabolites produced by molds, Aspergillus flavus and Aspergillus parasiticus, which frequently contaminate poultry feed ingredients. Ingestion of AF‐contaminated feed by chickens leads to deleterious effects, including decreased bird performance and reduced egg production. Moreover, AF residues in fertilized eggs result in huge economic losses by decreasing embryo viability and hatchability. This study investigated the efficacy of 2 generally recognized as safe phytochemicals, namely carvacrol (CR) and trans‐cinnamaldehyde (TC), in protecting chicken embryos from AF‐induced toxicity. Day‐old embryonated eggs were injected with 50 ng or 75 ng AF with or without 0.1% CR or TC, followed by incubation in an incubator for 18 d. Relative embryo weight, yolk sac weight, tibia weight, tibia length, and mortality were recorded on d 18 of incubation. The effect of phytochemicals and methanol (diluent) on embryo viability was also determined. Each experiment had ten treatments with 15 eggs/treatment (n = 150 eggs/experiment) and each experiment was replicated 3 times. Both phytochemicals significantly decreased AF‐induced toxicity in chicken embryos. At 75 ng of AF/egg, CR and TC increased the survival of chicken embryo by ˜55%. Moreover, CR and TC increased relative embryo weight by ˜3.3% and 17% when compared to eggs injected with 50 ng or 75 ng AF, respectively. The growth of embryos (tibia length and weight) was improved in phytochemical‐treated embryos compared to those injected with AF alone (P < 0.05). Phytochemical and methanol treatments did not adversely affect embryo survival, and other measured parameters as compared to the negative control (P > 0.05). Results from this study demonstrate that CR and TC could reduce AF‐induced toxicity in chicken embryos; however, additional studies are warranted to delineate the mechanistic basis behind this effect.

Effect of Dietary Minerals on Virulence Attributes of Vibrio cholerae

Vibrio cholerae is a water-borne pathogen responsible for causing a toxin-mediated profuse diarrhea in humans, leading to severe dehydration and death in unattended patients. With increasing reports of antibiotic resistance in V. cholerae, there is a need for alternate interventional strategies for controlling cholera. A potential new strategy for treating infectious diseases involves targeting bacterial virulence rather than growth, where a pathogen’s specific mechanisms critical for causing infection in hosts are inhibited. Since bacterial motility, intestinal colonization and cholera toxin are critical components in V. cholerae pathogenesis, attenuating these virulence factors could potentially control cholera in humans. In this study, the efficacy of sub-inhibitory concentration (SIC, highest concentration not inhibiting bacterial growth) of essential minerals, zinc (Zn), selenium (Se), and manganese (Mn) in reducing V. cholerae motility and adhesion to intestinal epithelial cells (Caco-2), cholera toxin production, and toxin binding to the ganglioside receptor (GM1) was investigated. Additionally, V. cholerae attachment and toxin production in an ex vivo mouse intestine model was determined. Further, the effect of Zn, Se and Mn on V. cholerae virulence genes, ctxAB (toxin production), fliA (motility), tcpA (intestinal colonization), and toxR (master regulon) was determined using real-time quantitative PCR. All three minerals significantly reduced V. cholerae motility, adhesion to Caco-2 cells, and cholera toxin production in vitro, and decreased adhesion and toxin production in mouse intestine ex vivo (P < 0.05). In addition, Zn, Se, and Mn down-regulated the transcription of virulence genes, ctxAB, fliA, and toxR. Results suggest that Zn, Se, and Mn could be potentially used to reduce V. cholerae virulence. However, in vivo studies in an animal model are necessary to validate these results.