The Challenges of Eliminating or Substituting Antimicrobial Preservatives in Foods

Consumers' criteria for evaluating food safety have evolved recently from considering the food's potential to cause immediate physical harm to considering the potential long-term effects that consumption of artificial ingredients, including antimicrobial preservatives, would have on health. As bacteriostatic and bactericidal agents to prevent microbial spoilage, antimicrobials not only extend shelf life, but they also enhance the product's safety. Antimicrobials and their levels that may be used in foods are specified by regulatory agencies. This review addresses the safety of antimicrobials and the potential consequences of removing those that are chemically synthesized or replacing them with antimicrobials from so-called natural sources. Such changes can affect the microbiological safety and spoilage of food as well as reduce shelf life, increase wastage, and increase the occurrence of foodborne illnesses.

Catalyst-Free Rearrangement of Allenyl Aryldiazoacetates into 1,5-Dihydro-4H-pyrazol-4-ones

Phenylpropargyl diazoacetates exist in equilibrium with 1-phenyl-1,2-dien-1-yl diazoacetate - allenes that are rapidly formed at room temperature through 1,3-acyloxy migration catalyzed by gold(I) or gold(III) compounds, and these catalysts react solely with the π-donor rather than with the diazo group. The product allene of the aryldiazoacetates undergoes rearrangement that is not catalyzed by gold in which the terminal nitrogen of the diazo functional group adds to the central carbon of the allene, initiating a sequence of bond-forming reactions, resulting in the production of 1,5-dihydro-4H-pyrazol-4-ones in good yields. These 1,5-dihydro-4H-pyrazol-4-ones undergo intramolecular 1,3-acyl migration to form an equilibrium mixture and can quantitatively transfer the acyl group to an external nucleophile with formation of 4-hydroxypyrazoles. Reactions of phenylpropargyl phenyldiazoacetates catalyzed by cationic gold complexes are initiated at the diazo functional group to form a gold carbene whose subsequent cascade process (intramolecular addition, then aromatic substitution) results in the formation of a product that is uniquely characteristic of this pathway.

Dinitrogen extrusion from enoldiazo compounds under thermal conditions: synthesis of donor-acceptor cyclopropenes

Donor-acceptor cyclopropenes are formed quantitatively or in high yield from enoldiazoacetates and enoldiazoacetamides under moderate thermal conditions. They are more versatile than their corresponding enoldiazocarbonyl compounds as carbene precursors.

Dirhodium(II)-Catalyzed Annulation of Enoldiazoacetamides with α-Diazoketones: An Efficient and Highly Selective Approach to Fused and Bridged Ring Systems

A dirhodium(II)-catalyzed annulation reaction between two structurally different diazocarbonyl compounds furnishes the donor-acceptor cyclopropane-fused benzoxa[3.2.1]octane scaffold with excellent chemo-, regio-, and diastereoselectivity under exceptionally mild conditions. The composite transformation occurs by [3+2]-cycloaddition between donor-acceptor cyclopropenes generated from enoldiazoacetamides and carbonyl ylides formed from intramolecular carbene-carbonyl cyclization in one pot with one catalyst. The annulation products can be readily transformed into benzoxa[3.3.1]nonane and hexahydronaphthofuran derivatives with exact stereocontrol. This method allows the efficient construction of three fused and bridged ring systems, all of which are important skeletons of numerous biologically active natural products.

Unprecedented Intramolecular [4 + 2]-Cycloaddition between a 1,3-Diene and a Diazo Ester

Diazo compounds that are well-known to undergo [3 + 2]-cycloaddition provide the first examples of the previously unknown [4 + 2]-cycloaddition with dienes that occur thermally under mild conditions and in high yields. Reactions are initiated from reactants prepared from propargyl aryldiazoacetates that undergo gold(I)-catalyzed rearrangement to activated 1,3-dienyl aryldiazoacetates. These reactions proceed to mixtures of both [4 + 2]-cycloaddition and the 1,3-dienyl aryldiazoacetate after long reaction times. At short reaction times, however, both E- and Z-1,3-dienyl aryldiazoacetates are formed and, after isolation, thermal reactions with the E-isomers form the products from [4 + 2]-cycloaddition with ΔH(‡)298 = 15.6 kcal/mol and ΔS(‡)298 = -27.3 cal/(mol·°C). The Z-isomer is inert to [4 + 2]-cycloaddition under these conditions. The Hammett relationships from aryl-substituted diazo esters (ρ = +0.89) and aryl-substituted dienes (ρ = -1.65) are consistent with the dipolar nature of this transformation.

Asymmetric synthesis of 1H-pyrrol-3(2H)-ones from 2,3-diketoesters by combination of aldol condensation with benzilic acid rearrangement

An efficient two-step protocol for the asymmetric synthesis of 1H-pyrrol-3(2H)-one derivatives in 99% ee from conveniently accessed 2,3-diketoesters has been developed.

Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections (AGORA)

Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients. The cornerstones in the management of complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance. The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria. An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs.

Emerging Viral Zoonoses from Wildlife Associated with Animal-Based Food Systems: Risks and Opportunities

Zoonotic viruses of wildlife origin have caused the majority of recent emerging infectious diseases (EIDs) that have had significant impacts on human health or economies. Animal consumption-based food systems, ranging from the harvest of free-ranging wild species (hereafter, wild harvest systems) to the in situ stocking of domestic or farmed wild animals (hereafter, animal production systems), have been implicated in the emergence of many of these viruses, including HIV, Ebola, SARS, and highly pathogenic avian influenza (HPAI).

Development of Models To Relate Microbiological and Headspace Volatile Parameters in Stored Atlantic Salmon to Acceptance and Willingness To Prepare the Product by Senior Consumers

Microbial spoilage of salmon occurs during extended refrigerated storage and is often accompanied by unpleasant aromas. When spoilage is detected, it is assumed that consumers will reject the product for consumption. Because sensory panels of trained individuals or consumers are expensive and labor intensive, identification of microbiological or chemical indicators to characterize the extent to which fish has spoiled is needed when experimental process and storage treatments are being evaluated. A consumer panel of 53 senior citizens (60 to 85 years of age) evaluated in duplicate raw salmon subjected to 10 storage conditions, and the fish quality was targeted to range from fresh to very spoiled. This population group was chosen because they would be expected to have a greater prevalence of olfactory impairments and higher odor thresholds than the general population; in turn, a shorter safety margin or time period between product rejection due to spoilage and the generation of Clostridium botulinum toxins would be likely. Low hedonic scores for aroma and overall acceptance (2 or 3 of 9), corresponding to "dislike very much" to "dislike moderately," did not equate with unwillingness to prepare the sample for consumption by up to seven panelists (13%) when the product was presumed to have already been purchased. Despite these outliers, significant models (P = 0.0000) were developed for the willingness of consumers to prepare the sample for consumption and the sample's aerobic and anaerobic microbiological populations and two volatile peaks with Kovats indices of 640 and 753. However, these models revealed that the levels of microbiological and chemical markers must be very high before some consumers would reject the sample; hence, spoilage detection by smell would likely not be an adequate safeguard against consuming salmon in which C. botulinum toxin had been generated.

Clostridium botulinum Toxin Production in Relation to Spoilage of Atlantic Salmon (Salmo salar) Packaged in Films of Varying Oxygen Permeabilities and with Different Atmospheres

Shelf life of fish packaged under modified atmosphere (MA) is extended, but within the United States, commercial application of MA with impermeable packaging films is restricted due to concerns that botulinum toxin production would precede spoilage when contaminated fish are held at abusive storage temperatures. Use of semipermeable packaging films has been advocated; however, previous studies are inconclusive in determining the oxygen transmission rate (OTR) of a film that is needed to achieve an acceptable margin of safety (i.e., toxin production occurs only after spoilage). This study was conducted to determine the influence of OTR (target OTRs of 3 to 15,000) on the development of spoilage volatiles and toxin in salmon inoculated with type E Clostridium botulinum and subjected to air, vacuum, or 75:25 CO2:N2 MA and storage temperatures of 4, 8, 12, or 16°C. The most dominant headspace volatile peak that was produced during spoilage of samples at 4, 8 or 12°C was a peak, having a Kovats retention index (KI) of 753, and at which external standards of 2- or 3-methyl 1-butanol also eluted. Under anaerobic conditions, both the aerobic microbial populations and the size of the KI 753 spoilage peak were less in inoculated samples compared with uninoculated samples. C. botulinum-inoculated samples that were stored at 12 or 16°C under conditions favorable for anaerobic growth were also characterized by a KI 688 peak. Using a previously developed model that related the percentage of elderly consumers who would prepare a sample having the KI 753 spoilage peak of a specific size, it was determined that for salmon packaged with 3 or 3,000 OTR films under any atmosphere and stored at 12 or 16°C, 2 to 61% of the consumers could potentially prepare toxin-contaminated samples. Hence, when abusive storage conditions are suspected, the fish should not be consumed.

Salmonella on Raw Poultry in Retail Markets in Guatemala: Levels, Antibiotic Susceptibility, and Serovar Distribution

The objective of this study was to determine Salmonella numbers on retail raw chicken carcasses in Guatemala and to phenotypically characterize the isolates (serotyping and antibiotic susceptibility). In total, 300 chicken carcasses were collected from seven departments in Guatemala. Salmonella numbers were determined using the most-probable-number method following the U. S. Department of Agriculture's Food Safety and Inspection Service protocol. In total, 103 isolates were obtained, all of which were tested for antibiotic susceptibility, whereas 46 isolates were serotyped. Overall, Salmonella prevalence and mean number (mean log most probable number per carcass) was 34.3% and 2.3 (95% confidence interval: 2.1 to 2.5), respectively. Significant differences (P < 0.05) in Salmonella prevalence were found by storage condition (refrigerated or ambient temperature), market type (wet markets, supermarkets, and independent poultry stores), chicken production system (integrated or nonintegrated production company), and chicken skin color (white or yellow). Chickens produced by integrated companies had lower Salmonella numbers (P < 0.05) than nonintegrated companies, and white-skin carcasses had lower numbers (P < 0.05) than yellow-skin carcasses. Among 13 different Salmonella serovars identified, Paratyphi B (34.8%) was most prevalent, followed by Heidelberg (16.3%) and Derby (11.6%). Of all the Salmonella isolates, 59.2% were resistant to one to three antibiotics and 13.6% to four or more antibiotics. Among all the serovars obtained, Salmonella Paratyphi B and Heidelberg were the most resistant to the antibiotics tested. Salmonella levels and antibiotic resistant profiles among isolates from raw poultry at the retail market level were high relative to other reports from North and South America. These data can be used by Guatemalan stakeholders to develop risk assessment models and support further research opportunities to control transmission of Salmonella spp. and antibiotic-resistant isolates from chicken meat to humans.

An efficient route to highly enantioenriched tetrahydroazulenes and β-tetralones by desymmetrization reactions of δ,δ-diaryldiazoaceto-acetates

A highly stereoselective desymmetrization reaction of δ,δ-diaryl-α-diazo-β-ketoesters catalyzed by chiral dirhodium carboxylates forms aromatic cycloaddition products in up to 97% ee.

Hg(OTf)2 Catalyzed Intramolecular 1,4-Addition of Donor-Acceptor Cyclopropenes to Arenes

A Hg(OTf)2 catalyzed intramolecular arene 1,4-addition reaction of N-benzyl donor-acceptor cyclopropenecarboxamides was developed to synthesize a series of [3.2.2]nonatriene derivatives. This novel reaction is also observed with silver(I) catalysts known to form metal carbene intermediates in competition with the Buchner reaction.