Combined Antimicrobial Effect of Thymol and Sodium Lactate against L isteria monocytogenes and S almonella Typhimurium in Fish Patty

Intrinsic properties and extrinsic factors of food matrix system affecting the effectiveness of essential oils in foods: a comprehensive review

Essential oils (EOs) have been proved as natural food preservatives because of their effective and wide-spectrum antimicrobial activity. They have been extensively explored for potential applications in food industry, and substantial progresses have been achieved. However well EOs perform in antibacterial tests in vitro, it has generally been found that a higher level of EOs is needed to achieve the same effect in foods. Nevertheless, this unsimilar effect has not been clearly quantified and elaborated, as well as the underlying mechanisms. This review highlights the influence of intrinsic properties (e.g., oils and fats, carbohydrates, proteins, pH, physical structure, water, and salt) and extrinsic factors (e.g., temperature, bacteria characteristics, and packaging in vacuum/gas/air) of food matrix systems on EOs action. Controversy findings and possible mechanism hypotheses are also systematically discussed. Furthermore, the organoleptic aspects of EOs in foods and promising strategies to address this hurdle are reviewed. Finally, some considerations about the EOs safety are presented, as well as the future trends and research prospects of EOs applications in foods. The present review aims to fill the evidenced gap, providing a comprehensive overview about the influence of the intrinsic and extrinsic factors of food matrix systems to efficiently orientate EOs applications.

The Antibacterial Activity of Thymol Against Drug-Resistant Streptococcus iniae and Its Protective Effect on Channel Catfish (Ictalurus punctatus)

Streptococcus iniae is a zoonotic pathogen, which seriously threatens aquaculture and human health worldwide. Antibiotics are the preferred way to treat S. iniae infection. However, the unreasonable use of antibiotics leads to the enhancement of bacterial resistance, which is not conducive to the prevention and treatment of this disease. Therefore, it is urgent to find new efficient and environmentally friendly antibacterial agents to replace traditional antibiotics. In this study, the antibacterial activity and potential mechanism of thymol against S. iniae were evaluated by electron microscopy, lactate dehydrogenase, DNA and protein leakage and transcriptomic analysis. Thymol exhibited potent antibacterial activity against S. iniae in vitro, and the MIC and MBC were 128 and 256μg/mL, respectively. SEM and TEM images showed that the cell membrane and cell wall were damaged, and the cells were abnormally enlarged and divided. 2MIC thymol disrupted the integrity of cell walls and membranes, resulting in the release of intracellular macromolecules including nucleotides, proteins and inorganic ions. The results of transcriptomic analysis indicated that thymol interfered with energy metabolism and membrane transport, affected DNA replication, repair and transcription in S. iniae. In vivo studies showed that thymol had a protective effect on experimental S. iniae infection in channel catfish. It could reduce the cumulative mortality of channel catfish and the number of S. iniae colonization in tissues, and increase the activities of non-specific immune enzymes in serum, including catalase, superoxide dismutase, lysozyme and acid phosphatase. Taken together, these findings suggested that thymol may be a candidate plant agent to replace traditional antibiotics for the prevention and treatment of S. iniae infection.

Natural Food Colorants and Preservatives: A Review, a Demand, and a Challenge

The looming urgency of feeding the growing world population along with the increasing consumers' awareness and expectations have driven the evolution of food production systems and the processes and products applied in the food industry. Although substantial progress has been made on food additives, the controversy in which some of them are still shrouded has encouraged research on safer and healthier next generations. These additives can come from natural sources and confer numerous benefits for health, beyond serving the purpose of coloring or preserving, among others. As limiting factors, these additives are often related to stability, sustainability, and cost-effectiveness issues, which justify the need for innovative solutions. In this context, and with the advances witnessed in computers and computational methodologies for in silico experimental aid, the development of new safer and more efficient natural additives with dual functionality (colorant and preservative), for instance by the copigmentation phenomena, may be achieved more efficiently, circumventing the current difficulties.

Edible flower essential oils: A review of chemical compositions, bioactivities, safety and applications in food preservation

In the context of consumers' growing concerns and boycotts of artificial and harmful chemicals, satisfying the demands for good-quality food products possessing clean and safe images is a challenge for food industry. Due to natural and avirulent images, various bioactivities as well as potentials to be used as safer substitutes for chemical preservatives, flower essential oils (EOs) have aroused increasing interests in the recent past. Many literatures have verified the biological activities of flower EOs, and have given high value to the preservative potentials of flower EOs in food systems. In this work, a review is done on the most recent publications associating the chemical constituents, bioactivities (antibacterial, antifungal, antioxidant and anti-pest abilities) and safety of flower EOs. The effects of flower EOs on food flavor are also discussed. Finally, the current combined preservation applications of flower EOs and other technologies are summarized.

The microbial safety of fish and fish products: Recent advances in understanding its significance, contamination sources, and control strategies

Microorganisms play a crucial and unique role in fish and fish product safety. The presence of human pathogens and the formation of histamine caused by spoilage bacteria make the control of both pathogenic and spoilage microorganisms critical for fish product safety. To provide a comprehensive and updated overview of the involvement of microorganisms in fish and fish product safety, this paper reviewed outbreak and recall surveillance data obtained from government agencies from 1998 to 2018 and identified major safety concerns associated with both domestic and imported fish products. The review also summarized all available literature about the prevalence of major and emerging microbial safety concerns, including Salmonella spp., Listeria monocytogenes, and Aeromonas hydrophila, in different fish and fish products and the survival of these pathogens under different storage conditions. The prevalence of antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs), two emerging food safety concerns, is also reviewed. Pathogenic and spoilage microorganisms as well as ARB and ARGs can be introduced into fish and fish products in both preharvest and postharvest stages. Many novel intervention strategies have been proposed and tested for the control of different microorganisms on fish and fish products. One key question that needs to be considered when developing and implementing novel control measures is how to ensure that the measures are cost and environment friendly as well as sustainable. Over the years, regulations have been established to provide guidance documents for good farming and processing practices. To be more prepared for the globalization of the food chain, harmonization of regulations is still needed.

Effect of active essential oils added to chicken tawook on the behaviour of Listeria monocytogenes, Salmonella spp. and Escherichia coli O157:H7 during storage

The objective of the study was to assess the antimicrobial effect of active essential oil components (EOs) namely (carvacrol (CA), cinnamaldehyde (CI) and thymol (TH)) on Listeria monocytogenes, Salmonella spp., and Escherichia coli O157:H7 in chicken tawook during storage at 4 and 10 °C. A marinade consisting of ingredients commonly used in the chicken tawook recipe was prepared and mixed with 1% and 2% v/v CA, CI or TH. The marinade with or without EOs was added to fresh chicken breast cubes inoculated with the foodborne pathogens. Afterward, marinated chicken "tawook" was stored at 4 and 10 °C covered with cling wrap to mimic chill and mild abuse storage conditions for up to 7 days. At 10 °C, the marinade decreased L. monocytogenes numbers on day 4 and 7 by about 2.4 log₁₀ CFU/g as compared to unmarinated samples. Adding EOs to chicken tawook did not change L. monocytogenes numbers during storage at 4 and 10 °C. For Salmonella spp., the marinade decreased the numbers during 10 °C storage on day 4 and 7 by about 4.9 log₁₀ CFU/g as compared to unmarinated samples. At 4 °C, EOs at 2% decreased Salmonella spp. on day 7 by 0.5 log₁₀ CFU/g. One percent CI significantly decreased Salmonella by 1.5 log₁₀ CFU/g, at day 4 of storage. At 10 °C, 1% CA, 2% CI, 1% and 2% TH decreased Salmonella spp. in the samples by 0.5 log₁₀ CFU/g on day 7. The marinade decreased E. coli O157:H7 numbers on the chicken samples during 10 °C storage on day 4 and 7 by about 3.3 log₁₀ CFU/g as compared to unmarinated samples. Regardless of storage day at 4 °C, EOs decreased E. coli O157:H7 populations in chicken tawook by ≤2.4 log₁₀ CFU/g compared to samples without EOs, where the decrease was ≤1.4 log₁₀ CFU/g. Moreover, no significant decrease in E. coli O157:H7 populations could be attributed to the addition of EOs in samples which were stored at 10 °C. Increasing the concentration of EOs from 1 to 2% seemed to have no significant effect in reducing the tested foodborne pathogen populations.

Impact of sodium lactate, encapsulated or unencapsulated polyphosphates and their combinations on Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus growth in cooked ground beef

Foodborne illnesses affect the health of consumers worldwide, and thus searching for potential antimicrobial agents against foodborne pathogens is given an increased focus. This research evaluated the influence of sodium lactate (SL), encapsulated (e) and unencapsulated (u) polyphosphates (PP; sodium tripolyphosphate, STP; sodium acid pyrophosphate, SPP), and their combinations on Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus growth in cooked ground beef during 30 day storage at 4 or 10 °C. pH, water activity (a_w), oxidation-reduction potential (ORP) and S. Typhimurium, E. coli O157:H7 and S. aureus counts were determined. S. Typhimurium was not found in SPP-SL combination groups after 30 day storage at 4 °C (P <0.05). Lower S. Typhimurium levels were determined in only SL containing groups stored at 10 °C than group with only tested microorganism (MO, P < 0.05). Although there was no change in S. Typhimurium load in all SL incorporated groups during 10 °C storage, S. Typhimurium count increased in other groups (P < 0.05). E. coli O157:H7 in MO and STP groups showed an increase at 4 °C, whereas it decreased in SPP-SL combination groups (P < 0.05). A gradual increase in E. coli O157:H7 at 10 °C was determined in MO and only PP incorporated groups, whereas there was a decrease in STP-SL or SPP-SL combination groups (P < 0.05). E. coli O157:H7 count was stable in SL containing groups during 10 °C storage. A gradual decrease in S. aureus was determined in all treatments at 4 °C, whereas S. aureus count increased in MO and uSTP groups during 10 °C storage (P < 0.05). There was no change in S. aureus level in only eSTP or uSPP or ueSTP containing groups at 10 °C, meantime it decreased in other groups (P < 0.05). The lowest S. aureus load was achieved by uSPP-SL or eSPP-SL or ueSPP-SL combinations after 30 days at both storage temperatures (P < 0.05). In general, pH was higher in samples with STP than those with SPP and control (P < 0.05). The lowest a_w was generally obtained in all SL containing groups at both storage temperatures (P < 0.05). Lower ORP was determined in all PP incorporated groups during storage at both temperatures compared to others (P < 0.05). ORP in all treatments generally increased (P < 0.05) during storage at both storage temperatures. This study showed that encapsulation is not a factor affecting antimicrobial efficiency of PP and using PP-SL combinations have synergistic effect on reducing the viability of S. Typhimurium, E. coli O157:H7 and S. aureus and their subsequent growth ability in cooked ground beef.

Beneficial Effects of Spices in Food Preservation and Safety

Spices have been used since ancient times. Although they have been employed mainly as flavoring and coloring agents, their role in food safety and preservation have also been studied in vitro and in vivo. Spices have exhibited numerous health benefits in preventing and treating a wide variety of diseases such as cancer, aging, metabolic, neurological, cardiovascular, and inflammatory diseases. The present review aims to provide a comprehensive summary of the most relevant and recent findings on spices and their active compounds in terms of targets and mode of action; in particular, their potential use in food preservation and enhancement of shelf life as a natural bioingredient.