Background: The antimicrobial activity of essential oils has been reported in hundreds of studies, however, the great majority of these studies attribute the activity to the most prevalent compounds without analyzing them independently. Therefore, the aim was to investigate the antibacterial activity of 33 free terpenes commonly found in essential oils and evaluate the cellular ultrastructure to verify possible damage to the cellular membrane. Methods: Screening was performed to select substances with possible antimicrobial activity, then the minimal inhibitory concentrations, bactericidal activity and 24-h time-kill curve studies were evaluated by standard protocols. In addition, the ultrastructure of control and death bacteria were evaluated by scanning electron microscopy. Results: Only 16 of the 33 compounds had antimicrobial activity at the initial screening. Eugenol exhibited rapid bactericidal action against Salmonella enterica serovar Typhimurium (2 h). Terpineol showed excellent bactericidal activity against S. aureus strains. Carveol, citronellol and geraniol presented a rapid bactericidal effect against E. coli. Conclusions: The higher antimicrobial activity was related to the presence of hydroxyl groups (phenolic and alcohol compounds), whereas hydrocarbons resulted in less activity. The first group, such as carvacrol, l-carveol, eugenol, trans-geraniol, and thymol, showed higher activity when compared to sulfanilamide. Images obtained by scanning electron microscopy indicate that the mechanism causing the cell death of the evaluated bacteria is based on the loss of cellular membrane integrity of function. The present study brings detailed knowledge about the antimicrobial activity of the individual compounds present in essential oils, that can provide a greater understanding for the future researches.

https://www.mdpi.com/1420-3049/24/13/2471/pdf

Antibacterial Activity of Terpenes and Terpenoids Present in Essential Oils.

Background Fish and other seafoods are highly perishable food products due basically to microbiological growth and lipid oxidation, which are known to be the principal causes of quality deterioration of such products. Therefore, offering safe and high quality seafoods combined with consumers' desire for natural products free from chemical preservatives creates real challenging problems. In the recent past, there has been extensive focus on antioxidant and antimicrobial effects of natural preservatives such as essential oils (EOs), as effective alternative to synthetic additives, in order to enhance oxidative and microbial stability of foods and extend their shelf life. Scope and approach In this review, the main spoilage mechanisms of fish and seafood products and the most common techniques used to preserve quality and extend shelf life of such products are first discussed. The chemistry and modes of action of some selected EOs are then briefly presented. The antioxidative and antimicrobial activities of some common EOs, either alone or in combination with other preservative systems, in fish and other seafoods are reviewed. Finally the limitations and the future trends are shown. Key findings and conclusions Several EOs have shown i) great antimicrobial activities versus many spoilage and pathogenic microorganisms, and ii) remarkable antioxidant powers against lipid oxidation in fish and other seafoods during processing or storage. However, much more works are still required in order to better understand the exact mechanism of action of EOs or their main components, the effective dose, and the best combination strategy.

Essential oils for antimicrobial and antioxidant applications in fish and other seafood products

Consumer demand for minimally processed seafood that retains its sensory and nutritional properties after handling and storage is increasing. Nevertheless, quality loss in seafood occurs immediately after death, during processing and storage, and is associated with enzymatic, microbiological, and chemical reactions. To maintain the quality, several synthetic additives (preservatives) are promising for preventing the changes in texture and color, development of unpleasant flavor and rancid odor, and loss of nutrients of seafood during storage at low temperature. However, the use of these preservatives has been linked to potential health hazards. In this regard, natural preservatives with excellent antioxidant and antimicrobial properties have been extensively searched and implemented as safe alternatives in seafood processing, with the sole purpose of extending shelf-life. Natural preservatives commonly used include plants extracts, chitosan and chitooligosaccharide, bacteriocins, bioactive peptides, and essential oils, among others. This review provides updated information about the production, mode of action, applications, and limitations of these natural preservatives in seafood preservation.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12390

Natural Preservatives for Extending the Shelf-Life of Seafood: A Revisit

Comparative efficacy and toxic effects of carvacryl acetate and carvacrol on sheep gastrointestinal nematodes and mice.

The objective of this study was to investigate and summarize the levels of incidence of Salmonella spp., Listeria monocytogenes, Staphylococcus aureus and Campylobacter spp. in poultry meat commercialized in Europe. After systematic review, incidence data and study characteristics were extracted from 78 studies conducted in 21 European countries. Pooled prevalence values from 203 extracted observations were estimated from random-effects meta-analysis models adjusted by pathogen, poultry type, sampling stage, cold preservation type, meat cutting type and packaging status. The results suggest that S. aureus is the main pathogen detected in poultry meat (38.5%; 95% CI: 25.4–53.4), followed by Campylobacter spp. (33.3%; 95% CI: 22.3–46.4%), while L. monocytogenes and Salmonella spp. present lower prevalence (19.3%; 95% CI: 14.4–25.3% and 7.10%; 95% CI: 4.60–10.8%, respectively). Despite the differences in prevalence, all pathogens were found in chicken and other poultry meats, at both end-processing step and retail level, in packed and unpacked products and in several meat cutting types. Prevalence data on cold preservation products also revealed that chilling and freezing can reduce the proliferation of pathogens but might not be able to inactivate them. The results of this meta-analysis highlight that further risk management strategies are needed to reduce pathogen incidence in poultry meat throughout the entire food chain across Europe, in particular for S. aureus and Campylobacter spp.

https://www.mdpi.com/2304-8158/7/5/69/pdf

Prevalence of Pathogens in Poultry Meat: A Meta-Analysis of European Published Surveys.

Activity of Thymus vulgaris essential oil against Anisakis larvae.

Activity of R(+) limonene on the maximum growth rate of fish spoilage organisms and related effects on shelf-life prolongation of fresh gilthead sea bream fillets.

Sushi and sashimi are traditional Japanese food, mostly consisting of raw seafood alone or in combination with rice. Eating sushi and sashimi has become popular in many countries even outside Japan. This food is not free from health risks such as ingestion of pathogenic bacteria or parasite. The aim of this study was to investigate on hygienic-sanitary quality of sushi and sashimi sold in the cities of Messina and Catania, Southern Italy. Fifty samples (38 sushi and 12 sashimi) were analysed to determinate the aerobic mesophilic bacteria (AMB), psycrophilic bacteria (PB), Enterobacteriaceae , specific spoilage organisms (SSOs), Pseudomonas spp., coagulase-positive staphylococci, micrococci, Vibrio spp., Bacillus cereus , Salmonella spp. and Listeria monocytogenes . In sushi, AMB ranged from 5.00 to 8.18 log CFU/g, PB from 4.70 to 7.13 log CFU/g, Enterobacteriaceae from 1.41 to 6.67 log CFU/g, while SSOs and Pseudomonas spp. from 3.49 to 7.72 and from 3.36 to 8.00 log CFU/g, respectively. Micrococci ranged from 3.53 to 5.03 log CFU/g and coagulase positive staphylococci were found in 16 samples (2.00 to 3.60 log CFU/g). Bacillus cereus was found in 3 samples (1.70 to 4.00 log CFU/g), while Vibrio spp. was found in 15 of the sushi samples (1.70 to 3.70 log CFU/g). In sashimi, the AMB, PB and SSOs values were higher than 7.00 log CFU/g, Pseudomonas spp. and Enterobacteriaceae were from 6.00 to 8.00 log CFU/g, while Vibrio spp. were found in six samples with means of 2.00 log CFU/g. No Salmonella spp. and Listeria monocytogenes were detected in all sushi and sashimi samples.

/pdf/hygienic-sanitary-evaluation-of-sushi-and-sashimi-sold-in-2n9wv7mzb2.pdf

Hygienic-Sanitary Evaluation of Sushi and Sashimi Sold in Messina and Catania, Italy.

Listeria monocytogenes has been reported as a cause of illnesses related to the consumption raw and processed foods, contaminated during and/or after processing. The ability of L. monocytogenes to multiply at 4°C makes the occurrence in ready-to-eat (RTE) of particular concern. Nowadays, different strategies are applied in order to control pathogens in food products and in particular on the use of essential oils (EOs). The inhibitory effect of thyme and rosemary EOs (0.025% and 0.05%) was determined on a mix of three strains of L. monocytogenes in Italian mortadella packaged in modified atmosphere and stored at 4°C for 30 days. Thymol and p-cymene were the main components of thyme EO, while α-pinene, camphor and eucalyptol of rosemary EO. The use of combined rosemary and thyme EOs exhibited bacteriostatic activity against L. monocytogenes. After 30 days of storage L. monocytogenes charges in treated samples was lower of 2.29 log CFU/g in Group A and 2.79 log CFU/g in Group B compared with control ...

Antimicrobial activity of combined thyme and rosemary essential oils against Listeria monocytogens in Italian mortadella packaged in modified atmosphere: Thyme & Rosemary EOs vs L. monocytogenes

Daniele Muscolino

Papers

Activity of Thymus vulgaris essential oil against Anisakis larvae.

Activity of R(+) limonene on the maximum growth rate of fish spoilage organisms and related effects on shelf-life prolongation of fresh gilthead sea bream fillets.

Hygienic-Sanitary Evaluation of Sushi and Sashimi Sold in Messina and Catania, Italy.

Antimicrobial activity of combined thyme and rosemary essential oils against Listeria monocytogens in Italian mortadella packaged in modified atmosphere: Thyme & Rosemary EOs vs L. monocytogenes

Activity of Tagetes minuta Linnaeus (Asteraceae) essential oil against L3 Anisakis larvae type 1.