Effect of oregano essential oil on microbiological and physico-chemical attributes of minced meat stored in air and modified atmospheres

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.

Application of multi-functional lactic acid bacteria strains in a pilot scale feta cheese production

Feta cheese is the most recognized Greek Protected Designation of Origin (PDO) product in the world. The addition of selected autochthonous lactic acid bacteria (LAB) strains to cheese milk as adjunct cultures is gaining more attention, since they can impact the nutritional, technological and sensory properties of cheeses, as well as improve the safety of the product. The aim of this study was to produce Feta cheese with enhanced quality and safety, and distinctive organoleptic characteristics by applying autochthonous lactic acid bacteria (LAB) with multi-functional properties as adjunct cultures. Feta cheeses were produced with the commercial lactococcal starter culture and the addition of 9 LAB strains (Lactococcus lactis SMX2 and SMX16, Levilactobacillus brevis SRX20, Lacticaseibacillus paracasei SRX10, Lactiplantibacillus plantarum FRX20 and FB1, Leuconostoc mesenteroides FMX3, FMX11, and FRX4, isolated from artisanal Greek cheeses) in different combinations to produce 13 cheese trials (12 Feta trials with the adjunct LAB isolates and the control trial). In addition, Feta cheese manufactured with FMX3 and SMX2 and control Feta cheese were artificially inoculated (4 log CFU/g) with Listeria monocytogenes (a cocktail of 4 acid or non-acid adapted strains). Cheese samples were monitored by microbiological and physicochemical analyses during ripening, and microbiological, physicochemical, molecular and sensory analyses during storage at 4°C. The results showed that after manufacture, the LAB population was ca. 9.0 log CFU/g at all samples, whereas during storage, their population declined to 6.5-7.0 log CFU/g. In the Listeria inoculated samples, Listeria was absent after 60 days (end of ripening) and after 90 days in the adjunct culture, and in the control trials, respectively. Moreover, the addition of selected strains, especially Lcb. paracasei SRX10, led to cheeses with desirable and distinctive organoleptic characteristics. Furthermore, randomly amplified polymorphic PCR (RAPD-PCR) molecular analysis confirmed that the multi-functional LAB strains were viable by the end of storage. Overall, the results of this study are promising for the use of autochthonous strains in various combinations with the commercial starter culture to satisfy industry requirements and consumer demands for traditional and high added value fermented products.

Antimicrobial Effects and Antioxidant Activity of Myrtus communis L. Essential Oil in Beef Stored under Different Packaging Conditions

The aim of this study was to assess the antimicrobial effects of myrtle (Myrtus communis L.) essential oil (EO) on pathogenic (E. coli O157:H7 NCTC 12900; Listeria monocytogenes ATCC BAA-679) and spoilage microbiota in beef and determine its minimum inhibitory concentration (MIC) and antioxidant activity. The behavior of LAB, Enterobacteriaceae, Pseudomonas spp., and fungi, as well as total mesophilic (TM) and total psychotropic (TP) counts, in beef samples, was analyzed during storage at 2 and 8 °C in two different packaging systems (aerobiosis and vacuum). Leaves of myrtle were dried, its EO was extracted by hydrodistillation using a Clevenger-type apparatus, and the chemical composition was determined using chromatographical techniques. The major compounds obtained were myrtenyl acetate (15.5%), β-linalool (12.3%), 1,8-cineole (eucalyptol; 9.9%), geranyl acetate (7.4%), limonene (6.2%), α-pinene (4.4%), linalyl o-aminobenzoate (5.8%), α-terpineol (2.7%), and myrtenol (1.2%). Myrtle EO presented a MIC of 25 µL/mL for E. coli O157:H7 NCTC 12900, E. coli, Listeria monocytogenes ATCC BAA-679, Enterobacteriaceae, and E. coli O157:H7 ATCC 35150 and 50µL/mL for Pseudomonas spp. The samples packed in aerobiosis had higher counts of deteriorative microorganisms than samples packed under vacuum, and samples with myrtle EO presented the lowest microbial contents, indicating good antimicrobial activity in beef samples. Myrtle EO is a viable natural alternative to eliminate or reduce the pathogenic and deteriorative microorganisms of meat, preventing their growth and enhancing meat safety.

Beyond Chemical Preservatives: Enhancing the Shelf-Life and Sensory Quality of Ready-to-Eat (RTE) Hummus with Vinegar and Other Natural Antimicrobials

Hummus is a traditional and very popular Mediterranean ready-to-eat (RTE) food, with growing popularity worldwide. However, it has a high water activity and is susceptible to microbial growth and post-process contamination that limit its quality and shelf-life. For this purpose, the present study compared the use of several antimicrobials, alone or in combination, for hummus preservation during storage (4 °C), for up to 45 days. The chemical preservative potassium sorbate 0.09% (S) was evaluated, along with three natural antimicrobials: garlic 1.25% (G); vinegar 5% (V); natamycin 0.002% (N); or their combination: garlic 1.25%-vinegar 5% (GV); vinegar 5%-natamycin 0.002% (VN); garlic 1.25%-natamycin 0.002% (GN); and garlic 1.25%-vinegar 5%-natamycin 0.002% (GVN) to increase the shelf-life of hummus. A thymol and carvacrol mixture 0.2% (O) was also assessed to preserve and develop a new oregano-flavored hummus. All treatments that included vinegar used alone or in combination had significantly higher antimicrobial effectiveness than the other treatments. They achieved 2.2-3.2, 1.8-3.1, and 1.4-2.1 log reductions in total aerobic counts (TAC), Pseudomonas spp., and lactic acid bacteria (LAB), respectively, as compared to the control samples © at day 21. Therefore, the shelf-life of C, S, N, G, GN, and O was around (ca.) 19 days, compared to an extended one of ca. 25 days for V and VN, and ca. 30 days for GV and GVN. Sensory analysis showed the highest acceptability for C, N, S, V, and VN, followed by GV and GVN, and the lowest was for G, GN, and finally O. The findings provide potential alternatives to chemical preservatives, which could be used for natural hummus preservation and shelf-life extension.

Microbiological safety of aged meat

The impact of dry-ageing of beef and wet-ageing of beef, pork and lamb on microbiological hazards and spoilage bacteria was examined and current practices are described. As 'standard fresh' and wet-aged meat use similar processes these were differentiated based on duration. In addition to a description of the different stages, data were collated on key parameters (time, temperature, pH and aw) using a literature survey and questionnaires. The microbiological hazards that may be present in all aged meats included Shiga toxin-producing Escherichia coli (STEC), Salmonella spp., Staphylococcus aureus, Listeria monocytogenes, enterotoxigenic Yersinia spp., Campylobacter spp. and Clostridium spp. Moulds, such as Aspergillus spp. and Penicillium spp., may produce mycotoxins when conditions are favourable but may be prevented by ensuring a meat surface temperature of -0.5 to 3.0°C, with a relative humidity (RH) of 75-85% and an airflow of 0.2-0.5 m/s for up to 35 days. The main meat spoilage bacteria include Pseudomonas spp., Lactobacillus spp. Enterococcus spp., Weissella spp., Brochothrix spp., Leuconostoc spp., Lactobacillus spp., Shewanella spp. and Clostridium spp. Under current practices, the ageing of meat may have an impact on the load of microbiological hazards and spoilage bacteria as compared to standard fresh meat preparation. Ageing under defined and controlled conditions can achieve the same or lower loads of microbiological hazards and spoilage bacteria than the variable log10 increases predicted during standard fresh meat preparation. An approach was used to establish the conditions of time and temperature that would achieve similar or lower levels of L. monocytogenes and Yersinia enterocolitica (pork only) and lactic acid bacteria (representing spoilage bacteria) as compared to standard fresh meat. Finally, additional control activities were identified that would further assure the microbial safety of dry-aged beef, based on recommended best practice and the outputs of the equivalence assessment.

Potential effects of essential oils in safeguarding the health and enhancing production performance of livestock animals: The current scientific understanding

The food sector competes in a cutthroat environment, and it constantly struggles to maintain or even grow its market share. For customer confidence and consumption to remain strong, consistent animal products are needed. The qualitative attributes of the derived goods appear to be improved by the addition of bioactive substances to food, such as essential oils (EOs), and consumers are shielded from the impacts of bacterial and oxidative deterioration. Due to the current controversy surrounding synthetic chemicals and their alleged carcinogenic potential, a substantial study has been done to find effective and safe substitutes. Aromatic plants and the corresponding EOs from them are considered natural products and are typically employed in ruminant nutrition. Since dietary supplementation has been demonstrated to be an easy and practical method to successfully suppress oxidative processes or microbial deterioration at their localized sites, the addition of EOs in animal diets is now becoming a regular practice. However, there is just a little amount of evidence supporting the notion that these compounds may improve nutrient absorption and gastrointestinal health. Additionally, a variety of factors affect how well EOs works in animal diets. These variables can be, on the one hand, the erratic composition, and the many additions to the diet, and, on the other hand, erratic animal genetic elements. Maximizing the use of EOs and creating high-quality products require a deeper understanding of the composition and activity of the gastrointestinal tract microbiota. Numerous EOs contain bioactive substances with the potential to serve as multifunctional feed supplements for animals, with impacts on growth performance, the digestive system, the growth of pathogenic bacteria, and lipid oxidation, among others. To establish their regular use in animal production and to determine their precise mechanism of action, more research is required. The potential advantages of EOs for livestock health and production are highlighted in the current article.

A review of food additives to control the proliferation and transmission of pathogenic microorganisms with emphasis on applications to raw meat-based diets for companion animals

Raw meat-based diets (RMBDs) or sometimes described as biologically appropriate raw food (BARFs) are gaining in popularity amongst dog and cat owners. These pet guardians prefer their animals to eat minimally processed and more “natural” foods instead of highly heat-processed diets manufactured with synthetic preservatives. The market for RMBDs for dogs and cats is estimated at $33 million in the United States. This figure is likely underestimated because some pet owners feed their animals raw diets prepared at home. Despite their increasing demand, RMBDs have been plagued with numerous recalls because of contamination from foodborne pathogens like Salmonella, E. coli, or Campylobacter. Existing literature regarding mitigation strategies in RMBD's for dogs/cats are very limited. Thus, a comprehensive search for published research was conducted regarding technologies used in meat and poultry processing and raw materials tangential to this trade (e.g., meats and poultry). In this review paper, we explored multiple non-thermal processes and GRAS approved food additives that can be used as potential antimicrobials alone or in combinations to assert multiple stressors that impede microbial growth, ultimately leading to pathogen inactivation through hurdle technology. This review focuses on use of high-pressure pasteurization, organic acidulants, essential oils, and bacteriophages as possible approaches to commercially pasteurize RMBDs effectively at a relatively low cost. A summary of the different ways these technologies have been used in the past to control foodborne pathogens in meat and poultry related products and how they can be applied successfully to impede growth of enteric pathogens in commercially produced raw diets for companion animals is provided.

Chemical, Microbiological, and Sensory Analysis Benefits Leading to Shelf-Life Extension of Minced Beef Meat Using Essential Oil of Oregano Contained in Xanthan Gum and Guar Gum Edible Coating

In the present study, the effect of oregano essential oil, which is contained in xanthan gum and guar gum edible coating, was investigated in regard to its ability to assist with the preservation and the extension of the shelf life of minced beef meat when stored at 4 °C. Minced beef meat samples were coated with a mixture of xanthan gum and guar gum containing oregano essential oil at various levels (1–3%). The coated samples were compared with the control sample (uncoated) for bacteriological (i.e., total viable count, coliforms, and Enterobacteriaceae), physicochemical (pH), and sensorial properties (color and odor) on specific storage days (0, 3, 6, 9, and 12). There was greater microbial growth noted in the uncoated minced beef meat in comparison to the coated ones. Odor, color, and overall acceptability were significantly improved in the coated samples (p < 0.05). The chemical, bacteriological, and sensory analyses that were performed, evidenced the benefits that edible coating with oregano essential oil may have on the shelf life and quality of minced beef meat.

Evaluating the Quality of Cheese Slices Packaged with Na-Alginate Edible Films Supplemented with Functional Lactic Acid Bacteria Cultures after High-Pressure Processing

The aim of the current study was to assess the efficacy of Na-alginate edible films as vehicles for delivering lactic acid bacteria (LAB) with functional properties to sliced cheeses, with or without high-pressure processing (HPP). A three-strain LAB cocktail (Lactococcus lactis Τ4, Leuconostoc mesenteroides Τ25 and Lacticaseibacillus paracasei Τ26) was incorporated into Na-alginate solution in a final population of 9 log CFU/mL. The cheese slices (without or with HPP treatment at 500 MPa for 2 min) were packaged in contact with the LAB edible films (LEFs), and subsequently vacuum packed and stored at 4 °C. Cheese slices without the addition of films, with or without HPP treatment, were used as controls. In all cases, microbiological, pH and sensory analyses were performed, while the presence and the relative abundance of each strain during storage was evaluated using Random Amplified Polymorphic DNA-PCR (RAPD-PCR). In addition, organic acid determination and peptide analysis were performed using high-performance liquid chromatography. The results showed that in cheeses without HPP treatment, the microbiota consisted mostly of mesophilic LAB and lactococci (>7.0 log CFU/g), while HPP caused a reduction in the indigenous microbiota population of approximately 1−1.5 log CFU/g. In the LEF samples, the populations of mesophilic LAB and lactococci were maintained at levels of >6.35 log CFU/g during storage, regardless of the HPP treatment. Sensory evaluation revealed that the LEF samples without HPP had a slightly more acidic taste compared to the control, whereas the HPP-LEF samples exhibited the best organoleptic characteristics. RAPD-PCR confirmed that the recovered strains were attributed to the three strains that had been entrapped in the films, while the strain distribution during storage was random. Overall, the results of the study are promising since the functional LAB strains were successfully delivered to the products by the edible films until the end of storage.

Production of Innovative Essential Oil-Based Emulsion Coatings for Fungal Growth Control on Postharvest Fruits

This work assessed the antimicrobial potential of natural essential oils (EOs) from cinnamon (CEO), zataria (ZEO), and satureja (SEO), applied natively or as coatings against Penicillium expansum and Botrytis cinerea during both in vitro and in vivo (on apple fruits) experiments. The induced inhibitory effect towards fungal growth, as a function of both EO type and concentration (75–1200 μL/L), was preliminarily investigated to select the most suitable EO for producing bacterial cellulose nanocrystals (BCNCs)/fish gelatin (GelA)-based emulsions. CEO and ZEO exhibited the best performances against P. expansum and B. cinerea, respectively. None of the pristine EOs completely inhibited the fungal growth and “disease severity”, properly quantified via size measurements of lesions formed on fruit surfaces. As compared to pristine CEO, coating emulsions with variable CEO concentration (75–2400 µL/L) curbed lesion spreading on apples, owing to the controlled CEO release during a 21-day temporal window. The strongest effect was displayed by BCNCs/GelA-CEO emulsions at the highest CEO concentration, upon which lesions on fruit skins were barely detectable. This work demonstrated the capability of EOs embedded in BCNCs/GelA-based nanocapsules to efficiently slow down microbial spoilage on postharvest fruits, thus offering viable opportunities for developing innovative antimicrobial packaging systems.

Synergistic inactivation of Listeria and E. coli using a combination of erythorbyl laurate and mild heating and its application in decontamination of peas as a model fresh produce

We investigated the synergistic antimicrobial activity of erythorbyl laurate (EL) and mild heating co-treatment on the Gram-positive Listeria innocua and Gram-negative Escherichia coli O157:H7 bacteria. EL (2 mM) and mild heating (55 °C for 3 min) resulted in 3.1 and 0.5 log colony forming units (CFU)/mL reductions in the number of L. innocua, respectively, compared to a 6.4 log CFU/mL reduction induced by the combined treatment of EL and mild heating in saline. EL (10 mM) and mild heating (55 °C for 3 min) resulted in 1.3 and 0.7 log CFU/mL reductions in the number of E. coli O157:H7, respectively, compared to a 6.2 log CFU/mL reduction with the combined treatment in saline. EL, a membrane-active compound, showed a strong synergistic effect with mild heating, possibly due to enhanced disruption of the bacterial cell membrane. The synergistic antibacterial effect was evaluated using inoculated English peas (Pisum sativum) and this combined treatment (2 mM EL and mild heating against L. innocua and 10 mM EL and mild heating against E. coli O157:H7) resulted in more than 7 log reductions in the numbers of L. innocua and E. coli O157:H7, inoculated on the surface of fresh peas. The treatments did not show significant difference in the color or texture of treated peas compared to the non-treated controls. This is the first report illustrating synergistic activity of EL and mild heating for both the gram positive (L. innocua) and the gram negative (E. coli O157:H7) bacteria on food. Overall, this research will illustrate the development of more effective and rapid antibacterial surface disinfection method for application in the processing of minimally processed foods.

Antimicrobial Effects of Plant Extracts against Clostridium perfringens with Respect to Food-Relevant Influencing Factors

ABSTRACT

The application of plant extracts (PEs) could be a promising option to satisfy consumers' demand for natural additives to inhibit growth of variable pathogenic bacteria. Thus, the aim of this study was to develop a standardized microdilution method to examine the antimicrobial effects of 10 hydrophilic PEs against two strains of Clostridium perfringens facing various food-relevant influencing factors. Because of the high opacity of PEs, resazurin was used as an indicator for bacterial growth instead of pellet formation. The highest value of the MIC of the replications of each PE was defined as effective plant extract concentration (EPC), whereas the next concentration beneath the lowest MIC was defined as the ineffective plant extract concentration (IEPC). The EPCs of seven PEs, allspice, cardamom, cinnamon, clove, coriander, ginger, and mace, were between 0.625 and 10 g/kg, whereas extracts of caraway, nutmeg, and thyme showed no antimicrobial activity up to the maximum concentration tested (10 g/kg) against C. perfringens in vitro. Two intrinsic factors, sodium chloride (NaCl) and sodium nitrite (NaNO2), displayed either synergistic or additive effects or no interaction with most PEs. By combination with PEs at their IEPC (0.08 to 1.25 g/kg), MIC of NaCl and NaNO2 decreased from between 25 and 50 g/kg to between 6 and 25 g/kg and from more than 200 mg/kg to between 0.2 and 100 mg/kg, respectively. In contrast, lipid (sunflower oil) at a low concentration inhibited the antimicrobial effects of all tested PEs. For extrinsic factors, only allspice, ginger, and coriander could maintain their antimicrobial effects after being heated to 78°C for 30 min. The synergistic effect between PEs and pH values (5.0 and 5.5) was also found for all PEs. The established screening method with resazurin and defining EPC and IEPC values allows the verification of antimicrobial effects of PEs under various food-relevant influencing factors in a fast and reproducible way.

HIGHLIGHTS

Effect of Adding Essential Oils of Caraway and Rosemary on Volatile Aroma Compounds Derived from Stored Vacuum Packaged Minced Turkey Meat

Changes in the odor of meat during its storage are one of the basic indicators affecting its assessment and possible disqualification. The aim of the study was to determine whether the addition of essential oils may affect the composition and concentration of volatile compounds included in the aroma of stored turkey meat. We investigated the effect of adding essential oil (EO) of caraway (0.02% v/w), rosemary (0.02% v/w) and a mixture of the two (0.01% each) on the composition of volatile compound fractions formed during 10-day storage of vacuum-packed minced turkey meat. The EOs used were also evaluated for their influence on microbial contamination (total viable count and lactic acid bacteria count), sensory quality (odor and taste) and the level of fat rancidity (acid value, peroxide value and p-anisidine value) and pH in chill-stored samples. In terms of sensory indicators, the greatest beneficial effect of adding EOs was noted in the odor of raw meat. Use of the HS-SPME/GC-MS (headspace-solid phase microextraction/gas chromatography-mass spectrometry) method showed that the addition of essential oils significantly reduced the amounts of benzeneacetaldehyde, 2-octenal and ethyl 2-methyloctanoate compared with the control sample. In addition, in the presence of essential oils of rosemary and caraway, decreases were noted in benzaldehyde and 9-octadecenal, respectively. These changes may potentially affect the reception of the odor. There was a beneficial effect of the EOs in reducing the levels of fat oxidation indicators, including peroxides. However, the oils at applied concentrations had no significant effect on the total viable count and LAB count.

Cinnamomum Species: Bridging Phytochemistry Knowledge, Pharmacological Properties and Toxicological Safety for Health Benefits

The genus Cinnamomum includes a number of plant species largely used as food, food additives and spices for a long time. Different traditional healing systems have used these plants as herbal remedies to cure diverse ailments. The aim of this comprehensive and updated review is to summarize the biodiversity of the genus Cinnamomum, its bioactive compounds, the mechanisms that underlie the pharmacological activities and molecular targets and toxicological safety. All the data in this review have been collected from databases and recent scientific literature including Web of Science, PubMed, ScienceDirect etc. The results showed that the bioactive compounds of Cinnamomum species possess antimicrobial, antidiabetic, antioxidant, anti-inflammatory, anticancer and neuroprotective effects. The preclinical (in vitro/in vivo) studies provided the possible molecular mechanisms of these action. As a novelty, recent clinical studies and toxicological data described in this paper support and confirm the pharmacological importance of the genus Cinnamomum. In conclusion, the obtained results from preclinical studies and clinical trials, as well as reduced side effects provide insights into future research of new drugs based on extracts and bioactive compounds from Cinnamomum plants.

Plant compounds for the potential reduction of food waste - a focus on antimicrobial peptides

A large portion of global food waste is caused by microbial spoilage. The modern approach to preserve food is to apply different hurdles for microbial pathogens to overcome. These vary from thermal processes and chemical additives, to the application of irradiation and modified atmosphere packaging. Even though such preservative techniques exist, loss of food to spoilage still prevails. Plant compounds and peptides represent an untapped source of potential novel natural food preservatives. Of these, antimicrobial peptides (AMPs) are very promising for exploitation. AMPs are a significant component of a plant's innate defense system. Numerous studies have demonstrated the potential application of these AMPs; however, more studies, particularly in the area of food preservation are warranted. This review examines the literature on the application of AMPs and other plant compounds for the purpose of reducing food losses and waste (including crop protection). A focus is placed on the plant defensins, their natural extraction and synthetic production, and their safety and application in food preservation. In addition, current challenges and impediments to their full exploitation are discussed.

Spoilage potential of Bacillus subtilis in a neutral-pH dairy dessert

The objective of this study was the characterization of the microbiota associated with spoilage of vanilla cream pudding during storage at different temperatures. Commercial cream samples were stored aerobically at 4, 8, 12 and 15 °C for a maximum time period of 40 days. At appropriate time intervals, cream samples were subjected to: (i) microbiological analyses, and (ii) high-performance liquid chromatography (HPLC). Furthermore, the spoilage microbiota was identified through repetitive extragenic palindrome-PCR, while selected isolates were further characterized based on sequencing of the V1-V3 region of the 16S rRNA gene. Microbial growth was observed only during storage of cream samples at 12 and 15 °C, with the applied genotypic analysis demonstrating that Bacillus subtilis subsp. subtilis was the dominant spoilage microorganism of this product. Based on the HPLC analysis results, citric acid and sucrose were the most abundant organic acid and sugar, respectively throughout storage of cream pudding, whereas notable changes mainly included: (i) increase in the concentration of lactic acid and to a lesser extent of formic and acetic acids, and (ii) increase in the concentration of glucose and fructose at the expense of sucrose and lactose. The results of this study should be useful for the dairy industry in detecting and controlling microbiological spoilage in cream pudding and other chilled, neutral-pH dairy desserts.

Radish powder and oregano essential oil as nitrite substitutes in fermented cooked sausages

Radish powder (0.5 and 1.0%) and oregano essential oil (OEO) (100 mg/kg) were applied in fermented cooked sausages without the addition of nitrite. The products were evaluated along processing and storage at 4 °C and 20 °C during 30 and 60 days. Carvacrol (77.19%), p-cymene (8.78%), γ-terpinene (4.78%) and thymol (3.53%) were the main compounds identified in OEO, which are responsible for its antioxidant capacity. The use of radish powder resulted in an adequate development of colour (12.5-13.5 for a*), nitrite formation (1.9-2.4 mg/kg), pH (5.0-5.2), a_w (0.91-0.92), weight loss (35.8-37.7%) and texture (70-75 N) properties for this type of fermented meat products, and it was also efficient in the decrease of mesophilic bacteria counts (2.3-2.4 log CFU/g in samples with 0.5% radish powder). Sensory analysis showed the consumer's preference regarding aroma for treatments added of OEO and no differences were found in overall acceptance among all treatments, indicating that despite the absence of synthetic nitrite in formulations, the combination of radish powder and OEO was approved by the consumers. However, lipid oxidation was not controlled during storage, since higher TBARS values were found in nitrite-free treated sausages, especially in those stored at 20 °C (2.80 mg MDA/kg in samples with 1% radish powder). Therefore, the use of radish powder and OEO showed promising results to development of fermented cooked sausages from a natural source of nitrite, mainly regarding their physicochemical stability and sensory acceptance.

Extraction Techniques and Analytical Methods for Characterization of Active Compounds in Origanum Species

Phytochemical research based on ethnopharmacology is gaining interest in industries such as functional food, nutraceuticals, cosmetics and pharmaceutical industries. Plants and plant extracts are a rich source of bioactive secondary metabolites. These compounds are often involved in plant protection against biotic or abiotic stresses. The exploitation of available technologies should be oriented and intensified to extend and enhance the continued usefulness of the plants as renewable sources of chemicals, especially medicinal compounds. This current contribution is focused on extraction and analytical techniques for their isolation from the oregano species, their characterization and their potential antioxidative, as well as their antimicrobial, antifungal and anticarcinogenic properties. The work is structured rendering to the different steps involved in the research; starting with extraction and sample preparation, followed by discussing the analytical techniques employed for the isolation and identification of compound/s responsible for the biological activity and methods and techniques for biological activity assessment.

Antimicrobial effect of thymol and carvacrol added to a vinegar-based marinade for controlling spoilage of marinated beef (Shawarma) stored in air or vacuum packaging

Controlling spoilage of the popular ethnic marinated beef "Shawarma" is crucial to achieve high quality, extend shelf-life, reduce food waste and meet the need of the globalized supply chain. Active essential oil (EO) components (thymol and carvacrol) were added at 0.4% and 0.8% (w/w) to preserve marinated beef, stored under aerobic or vacuum packaging. Microbiological and sensory (odor) parameters were assessed during 21 days at 4 °C. The treatments with higher EO concentration achieved higher antimicrobial activity than the lower ones and significantly reduced the mesophilic total viable count (TVC), lactic acid bacteria (LAB), Brochothrix thermosphacta, Pseudomonas spp., total coliforms, Escherichia coli, yeasts and molds. The higher EO concentration extended the microbiological shelf-life by 6 days, as judged by TVC and compared to the controls (aerobic and vacuum packaging) but was unacceptable sensorially. The lower EO concentration increased the microbiological shelf-life by 3 days and the sensorial shelf-life by 9 and > 12 days, under aerobic and vacuum conditions, respectively.

Freeze-dried, oven-dried, and microencapsulation of essential oil from Allium sativum as potential preservative agents of minced meat

The present study was conducted to compare the antibacterial activity of oven-dried and freeze-dried Allium sativum along with its spray-dried microencapsulated essential oil in the preservation of minced beef meat. Allium sativum extracts were tested against mesophilic aerobic microorganisms, coagulase-positive staphylococci, Escherichia coli, Salmonella sp., and the sulfite-reducing anaerobes. A difference between the chemical compositions of powders obtained by the conventional oven-drying and freeze-drying has been verified by HPLC-MS2, freeze-dried fresh garlic powder contains 74% of allicin, and 12% cysteine sulfoxides comparing to the oven-drying garlic powder in which is detected two thiosulfinate isomers: allicin (67%) and allyl-1-propenyl thiosulfinate (21%). CIELAB color analysis was performed to assess the effect of drying temperature on powders. The microflora-inhibiting effect of freeze-dried fresh garlic and the spray-dried microencapsulated essential oil at a concentration of 20% represents a promising way to be used in food systems such as meat and meat products preservation, at 4-8°C.

Antioxidant and antimicrobial properties of oregano extract (Origani vulgaris herba L.)

Introduction. Some ingredients of plant origin possess both antioxidant and bacteriostatic properties. If used in the food industry, they can inhibit microbiological and oxidative damage, thus increasing the shelf life of meat products. Oregano extract is one of such substances, which means that it can be used as an antioxidant and preservative. Therefore, the study of this plant has a significant theoretical and practical potential for the food industry. Study objects and methods. The present research featured ground trimmed beef. The samples with 20% of fat tissue were used to determine the microbiological parameters, while the samples with 30% of fat were used to obtain data on oxidative stability. The control sample contained no additional ingredients. The sample with food additives was pre-treated with acidity regulators and antioxidants, namely sodium acetate E262, ascorbic acid E300, sodium ascorbate E301, sodium citrate E331, and rosemary extract E392. The sample with oregano extract was pre-treated with oregano extract (Origani vulgaris herba L.) in the ratio of 5 g of extract per 1 kg of meat. The extract had been dissolved in 100 g of water. The samples were stored at 4 ± 2°C for 12 days. A CM5 spectrophotometer (Konica Minolta, Japan) was used to determine the color characteristics. The induction period of oxidative stability was determined using an Oxitest oxidative stability analyzer (Velp Scientifica, Italy). The studies were conducted in Austria, Linz. Results and discussion. Oregano extract stabilized the redness rating. For the sample with oregano extract, the induction period of oxidative stability was twice as long as for the control sample and the sample with antioxidants. In addition, oregano inhibited the growth of aerobic and anaerobic microorganisms. Conclusion. The antioxidant and antimicrobial properties of oregano extract prolong the shelf life of ground beef, which makes it possible to reduce the amount of food additives.

Combined Effect of Vacuum Packaging, Fennel and Savory Essential Oil Treatment on the Quality of Chicken Thighs

The aim of the present work was to evaluate the microbiological quality of chicken thighs after treatment by fennel (Foeniculum vulgare) and savory (Satureja hortensis) essential oil, stored under vacuum packaging (VP) at 4 ± 0.5 °C for a period of 16 days. The following treatments of chicken thighs were used: Air-packaging control samples (APCS), vacuum-packaging control samples (VPC), vacuum-packaging (VP) control samples with rapeseed oil (VPRO), VP (vacuum-packaging) with fennel essential oil at concentrations 0.2% v/w (VP + F), and VP with savory essential oil at concentration 0.2% v/w (VP + S). The quality assessment of APCS, VPC, VPRO, VP + F and VP + S products was established by microbiological analysis. The microbiological parameters as the total viable counts of bacteria of the Enterobacteriaceae family, lactic acid bacteria (LAB), and Pseudomonas spp. were detected. Bacterial species were identified with the MALDI-TOF MS Biotyper. The combination of essential oils and vacuum packaging had a significant effect (p < 0.05) on the reduction of total viable counts (TVC) compared with control group without vacuum packaging and the untreated control group. Though 15 genera and 46 species were isolated with scores higher than 2.3 from the chicken samples.

Hyperbaric storage at variable room temperature - a new preservation methodology for minced meat compared to refrigeration

Hyperbaric storage (HS) at variable room temperature (RT) has been proposed as an alternative to refrigeration at atmospheric pressure (RF/AP) for food preservation. Little information is available regarding the effect of HS in meat products. In this study the RT/HS effect was evaluated at 100 MPa and variable RT (≈20 °C) for minced meat preservation up to 24 h, initially for one batch. A further two different batches were studied independently. Microbiological and physicochemical parameters were analyzed to assess the feasibility of RT/HS, using storage at RF/AP and variable RT/AP (≈20 °C), for comparison. A post-hyperbaric storage (post-HS) was also tested over 4 days at RF/AP. For the first batch the results showed that RT/HS allowed a decrease of the total aerobic mesophile value (P < 0.05) when compared to the initial sample, whereas at RF/AP and RT/AP, values increased to > 6 Log CFU g^-1 after 24 h. Similarly, Enterobacteriaceae increased > 1 and > 2 Log CFU g^-1 at RF/AP and RT/AP, respectively, while yeasts and molds presented similar and lower overall loads compared to the initial samples for all storage conditions, whereas RT/HS always allowed lower counts to be obtained. Regarding pH, lipid oxidation, and color parameters, RT/HS did not cause significant changes when compared to RF/AP, except after 24 h, where pH increased. The three batches presented similar results, the differences observed being mainly due to the heterogeneity of the samples. RT/HS is a potential quasi-energetic costless alternative to RF for at least short-term preservation of minced meat. © 2018 Society of Chemical Industry.

Combined effects of thymol, carvacrol and packaging on the shelf-life of marinated chicken

The demand for marinated chicken worldwide, is continuously growing. To date, limited data on addition of active components of Essential Oils (EOs) to marinades for chicken preservation are available. The antimicrobial effect of carvacrol and thymol, added at 0.4 and 0.8% v/w to marinated fresh chicken, stored in air and under vacuum packaging (VP), for 21 days at 4 °C, was examined. The samples were monitored for microbiological (total viable count (TVC), lactic acid bacteria (LAB), Brochothrix thermosphacta, Pseudomonas spp., total coliforms, Escherichia coli, yeasts and molds) and sensory attributes (odor characteristics). Our data supports that among the tested microorganisms, Pseudomonas spp., LAB and B. thermosphacta were the most dominant microbiota in the marinated chicken samples. Additionally, the use of active EOs components, especially the higher concentration (0.8% v/w) in combination with VP, retarded the growth of spoilage microbiota and resulted in a significant reduction of about 2.9-3.1 log cfu/g and a microbiological shelf-life extension of marinated chicken by >6 days, as judged by TVC data. Interestingly, the combination of active components of EOs at the lower concentration (0.4% v/w) and packaging (air or vacuum) resulted in a significant sensorial shelf-life extension of 15 and >21 days, as compared to the controls' shelf-life of 9 days. The results of our study demonstrated the potential of the active components, carvacrol and thymol, as natural effective antimicrobial hurdles to control the growth of spoilage microorganisms in marinated chicken meat.

Biocontrol strategies for Mediterranean-style fermented sausages

Naturally fermented meat sausages have a long tradition in Mediterranean countries and are one of the most important groups of traditional foods consumed throughout Europe. Despite all the advances in food science and technology and increased regulatory requirements and concerns for safety and quality during the last decades, the challenge to control important foodborne pathogens in this type of meat products still persists. Simultaneously, growing consumer interest in safe, high quality and minimal processed products, with less additives/preservatives have driven the food industry and scientists in a crusade for innovative technologies to maintain the safety of these products by natural means. Biological control (biocontrol) fits well within this tendency. This review summarizes the latest achievements on biocontrol strategies applied to Mediterranean-style fermented sausages, namely: (i) bioprotective cultures; (ii) bacteriocins; and, (iii) essential oils (EOs).

Effect of thyme and oregano aqueous tea infusions on the microbiological characteristics of sausages

In this work the antimicrobial effect of Thymus vulgare and Origanum vulgare aqueous tea infusion on the total mesophilic bacterial count (TVC), psychrotrophic bacteria count (PBC) and enterococci count in the heat treated meat product - sausages were evaluated. To prepare 1 kg of sausage in experimental groups were used 10 cm3 of Thymus vulgare resp. Origanum vulgare aqueous tea infusions. It was found that value of TVC and PBC in the experimental groups of sausages with Thymus vulgare addition after 7 days of storage (4 °C) were 2.78 resp. 2.14 log cfu.g-1 and with the Origanum vulgare addition were 2.49 resp. 1.90 log cfu.g-1. The value of TVC and PBC in the control group of sausage were 3.13 resp. 2.72 log cfu.g-1. During 10 days of storage (4 °C) the TVC and PBC in the sausages with Thymus vulgare addition increase and reached the value 4.81 resp. 3.52 log cfu.g-1. In the sausages with the Origanum vulgare addition TVC and PBC after 10 days of storage reached the value 3.67 resp. 1.60 log cfu.g-1. The value of TVC and PBC in the control group of sausage after 10 days of storage were 6.47 resp. 5.47 log cfu.g-1. Counts of enterococci in control and experimental groups of sausages during 10 days of storage were not detected. Thyme and origanum aqueous tea infusions suppressed the development of TVC and PBC compare to control samples.

Antibacterial activity of soy edible coatings incorporated with thyme and oregano essential oils on beef against pathogenic bacteria

Inhibitory effects of soy-protein edible coatings incorporated with 1, 2, or 3% of thyme or oregano essential oils (EOs) were determined against Escherichia coli O157:H7 (EC), Listeria monocytogenes (LM), and Staphylococcus aureus (SA) in vitro and on fresh beef during refrigerated storage for 14 days. The soy-protein coatings with oregano and thyme EOs exhibited similar antimicrobial activity against the test bacteria. Greater antimicrobial activity of soy edible coatings was demonstrated against SA when 3% of EOs were added. Coatings with 3% thyme and oregano EOs exhibited 2.86 and 2.59, 1.97 and 1.90, and 1.87 and 1.83 log CFU/g reductions in SA, LM, and EC populations, respectively, as compared with the control by Day 14. This study demonstrated that application of edible coatings containing oregano and thyme EOs on fresh beef cuts could have a potential for controlling pathogenic bacteria and enhancing color stability with acceptable sensory characteristics.

An automated ranking platform for machine learning regression models for meat spoilage prediction using multi-spectral imaging and metabolic profiling

Over the past decade, analytical approaches based on vibrational spectroscopy, hyperspectral/multispectral imagining and biomimetic sensors started gaining popularity as rapid and efficient methods for assessing food quality, safety and authentication; as a sensible alternative to the expensive and time-consuming conventional microbiological techniques. Due to the multi-dimensional nature of the data generated from such analyses, the output needs to be coupled with a suitable statistical approach or machine-learning algorithms before the results can be interpreted. Choosing the optimum pattern recognition or machine learning approach for a given analytical platform is often challenging and involves a comparative analysis between various algorithms in order to achieve the best possible prediction accuracy. In this work, "MeatReg", a web-based application is presented, able to automate the procedure of identifying the best machine learning method for comparing data from several analytical techniques, to predict the counts of microorganisms responsible of meat spoilage regardless of the packaging system applied. In particularly up to 7 regression methods were applied and these are ordinary least squares regression, stepwise linear regression, partial least square regression, principal component regression, support vector regression, random forest and k-nearest neighbours. MeatReg" was tested with minced beef samples stored under aerobic and modified atmosphere packaging and analysed with electronic nose, HPLC, FT-IR, GC-MS and Multispectral imaging instrument. Population of total viable count, lactic acid bacteria, pseudomonads, Enterobacteriaceae and B. thermosphacta, were predicted. As a result, recommendations of which analytical platforms are suitable to predict each type of bacteria and which machine learning methods to use in each case were obtained. The developed system is accessible via the link: www.sorfml.com.

Effect of different marinating conditions on the evolution of spoilage microbiota and metabolomic profile of chicken breast fillets

Five different marinades were prepared containing lemon juice, apple cider vinegar, pomegranate juice and combinations of them. Three different temperatures (4, 10, and 20 °C) and five marinating time intervals (1, 3, 6, and 9 h) were tested. Microbial, physicochemical as well as sensory analyses were performed to assess marination. Noticeable microbial reductions and satisfactory sensory results were observed only in samples treated for short time (1 and 3 h). The marinade in which pomegranate and lemon juices were combined caused a decrease in microbial counts and led to desirable sensory attributes. Each of the marinades was characterized by a distinguishable organic acid profile, while the discrimination of the samples, based on organic acid concentration, between low (1 and 3) and high (6 and 9) marinating time was feasible. It can be concluded that marinating time affected the indigenous microbiota and the sensory characteristics of chicken meat while pomegranate could be a promising marinating ingredient from a microbiological and physicochemical perspective.

Antimicrobial activity of Olea europaea Linné extracts and their applicability as natural food preservative agents

The antimicrobial activity of phenolic compounds from Olea (O.) europaea Linné (L.) is part of the scientific discussion regarding the use of natural plant extracts as alternative food preservative agents. Although, the basic knowledge on the antimicrobial potential of certain molecules such as oleuropein, hydroxytyrosol or elenolic acid derivatives is given, there is still little information regarding their applicability for food preservation. This might be primarily due to the lack of information regarding the full antimicrobial spectrum of the compounds, their synergisms in natural or artificial combinations and their interaction with food ingredients. The present review accumulates available literature from the past 40 years, investigating the antimicrobial activity of O. europaea L. derived extracts and compounds in vitro and in food matrices, in order to evaluate their food applicability. In summary, defined extracts from olive fruit or leaves, containing the strongest antimicrobial compounds hydroxytyrosol, oleacein or oleacanthal in considerable concentrations, appear to be suitable for food preservation. Nonetheless there is still need for consequent research on the compounds activity in food matrices, their effect on the natural microbiota of certain foods and their influence on the sensorial properties of the targeted products.

Antibacterial Activity and Mechanism of Action of Black Pepper Essential Oil on Meat-Borne Escherichia coli

The aim of this study was to investigate the antibacterial activity of black pepper essential oil (BPEO) on Escherichia coli, further evaluate the potential mechanism of action. Results showed that the minimum inhibition concentration (MIC) of BPEO was 1.0 μL/mL. The diameter of inhibition zone values were with range from 17.12 to 26.13 mm. 2 × MIC treatments had lower membrane potential and shorter kill-time than 1 × MIC, while control had the highest values. E. coli treated with BPEO became deformed, pitted, shriveled, adhesive, and broken. 2 × MIC exhibited the greatest electric conductivity at 1, 3, 5, 7, 9, 11, and 13 h, leaked DNA materials at 4, 8, 12, 16, 20, 24, and 28 h, proteins at 4, 6, 8, 10, 12, 14, and 16 h, potassium ion at 0, 0.5, 1, 1.5, and 2 h, phosphate ion at 0.5, 1, 1.5, and 2 h and ATP (P < 0.05); 1 × MIC had higher values than control. BPEO led to the leakage, disorder and death by breaking cell membrane. This study suggested that the BPEO has potential as the natural antibacterial agent in meat industry.