The Meat and the meat products are excellent sources of the nutrients for the humans. The Meat and the meat products also provide a favorable environment for the microbial growth. In order to prevent the microbiological contamination of the livestock foods, the synthetic preservatives, including the nitrites, the nitrates, and the sorbates, have been widely used in the food processing due to their low cost and the strong antibacterial activity. The Use of the synthetic chemical preservatives is recently being considered by the customers due to the concerns related to the negative health issues. The demand for the natural substances as the food preservatives has increased with the use of the plant origin and the animal origin products, and the microbial metabolites. The natural preservatives inhibit the growth of the spoilage microorganisms or the foodborne pathogenic microorganisms by increasing the permeability of the microbial cell membranes, the interruption of the protein synthesis, and the cell metabolism. The Natural preservatives can extend the shelf-life and inhibit the growth of the microorganisms. The natural preservatives can influence the food sensory properties, including the flavor, the taste, the color, the texture, and the acceptability of the food. To increase the applicability of the natural preservatives, a number of the strategies, including the combinations of different preservatives or the food preservation methods, such as the active packaging systems and the encapsulation, have been explored. The applications of the natural preservatives for the meat and the meat products.

The Foodborne pathogenic microorganisms, including the Listeria monocytogenes, the Staphylococcus aureus, the pathogenic Escherichia coli, the Clostridium perfringens, the Campylobacter spp., and the Vibrio spp., cause a large number of the illnesses, with substantial damage to the human health and the economy. The World Health Organization (the WHO), the food contaminated with the foodborne pathogenic microorganisms, the chemicals, and the allergens results in 600 million cases of the foodborne illness and four hundred thousand deaths worldwide/ year, Moreover, fifty-six million people die /year and 7.7% of people worldwide suffer from the foodborne diseases. The Meat and the meat products are essential nutrient sources for the humans due to their excellent protein content, the essential amino acids, the vitamin B groups, and the minerals. The meat and the meat products also provide an appropriate environment for the spoilage microorganisms or the foodborne pathogenic microorganisms due to their high-water activity and the nutrient factors [1-7]. The food processing has advanced worldwide, resulting in an enhanced the threat of the food contamination by the pathogenic microorganisms, the chemical residues, the harmful food additives, and the toxins. The multiplication of the spoilage and the pathogenic microorganisms should be controlled to ensure the food safety. The food preservation techniques for protecting the food from the pathogenic microorganisms and extending the shelf-life include the chemical methods, such as the use of the preservatives; the physical methods, such as the heat treatment, the drying, the freezing, and the packaging; and the biological methods using the microorganisms that have an antagonistic effect on the pathogenic microorganisms and produce the bacteriocins. Among them, the addition of the food preservatives that inhibit the growth of the microorganisms is a widely used food protection technique. The countries in the world has different regulations for the food preservatives [8-14]. The Synthetic preservatives have the advantage for the meat processing due to low cost, guaranteed the antibacterial effect or the shelf-life extending activity, and the little effect on the taste, the flavor, the color, and the texture. However, the synthetic preservatives tend to be less preferred by the food consumers because of a number of health concerns regarding their side effects. The food consumers selected preservatives as the most concerned food additive owing to their negative impacts on the health. The Sorbic acid, the benzoic acid, and their salts have been reported to promote the mutagenic and the carcinogenic compounds. The Nitrites and the nitrate, used as preservative and coloring agents in the meat, have been associated with the leukemia, the colon cancer, the bladder cancer, and others. The Natural preservatives have emerged as alternatives to the synthetic preservatives. The Natural preservatives have shown potential to provide the effective antimicrobial activity while reducing the negative health effects. The Meat and the meat products containing the synthetic additives, are a major concern for the human health. Hence, the meat manufacturers and the researchers have begun to consider the use of the natural rather than the synthetic preservatives [15-21]. Representatively, the ‘clean label’ food trends, including the meat and the meat products, began and possessed an important source of the food marketing. It includes consumer-friendly characteristics, such as the synthetic additive-free, the least processing, a brief list of the food ingredients, and the procedure of the traditional methods. The clean label food material market, including the natural preservatives, is likely to value, mostly owing to growing consumer requests for all the natural products. The natural preservatives such as the nisin, the natamycin, the ε-polylysine, and the grapefruit seed extract are registered, but they are not approved for the meat products, or their concentration is not specified. The replacement of synthetic preservatives with the natural preservatives has major positive effects and is being accepted by the customers. The food producers also encounter challenges, including a decrease in price competitiveness due to the relatively high price of the natural preservatives and a decrease in the antibacterial effect due to the food ingredients, such as the carbohydrates, the proteins, and the lipids. In the case of the plant origin substances, the standardization is problematic because of the influence of the country of origin, the soil, and the harvest seasons. The toxicity evaluation or identification of exact compounds for several plant origin compounds contained in extracts and the essential oils have been performed. To solve these problems, various studies have been conducted to optimize the extraction process, combine other antimicrobial substances, apply active packaging, and encapsulate antibacterial substances to improve their utilization [22-28]. 

This review summarizes the current knowledge about the application of the natural preservatives for the meat and the meat products against the foodborne pathogenic microorganisms and the spoilage microorganisms.

The Application Technique of the Natural Preservatives to the Meat and the Meat Products

The Natural preservatives are manufactured in a variety of formulations including powder formed by drying methods and liquid forms such as essential oils. The Natural preservatives are directly added to the meat products and extend the shelf-life by inhibiting the bacterial growth. It is possible to increase the antibacterial effect of the natural preservatives through a combination of the other food processing methods [29-35]. In the case of the plant origin natural preservatives, it is necessary to consider the form applied to the food. The Natural preservatives are commonly prepared in the form of extracts using organic solvents, water, and essential oils. The plant extracts obtained from rosemary, chestnut, sage, cranberry, oregano, grape seed, and others have been used as the meat preservatives. Many studies have been conducted to apply the plant origin substances to the meat products in the form of the essential oil because the antibacterial effect of essential oil type is better than that of extract type. It is difficult to apply large amounts of the essential oil to the food because of its distinct organoleptic properties. The Recent developments have attempted to solve this problem by applying essential oils with other antibacterial substances. The advantage of this application is that it reduces the amounts of essential oils with strong flavor and increases antioxidant and antibacterial effects through synergistic effects. In terms of industrial perspective, if synthetic preservatives cannot be completely replaced with the natural preservatives, due to the industrial problems, such as increasing the economic costs or the complexity of the product manufacturing process, they could be replaced gradually by composing a mixed formulation of the synthetic preservatives and the natural preservatives [36-42]. The gamma irradiation and the high-pressure processing (the HPP) treatment are the physical food-processing methods that can further increase the antibacterial efficacy of the natural preservatives. The Unlike thermal food processing, these two food processing techniques could be used for the pasteurization of the raw meat because it has a minor effect on the food composition. In 1997, the WHO, the Food and Agricultural Organization (FAO), and the International Atomic Energy Agency (the IAEA) concluded that foods processed in the proper doses of the irradiation are nutritionally sufficient and safe to consume. The irradiation is permitted for the food preservation in more than sixty countries. Recent approaches in the food irradiation have involved the use of combined treatments with the natural preservatives to reduce irradiation doses. The gamma irradiation of medium doses (2–6 kGy) with the natural compounds and active packaging has been applied to extend the shelf-life of the meat and the meat products. The HPP is also a non-thermal technique for the food preservation that inhibits the growth of the microorganisms and maintains the natural properties of the food. The HPP is performed under high pressures (100–800 MPa) at mild temperature or the weak heating. The Previous studies have reported the potential capability of combining the HPP and the natural preservatives including the essential oil and the antibacterial peptides in alleviating both the processing conditions of the HPP and the concentration of the natural preservatives while maintaining antibacterial effects [43- 49]. The Encapsulation is one of the effective approaches for expanding the applicability of the natural preservatives to the food. The encapsulation was performed with GRAS (generally recognized as safe) materials such as the alginate, the chitosan, the starch, the dextrin, and the proteins using the various techniques including the spray-drying, the extrusion, the freeze-drying, the coacervation, and the emulsification. The application of the natural preservatives to the meat is limited due to their characteristics, such as low solubility and the bioavailability, the rapid release, and the easy degradation. The environmental conditions, such as the pH, the storage temperature and the time, the oxygen and the light exposures could influence the efficacy of the natural preservatives. Through the encapsulation, the natural preservatives, especially hydrophobic compounds (e.g., the essential oil), could improve its stability and expand the versatility of the food processing while maintaining the antibacterial effect [50-56]. The Active packaging is an innovative packaging technology that allows for an interaction with the product and its environment to extend the shelf-life and to ensure its microbial safety while keeping the original properties of the packaged food. In relation to the European Union Guidance to the Commission Regulation (the EUGCR), active packaging is a type of the food packaging with a further beneficial function, while providing a protective barrier against the external influence. In the meat processing, the antimicrobial active packaging could be applied in several methods which are the incorporation of the natural preservatives into a sachet inside the packaging, the packaging film composition with the natural preservatives, the packaging coated with the natural preservatives onto the surface of the food, and use of the antimicrobial polymers as the packaging materials [57-63]. The application of the microorganism origin natural preservatives, known as the bio-preservation, in which the useful microorganisms or their antibacterial substances have antagonistic effects on the pathogenic or the spoilage microorganisms, are used is also a meat preservation method in the spotlight. This method is mainly involved in the lactic acid bacteria, the Lactobacillus spp., the Leuconostoc spp., the Pediococcus spp., and the Lactococcus spp., that have a GRAS status, widely participate in the fermentation processes, and produce the various antibacterial metabolites such as the organic acids, the hydrogen peroxide, and the bacteriocins. In terms of the application to the meat products, the bio-preservation methods included the direct inoculation with the lactic acid bacteria, which has an inhibitory effect on the spoilage or the pathogenic bacteria, the inclusion of the bacterial strains producing the antimicrobial substances in the fermentation starter, and the treatment with the purified bacteriocins [64- 70].

The Natural Preservatives from the Plants and Their Application for the Meat and the Meat Products

The antibacterial effect of the plant origin natural preservatives is closely related to the polyphenols, the phenolics, and the flavonoids. The Plant origin polyphenols have various classifications and structures, as the phenolic acids (the caffeic acid, the rosmarinic acid, the gallic acid, the ellagic acid, the cinnamic acid), the flavones (the luteolin, the apigenin, the chrysoeriol), the flavanols (the catechin, the epicatechin, the epigallocatechin, the gallocatechin, and their gallate derivatives), the flavanones (the hesperidin, the hesperetin, the heridictyol, the naringenin), the flavonols (the quercetin, the kaempferol, the myricetin), the isoflavones (the geinstein, the daidzin, the formononetin), the coumarins (the coumarin, the warfarin, the 7-hydroxycourmarin), the anthocyanins (the pelagonidin, the delphinidin, the cyanidin, the malvidin), the quinones (the naphthoquinones, the hypericin), the alkaloids (the caffeine, the berberine, the harmane), and the terpenoids (the menthol, the thymol, the lycopene, the capsaicin, the linalool) [71-77]. The Polyphenols have been recognized for their effective antimicrobial properties. Although the antimicrobial mechanism has not yet been clearly elucidated, the cell membrane-disturbing molecules, such as the hydroxy group (OH-), which induces the leakage of intracellular components, inactivation of metabolic enzymes, and extinction of the adenosine triphosphate (the ATP) structure; direct pH change in the environment by the improvement in proton concentration, reduction of the intracellular pH by separation of acid molecules, and modification of the bacterial membrane permeability; an organic acid in the plant extracts may influence the oxidation of the nicotinamide adenine dinucleotide (the NADH), the eliminating, the reducing agent used in the electron transport system [78- 84].

The Rosemary

The Rosemary (the Rosmarinus officinalis L.) is a perennial herb with the woody, the aromatic, and the evergreen needle-like leaves. Originally from the Mediterranean region, it is broadly distributed throughout the globe. The Rosemary has been used as a spice and the flavoring agent in the food. The Rosemary essential oil is known to contain fifteen kinds of the bioactive compounds. The principal compound was 1,8-cineole (35.32%). Other major compounds were the camphor, the α-pinene, the trans-caryophyllene, the α-thujone, and the borneol [85- 91]. The antibacterial effect of the rosemary ethanol extracts against the L. monocytogenes in the beef. The application of 45% rosemary ethanol extract for the L. monocytogenes on the beef led to a 2 log colony-forming unit (CFU)/ gram reduction in the incubation at 4 °C for 9 days. In the chicken meat, the effect of the rosemary essential oil on the inhibition of the Salmonella Enteritidis and the spoilage protective effects at 4 and 18 °C was investigated. The 5 mg/mL of the rosemary essential oil induced the decrease in the coliform, the aerobic microorganisms, the lactic acid bacteria, and the anaerobic microorganisms at 18 °C for 24 hours. In Comparing with the untreated chicken meat, the reductions of 1.75 log CFU/ gram (the coliform), 0.87 log CFU/ gram (the aerobic microorganisms), 1.05 log CFU/ gram (the lactic acid microorganisms) and 1.28 log CFU/ gram (the anaerobic microorganisms) were observed in the group treated with rosemary essential oil at 18 °C. The Rosemary oil reduced the S. Enteritidis by more than 2 log CFU/ gram at 18 °C, but less than 1 log CFU/ gram at 4 °C (92- 98). The rosemary essential oil applied with modified atmosphere packaging for the inhibition of the foodborne pathogenic microorganisms (the S. Typhimurium and the L. monocytogenes) in the poultry filets under the refrigerated conditions for 7 d was investigated. The 0.2% rosemary essential oil did not affect the sensory profile and inhibited the growth of both pathogenic microorganisms in laboratory media within 24 hours Treatment with 0.2% rosemary essential oil did not affect the reduction in the S. Typhimurium, but showed weak antibacterial activity against the L. monocytogenes until the first day of the storage (0.1 log CFU/ gram the reduction compared to the control) [99- 105].

The Sage

The Sage (the Salvia officinalis L.), belonging to the Lamiaceae family, has been used since prehistoric eras because of its flavor, taste, therapeutic, and preservative properties. The Sage is known to contain considerable amounts of the rosemary acid, the p-coumaric acid, and the benzoic acid. The Sage essential oils, the camphor, the carvacrol, the R(+) limonene, and the linalool are the major components in terms of content [106-111]. The antibacterial effects of various sage preparations were assessed for low-pressure mechanically separated meat (MSM) in vacuum packaging stored at −18 °C for 9 months. The MSM from the chickens with the addition of the sage extracts inhibited the growth of all groups of the microorganisms (the mesophilic aerobic microorganisms, the psychrotrophic microorganisms, the Enterobacteriaceae, the coliforms, and the enterococci). The most effective antibacterial effect was exhibited by the 0.1% sage essential oil-treated groups [112-117]. The antibacterial effect of the sage essential oil (0.625%) on the survival of the L. monocytogenes in the Sous-vide cook-chill beef stored in the refrigerated storage (2 or 8 °C) for 28 days. The decrease of 1 log CFU/ gram of the L. monocytogenes was detected in the sage essential oil-treated groups compared to the control at 2 °C. Although the exponential growth was observed from the day 14, lower the L. monocytogenes counts of 1 log CFU/ gram were detected in the sage essential oil-treated samples stored at 8 °C [118-123].

The Thyme

The Thyme (the Thymus vulgaris) is a representative herb used together with the meat and the meat products. The application of the thyme in the meat products can elevate the antioxidant, the antibacterial, the shelf-life extension, and the sensory properties. In the meat sausage, the thyme essential oil inhibited 2.69 log CFU/ gram of coagulase-positive Staphylococcus and 4.41 log CFU/ gram of aerobic mesophilic microorganisms, respectively, at a concentration of 0.95% by mixing with 1% (w/w) powdered beet juice. Moreover, the sensory properties, odor, flavor, and overall acceptability improved [124-129]. The 1% thyme oil led to the reduction in the S. enterica by 3 log CFU/ gram during the margination process with lemon juice and 0.5% Yucca schidigera extract in the raw chicken breast. The major composition of the thyme oil revealed 51.1% and 24.1% thymol and O-cymene, respectively. The antibacterial effects of thyme may be due to additive or synergistic effects with its major and/or minor components. The Thymol and its synergistic effect with other phenolic compounds, such as the carvacrol, the p-cymene, and the γ-terpinene, can change the permeability of the bacterial cell wall, leading to cell death [130-135]. The Thyme essential oil encapsulated with the casein and the maltodextrin was evaluated for its antibacterial potential in the vitro and in the situ (the hamburger-like meat products). The encapsulated thyme essential oil showed the same minimum inhibitory concentration (0.1 mg/mL) against the E. coli, the S. Typhimurium, the S. aureus, and the L. monocytogenes as that of the unencapsulated thyme essential. In the treated groups with 1% (v/v) of the encapsulated thyme essential oil for the meat, the E. coli counts were decreased from 23 most probable number (the MPN)/ gram to 0 MPN/ gram, which was similar to the conventional preservative (the sodium nitrate) used as a control until 14 days of the refrigerated storage (4 °C) [136-141].

The Oregano

The Oregano (the Origanum vulgare) is regularly used in the Mediterranean foods. The oregano essential oil has recognized antibacterial and antioxidant properties for the extension of the shelf-life. The antibacterial effects of the oregano were due to two bioactive the polyphenols, the thymol and the carvacrol [142-147]. The component of the oregano essential oil and its impact on the shelf-life of the black wildebeest Biceps femoris muscles was investigated at 2.6 °C. The components of the oregano oil were the thymol, the carvacrol, the ρ-cymene, the β-caryophyllene, the γ-terpinene, the α-humulene, and the α-pinene; among them, the carvacrol (42.94%) and the thymol (17.40%) were the highest. The total viable counts and the lactic acid bacteria reached the spoilage limit (7 log CFU/ gram) after 3 days. The growth rates for the total viable counts and the lactic acid microorganisms in the treated group were 40% higher than those in the untreated groups [148-153]. The combinatorial effect of the oregano essential oil with the caprylic acid was studied in the vacuum-packed minced beef. The addition of 0.2% oregano essential oil with 0.5

The Meat and the meat products are excellent nutrient sources due to their abundant protein content, the essential amino acids, the vitamins, and the minerals. The meat and meat products are susceptible to the contamination by the foodborne pathogenic microorganisms and the various spoilage microorganisms because of their high water activity and the nutrient content. The application of the preservatives is an indispensable element in the livestock food processing to prevent the food poisoning, delay the spoilage, and extend their shelf life. The Industrial preservatives, commonly made up of the synthetic chemicals, are not demanded by the food customers because of their negative health concerns. The natural preservatives derived from the plants (the rosemary, the sage, the chestnut, the GSE, and the tumeric), the animals (the lysozyme, the lactoferrin, the lactoferoxidase, the ovotransferrin, and others), and the microorganisms (the organic acids, the bacteriocins, and the BLIS) have been explored as alternatives to the synthetic chemical preservatives. The versatility of the natural preservatives compared to the synthetic preservatives is limited due to the production cost, the standardization, the insufficient toxicity studies, and the negative sensory effects on the food. To compensate for these disadvantages, various applications have been studied for their synergistic effect with the other natural preservatives with reduced the application concentrations compared to single use, the application of the physical treatment (the gamma irradation, the high pressure processing, and the drying), the encapsulation, and the possibility of the packaging materials. The various natural preservatives and the application methods to inhibit the growth of the foodborne pathogenic microorganisms and the spoilage microorganisms in the livestock foods. The Natural preservatives are expected to be in high demand due to the consumer and the industrial requests. Therefore, it is necessary to explore various applications of the existing natural preservatives, while continuously searching for the novel ones.

The author declare no conflicts of interest