Antimicrobial activity of clove and cinnamon essential oils against Listeria monocytogenes in pasteurized milk

Plant extracts and essential oils in the dairy industry: A review

Plants have been used as food additives worldwide to enhance the sensory qualities of foods and extend their shelf life by reducing or eliminating foodborne pathogens. They also serve as therapeutic agents due to their beneficial effects on human health through their anti-cancerous, anti-inflammatory, antioxidant, and immune-modulatory properties. Plants can be added to food as a dry powder, grated material, paste, juice, or as an extract that can be produced by a variety of methods. Plant extracts and essential oils are concentrated sources of bioactive phytochemicals that can be added to food in small amounts in a variety of forms. These forms include liquid, semi-solid, or dry powder for easy and uniform diffusion. Encapsulation can protect bioactive compounds from temperature, moisture, oxidation, and light, as well as allow for controlling the release of the encapsulated ingredients. Nanoemulsions can enhance the bioactivity of active components. This review explains how plant extracts and essential oils are used in the dairy industry as antimicrobial materials, analyzing their impact on starter bacteria; as natural antioxidants to prevent the development of off-flavors and increase shelf life; and as technological auxiliaries, like milk-clotting enzymes, stabilizers, and flavoring agents. Therefore, plant extracts and essential oils are a better choice for the dairy industry than plants or their parts due to a wide range of applications, homogeneous dispersion, and ability to control the concentration of the bioactive ingredients and enhance their efficiency.

Food matrix design can influence the antimicrobial activity in the food systems: A narrative review

Antimicrobial agents are safe preservatives having the ability to protect foods from microbial spoilage and extend their shelf life. Many factors, including antimicrobials' chemical features, storage environments, delivery methods, and diffusion in foods, can affect their antimicrobial activities. The physical-chemical characteristics of the food itself play an important role in determining the efficacy of antimicrobial agents in foods; however the mechanisms behind it have not been fully explored. This review provides new insights and comprehensive knowledge regarding the impacts of the food matrix, including the food components and food (micro)structures, on the activities of antimicrobial agents. Studies of the last 10 years regarding the influences of the food structure on the effects of antimicrobial agents against the microorganisms' growth were summarized. The mechanisms underpinning the loss of the antimicrobial agents' activity in foods are proposed. Finally, some strategies/technologies to improve the protection of antimicrobial agents in specific food categories are discussed.

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.

Essential oils and their active components applied as: free, encapsulated and in hurdle technology to fight microbial contaminations. A review

Microbial contaminations are responsible for many chronic, healthcare, persistent microbial infections and illnesses in the food sector, therefore their control is an important public health challenge. Over the past few years, essential oils (EOs) have emerged as interesting alternatives to synthetic antimicrobials as they are biodegradable, extracted from natural sources and potent antimicrobials. Through their multiple mechanisms of actions and target sites, no microbial resistance has been developed against them till present. Although extensive documentation has been reported on the antimicrobial activity of EOs, comparisons between the use of whole EOs or their active components alone for an antimicrobial treatment are less abundant. It is also essential to have a good knowledge about EOs to be used as alternatives to the conventional antimicrobial products such as chemical disinfectants. Moreover, it is important to focus not only on planktonic vegetative microorganisms, but to study also the effect on more resistant forms like spores and biofilms. The present article reviews the current knowledge on the mechanisms of antimicrobial activities of EOs and their active components on microorganisms in different forms. Additionally, in this review, the ultimate advantages of encapsulating EOs or combining them with other hurdles for enhanced antimicrobial treatments are discussed.

Bactericidal and antibiofilm properties of Rumex japonicus Houtt. on multidrug-resistant Staphylococcus aureus isolated from milk

Multidrug-resistant (MDR) Staphylococcus aureus and its biofilm formation have been challenging to control in milk and dairy industries. Biofilms formed by Staph. aureus may result in the failure of antibacterial agents and disinfectants to penetrate the biofilm in an attempt to control contamination. Novel natural antibacterial agents are required to combat MDR bacteria and biofilms. In this study, we evaluated the bactericidal, antibiofilm, and antimotility effects of Rumex japonicus Houtt. (RJH) extract on MDR Staph. aureus isolated from milk. The RJH extract exhibited good antibacterial activity against MDR strains with minimum inhibitory concentrations (MIC) ranging from 0.78 to 6.25 mg/mL and minimum bactericidal concentrations ranging from 3.125 to 12.5 mg/mL. The extract showed strong inhibition of biofilm formation (81.9%) at sub-MIC value and eradication of biofilm at higher concentrations. The motility of Staph. aureus was effectively blocked by the extract. Major compounds emodin, chrysophanol, and physcion were identified in RJH extract using HPLC-linear trap quadrupole (LTQ)/Orbitrap-mass spectrometry. The extract was nontoxic to human epithelial cell lines such as Caco-2 and HT-29 cell lines at concentrations ranging from 0.1 to 0.5 mg/mL, and from 0.1 to 0.75 mg/mL, respectively. These findings suggest that RJH extract could be an alternative to synthetic preservatives in milk and dairy products.

A Study of the Antimicrobial Activity of Combined Black Pepper and Cinnamon Essential Oils against Escherichia fergusonii in Traditional African Yoghurt

The antimicrobial activity of the essential oils of black pepper (BPE) and cinnamon bark (CE) extracts against E. fergusonii was assessed in pasteurized full cream milk during and post-fermentation. The milk was fermented with 1% (v/v) of Lactobacillus delbrueckii subspecies bulgaricus (NCIMB 11778) and Streptococcus thermophilus (NCIMB 10387) (approx. 10⁶ cfu/mL each) and incubated and stored at 25 °C for 5 days (144 h) or at 43 °C for 24 h and then stored at 25 °C for 120 h. The milk was spiked with E. fergusonii at the start of fermentation by the lactic acid bacteria (pre-fermentation contamination) for after fermentation (post fermentation contamination). BPE and CE were applied at concentrations based on their minimum inhibitory concentration of 0.5% and 0.25% respectively as follows: 0.5% BPE alone; 0.125% BPE with 0.1875% CE; 0.25% BPE with 0.125% CE; 0.375% BPE with 0.0625% CE; 0.25% CE alone. Results showed that during fermentation at 25 °C, E. fergusonii grew to a similar level (approx. 10⁹ CFU/mL) in control samples and 10⁸ CFU/mL when BPE or CE were added alone. Whereas, in the samples with the combined essential oils, the bacterium grew to 10⁶–10⁷ CFU/mL only. During the milk fermentation at 43 °C, E. fergusonii grew to approx. 10⁹ CFU/mL in samples without treatment. However, it was not detected in samples containing mixed BPE with CE after 8, 10 and 12 h of fermentation. Subsequent storage at 25 °C resulted in undetectable levels of the bacterium in all the samples treated with BPE or CE after 24 h of storage. These results indicated that BPE in combination with CE reduced growth during fermentation and was bactericidal during storage.

Synergistic Antimicrobial Activities of Combinations of Vanillin and Essential Oils of Cinnamon Bark, Cinnamon Leaves, and Cloves

Plant bioactive compounds have antimicrobial and antioxidant activities that allow them to be used as a substitute for synthetic chemical additives in both food and food packaging. To improve its sensory and bactericidal effects, its use in the form of effective combinations has emerged as an interesting possibility in the food industry. In this study, the antimicrobial activities of essential oils (EOs) of cinnamon bark, cinnamon leaves, and clove and the pure compounds vanillin, eugenol, and cinnamaldehyde were investigated individually and in combination against Listeria monocytogenes and Escherichia coli O157:H7. The possible interactions of combinations of pure compounds and EOs were performed by the two-dimensional checkerboard assay and isobologram methods. Vanillin exhibited the lowest antimicrobial activity (MIC of 3002 ppm against L. monocytogenes and 2795 ppm against E. coli O157:H7), while clove and cinnamon bark EOs exhibited the highest antimicrobial activity (402–404 against L. monocytogenes and 778–721 against E. coli O157:H7). For L. monocytogenes, pure compound eugenol, the main component of cinnamon leaves and clove, showed lower antimicrobial activity than EOs, which was attributed to the influence of the minor components of the EOs. The same was observed with cinnamaldehyde, the main component of cinnamon bark EO. The combinations of vanillin/clove EO and vanillin/cinnamon bark EO showed the most synergistic antimicrobial effect. The combination of the EOs of cinnamon bark/clove and cinnamon bark/cinnamon leaves showed additive effect against L. monocytogenes but indifferent effect against E. coli O157:H7. For L. monocytogenes, the best inhibitory effects were achieved by cinnamon bark EO (85 ppm)/vanillin (910 ppm) and clove EO (121 ppm)/vanillin (691 ppm) combinations. For E. coli, the inhibitory effects of clove EO (104 ppm)/vanillin (1006 ppm) and cinnamon leaves EO (118 ppm)/vanillin (979 ppm) combinations were noteworthy. Some of the tested combinations increased the antimicrobial effect and would allow the effective doses to be reduced, thereby offering possible new applications for food and active food packaging.

Antimicrobial activity of Citrus spp. and Anethum graveolens components against Candida metapsilosis in ranch sauce

In this paper, a study was carried out to test the inhibitory effect of a natural food compound (NFC), based on flavonoids (naringenin, hesperetin, tangeritin, luteolin, apigenin and kaempferol) from citrus and dill, in ranch sauce. A strain of C. metapsilosis, isolated from a spoiled sample of ranch sauce, was used as target pathogen microorganism. The inhibitory effect of NFC was compared with a common mixture of chemical preservatives used in this type of sauces: potassium sorbate and sodium benzoate (S/B). An in vitro test was performed by the microtiter plate assay at 10, 25 and 37 °C for 24 h in modified Tryptic Soy Broth. An additive antimicrobial effect had been observed in the combination of acetic acid and NFC. The results of the microtiter assay were validated in a challenge test in ranch sauce at 5, 25 and 37 °C for 10 weeks. NFC showed partial fungicidal effect against C. metapsilosis, reducing two logarithmic units at 5 °C for 10 weeks. At 5 °C, the traditional doses of S/B used in ranch sauce decreased viable cells to non-detectable counts from the second week of the experiment. At 25 and 37 °C, the use of S/B mixture or the use of NFC showed the same fungicidal effect. The incorporation of NFC, alone or in combination with acetic acid, opens the possibility of formulating clean label sauces with good protection against the development of the acid resistant yeast C. metapsilosis.

Encapsulation of Essential Oils via Nanoprecipitation Process: Overview, Progress, Challenges and Prospects

Essential oils are of paramount importance in pharmaceutical, cosmetic, agricultural, and food areas thanks to their crucial properties. However, stability and bioactivity determine the effectiveness of essential oils. Polymeric nanoencapsulation is a well-established approach for the preservation of essential oils. It offers a plethora of benefits, including improved water solubility, effective protection against degradation, prevention of volatile components evaporation and controlled and targeted release. Among the several techniques used for the design of polymeric nanoparticles, nanoprecipitation has attracted great attention. This review focuses on the most outstanding contributions of nanotechnology in essential oils encapsulation via nanoprecipitation method. We emphasize the chemical composition of essential oils, the principle of polymeric nanoparticle preparation, the physicochemical properties of essential oils loaded nanoparticles and their current applications.

Essential Oil Based PVP-CMC-BC-GG Functional Hydrogel Sachet for 'Cheese': Its Shelf Life Confirmed with Anthocyanin (Isolated from Red Cabbage) Bio Stickers

‘Gouda cheese’ is one of the most popular varieties of cheese eaten worldwide. The preservation problem of gouda arises due to microbial contamination and infestation. Therefore, essential oil (EO) based PVP-CMC-BC-GG hydrogel film was prepared to solve the problem and to extend the shelf-life of ‘Gouda cheese’. Anthocyanin (isolated from red cabbage) based pH stickers are integrated into the packaging system to recognize the spoilage of ‘cheese’. EOs (clove and/or cinnamon) are added to PVP-CMC-BC-GG hydrogel film to improve its antimicrobial, physical, mechanical, and thermal properties as well as shelf-life of cheese. The films are assessed based on their physical, structural, and functional properties, real-time assessment on cheese, and biodegradability. The results revealed that although the addition of oils to the PVP-CMC-BC-GG hydrogel films enhanced its mechanical, hydrophobic, and antimicrobial properties, the biodegradability of PVP-CMC-BC-GG films declined with the addition of EOs. The thermal properties remained the same irrespective of the addition of EOs. The shelf life of cheese was extended for more than 10–12 days, inside the PVP-CMC-BC-GG hydrogel sachet compared to the conventional PE packaging system. Hence the use of the PVP-CMC-BC-GG sachet (containing EO or without EO) is recommended for cheese packaging along with the use of PVP-CMC-BC-GG anthocyanin bio stickers for monitoring the quality of cheese.

Evaluating the Antimicrobial Efficacy of White Mustard Essential Oil Alone and in Combination with Thymol and Carvacrol against Salmonella

It is estimated that nontyphoidal Salmonella causes approximately 1 million illnesses and 378 deaths per year in the United States. Reduction of Salmonella-related foodborne infections can be achieved through application of food antimicrobials. Essential oils in combination with other antimicrobials can be added to food products to reduce the levels of the organism below the infectious dose for healthy individuals. The purpose of this study was to investigate the antimicrobial efficacy of white mustard essential oil (WMEO) against serovars of Salmonella and its potential to be used with carvacrol or thymol to control Salmonella. Results showed that WMEO at the highest concentration of 0.84% (v/v) compared with the positive control had approximately a 6- to 7-log reduction for all serovars. It was found that no difference in susceptibility existed among the serovars tested (P > 0.05). In addition, the MICs were determined to be 0.5, 0.02, and 0.02% for WMEO, carvacrol, and thymol, respectively, against Salmonella Typhimurium. The fractional inhibitory concentration index was calculated. A score of 1 indicated an additive effect occurred when WMEO was combined with thymol or carvacrol. Combining WMEO with carvacrol or thymol indicated that the concentration of individual essential oils needed to inhibit Salmonella can be reduced using these combinations and warrants further study to determine potential use in controlling Salmonella in commercial food products.

Antibacterial Effects of Ultrasound, Cinnamon Essential Oil, and Their Combination Against Listeria monocytogenes and Salmonella Typhimurium in Milk

The antibacterial effects of ultrasound (US) and cinnamon essential oil (CEO), individually and combined, were investigated against Listeria monocytogenes and Salmonella Typhimurium in low- and high-fat milk during 6-day storage. At the end of storage, CEO alone decreased 2 and 2.2 log cycles of Salmonella Typhimurium and 2.5 and 3 log cycles of L. monocytogenes populations in low- and high-fat milk, respectively. US alone reduced 1.6 log cycle of Salmonella Typhimurium and 0.7 log cycle of L. monocytogenes in both milk type. The combined treatment could reduce 2.7 log cycle of Salmonella Typhimurium in low-fat milk and 3.8 log cycle in high-fat milk. The combined treatment also achieved 4.3 and 4.5 log cycle reductions of L. monocytogenes in low- and high-fat milk, respectively. The results of this study showed that the combination of CEO and US could be used as an effective antibacterial treatment in milk. PRACTICAL APPLICATIONS: Due to adverse effects of thermal processing on the sensory and nutritional properties of food and the potentially harmful effects of chemical preservatives, nonthermal preservation methods and natural antimicrobials have been gained much attention. In this study, the antibacterial effects of ultrasound (US) and cinnamon essential oil (CEO), individually and combined, were investigated against Listeria monocytogenes and Salmonella Typhimurium in low- and high-fat milk. The results indicated that combination of US and CEO could significantly decrease L. monocytogenes and Salmonella Typhimurium populations in milk. Then, this combined treatment may be used as an effective alternative method to microbial inactivation in milk.

Antibacterial Effect of a Mixed Natural Preservative against Listeria monocytogenes on Lettuce and Raw Pork Loin

A mixed natural preservative, including grapefruit seed extract (GSE), cinnamaldehyde (CA), and nisin, was investigated for the reduction of Listeria monocytogenes growth on lettuce and raw pork loin. The MIC of each natural preservative was investigated for L. monocytogenes strains tested. Following central composite design, lettuce and pork loin were inoculated with a cocktail of three strains of L. monocytogenes (ATCC 15313, H7962, and NADC 2045 [Scott A]) and treated with the mixed natural preservative that included GSE (0.64 to 7.36 ppm), CA (1.6 to 18.4 ppm), and nisin (0.48 to 5.5 ppm). The MIC of GSE was 31.25 ppm in tested L. monocytogenes strains, and of CA was 500 and 1,000 ppm in L. monocytogenes ATCC 15313 and the other L. monocytogenes strains, respectively. The MIC of nisin was 250 ppm. The R2 value of this model was more than 0.9, and the lack of fit was not significant. The mixed natural preservative showed a synergistic antimicrobial effect and reduced the growth of L. monocytogenes by 4 to 5 log CFU/g on lettuce. In addition, the reduction of L. monocytogenes on pork loin was 3 log CFU/g. The mixed natural preservative, which consisted of GSE (6 to 8 ppm), CA (15 to 20 ppm), and nisin (5 to 6 ppm), increased the antibacterial effect against L. monocytogenes. These results suggest that the use of the mixed natural preservative could reduce the economic cost of food preparation, and response surface methodology is considered effective when measuring synergy among antimicrobials.

Food Safety through Natural Antimicrobials

Microbial pathogens are the cause of many foodborne diseases after the ingestion of contaminated food. Several preservation methods have been developed to assure microbial food safety, as well as nutritional values and sensory characteristics of food. However, the demand for natural antimicrobial agents is increasing due to consumers' concern on health issues. Moreover, the use of antibiotics is leading to multidrug resistant microorganisms reinforcing the focus of researchers and the food industry on natural antimicrobials. Natural antimicrobial compounds from plants, animals, bacteria, viruses, algae and mushrooms are covered. Finally, new perspectives from researchers in the field and the interest of the food industry in innovations are reviewed. These new approaches should be useful for controlling foodborne bacterial pathogens; furthermore, the shelf-life of food would be extended.

Antibacterial Interactions of Colloid Nanosilver with Eugenol and Food Ingredients

This study was conducted to investigate antibacterial properties of the colloidal silver nanoparticles (SNPs) and eugenol, alone and in combination, on Staphylococcus aureus and Salmonella Typhimurium and their interactions with food constituents (fat, protein, and carbohydrate). We examined antibacterial activities of SNPs and eugenol in Luria-Bertani (LB) broth and 1.5 and 3% fat ultrahigh-temperature (UHT) milk. MICs of eugenol and SNPs (particle size of 31.3 nm) were also investigated in the presence of sunflower oil, meat extract, and starch at concentrations of 2, 5, and 10% to examine the interactions between food constituents and antimicrobial agents. MICs and MBCs of eugenol and SNPs for both bacteria were at 2,500 and 25 μg/mL, respectively. Combinations of the two substances had additive and synergistic effects on Salmonella Typhimurium and S. aureus, respectively. Both compounds had bactericidal activity. In food matrices, results indicated that eugenol only in sunflower oil at 5 and 10% concentrations had significant antibacterial activity. A similar result was achieved for SNPs with 10% meat extract. In LB broth, eugenol at 2,500 and 5,000 μg/mL achieved 6-log reductions in the microbial population of both bacteria after 3 h, while SNPs achieved the same effect after 9 h. In UHT milk with 1.5% fat, eugenol at 5,000 μg/mL and SNPs at 25 μg/mL achieved 6-log reductions in bacterial populations after 24 h. Thus, the antimicrobial activity of both eugenol and SNPs depended on the medium in which the experiment was conducted, and the combination of both antimicrobial agents increased the antimicrobial effect.

Antifungal Activity of Selected Natural Preservatives against Aspergillus westerdijkiae and Penicillium verrucosum and the Interactions of These Preservatives with Food Components

The present study examined the influence of primary food components on the antifungal activity of the essential oil of Origanum vulgare, carvacrol, thymol, eugenol, and trans-cinnamaldehyde against Penicillium verrucosum and Aspergillus westerdijkiae. The MIC was determined in food model media enriched with proteins (1, 5, or 10%), carbohydrates (1, 4, or 6%), or oil (1, 5, or 10%). Proteins increased the antifungal activity of O. vulgare essential oil, carvacrol, thymol, and eugenol, whereas the effect of trans-cinnamaldehyde decreased with increasing protein content. The presence of carbohydrates diminished the inhibitory effect of the natural preservatives on A. westerdijkiae; for P. verrucosum, their inhibitory effect increased with carbohydrates. Only the antifungal activity of trans-cinnamaldehyde did not depend on the carbohydrate content. The presence of oil had the strongest influence. At a concentration of 1% oil, the antifungal activity decreased significantly, and at 10% oil, almost no inhibition was observed. To investigate the effect of the antifungal agents on the morphology of the target molds, they were grown on malt extract agar containing carvacrol and trans-cinnamaldehyde and were examined by scanning electron microscopy. The hyphae, conidiophores, vesicles, and phialides were severely altered and deformed, and spore formation was clearly suppressed.

Effect of oregano (Origanum vulgare L. ssp. hirtum) and clove (Eugenia spp.) nanoemulsions on Zygosaccharomyces bailii survival in salad dressings

This work aimed to evaluate the in vitro effect of encapsulated oregano and clove essential oils on oil-in-water nanoemulsions against Zygosaccharomyces bailii. The antifungal efficacy of these nanoemulsions and their sensory acceptance were tested in salad dressings. Both essential oils were effective inhibitors against the target yeast, with minimal inhibitory and fungicidal concentrations of 1.75 mg/mL. In the in vitro assay done with the nanoemulsions, no yeast growth was observed for any tested essential oil concentration. In the salad dressings, all the formulations were able to reduce Z. bailii growth compared to the control, and only those samples with 1.95 mg/g of essential oil were capable of inhibiting yeast development after 4 inoculation days. The sensory acceptance of the dressing containing the nanoemulsions was similar to the control dressing in appearance, consistency and colour terms. These results evidence the antifungal activity of oregano and clove nanoemulsions against Z. bailii.

Novel natural food preservatives and applications in seafood preservation: a review

Food preservative additives are natural or synthetic substances which delay degradation in foods caused by microbial growth, enzyme activity, and oxidation. Until recently, the use of synthetic additives in food was more common. However, synthetic additives have not been widely accepted by consumers in recent years due to their assumed adverse effects on their health. Therefore, the tendency of consumers to natural additives is increasing day-by-day. Seafood is an easily perishable food due to its chemical composition. Immediately after harvest, changes in odor, taste, and texture in fishery products can be noticed. For this reason, measures to protect the product must be taken immediately after harvest or catching. Various preservation methods have been developed. In addition to various technological methods, preservative additives are used in fresh or processed seafood as well as in other foods. This review focuses on novel natural preservatives from different sources such as plants, bacteria, fungi, animals and algae, and their use in seafood to protect quality and prolong shelf life. © 2018 Society of Chemical Industry.

Improving the Efficacy of Essential Oils as Antimicrobials in Foods: Mechanisms of Action

The consumer preference for clean-label products is requiring the food industry to reformulate their products by replacing artificial additives with natural alternatives. Essential oils are natural antimicrobials isolated from plant sources that have the potential to combat many foodborne pathogens and spoilage organisms. This review begins by discussing the antimicrobial properties of essential oils, the relationships between their chemical structure and antimicrobial efficacy, and their potential limitations for commercial applications (such as strong flavor, volatility, and chemical instability). We then review the commonly used methods for screening the antimicrobial efficacy of essential oils and elucidating their mechanisms of action. Finally, potential applications of essential oils as antimicrobials in foods are reviewed and the major types of food-grade delivery systems available for improving their efficacy are discussed.

Antiviral effects of blueberry proanthocyanidins against Aichi virus

Blueberry polyphenols are known for their high antioxidant and antimicrobial potential. Aichi virus (AiV) is an emerging human enteric virus that causes gastroenteritis outbreaks worldwide. This study aimed to (1) determine the time- and dose-dependent effects of blueberry proanthocyanidins (B-PAC) against AiV over 24 h at 37 °C; (2) gain insights on their mode of action using pre- and post-treatment of host cells and Transmission Electron Microscopy; and (3) determine their anti-AiV effects in model foods and under simulated gastric conditions. AiV at ∼5 log PFU/ml was incubated with equal volumes of commercial blueberry juice (BJ, pH 2.8), neutralized BJ (pH 7.0), B-PAC (2, 4, and 10 mg/ml) prepared either in 10% ethanol, apple juice (AJ), 2% milk, simulated gastric fluid (SGF, pH 1.5) or simulated intestinal fluid (SIF, pH 7.5), and controls (malic acid (pH 3.0), phosphate buffered saline (pH 7.2), apple juice (pH 3.6) and 2% milk) over 24 h at 37 °C, followed by standard plaque assays. Each experiment was replicated thrice and data were statistically analyzed. Differences in AiV titers with 1 mg/ml B-PAC were 2.13 ± 0.06 log PFU/ml lower after 24 h and ≥3 log PFU/ml (undetectable levels) lower with 2 and 5 mg/ml B-PAC compared to AiV titers in PBS after 24 h and 3 h, respectively. BJ at 37 °C resulted in titer differences (lower titers compared to PBS) of 0.17 ± 0.06, 1.27 ± 0.01, and 1.73 ± 0.23 log PFU/ml after 1, 3, and 6 h and ≥3 log PFU/ml after 24 h. Pre- and post-treatment of host cells with 0.5 mg/ml B-PAC caused titer decreases of 0.62 ± 0.33 and 0.30 ± 0.06 log PFU/ml, respectively suggesting a moderate effect on viral-host cell binding. B-PAC at 2 mg/ml in AJ caused titer differences of ≥3 log PFU/ml after 0.5 h, while differences of 0.84 ± 0.03 log PFU/ml with 5 mg/ml B-PAC in milk, and ≥3 log PFU/ml with B-PAC at 5 mg/ml in SIF after 30 min were obtained. This study shows the ability of BJ and B-PAC to decrease AiV titers to potentially prevent AiV-related illness and outbreaks.

Plants of Genus Mentha: From Farm to Food Factory

Genus Mentha, a member of Lamiaceae family, encompasses a series of species used on an industrial scale and with a well-described and developed culture process. Extracts of this genus are traditionally used as foods and are highly valued due to the presence of significant amounts of antioxidant phenolic compounds. Many essential oil chemotypes show distinct aromatic flavor conferred by different terpene proportions. Mint extracts and their derived essential oils exert notable effects against a broad spectrum of bacteria, fungi or yeasts, tested both in vitro or in various food matrices. Their chemical compositions are well-known, which suggest and even prompt their safe use. In this review, genus Mentha plant cultivation, phytochemical analysis and even antimicrobial activity are carefully described. Also, in consideration of its natural origin, antioxidant and antimicrobial properties, a special emphasis was given to mint-derived products as an interesting alternative to artificial preservatives towards establishing a wide range of applications for shelf-life extension of food ingredients and even foodstuffs. Mentha cultivation techniques markedly influence its phytochemical composition. Both extracts and essential oils display a broad spectrum of activity, closely related to its phytochemical composition. Therefore, industrial implementation of genus Mentha depends on its efficacy, safety and neutral taste.

Comparison of Cinnamon Essential Oils from Leaf and Bark with Respect to Antimicrobial Activity and Sensory Acceptability in Strawberry Shake

Cinnamon leaf and bark essential oils have long been used as natural preservatives and flavoring agents in foods. This study determined antimicrobial effects of leaf and bark of cinnamon essential oils (CEOs) against 2 foodborne pathogens, Salmonella Typhimurium (S.T.) and Listeria monocytogenes (L.m.), at 2 initial bacterial levels (4- and 9-log CFU/mL) in strawberry shakes. The antimicrobial study of CEOs at 0.1% and 0.5% in strawberry shakes against S.T. and L.M. showed a significant difference (P < 0.05) in log reductions of both bacterial growth at low (4-log CFU/mL) and high (9-log CFU/mL) initial bacterial levels. Addition of 0.5% CEOs into strawberry shakes at 4 °C completely inhibited both bacteria after a period of 8 d storage. Shelf-life study showed that acidity and total solid content were not affected during storage. The strawberry shakes containing bark CEO had higher ratings of sensory acceptability compared to leaf CEO, with or without the addition of 1% masking agent. In conclusion, this study demonstrated that CEO derived from bark was better than that from leaf in terms of their antimicrobial activity and sensory aspect.

PRACTICAL APPLICATION

This study demonstrates that essential oils derived from cinnamon bark and leaf have the potential to be used as natural antimicrobial ingredient in milk beverages with respect to sensory aspect. This finding promotes the acceptance of natural antimicrobials among consumers, while providing enhanced safer products to the food industry application.

Control of Listeria monocytogenes in whole milk using antimicrobials applied individually and in combination

Dairy product recalls and dairy-related illnesses are often the result of contamination with Listeria monocytogenes, which can occur throughout the dairy production and supply chains. The use of antimicrobial compounds is one practical approach for controlling pathogen survival and growth in foods. The goal of this study was to use fluid milk as a model system to identify listeristatic or listericidal treatments that show promise for application in fluid milk and for further evaluation in other dairy products (e.g., cheese). Caprylic acid (CA), ε-polylysine (EPL), hydrogen peroxide, lauric arginate (LAE), and sodium caprylate (SC) were added individually or in combination to whole milk inoculated with L. monocytogenes at ˜4 log₁₀ cfu/mL. Samples were stored at 7°C for 21 d, and L. monocytogenes counts were determined weekly. Inhibitory concentrations of LAE (800 mg/L) and EPL (100-400 mg/L), as well as SC and CA (3,200 mg/L each), were identified. The addition of EPL at 800 mg/L reduced L. monocytogenes counts by >3 log₁₀ cfu/mL from initial inoculation levels after 21 d. Addition of hydrogen peroxide to milk reduced counts by >3 log₁₀ cfu/mL from initial inoculation within 24 h (400 and 800 mg/L) or by d 7 (200 mg/L). Although the combinatory treatments of EPL + CA, EPL + LAE, and LAE + SC were characterized as indifferent, EPL + SC worked synergistically to reduce L. monocytogenes populations in milk over 21 d. Overall, these data identify potential antimicrobial treatments to control L. monocytogenes in milk and serve as a foundation for the continued development of antimicrobial controls for L. monocytogenes in dairy products.

Control of Native Spoilage Yeast on Dealcoholized Red Wine by Preservatives Alone and in Binary Mixtures

In order to preserve a commercial dealcoholized red wine (DRW), a study with 4 preservatives and binary mixtures of them were performed against 2 native spoilage yeasts: Rhodotorula mucilaginosa and Saccharomyces cerevisiae. Minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) for potassium sorbate, sodium benzoate, sodium metabisulfite and dimethyl dicarbonate (DMDC) were evaluated in DRW stored at 25 °C. MICs of potassium sorbate and sodium metabisulfite were 250 and 60 mg/kg, respectively for both target strains. However for sodium benzoate, differences between yeasts were found; R. mucilaginosa was inhibited at 125 mg/kg, while S. cerevisiae at 250 mg/kg. Regarding MFC, differences between strains were only found for sodium metabisulfite obtaining a MFC of 500 mg/kg for R. mucilaginosa and a MFC of 250 mg/kg for S. cerevisiae. Potassium sorbate and sodium benzoate showed the MFC at 1000 mg/kg and DMDC at 200 mg/kg. Regarding the effect of binary mixtures the Fractional Fungicidal Concentration Index (FFC_i ) methodology showed that binary mixtures of 100 mg/kg DMDC/200 mg/kg potassium sorbate (FFC_i = 0.7) and 50 mg/kg DMDC / 400 mg/kg sodium benzoate (FFC_i = 0.65) have both synergistic effect against the 2 target strains. These binary mixtures can control the growth of spoilage yeasts in DRW without metabisulfite addition. The results of this work may be important in preserving the health of DRW consumers by eliminating the use of metabisulfite and reducing the risk of growth of R. mucilagosa, recently recognized as an emerging pathogen.

Influence of Food Characteristics and Food Additives on the Antimicrobial Effect of Garlic and Oregano Essential Oils

Utilization of essential oils (EOs) as antimicrobial agents against foodborne disease has gained importance, for their use as natural preservatives. Since potential interactions between EOs and food characteristics may affect their antimicrobial properties, the present work studies the influence of fat, protein, pH, aw and food additives on the antimicrobial effect of oregano and garlic EOs against Salmonella spp. and Listeria monocytogenes. Results showed that protein, pH, aw, presence of beef extract, sodium lactate and nitrates did not influence their antimicrobial effect. In contrast, the presence of pork fat had a negative effect against both EOs associated with their dilution of the lipid content. The addition of food phosphates also exerts a negative effect against EOs probably associated with their emulsification properties as observed with the addition of fat. The results may help the food industry to select more appropriate challenges to guarantee the food safety of foodstuffs.

Star Anise (Illicium verum Hook. f.) as Quorum Sensing and Biofilm Formation Inhibitor on Foodborne Bacteria: Study in Milk

Bacteria use quorum sensing (QS) systems to communicate with each other and regulate microbial group behavior, such as the secretion of virulence factors, including biofilm formation. In order to explore safe, edible agents, the potential of star anise (SA) as an anti-QS and antibiofilm agent and its possible application in milk safety were investigated. Staphylococcus aureus , Salmonella Typhimurium, Pseudomonas aeruginosa , and biosensor strain Chromobacterium violaceum were selected as test strains for QS, biofilm, and exopolysaccharide assays. The percent acidities and total plate counts were determined to evaluate the quality of biofilm-inoculated and noninoculated milk. The yield of SA extraction was 25.90% ± 0.2% (w/w). At sub-MIC, SA extract did not show any effect on bacterial growth. The production of violacein was inhibited by 89% by SA extract. The extract also inhibited the formation of biofilm by up to 87% in a dose-dependent manner. Inhibition rates of 70.45%, 42.82%, and 35.66% were found for exopolysaccharide production. The swarming motility of S. aureus was reduced by about 95.9% by SA extract. Confocal laser scanning microscopy analysis confirmed that the development of biofilm architecture was hampered. It was found that SA extract could delay the spoilage of milk. In the endeavor to avoid drug resistance, pathogenesis, and resistance to biocides while improving food safety and avoiding health hazard issues arising from synthetic chemicals, SA extract could be used as a potential QS and biofilm inhibitor.

Biogenic synthesis of Zinc oxide nanostructures from Nigella sativa seed: Prospective role as food packaging material inhibiting broad-spectrum quorum sensing and biofilm

Bacterial spoilage of food products is regulated by density dependent communication system called quorum sensing (QS). QS control biofilm formation in numerous food pathogens and Biofilms formed on food surfaces act as carriers of bacterial contamination leading to spoilage of food and health hazards. Agents inhibiting or interfering with bacterial QS and biofilm are gaining importance as a novel class of next-generation food preservatives/packaging material. In the present study, Zinc nanostructures were synthesised using Nigella sativa seed extract (NS-ZnNPs). Synthesized nanostructures were characterized hexagonal wurtzite structure of size ~24 nm by UV-visible, XRD, FTIR and TEM. NS-ZnNPs demonstrated broad-spectrum QS inhibition in C. violaceum and P. aeruginosa biosensor strains. Synthesized nanostructures inhibited QS regulated functions of C. violaceum CVO26 (violacein) and elastase, protease, pyocyanin and alginate production in PAO1 significantly. NS-ZnNPs at sub-inhibitory concentrations inhibited the biofilm formation of four-food pathogens viz. C. violaceum 12472, PAO1, L. monocytogenes, E. coli. Moreover, NS-ZnNPs was found effective in inhibiting pre-formed mature biofilms of the four pathogens. Therefore, the broad-spectrum inhibition of QS and biofilm by biogenic Zinc oxide nanoparticles and it is envisaged that these nontoxic bioactive nanostructures can be used as food packaging material and/or as food preservative.

Blueberry proanthocyanidins against human norovirus surrogates in model foods and under simulated gastric conditions

Blueberry proanthocyanidins (B-PAC) are known to decrease titers of human norovirus surrogates in vitro. The application of B-PAC as therapeutic or preventive options against foodborne viral illness needs to be determined using model foods and simulated gastric conditions in vitro. The objective of this study was to evaluate the antiviral effect of B-PAC in model foods (apple juice (AJ) and 2% reduced fat milk) and simulated gastrointestinal fluids against cultivable human norovirus surrogates (feline calicivirus; FCV-F9 and murine norovirus; MNV-1) over 24 h at 37 °C. Equal amounts of each virus (5 log PFU/ml) was mixed with B-PAC (1, 2 and 5 mg/ml) prepared either in AJ, or 2% milk, or simulated gastric fluids and incubated over 24 h at 37 °C. Controls included phosphate buffered saline, malic acid (pH 7.2), AJ, 2% milk or simulated gastric and intestinal fluids incubated with virus over 24 h at 37 °C. The tested viruses were reduced to undetectable levels within 15 min with B-PAC (1, 2 and 5 mg/ml) in AJ (pH 3.6). However, antiviral activity of B-PAC was reduced in milk. FCV-F9 was reduced by 0.4 and 1.09 log PFU/ml with 2 and 5 mg/ml B-PAC in milk, respectively and MNV-1 titers were reduced by 0.81 log PFU/ml with 5 mg/ml B-PAC in milk after 24 h. B-PAC at 5 mg/ml in simulated intestinal fluid reduced titers of the tested viruses to undetectable levels within 30 min. Overall, these results show the potential of B-PAC as preventive and therapeutic options for foodborne viral illnesses.

Antimicrobial Activity of Cinnamaldehyde, Carvacrol, and Lauric Arginate against Salmonella Tennessee in a Glycerol-Sucrose Model and Peanut Paste at Different Fat Concentrations

The objective of this study was to investigate the antimicrobial activities of carvacrol, cinnamaldehyde, and lauric arginate (LAE) against Salmonella in a low water activity (aw ) glycerol-sucrose model and in peanut paste with different fat concentrations. Salmonella Tennessee was inoculated into the model and the low fat (<5%) and high fat (50%) peanut paste adjusted to aw 1.0, 0.7, 0.5, and 0.3 and with or without cinnamaldehyde, carvacrol, or LAE. The survival of the bacterium over 3 or 5 days at 25°C was evaluated. Reduced aw alone decreased the viable population over time, with the highest reduction at the lowest aw. In the glycerol-sucrose model, all antimicrobial agents significantly reduced the population over time (P < 0.05) compared with the controls. LAE was more lethal than the essential oil components, reducing the population to undetectable levels by day 2 for all aw. Cinnamaldehyde was more effective than carvacrol at aw 0.5 and 0.3 (2.7- to 2.9-log versus 0.39- to 1.97-log reductions on day 3). In low-fat peanut paste, none of the antimicrobial agents inhibited growth of the pathogen at aw 1.0. However, inactivation was enhanced at reduced aw. Cinnamaldehyde and LAE both reduced the pathogen population to undetectable levels on day 5 at the highest concentration tested (ca. 10 times higher than that in the glycerol-sucrose model). Inactivation efficacy of all antimicrobial agents was greatly decreased but not eliminated in 50% fat peanut paste. Results suggest that the test antimicrobial agents were effective under low aw conditions, but significantly higher concentrations are needed for potential food applications, and fat concentration can negatively impact the efficacy of these antimicrobial agents.