Antimicrobial Food Additives Research Articles

Evaluation of the Effects of Edible Coatings of Ocimum sanctum and Aloe vera on Jaggery Shelf Life

Background: In western Uttar Pradesh, jaggery is a widespread cottage enterprise based on agriculture, and farmers are forced to sell their product at a lesser price when it is still fresh. Therefore, it was thought to be desirable to create better storage techniques in order to extend its shelf life. Aloe vera, and Ocimum sanctum, often known as "Tulsi," are frequently utilised as antimicrobial food additives because they offer a host of other health advantages in addition to their well-known antibacterial qualities. Because the edible coatings made of these herbs provide a semi-permeable barrier to gases and water vapours, they may prolong the shelf life of jaggery by preventing degradation. Objective: The goal of the current study was to assess the ability of edible coatings of common Indian herbs, such as tulsi and Aloe vera,, to extend the shelf life of jaggery while maintaining attributes that are equal to those of fresh jaggery, in accordance with the guidelines set forth by the Food Safety and Standards Authority of India (FSSAI). Methodology: The physicochemical characteristics, antioxidant activity, total viable count, and antibacterial activity of tulsi-Aloe vera, coated (TAC), Ocimum sanctum, and Aloe vera, (AC) jaggery were assessed and compared with non-coated control. The physicochemical properties were ascertained using standard methodology for measurement of reducing sugars, proteins, phenols, saponins, tannin, alkaloids, and flavonoids. The antimicrobial activity was ascertained by means of the agar double diffusion method. According to established protocol, antioxidant activity was assessed using the DPPH radical scavenging assay and the reducing power assay. Results: According to the research, there is no discernible microbiological deterioration and the edible coatings containing tulsi and Aloe vera, extend the shelf life of jaggery during storage. When compared to uncoated jaggery, coatings were efficient at preventing the growth of both Gramme positive and Gramme negative microorganisms. Over the course of six months, the herb-infused coatings also retained their phenolic, flavonoid, and tannin contents, which improved their anti-oxidant efficacy when compared to the untreated control group.

Polyphenol-Rich Extracts and Essential Oil from Egyptian Grapefruit Peel as Potential Antioxidant, Antimicrobial, and Anti-Inflammatory Food Additives

Grapefruit (GF) processing generates significant nutrient and economic losses due to the production of 50% by-products, primarily peels. GF peels are a rich and sustainable source of bioactive compounds (BCs), such as essential oils (EOs) and phenolic compounds. Thus, finding value-added solutions based on a circular economy is paramount. This research aims to assess the antioxidant, anti-inflammatory, and antimicrobial properties of a hydroethanolic polyphenol-rich extract from crude GF peels (GF-CE), essential oil (GF-EO), and polyphenol-rich extract from GF peels after essential oil extraction (GF-PE). The GF-CE and GF-PE showed high concentrations of naringenin (7.71 and 48.60 mg/g dry extract (DE)), narirutin (15.03 and 28.73 mg/g DE), and hesperidin (0.67 and 0.29 mg/mL), respectively. Extracting firstly EOs from GF improved the release of phenolic acids (p-coumaric, ferulic, and chlorogenic acid). The GF-CE exhibited stronger free radical scavenging activity mainly in DPPH (IC50 = 75.69 ± 0.81 µg/mL) than GF-EO (1271 ± 0.85 µg/mL) and GF-PE (113.45 ± 0.85 µg/mL). The GF-EO demonstrated moderate antimicrobial activity against Gram-positive bacteria compared to the reference standard (amoxicillin) and strong activity against the yeast Candida albicans (inhibition zone of 16 mm). The major compounds in the GF-EO included D-limonene (25%), nootkatone (24%), and β-pinene (8%). Both polyphenol-rich extracts showed promising activities as COX1 and COX2 inhibitors with IC50 values of 25 ± 0.1 and 0.28 ± 0.00 µg/mL (compared to celecoxib (97.5 ± 0.1 and 0.31 ± 0.01 µg/mL) and indomethacin (6.25 ± 0.00 and 0.52 ± 0.01 µg/mL) as the standards), respectively. The study concludes that GF peels are a valuable source of BCs with significant bioactivities, offering a sustainable multi-cascade approach to recovering value-added compounds from GF peels in alignment with circular economy principles and open opportunities as functional ingredients for food applications.

Antimicrobial effect of garlic against foodborne pathogens in ground mutton

The antimicrobial effect of fresh garlic (20, 30, and 50 g/kg) and the equivalent concentrations of garlic oil (80, 120, and 200 mg/kg) was investigated in ground mutton during storage at 4 °C. By day 6 and thereafter, mutton meatballs treated with 50 g/kg of fresh garlic and 200 mg/kg garlic oil exhibited a significant decline in psychrotrophic and Pseudomonas counts in comparison with control. Fresh garlic added at a concentration of 50 g/kg exhibited the highest antimicrobial effect, followed by garlic oil at 200 mg/kg, fresh garlic at 30 g/kg, and garlic oil at 120 mg/kg. By the 15th day of storage, the fresh garlic added at concentrations of 50 and 30 g/kg and garlic oil added at concentrations of 120, and 200 mg/kg inactivated the populations of foodborne pathogens artificially inoculated into ground mutton and exhibited significant (P < 0.01) lower counts in Salmonella Typhimurium, Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus by more than 3 logs CFU/g, in comparison to control. Therefore, fresh garlic and garlic oil can be used as natural antimicrobial food additives to extend the shelf life and inactivate the populations of foodborne pathogens in meat products.

The impact of antimicrobial food additives and sweeteners on the growth and metabolite production of gut bacteria.

Metabolic disorders caused by the imbalance of gut microbiota have been associated with the consumption of processed foods. Thus, this study aimed to evaluate the effects of antimicrobial food additives (benzoate, sorbate, nitrite, and bisulfite) and sweeteners (saccharin, stevia, sucralose, aspartame, and cyclamate) on the growth and metabolism of some gut and potentially probiotic bacterial species. The effects on the growth of Bifidobacterium longum, Enterococcus faecium, Lactobacillus acidophilus, and Lactococcus lactis subsp. lactis cultures were investigated using a turbidimetric test and by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). To evaluate the metabolic activity, the cultures were exposed to compounds with the highest antimicrobial activity, subjected to cultivation with inulin (1.5%), and analyzed by liquid chromatography for the production of short-chain fatty acids (acetate, propionate, and butyrate). The results showed that potassium sorbate (25mg/mL), sodium bisulfite (0.7mg/mL), sodium benzoate, and saccharin (5mg/mL) presented greater antimicrobial activity against the studied species. L. lactis and L. acidophilus bacteria had reduced short-chain fatty acid production after exposure to saccharin and sorbate, and B. longum after exposure to sorbate, in comparison to controls (acetic acid reduction 1387μg/mL and propionic 23μg/mL p < 0.05).

Essential Oils: Recent Advances on Their Dual Role as Food Preservatives and Nutraceuticals against the Metabolic Syndrome.

Essential oils (EO) are compounds synthesized by plants as secondary products and are a complex mixture of volatile molecules. Studies have demonstrated their pharmacological activity in the prevention and treatment of metabolic syndrome (MetS). Moreover, they have been used as antimicrobial and antioxidant food additives. The first part of this review discusses the role of EO as nutraceuticals to prevent metabolic syndrome-related disorders (i.e., obesity, diabetes, and neurodegenerative diseases), showing results from in vitro and in vivo studies. Likewise, the second part describes the bioavailability and mechanisms of action of EO in preventing chronic diseases. The third part presents the application of EO as food additives, pointing out their antimicrobial and antioxidant activity in food formulations. Finally, the last part explains the stability and methods for encapsulating EO. In conclusion, EO dual role as nutraceuticals and food additives makes them excellent candidates to formulate dietary supplements and functional foods. However, further investigation is needed to understand EO interaction mechanisms with human metabolic pathways and to develop novel technological approaches to enhance EO stability in food systems to scale up these processes and, in this way, to overcome current health problems.

In vitro antibacterial activity of Loxostylis alata extracts and isolated compounds against Salmonella species

BackgroundOwing to antibiotic resistance, alternative antimicrobials from medicinal plants are receiving attention as leads for anti-infective agents. This study aimed to investigate selected tree species and their constituents for activity against bacterial foodborne pathogens, particularly Salmonella serovars.MethodsAntibacterial activity of ten plant species was determined by serial microdilution against bacteria implicated in causing gastrointestinal ailments. Active compounds were isolated from Loxostylis alata using bioassay-guided fractionation. Antioxidant activity was determined using free-radical scavenging assays. Cytotoxicity and genotoxicity of the extracts was ascertained on Vero cells, and using the Ames assay respectively.ResultsExtracts had low to moderate MIC values from 0.04 to 2.5 mg/mL. Protorhus longifolia and Loxostylis alata were most active and L. alata had the highest selectivity index value (2.51) against Salmonella Typhimurium, as well as high antioxidant activity. Cytotoxicity values ranged from 0.02 to 0.47 mg/mL, while tested extracts were not genotoxic. Bioactive compounds isolated from L. alata included delicaflavone and a polymethoxyflavone.ConclusionsThe Loxostylis alata leaf extract had strong activity against Salmonella serovars but isolated compounds were less active, indicating likely synergistic effects. Extracts of L. alata are promising candidates for development of antimicrobial preparations or food additives against microbial contamination.

Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder.

Some Salmonella enterica strains survive well in low-water activity (low-aw) foods and cause frequent salmonellosis outbreaks in these products. Methods are needed to overcome such desiccation-resistant Salmonella and to improve the safety of low-aw foods. Building on a recent finding, we hypothesized that natural antimicrobial food additives, which are active against cytoplasmic membrane, could overcome this desiccation resistance phenomenon, and thus, sensitize the pathogen to drying and mild processing. Food additives were screened for the ability to cause leakage of intracellular potassium ions; retention of these ions is vital for protecting Salmonella against desiccation. Two antimicrobial food additives, carvacrol and thymol, caused considerable potassium leakage from the desiccation-resistant S. enterica serovars, Tennessee and Livingstone. Thus, carvacrol and thymol were investigated for their ability to sensitize the desiccation-adapted S. enterica to heat treatment. The combined use of food additives, at their minimum inhibitory concentrations, with heat treatment at 55 °C for 15 min caused 3.1 ± 0.21 to more than 5.5 log colony forming unit (CFU)/mL reduction in desiccation-adapted S. enterica, compared to 2.4 ± 0.53–3.2 ± 0.11 log CFU/mL reduction by sole heat treatment. Carvacrol was the additive that caused the greatest potassium leakage and sensitization of Salmonella to heat; hence, the application of this compound was investigated in a food model against Salmonella Typhimurium ASD200. Addition of carvacrol at 200 or 500 ppm into liquid milk followed by spray-drying reduced the strain’s population by 0.9 ± 0.02 and 1.3 ± 0.1 log CFU/g, respectively, compared to 0.6 ± 0.02 log CFU/g reduction for non-treated spray-dried milk. Additionally, freeze-drying of milk treated with high levels of carvacrol (5000 ppm) reduced the population of Salmonella Typhimurium ASD200 by more than 4.5 log CFU/g, compared to 1.1 ± 0.4 log CFU/g reduction for the freeze-dried untreated milk. These findings suggest that carvacrol can combat desiccation-resistant S. enterica, and thus, potentially improve the safety of low-aw foods.

Charting the structural and thermodynamic determinants in phenolic acid natural product – cyclodextrin encapsulations

Cyclodextrins are pliable platforms that have served to optimize the pharmaceutic profile of numerous compounds and to enhance the stability of natural food additives. Caffeic and rosmarinic acid are natural products with proven health benefits, though their full therapeutic potential has not been exploited. To enhance their pharmaceutic profile, we developed cyclodextrin-based formulates and unveiled their thermodynamic and structural principles. The complexes’ stoichiometry was determined by ESI-MS. Solid-state and liquid NMR spectroscopy revealed the interactions and the topographical location of the caffeic and rosmarinic acid inside the cyclodextrin cavity. The theoretically analyzed HP-β-CD’s degree of substitution (DS) of caffeic and rosmarinic acids can explain the intensities obtained by 2D NOESY experiments. The thermodynamics and the affinity of the complexes were evaluated through isothermal titration calorimetry. In addition, the rosmarinic and caffeic acids as, also, their complexes showed considerable antimicrobial activity against common food spoilage and pathogenic bacteria. The generated data could provide the basis to understand the structural and thermodynamic determinants implicated in natural products – CD recognition and to develop platforms for the optimization of their pharmaceutical and stability profiles in order to be utilized as safe and stable natural antimicrobial food additives. Communicated by Ramaswamy H. Sarma

Food Preservatives Induce Proteobacteria Dysbiosis in Human-Microbiota Associated Nod2-Deficient Mice.

The worldwide incidence of many immune-mediated and metabolic diseases, initially affecting only the wealthy Western countries, is increasing rapidly. Many of these diseases are associated with the compositional and functional alterations of gut microbiota, i.e., dysbiosis. The most consistent markers of the dysbiosis are a decrease in microbiota diversity and an expansion of Proteobacteria. The role of food preservatives as potential triggers of gut microbiota dysbiosis has been long overlooked. Using a human microbiota-associated mouse model, we demonstrate that a mixture of common antimicrobial food additives induces dysbiosis characterised by an overgrowth of Proteobacteria phylum and a decrease in the Clostridiales order. Remarkably, human gut microbiota in a Nod2-deficient genetic background is even more susceptible to the induction of Proteobacteria dysbiosis by additives than the microbiota in a wild-type background. To conclude, our data demonstrate that antimicrobial food additives trigger gut microbiota dysbiosis in both wild-type and Nod2-deficient backgrounds and at the exposure levels reached in European populations. Whether this additive-modified gut microbiota plays a significant role in the pathogenesis of immune-mediated and metabolic diseases remains to be elucidated.

Human gut microbes are susceptible to antimicrobial food additives in vitro.

The aim of this work was to test the hypothesis that antimicrobial food additives may alter the composition of human gut microbiota by selectively suppressing the growth of susceptible gut microbes. To explore the influence of antimicrobial food additives on the composition of the human gut microbiota, we examined the susceptibility of both aerobic and anaerobic gut bacteria to sodium benzoate, sodium nitrite, and potassium sorbate, and their combinations, using a broth microdilution method. The tested bacteria exhibited a wide range of susceptibilities to food additives. For example, the most susceptible strain, Bacteroides coprocola, was almost 580 times more susceptible to sodium nitrite than the most resistant strain, Enterococcus faecalis. However, most importantly, we found that gut microbes with known anti-inflammatory properties, such as Clostridium tyrobutyricum or Lactobacillus paracasei, were significantly more susceptible to additives than microbes with known proinflammatory or colitogenic properties, such as Bacteroides thetaiotaomicron or Enterococcus faecalis. Our data show that some human gut microbes are highly susceptible to antimicrobial food additives. We speculate that permanent exposure of human gut microbiota to even low levels of additives may modify the composition and function of gut microbiota and thus influence the host's immune system. Whether the effect of additive-modified gut microbiota on the human immune system could explain, at least in part, the increasing incidence of allergies and autoimmune diseases remains to be shown.

Combinatorial effect of magnolia bark extract and ethyl lauroyl arginate against multi-species oral biofilms: Food additives with the potential to prevent biofilm-related oral diseases

The use of novel antimicrobial food additives that display anti-biofilm properties offers an alternative approach to prevent biofilm-related oral diseases. We evaluated the individual and combined effect of two food additives, magnolia bark extract (MBE) and ethyl-lauroyl-arginate (LAE), against multi-species oral biofilms. Using static and microfluidic in-vitro biofilm models, multi-species oral biofilms were treated with different concentrations of MBE, LAE or combinations of both. Biofilms were imaged using confocal laser scanning microscopy, and biomass, thickness and viability were determined. Both actives significantly reduced biomass, thickness and viability of developed biofilms, although some antimicrobial/anti-biofilm effects differed between the static and microfluidic models. When both actives were combined, the association of 0.005% MBE and 0.0025% LAE was the most effective. In conclusion, MBE and LAE exhibited anti-biofilm and antimicrobial effects. The combination of MBE and LAE improved their individual effect.

Physico-chemical and antimicrobial properties of d-limonene oil nanoemulsion stabilized by whey protein-maltodextrin conjugates.

In the present investigation d-limonene oil (4-isopropenyl-1-methylcyclohexene) was encapsulated by ultra-sonication method using whey protein (WP)-maltodextrin (MD) conjugates as coating material and their characterization was done with respect to physico-chemical and antimicrobial properties. Antimicrobial activity of limonene oil (LO) nanoemulsion and bulk LO dissolved in dimethyl sulphoxide (DMSO) were assessed by agar well diffusion method. Stable formulation of d-limonene oil nanoemulsion [5.0% LO + 9.0% WP-MD (1:2 w/w) conjugate] had shown mean particle size, zeta potential and poly dispersity index of 116.60 ± 5.30nm, - 19.64 ± 0.23mV and 0.205 ± 0.02 respectively. LO nanoemulsion were stable to different food processing conditions like heat treatments, ionic strength (0.1-1.0M) and pH (3.0-7.0). LO nanoemulsion was stable for 15days at 25°C and it had shown particle size of 332.20 ± 5.40nm at 15th day. It was observed that minimum inhibitory concentration (MIC) of both LO nanoemulsion and bulk LO dissolved in DMSO were at 12.50µl/ml against Bacillus cereus (ATCC 14459), Escherichia coli (ATCC 25922), Enterococcus faecalis (NCDC 115) and Salmonella typhi (NCDC 6017). Since d-limonene has been considered to be a safer alternative compared to synthetic antimicrobial food additives, the present investigation will be helpful in developing a more effective antimicrobial system for the production and preservation of foods.

Preparation and Characterisation of Carvacrol Encapsulated in Gellan Gum Hydrogel

Studies on plant materials as natural compound such as carvacrol (Carv) have gained much attention. Carv exhibits numerous potential as antimicrobial agent, food additives, antioxidant and etc. However, this free standing bioactive compound is unstable in the harsh environment conditions. Hence, the encapsulation technology provides protection to enhance the effectiveness in release manner. In this study, the preparation of Carv encapsulated in gellan gum hydrogel forming thin film (GG-Carv TF) was achieved by using 1.0 g of gellan gum at different concentrations of Carv (0.01-0.04 M). The FTIR spectra of GG-Carv TF revealed the combination of both functional groups from GG and Carv. The Carbon, Hydrogen and Nitrogen, CHN analysis further confirmed the encapsulation with the changes in the element percentage. Both swelling and degradation percentage increased with time and showed decreasing patterns in the range of 680.79-666.78 % and 26.83-19.15 % which can be observed as the concentration of Carv increased, respectively.

The invitro and invivo protective effects of tannin derivatives against Salmonella enterica serovar Typhimurium infection.

In this study, we investigated the protective effects of tannin-derived components, gallic acid (GA) and tannic acid (TA), invitro and invivo against Salmonella infection in mice. Both GA and TA showed antibacterial effects against Salmonella (S.) Typhimurium as well as inhibitory effects on the adherence, invasion, and intracellular growth of the pathogens in macrophages. Following a lethal dose of Salmonella infection in mice, reduced virulence in both GA- and TA-treated groups was observed based on reduced mortality rates. In the non-infected groups, the average weights of the spleens and livers of GA- or TA-treated mice were not significantly different with the control group. In addition, the average weights of these organs in all of the Salmonella-infected groups were not significantly different but the numbers of bacteria in the spleens and livers in both GA- and TA-treated mice were significantly reduced. The levels of cytokine production in non-infected mice revealed that GA-treated and TA-treated mice elicited an increased level of IFN-γ, and both IFN-γ and MCP-1, respectively, as compared with the PBS-treated group. These findings highlight the potential of GA and TA as alternatives for the treatment of salmonellosis and as supplements to conventional antimicrobial food additives.

Improving the water solubility and antimicrobial activity of silymarin by nanoencapsulation

The aims of this study were to improve the water solubility and antimicrobial activity of milk thistle silymarin by nanoencapsulation and to assess the functions of silymarin nanoparticle-containing film as an antimicrobial food-packaging agent. Silymarin nanoparticles were prepared using water-soluble chitosan (WCS) and poly-γ-glutamic acid (γ-PGA). As the WCS and silymarin concentrations increased, particle size and polydispersity index (PDI) significantly increased. Nanoencapsulation significantly improved the water solubility of silymarin 7.7-fold. Antimicrobial activity of silymarin was effectively improved when silymarin was entrapped within the nanocapsule compared to when it was not entrapped. Films incorporating silymarin nanoparticles had better antimicrobial activity than films incorporating free silymarin. The results suggest that silymarin nanoparticles have applications in antimicrobial food additives and food packing.

Oregano Essential Oil as an Antimicrobial and Antioxidant Additive in Food Products

ABSTRACTFood consumers and industries urged the need of natural alternatives to assure food safety and quality. As a response, the use of natural compounds from herbs and spices is an alternative to synthetic additives associated with toxic problems. This review discusses the antimicrobial and antioxidant activity of oregano essential oil (OEO) and its potential as a food additive. Oregano is a plant that has been used as a food seasoning since ancient times. The common name of oregano is given to several species: Origanum (family: Lamiaceae) and Lippia (family: Verbenaceae), amongst others. The main compounds identified in the different OEOs are carvacrol and thymol, which are responsible for the characteristic odor, antimicrobial, and antioxidant activity; however, their content may vary according to the species, harvesting season, and geographical sources. These substances as antibacterial agents make the cell membrane permeable due to its impregnation in the hydrophobic domains, this effect is higher against gram positive bacteria. In addition, the OEO has antioxidant properties effective in retarding the process of lipid peroxidation in fatty foods, and scavenging free radicals. In this perspective, the present review analyzes and discusses the state of the art about the actual and potential uses of OEO as an antimicrobial and antioxidant food additives.

Use of Antimicrobial Food Additives as Potential Dipping Solutions to Control Pseudomonas spp. Contamination in the Frankfurters and Ham.

This study evaluated the effect of sodium diacetate and sodium lactate solutions for reducing the cell count of Pseudomonas spp. in frankfurters and hams. A mixture of Pseudomonas aeruginosa (NCCP10338, NCCP10250, and NCCP11229), and Pseudomonas fluorescens (KACC10323 and KACC10326) was inoculated on cooked frankfurters and ham. The inoculated samples were immersed into control (sterile distilled water), sodium diacetate (5 and 10%), sodium lactate (5 and 10%), 5% sodium diacetate + 5% sodium lactate, and 10% sodium diacetate + 10% sodium lactate for 0-10 min. Inoculated frankfurters and ham were also immersed into acidified (pH 3.0) solutions such as acidified sodium diacetate (5 and 10%), and acidified sodium lactate (5 and 10%) in addition to control (acidified distilled water) for 0-10 min. Total aerobic plate counts for Pseudomonas spp. were enumerated on Cetrimide agar. Significant reductions (ca. 2 Log CFU/g) in Pseudomonas spp. cells on frankfurters and ham were observed only for a combination treatment of 10% sodium lactate + 10% sodium diacetate. When the solutions were acidified to pH 3.0, the total reductions of Pseudomonas spp. were 1.5-4.0 Log CFU/g. The order of reduction amounts of Pseudomonas spp. cell counts was 10% sodium lactate > 5% sodium lactate ≥ 10% sodium diacetate > 5% sodium diacetate > control for frankfurters, and 10% sodium lactate > 5% sodium lactate > 10% sodium diacetate > 5% sodium diacetate > control for ham. The results suggest that using acidified food additive antimicrobials, as dipping solutions, should be useful in reducing Pseudomonas spp. on frankfurters and ham.

Effects of nisin on the antimicrobial activity of d-limonene and its nanoemulsion

d-Limonene has been considered to be a safer alternative compared to synthetic antimicrobial food additives. However, its hydrophobic and oxidative nature has limited its application in foods. The purpose of this research was to study effects of nisin on the antimicrobial activity of d-limonene and its nanoemulsion and develop a novel antimicrobial delivery system by combining the positive effect of these two antibacterial agents at the same time. By the checkerboard method, both the synergistic and additive effects of d-limonene and nisin were found against four selected food-related microorganisms. Then, d-limonene nanoemulsion with or without nisin was prepared by catastrophic phase inversion method, which has shown good droplet size and stability. The positive effects and outstanding antimicrobial activity of d-limonene nanoemulsion with nisin were confirmed by MICs comparison, scanning electron microscopy and determination of cell constituents released. Overall, the research described in the current article would be helpful in developing a more effective antimicrobial system for the production and preservation of foods.

Egyptian honeybee pollen as antimicrobial, antioxidant agents, and dietary food supplements

In this study, three Egyptian bee pollen types from different plant sources, namely maize (Zea mays), clover (Trifolium alexandrinum), and date palm (Phoenix dactylifera), were evaluated as natural antimicrobial agents, antioxidants, and food additives. A methanolic extract of maize bee pollen exhibited the highest antibacterial activity, followed by clover and date palm bee pollen. Staphylococcus aureus and Escherichia coli were the most sensitive, followed by Listeria monocytogenes, Salmonella enteritidis, and Pseudomonas aeruginosa. In ghee, all methanolic extracts, especially that of maize bee pollen, showed high antioxidant activities as radical scavenger substances and as inhibitors of lipid peroxidation. Sensory evaluation of yoghurt supplemented with different bee pollens revealed that maize bee pollen improve texture, increased gel strength, and decreased syneresis and had favorable nutty flavor, while clover and date palm pollen added a sweet taste and bean-like flavor, respectively. These findings establish the potential of Egyptian maize and clover bee pollen as antioxidants, antimicrobial agents, promising natural food supplements, and natural preservatives.

Effects of cyclodextrins on the antimicrobial activity of plant-derived essential oil compounds

Essential oils (EOs) from plants are considered to be a safer alternative when compared to synthetic antimicrobial food additives. However, a major drawback of many EOs is their hydrophobic nature, which makes them insoluble in water based media and matrices. Although cyclodextrins (CDs) can increase the solubility of EO compounds, the effects of CDs on the antimicrobial activity of EOs have not been reported. In this paper, four different EO compounds (carvacrol, eugenol, linalool and 2-pentanoylfuran) were chosen to study the influence of CDs on the solubility and antimicrobial activity on bacteria and yeast. The greatest enhancement with regards to solubility of the four test compounds was achieved by hydroxypropyl-β-CD. In most instances, not only were the minimal antimicrobial concentrations of EO compounds decreased, but the interactivity of two combined EO compounds could be strengthened by the co-addition of CDs. Furthermore, the combination of carvacrol with hydroxypropyl-β-CD caused a marked change in the major membrane lipid composition of all microorganisms investigated; while scanning electron microscopy revealed that cellular integrity was significantly affected by 2× MIC, ultimately resulting in cell lysis.