Assessment of Oligogalacturonide from Citrus Pectin as a Potential Antibacterial Agent against Foodborne Pathogens

Foodborne diseases are an important public health problem in the world. The bacterial resistance against presently used antibiotics is becoming a public health issue; hence, the discovery of new antimicrobial agents from natural sources attracts a lot of attention. Antibacterial activities of oligogalacturonide from commercial microbial pectic enzyme (CPE) treated citrus pectin, which exhibits antioxidant and antitumor activities, against 4 foodborne pathogens including Salmonella Typhimurium, Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas aeruginosa was assessed. Pectin hydrolysates from CPE hydrolysis exhibited antibacterial activities. However, no antibacterial activity of pectin was observed. Citrus oligogalacturonide from 24‐h hydrolysis exhibited bactericidal effect against all selected foodborne pathogens and displayed minimal inhibitory concentration at 37.5 μg/mL for P. aeruginosa, L. monocytogenes, and S. Typhimurium, and at 150.0 μg/mL for S. aureus.     

Antioxidant and Antibacterial Activities on Foodborne Pathogens of Artocarpus heterophyllus Lam. (Moraceae) Leaves Extracts

Abstract: Total water extract, ethyl acetate, and aqueous fractions from the leaves of Artocarpus heterophyllus were evaluated for phenolic content, antioxidant, and antibacterial activities against some foodborne pathogens such as E. coli, Listeria monocytogenes, Salmonella typhimurium, Salmonella enterica, Bacillus cereus, Enterococcus faecalis, and Staphylococcus aureus. The minimum inhibitory concentration (MICs) of extract and fractions determined by the agar dilution method were ranged from 221.9 μg/mL for ethyl acetate fraction to 488.1 μg/mL for total extract. In the agar diffusion method the diameters of inhibition were 12.2 for the total extract, 10.7 and 11.5 for ethyl acetate and aqueous fractions, respectively. A. heterophyllus showed significant antioxidant activity tested in different in vitro systems (DPPH, ABTS, FRAP, and Fe²⁺ chelating activity assay). In particular, in DPPH assay A. heterophyllus total extract exhibited a strong antiradical activity with an IC₅₀ value of 73.5 μg/mL while aqueous fraction exerted the highest activity in FRAP assay (IC₅₀ value of 72.0 μg/mL). The total phenols content by Folin–Ciocalteau method was determined with the purpose of testing its relationship with the antioxidant and antibacterial activities. Practical Application: The appearance of food is one of the major determinants of its appeal to consumers and consequently, sales of the product. Microbial contamination and lipid oxidation are the main factors that determine food quality loss and shelf-life reduction. Therefore, preventing microbial contamination and delaying lipid oxidation are highly relevant to food processors. The growth of microorganisms in food products may cause spoilage or foodborne diseases. Oxidative processes in food products lead to the degradation of lipids and proteins which, in turn, contribute to the deterioration in flavor, texture, and color of the products. A. heterophyllus leaves extracts demonstrated interesting biological properties that suggest its use as a new potential source of natural antioxidant and antimicrobial agent.     

Antimicrobial Efficacy of Poly (DL‐lactide‐co‐glycolide) (PLGA) Nanoparticles with Entrapped Cinnamon Bark Extract against Listeria monocytogenes and Salmonella typhimurium

Nanoencapsulation of active compounds using poly‐(d,l ‐lactide‐co‐glycolide) (PLGA) is commonly used in the pharmaceutical industry for drug delivery and may have important applications in the food industry. Control of growth of foodborne bacteria with the goals of reducing the number of foodborne illness outbreaks, assuring consumers a safer food supply remains a priority in the food industry. Natural antimicrobials are an excellent way to eliminate pathogens without introducing chemical preservatives that consumers may find undesirable. Cinnamon bark extract (CBE) is an effective pathogen inhibitor isolated from cinnamon spice. PLGA nanoparticles containing CBE were produced using an emulsion‐solvent evaporation method and characterized for size, polydispersity, morphology, entrapment efficiency, in vitro release and pathogen inhibition. PLGA with 2 different ratios of lactide to glycolide (65:35 and 50:50) were used to determine how polymer composition affected nanoparticle characteristics and antimicrobial potency. The size of the nanoparticles ranged from 144.77 to 166.65 nm and the entrapment efficiencies of CBE in 65:35 PLGA and 50:50 PLGA were 38.90% and 47.60%, respectively. The in vitro release profile at 35 °C showed an initial burst effect for both types of PLGA followed by a more gradual release of CBE from the polymer matrix. Both types of PLGA nanoparticles loaded with CBE were effective inhibitors of Salmonella enterica serovar Typhimurium and Listeria monocytogenes after 24 and 72 h at concentrations ranging from 224.42 to 549.23 μg/mL. The PLGA encapsulation improved delivery of hydrophobic antimicrobial to the pathogens in aqueous media.     

Bactericidal Activities of Health‐Promoting,Food‐Derived Powders Against the Foodborne Pathogens Escherichia coli,Listeria monocytogenes,Salmonella enterica,and Staphylococcus aureus

We evaluated the relative bactericidal activities (BA₅₀) of 10 presumed health‐promoting food‐based powders (nutraceuticals) and, for comparison, selected known components against the following foodborne pathogens: Escherichia coli O157:H7, Salmonella enterica, Listeria monocytogenes, and Staphylococcus aureus. The relative activities were evaluated using quantitative bactericidal activity [(BA₅₀ value, defined as the percentage of the sample in the assay mixture that resulted in a 50% decrease in colony forming units]. The BA₅₀ values were determined by fitting the data to a sigmoidal curve by regression analysis using concentration–antimicrobial response data. Antimicrobial activity is indicated by a low BA₅₀ value; meaning less material is needed to kill 50% of the bacteria. Olive pomace, olive juice powder, and oregano leaves were active against all 4 pathogens, suggesting that they behave as broad‐spectrum antimicrobials. All powders exhibited strong antimicrobial activity against S. aureus. The following powders showed exceptionally high activity against S. aureus (as indicated by the low BA₅₀ values shown in parentheses): apple skin extract (0.002%); olive pomace (0.008%); and grape seed extract (0.016%). Listeria bacteria were also highly susceptible to apple skin extract (0.007%). The most active substances provide candidates for the evaluation of antimicrobial effectiveness in human food and animal feed. Practical Application : Plant‐derived health‐promoting food supplements, high in bioactive compounds, are candidates for use as antimicrobials in food.     

Enhanced antimicrobial activity of nisin in combination with allyl isothiocyanate against Listeria monocytogenes,Staphylococcus aureus,Salmonella Typhimurium and Shigella boydii

This study was designed to evaluate the synergistic antimicrobial effect of nisin and allyl isothiocyanate (AITC) against Listeria monocytogenes, Staphylococcus aureus, Salmonella Typhimurium and Shigella boydii. The synergistic interactions between nisin and AITC were observed against all foodborne pathogens, showing the fractional inhibitory concentrations <1. The populations of L. monocytogenes and S. aureus at the combined treatment of nisin and AITC were decreased to below 1 log CFU mL^?1 after 10‐h incubation at 37 °C. The changes in fatty acid profiles of all strains were substantially influenced by nisin alone and the combined treatment of nisin and AITC. A good agreement was observed among cell viability, membrane permeability and depolarisation activity in response to nisin and AITC. The results suggest that nisin and AITC as synergistic inhibitors could be an effective approach to achieve satisfactory antimicrobial activity against a wide range of foodborne pathogens.     

Hurdle Effect of Antimicrobial Activity Achieved by Time Differential Releasing of Nisin and Chitosan Hydrolysates from Bacterial Cellulose

We investigated the combined antimicrobial effect of nisin and chitosan hydrolysates (CHs) by regulating the antimicrobial reaction order of substances due to differential releasing rate from hydroxypropylmethylcellulose‐modified bacterial cellulose (HBC). The minimum inhibitory concentration of nisin against Staphylococcus aureus and that of CHs against Escherichia coli were 6 IU and 200 μg/mL, respectively. Hurdle and additive effects in antimicrobial tests were observed when nisin was used 6 h before CH treatment against S. aureus; similar effects were observed when CH was used before nisin treatment against E. coli. Simultaneously combined treatment of nisin and CHs exhibited the low antimicrobial effect. HBC was then selected as the carrier for the controlled release of nisin and CHs. A 90% inhibition in the growth of S. aureus and E. coli was achieved when 30 IU‐nisin‐containing HBC and 62.5 μg/mL‐CH‐containing HBC were used simultaneously. The controlled release of nisin and CHs by using HBC minimized the interaction between nisin and CHs as well as increased the number of microbial targets.     

Antimicrobial activity of Yerba Mate (Ilex paraguariensis) aqueous extracts against Escherichia coli O157:H7 and Staphylococcus aureus

Abstract: Bioactive compounds from natural plant sources are becoming increasingly important to the food industry. Ilex paraguariensis is used in the preparation of a widely popular tea beverage (Yerba Mate) in the countries of Uruguay, Paraguay, Argentina, and Brazil. In this study, extracts of 4 brands of commercial tea, derived from the holly plant species, Ilex paraguariensis, were evaluated for their ability to inhibit or inactivate bacterial foodborne pathogens. The ultimate goal was to evaluate potential use of the extracts in commercial applications. Dialyzed aqueous extracts were screened for antimicrobial activity against Escherichia coli O157:H7 and Staphylococcus aureus. S. aureus was found to be the more sensitive to extracts than E. coli O157:H7. Minimum bactericidal concentrations (MBCs) were determined to be approximately 150 to 800 μg/mL and 25 to 50 μg/mL against E. coli O157:H7 and S. aureus, respectively. A Uruguayan brand had reduced activity against E. coli O157:H7 compared to the Argentinean brands tested. It was concluded that Yerba Mate could be used as a potential antimicrobial in foods and beverages against these pathogenic bacteria. Practical Application: Soluble extracts from Yerba Mate are natural antimicrobials that can be incorporated into food products to achieve longer shelf life.     

SSEL,a selective enrichment broth for simultaneous growth of Salmonella enterica,Staphylococcus aureus,Escherichia coli O157: H7, and Listeria monocytogenes

Salmonella enterica, Staphylococcus aureus, Escherichia coli O157: H7, and Listeria monocytogenes may contaminate similar types of food and cause foodborne disease. The objective of this study was to develop a selective enrichment broth for simultaneous enrichment of Salmonella enterica, Staphylococcus aureus, Escherichia coli O157: H7, and Listeria monocytogenes (SSEL) using nalidixic acid, acriflavine, lithium chloride, and sodium cholate as selective agents. Developed SSEL broth not only enriched the target pathogens to 5 log10 CFU/ml after 18 hr incubation at 37°C with 10–100 CFU/mL of inoculation concentration, but also could successfully support the simultaneous enrichment of target pathogens with similar growth rates and inhibit the growth of most nontarget bacteria effectively. The enrichment effect of SSEL was confirmed by artificial contamination test coupled with multiplex PCR. In summary, SSEL has been shown to be a promising multiplex selective enrichment broth for the detection of the four pathogens on a single-assay platform.     

Inhibitor‐Assisted High‐Pressure Inactivation of Bacteria in Skim Milk

The combined inactivation effects of high hydrostatic pressure (HHP) and antimicrobial compounds (potassium sorbate and ε‐polylysine [ε‐PL]) on 4 different bacterial strains present in skim milk and the effect of these treatments on milk quality were investigated in this study. HHP treatment at 500 MPa for 5 min reduced the populations of Escherichia coli, Salmonella enterica Typhimurium, Listeria monocytogenes, and Staphylococcus aureus from 6.5 log colony‐forming units (CFUs) or higher to less than 1 log CFU/mL. Compared to HHP alone, HHP with potassium or ε‐PL resulted in significantly higher reductions in the bacterial counts. After 5 min of treatment with HHP (500 MPa) and ε‐PL (2 mg/mL), no growth of E. coli, S. enterica Typhimurium, or L. monocytogenes in skim milk was observed during 15 d of refrigerated storage (4 ± 1 °C). Scanning electron microscopy analysis revealed that the synergistic treatments caused more serious damage to the bacterial cell walls. Quality assessments of the treated samples indicated that the combined treatments did not influence the color, the turbidity, the concentrations of –SH group of the proteins, or the in vitro digestion patterns of the milk. This study demonstrates that HHP with potassium or ε‐PL may be useful in the processing of milk or milk‐containing foods.     

Antimicrobial activity of greater galangal [Alpinia galanga (Linn.) Swartz.] flowers

Using the agar disc diffusion method, the potential antimicrobial activity of edible galangal [Alpinia galanga (Linn.) Swartz.] flower against Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus, and Shigella, and the effects of different drying methods and solvent types on the flowers’ antimicrobial activity were investigated. Oven-dried ethanol (OD Ethanol) extract from galangal flower was the most effective against S. aureus with inhibition zone of about 26–31 mm and the minimum inhibitory concentration (MIC) ranging from 0.352–0.547 mg/mL. No antimicrobial activity was observed on E. coli O157:H7 and Salmonella. Overall antimicrobial activity of oven-dried samples extracted with ethanol (OD Ethanol) was the highest with inhibition zone of 8.94 mm and MIC of 1.457 mg/mL. In contrast, freeze-dried samples extracted with ethanol (FD Ethanol) exhibited the lowest overall antimicrobial activity (7.05 mm and 2.470 mg/mL). This is the first report describing antimicrobial activity of galangal flowers against Grampositive S. aureus.     

陕西省常见食源性致病菌耐药性研究进展

近年来食品安全问题层出不穷,而食源性致病菌则是引起食品安全问题的主要因素之一,严重危害了人类的健康.引发食源性疾病的常见致病菌主要有大肠杆菌、沙门氏菌、金黄色葡萄球菌、单核细胞增生李斯特菌等.研究表明,在过去的几十年里,由于在医疗、养殖业等领域中过度使用抗生素,造成细菌耐药现象日趋严重,这更加重了食源性致病菌的潜在危险...     

Stability and Antimicrobial Activity of Allyl Isothiocyanate during Long-Term Storage in an Oil-in-Water Emulsion

Abstract: This study investigated the stability and antimicrobial activity of allyl isothiocyanate (AITC) in medium chain triglyceride (MCT) or soybean oil (SBO) dispersed in an oil-in-water (o/w) system during long-term storage. Oil type, content, and oxidative stability affect the stability and antimicrobial activity of AITC during storage. High oil content is favorable for AITC stability in the emulsion. Notably, AITC with MCT is more stable than AITC with SBO with the same oil content. Consequently, AITC with MCT is more effective than AITC with SBO in inhibiting G(−) bacteria (E. coli O157:H7, Salmonella enterica, and Vibrio parahaemolyticus) and G(+) bacteria (Staphylococcus aureus and Listeria monocytogenes).     

Antimicrobial Effects of Lactoferrin, Lysozyme, and the Lactoperoxidase System and Edible Whey Protein Films Incorporating the Lactoperoxidase System Against Salmonella enterica and Escherichia coli O157:H7

Lactoferrin (LF), lysozyme (LZ), the lactoperoxidase system (LPOS), and edible whey protein isolate (WPI) films incorporating LPOS were studied for inhibition of Salmonella enterica and Escherichia coli O157:H7. Antimicrobial effects of LF (5 to 40 mg/mL), LZ (1 to 20 mg/mL), and LPOS (0.5% to 5.0% [w/v] [0.03–.25 g/g, dry basis]) were examined by measuring turbidity of antimicrobial‐containing media after inoculation and by examining cell inhibition by WPI films incorporating LPOS (LPOS‐WPI films) on an agar recovery medium. Elastic modulus (EM), tensile strength (TS), percent elongation (%E), oxygen permeability (OP), and Hunter L, a and b of WPI films incorporating 0.03 to 0.25 g/g of LPOS were compared with those of plain WPI films without LPOS. The growth of S. enterica and E. coli O157:H7 (4 log colony‐forming units [CFU]/mL) in tryptic soy broth (TSB) was not prevented by LF at ≥20 and ≥40 mg/mL, respectively. S. enterica and E. coli O157:H7 in TSB were not inhibited by LZ at ≥ 6 and ≥ 20 mg/mL, respectively. LPOS at concentrations of 2.75% (w/v) and 1.0% (w/v) reduced S. enterica and E. coli O157:H7 to below the limit of detection (1 CFU/mL) in TSB, respectively. LPOS‐WPI films (0.15 g/g) completely inhibited S. enterica and E. coli O157:H7 (4 log CFU/cm²), inoculated either onto agar before placing the film disc or onto top of the film disc. Incorporation of 0.25 g/g of LPOS decreased EM, TS, and %E. The oxygen barrier property of WPI films was improved with the incorporation of LPOS at 0.15 to 0.25 g/g.     

Rational construction of citrus essential oil nanoemulsion with robust stability and high antimicrobial activity based on combination of emulsifiers

We have successfully constructed citrus essential oil (CEO, d-limonene is its main active component) nanoemulsion by the high-pressure homogenization method, whose droplet size, polydispersity index, and zeta potential were 34.23 nm, 0.235, and −25.87 mV, respectively. The effects of thermal treatment (−20–48 °C), pH (5–9), ionic strength (100–500 mM NaCl) and storage time (200 days) were examined on the physicochemical properties of all treatments. The antimicrobial activity of nanoemulsion was tested by determining the minimal inhibitory concentration against the four foodborne microorganisms (Escherichia coli (10 mg/mL), Staphylococcus aureus (0.150 mg/mL), Bacillus subtilis (0.312 mg/mL) and Saccharomyces cerevisiae (0.312 mg/mL)). Especially, compared with pure CEO, the antibacterial activity of its nanoemulsion against S. aureus (0.150 mg/mL) and B. subtilis (0.312 mg/mL) was increased by 43 and 86 times respectively. Industrial relevance: In this work, we constructed robust CEO nanoemulsions based on a combination of emulsifiers via the high-pressure homogenization method, which bring new insights into the preparation of nanoemulsions. There is great potential for nanoencapsulation of natural compounds in the field of food preservation. Furthermore, the results may provide valuable data for industrial scale-up application.     

Effect of Chitosan Physical Form on Its Antibacterial Activity Against Pathogenic Bacteria

The antibacterial activity of chitosan (CS) nanospheres, in comparison with other physical forms, was investigated against Salmonella enterica serovar Typhimurium and Staphylococcus aureus, which are 2 foodborne harmful pathogens. Results showed that the antibacterial efficacy of CS nanospheres: (1) was superior to that displayed by CS in powder and solution form; (2) was higher against S. aureus than against Salmonella Typhimurium; and (3) was dependent on the temperature and pH of the medium depending on the strain. For S. Typhimurium, a higher activity was displayed at 37 °C, in which 99.9% of the population was eradicated independently of the pH, followed by 20 °C and 7 °C, in which acidic pH conditions favored a higher susceptibility of bacteria to the effect of CS. On the contrary, S. aureus was less susceptible to the pH and temperature conditions of the medium, and no statistical difference in the antibacterial effect was observed for pH 5.8 and 8.0 at 20 °C and 37 °C. However, at 7 °C a slightly higher activity was displayed at pH 5.8 than at 8.0.     

Chemical Composition and Antioxidative Activity of Echinophora platyloba DC. Essential Oil,and Its Interaction with Natural Antimicrobials against Food‐Borne Pathogens and Spoilage Organisms

Abstract: This study was undertaken to determine the chemical composition and antioxidative capacity of Echinophora platyloba DC. essential oil, and its antimicrobial potency against Listeria monocytogenes, Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Salmonella typhimurium, Escherichia coli O157:H7, Pseudomonas aeruginosa, Candida albicans, Candida tropicalis, Rhodotorula rubra, and Rhodotorula mucilaginosa. The essential oil was analyzed by GC and GC‐MS; and evaluated for its antioxidative and antimicrobial (singly or in combination with chitosan, nisin, monolaurin, or amphotericin B) activity. Thirty‐three components were characterized representing 95.69% of the total oil composition in which thymol, trans‐ocimene, carvacrol, and (E)‐sesqui‐lavandulol were the major constituents. The oil exhibited high scavenging (IC₅₀: 49.7 ± 2.3 μg/mL) and relative antioxidative activity (RAA%: 85.21 ± 0.4) in 1,1‐diphenyl‐2‐picrylhydrazyl radicals and β‐carotene/linoleic acid bleaching assays, respectively. The oil showed antimicrobial activity against L. monocytogenes, B. cereus, B. subtilis, S. aureus, S. typhimurium, E. coli O157:H7, P. aeruginosa, C. albicans, C. tropicalis, R. Rubra, and R. mucilaginosa. Moreover, R. mucilaginosa and P. aeruginosa were the most susceptible and most resistant organisms, respectively. Regarding the checkerboard data, 47 fractional inhibitory concentration index (FICIs) (≤0.5) indicated synergistic, whereas 7 FICIs (>0.5 to 1) indicated additive effect. Consequently, E. platyloba DC. essential oil could be used as a recommended natural antioxidant and antimicrobial substance for food preservation.     

Variability of<Emphasis Type="Italic"> Satureja cuneifolia</Emphasis> Ten. essential oils and their antimicrobial activity depending on the stage of development

The essential oils obtained from Satureja cuneifolia Ten. harvested in the central part of Dalmatia at three ontogenetic stages were evaluated for their chemical composition and antimicrobial activity against food pathogens. The GC/MS analyses allowed 32 compounds to be determined; the main constituents of the essential oils were linalool (18.2–17.2%), carvacrol (16.0–5.0%), p-cymene (14.8–4.0%), -pinene (12.0–5.8%) and limonene (11.0–1.8%). The compounds linalool and borneol appeared to be relatively constant but carvacrol, limonene and -pinene showed variability during the growth cycles. The oils had a broad-spectrum antimicrobial activity against food pathogens in broth microdilution bioassays. Maximum activity was observed against the yeast Candida albicans, the Gram-negative bacteria Escherichia coli, Salmonella typhimurium and Proteus mirabilis and the Gram-positive bacteria Staphylococcus aureus and Bacillus cereus. The essential oils showed good antibacterial effects against E. coli with a minimum inhibitory concentration of 0.06% and a minimum bactericidal concentration of 0.12% during the flowering stage. These inhibitory effects are interesting in relation to the prevention of microbial contamination in many foods and, therefore, essential oils of S. cuneifolia could be used as substitutes for synthetic antimicrobial compounds.     

Evaluation of Thin Agar Layer Method for Recovery of Heat-Injured Foodborne Pathogens

ABSTRACT The Thin Agar Layer (TAL) method of Kang and Fung 1998 was used to enumerate heat‐injured (55 °C for 10 min) foodborne pathogens. This method involves overlaying 14 mL of nonselective medium (Tryptic Soy Agar, TSA) onto a prepoured, pathogen‐specific, selective medium. The recovery rate with the TAL method was compared with the rate for TSA and pathogen‐specific, selective media. No significant differences occurred between TSA and TAL (P > 0.05) for enumeration of heat‐injured Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, Staphylococcus aureus, and Yersinia enterocolitica, and both recovered significantly higher numbers than selective media (P < 0.05). The TAL method is a 1‐step, convenient procedure for recovery of heat‐injured cells.     

Short communication: Screening inhibition of dairy-relevant pathogens and spoilage microorganisms by lactose oxidase

The inhibitory effect of lactose oxidase on the growth of foodborne pathogens and spoilage microorganisms associated with dairy products was evaluated through an overlay inhibition assay. Lactose oxidase generates hydrogen peroxide via lactose oxidation into lactobionic acid. Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica ser. Typhimurium, Staphylococcus aureus, Pseudomonas fragi, and Penicillium chrysogenum were used as indicators. A commercially available solution of lactose oxidase was applied at different concentrations (0, 0.12, 1.2, and 12 g/L) in 4 types of media [brain heart infusion agar (BHI), BHI + sodium thiocyanate (NaSCN), BHI + lactose, and BHI + NaSCN + lactose] to evaluate the effect of lactose and thiocyanate on microbial inhibition. Lactose oxidase inhibited the growth of all the indicators at a concentration of 12 g/L of the enzyme solution in the presence of lactose alone and in combination with NaSCN. However, supplementation with NaSCN had no effect on the magnitude of microbial inhibition. Staphylococcus aureus was the most sensitive pathogen, and Ps. fragi was the most sensitive of all the indicators in general to lactose oxidase. Listeria monocytogenes and Ps. fragi showed higher susceptibility to the antimicrobial effect of lactose oxidase at 6°C than at their corresponding optimum growth temperature. The inhibitory effect was attributed to the generation of hydrogen peroxide from the oxidation of lactose. Findings from this study demonstrate that lactose oxidase could be used as a novel approach to inhibit the growth of mold and bacteria. It could also be applied as a label-friendly preservative in dairy foods.     

Antioxidant and antimicrobial properties of Thai propolis extracted using ethanol aqueous solution

The potential of using propolis collected from Thailand as a natural antioxidant and antimicrobial agent for food applications was investigated. The propolis extract was prepared by using different ethanol aqueous solutions, including 30%, 40%, 50% and 70%. Total phenolic content (TPC), phenolic compound and antioxidant activity of the propolis were determined using Folin–Ciocalteau method, high performance liquid chromatography (HPLC) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging activity, respectively. The antimicrobial ability was tested against Staphylococcus aureus (TISTR 118), Salmonella enteritidis (DMST 17368), Escherichia coli (TISTR 780) and Pseudomonas aeruginosa (ATCC 27853) using disc diffusion technique. The major phenolic compounds found in Thai propolis were rutin, quercetin and naringin. The TPC and DPPH radical scavenging activity increased with increasing ethanol concentration in the solvent. Propolis extract showed antimicrobial activity, in terms of inhibitory zone for S. aureus and limited growth underneath paper discs, against all tested bacteria.