Arcopilus eremanthusum sp. nov. as sources of antibacterial and antioxidant metabolites.

In this study, we evaluated the antibacterial and antioxidant activities of ethyl acetate (EtOAc) extracts of Arcopilus eremanthusum sp. nov. (CML3766) isolated from E. erythopappus. The fungi were identified using the sequences of the internal transcribed spacer (ITS), large subunit (LSU), and RNA polymerase II second largest subunit (RPB2). Antibacterial activity was determined using the minimum bactericidal concentration (MBC) method. Antioxidant activity was evaluated using free radical scavenging methods with 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS•+) assays and the ß-carotene-linoleic acid system. The total phenolic compound content was measured using the Folin-Ciocalteu method. The endophytic fungal extract presented bactericidal activity, with an MBC of 2.44 and 19.5 µg/mL against Staphylococcus aureus GL 8702 and GL 5674, respectively, and 625 µg/mL for Salmonella enterica serovar Enteritidis. In addition, this fungus demonstrated an antioxidant activity of 52.30% protection in the ß-carotene method. The total concentration of phenolic compounds was 23.73 mg gallic acid equivalent (GAE)/g. Ferulic acid, trans-cinnamic acid, chlorogenic acid, catechin, vanillin, p-coumaric acid, and caffeic acid were quantified using high-performance liquid chromatography with diode array detection. The results demonstrate the potential of A. eremanthusum sp. nov. to serve as a source of antibacterial and antioxidant metabolites with possible future biotechnological applications.

Effect of Brazilian green propolis on microorganism contaminants of surface of Gorgonzola-type cheese.

Blue cheeses are susceptible to yeast and bacterial growth on their surface, which causes spoilage during ripening process and the formation of slime. The dairy industry frequently control the proliferation of undesirable microorganisms with natamycin and high salt concentration. The green propolis is a complex of substances that presents antimicrobial properties with great potential as preservative in the food industry. The aims of the present study were to identify the mesophilic aerobic microorganisms present on the surface of Gorgonzola-type cheese, evaluate the antifungal and antibacterial effects of the ethanol extract of green propolis (EEP) on the development of those microorganisms and verify the effects of EEP on the sensory quality of cheese. Ten yeast species belonging to genera Yarrowia, Candida, Debaryomyces and Saccharomyces were identified, as well as seven species of bacteria belonging to genera Staphylococcus, Bacillus, Enterococcus, Corynebacterium and Proteus. The EEP showed minimum biocide concentration (MBC), between 0.3% (weight/weight) and 5% for Bacillus cereus and Proteus vulgaris, respectively. Saccharomyces cerevisiae was the most sensitive species (MBC of 0.63%) and Candida parapsilosis the most resistant one (MBC of 5%). In the sensory analysis, the cheeses involved with EEP at 5% concentration did not differ from the control, while at 10%, there was a slight decrease in acceptance. The EEP has potential and feasibility to be used in Gorgonzola-type cheese, inhibiting the main bacteria and yeasts without affecting largely the sensory characteristics of the product.

Technological and sensory characteristics in development of innovative symbiotic boneless dry-cured lamb meat snack.

Novel shelf-stable and high-protein meat products that are affordable, convenient, and healthy are hot topic in current food innovation trends. To offer technological databases for developing new functional lamb meat products, this study aimed to evaluate the technological and sensory aspects of dry-cured lamb meat snacks incorporated with the probiotic culture Lactobacillus paracasei and the prebiotic lactulose. Four formulations were analyzed: control (without prebiotic or probiotic); PREB (with 2% lactulose); PROB (with 107 CFU/g of L. paracasei); and SYMB (with 2% lactulose and 107 CFU/g of L. paracasei). Fitted curves revealed that weight-loss behavior during snack ripening was not affected (P > 0.05) by treatments. Snack moisture, water activity, pH, titratable acidity, lipid oxidation, and residual nitrite were affected (P < 0.05) only by ripening time. The target probiotic strain stood out against competitive flora and was detected at 107 CFU/g in the snack-supplemented formulations (PROB and SYMB). In snacks supplemented with prebiotics (PREB and SYMB), the lactulose content was maintained at 2.17%. Significant differences were not observed in the chemical composition, texture profiles, and CIE color indices between the proposed functional snacks and the control. In addition to texture, flavor, and overall impression evaluation, only color attributes were positively impacted (P < 0.05) in the acceptance and multiple comparison tests against the control. The proposed formulation and bench process parameters produced potential nutritionally and sensory-appreciated, microbiologically stable, and safe (multi-hurdle perspective) functional high-protein restructured lamb snacks.

Reduction of Aeromonas hidrophyla biofilm on stainless stell surface by essential oils.

This study demonstrates the possibility of using sanitizing detergents based on natural products for the elimination and/or reduction of Aeromonas hydrophila biofilm formed on stainless steel surfaces. The goal of this work was to determine the reduction effect of sanitizing detergents containing essential oils of Thymus vulgaris (thyme) and Cymbopogon citratus (lemongrass) on biofilm formed by A. hydrophila on AISI 304 stainless steel coupons, using UHT skimmed milk as substratum. There was adhesion and biofilm formation by A. hydrophila at 28 °C, presenting 7.60 log cfu.cm(-2) after the fourth day of cultivation. There was no significant difference between the lemongrass treatment and that of the thyme oil (p < 0.05). However, both treatments significantly reduced the biofilm, differing significantly from the NaOH control (p > 0.05). The treatment with lemongrass solution reduced the biofilm by 4.51 log cfu cm(-2) at 25 °C. The thyme detergent also reduced the number of cfu cm(-2) by 3.84 log cycles at 25 °C. The use of the lemongrass and thyme solutions efficiently reduced the A. hydrophila biofilm.

Homologous and Heterologous Adaptation and Thermochemical Inactivation of Staphylococcus aureus with Exposure to Cinnamaldehyde.

ABSTRACT: Staphylococcus aureus causes food intoxication and can become resistant to a large number of antibacterial drugs. Thus, there is a growing interest in understanding the mechanisms involved in the adaptation of bacterial cells to environmental stresses or to antimicrobial agents. In this context, we evaluated the cinnamaldehyde (CIN) MBC for two contaminating food strains of S. aureus (GL 5674 and GL 8702) and tested the hypothesis that exposure of these strains to sublethal CIN concentrations and pH values could increase their resistance to this antimicrobial agent, to acid stress, and also to stress at high temperatures. Thus, the ability of the strains to adapt to CIN and acid stress was evaluated, as well as the cross-adaptation between acid stress and CIN. Strains GL 5674 and GL 8702 of S. aureus are sensitive to CIN in MBCs of 0.25 and 0.5% respectively, proving the antibacterial potential of this compound, but we proved the hypothesis of homologous adaptation to CIN. The strains grew in concentrations higher than the MBC after being previously exposed to sublethal concentrations of CIN. We also observed heterologous adaptation of the strains, which after exposure to the minimum pH for growth, were able to grow in concentrations of CIN greater than the MBC. GL 5674 showed greater adaptive plasticity, considerably reducing its minimum inhibitory pH and increasing its MBC after adaptation. Our results show a positive effect of adaptation to CIN on the resistance of S. aureus (P < 0.0001) to CIN at a temperature of 37°C. However, in the absence of adaptation, the presence of CIN in S. aureus cultures maintained at 37°C showed an efficient bactericidal effect associated with increased exposure time. Our results call attention to the conscious use of CIN as an antimicrobial agent and present the possibility of using CIN, in association with a temperature of 37°C and an exposure time of 35 min, as a promising measure for the elimination of pathogenic strains.

Biofilm formation by Listeria monocytogenes on stainless steel surface and biotransfer potential.

An experimental model was proposed to study biofilm formation by Listeria monocytogenes ATCC 19117 on AISI 304 (#4) stainless steel surface and biotransfer potential during this process. In this model, biofilm formation was conducted on the surface of stainless steel coupons, set on a stainless steel base with 4 divisions, each one supporting 21 coupons. Trypic Soy Broth was used as bacterial growth substrate, with incubation at 37 °C and stirring of 50 rpm. The number of adhered cells was determined after 3, 48, 96, 144, 192 and 240 hours of biofilm formation and biotransfer potential from 96 hours. Stainless steel coupons were submitted to Scanning Electron Microscopy (SEM) after 3, 144 and 240 hours. Based on the number of adhered cells and SEM, it was observed that L. monocytogenes adhered rapidly to the stainless steel surface, with mature biofilm being formed after 240 hours. The biotransfer potential of bacterium to substrate occurred at all the stages analyzed. The rapid capacity of adhesion to surface, combined with biotransfer potential throughout the biofilm formation stages, make L. monocytogenes a potential risk to the food industry. Both the experimental model developed and the methodology used were efficient in the study of biofilm formation by L. monocytogenes on stainless steel surface and biotransfer potential.

Probiotic potential of yeasts isolated from pineapple and their use in the elaboration of potentially functional fermented beverages.

Pineapple (Ananas comosus (L.) Merril) is a tropical fruit rich in nutrients characterized by a pleasant taste and widely consumed in several countries. It is used to produce juice, jams and wine. In this work, 150 yeasts isolates were obtained from peel (18) and spontaneously fermented pineapple pulp (132). The probiotic potential of 50 isolates was studied. Survival at pH 2.0, pepsin 3.0 g/L, and tolerance of bile salts (0.1 and 1% (w/v) were determined as indicators of survival potential of the isolates during the passage through the human gastrointestinal tract in simulated conditions. The selected isolates were also evaluated for their resistance to 6 antibiotics, antimicrobial activity against 6 pathogenic bacteria and autoaggregation and hydrophobicity properties. Five of them survived to gastrointestinal conditions, showed antibiotic resistance and autoaggregation properties. They were identified by MALDI-TOF MS and sequencing of ITS region as Candida lusitaniae (3) and Meyerozyma caribbica (2). Among these isolates, M. caribbica 9 D was evaluated in the production of a fermented pineapple beverage. The Saccharomyces cerevisiae var. boulardii was used as control, due to the fact that it is the only commercially available probiotic yeast. With M. caribbica inoculum, the beverage produced showed higher concentrations of residual glucose (24.19 g/L) and fructose (8.67 g/L), lower concentration of acetic acid (0.22 g/L); higher total phenolic compounds (196.93 mg/L), catechin (155.56 mg/L), chlorogenic acid (3.64 mg/L), vanillin (0.18 mg/L) and ferulic acid (33.2 mg/L). It was observed that M. caribbica population remained stable during refrigerated storage with cell counts greater than 7.00 log CFU/mL over 21 days. Compared to beverage produced with S. cerevisiae var. boulardii, the one produced with M. caribbica presented greater acceptance in the sensorial analysis for taste, aroma and general acceptance. The fermented pineapple beverage prepared with M. caribbica proved to be a good alternative in development of a potential probiotic beverage with different sensory and nutritional properties.

Antibacterial activity and in vivo wound healing potential of phenolic extracts from jaboticaba skin.

In this study, different phenolic extracts were obtained from the jaboticaba skin meal (JSM), whose phenolic compounds were characterized and their antibacterial activities were assessed. Moreover, the activity of lyophilized ethanolic extract of jaboticaba skin (EEJS) on wound healing was analyzed in rats. The JSM phenolic extracts were obtained in four ways: aqueous, methanolic, ethanolic, and acetone extracts. The phenolic compounds were characterized in these extracts by high-performance liquid chromatography, and their antibacterial activities were evaluated. The in vivo experiment was divided into four groups and received the following treatments: G1-silver sulfadiazine (positive control); G2-EEJS at 10%; G3-EEJS at 5%, and G4-EEJS at 2.5%. The aqueous extract did not inhibit the growing of any bacterium. The ethanolic, acetone, and methanolic extracts inhibited the growing of all bacteria tested at the concentrations of 1.25%, 2.50%, and 5.00%, respectively. The ethanolic extract was the one that showed the highest bacterial inhibition potential and the highest contents of phenolic compounds, especially of catechin, epicatechin gallate, and epicatechin. The G3 and G4 treatments presented faster wound healing compared to the G1 one, as it promoted a less intense inflammatory reaction and full closure of the wounds at an accelerated rate.

Linalool, citral, eugenol and thymol: control of planktonic and sessile cells of Shigella flexneri.

The antimicrobial activity of linalool, citral, eugenol and thymol was determined in growth studies of both planktonic (PC) and biofilm cells (BC) Shigella flexneri. These components were evaluated either in isolation or in combinations using a sequential experimental strategy with Plackett & Burman and central composite rotational designs totaling 47 treatments. The minimum inhibitory concentration for PC was 0.125% (v v-1) for linalool and 0.5% (v v-1) for citral, eugenol and thymol. The biofilm minimum bactericidal concentration was 3 and 1% (v v-1) for linalool and citral, respectively, and 2% (v v-1) for eugenol and thymol. In the mixtures, the minimum concentrations in the efficient assays for PC growth inhibition were 0.0003, 0.0443 and 0.0443% (v v-1), for linalool, citral and thymol, respectively. In the BC, only two assays with concentrations of 0.0558, 0.0558 and 0.319% (v v-1) and 0.035, 0.035 and 0.3999% (v v-1) for linalool, citral and thymol, respectively, inhibited Shigella growth. Synergism was observed among the components, where PC and BC growth inhibition occurred at lower concentrations than those noted individually. The bactericidal effect of the components in microplate was different from the observed in stain steel coupons. Therefore, the obtained model can describe and predict the PC count of S. flexneri in medium with the tested compounds and they could be an alternative for the use in microbiological control in food industry.

Extraction and identification of antimicrobial peptides from the Canastra artisanal minas cheese.

Canastra artisanal Minas cheese samples were collected in Minas Gerais - Brazil. The samples were evaluated in order to observe the presence of antimicrobial peptides during 30 days of ripening. Soluble peptides extracted from the cheeses were fractionated by reverse phase liquid chromatography and their fractions evaluated for inhibitory action of E. coli. Fractions containing antimicrobial activity were analyzed by MALDI-TOF/TOF and then peptides were sequenced and identified using MASCOT Daemon coupled with UniProt database. The identified peptides were then validated by SCAFFOLD application. The peptides present in fractions with antimicrobial activity were RPKHPIKHQ, RPKHPIKHQG, RPKHPIKHQGLPQ and RPKHPIKHQGLPQE, HQPHQPLPPT and MHQPHQPLPPT. Peptide sequences PKHPIKHQ, RPKHPIKHQG, RPKHPIKHQGLPQ and RPKHPIKHQGLPQE were originated from αs1-casein and are their fragments belonging to Isracidine, which in turn is a well known antimicrobial peptide. The HQPHQPLPPT and MHQPHQPLPPT peptides were related to ß-casein and were isolated in other studies, but their biological activities are still unknown.

Predictive modeling of Pseudomonas fluorescens growth under different temperature and pH values.

Meat is one of the most perishable foods owing to its nutrient availability, high water activity, and pH around 5.6. These properties are highly conducive for microbial growth. Fresh meat, when exposed to oxygen, is subjected to the action of aerobic psychrotrophic, proteolytic, and lipolytic spoilage microorganisms, such as Pseudomonas spp. The spoilage results in the appearance of slime and off-flavor in food. In order to predict the growth of Pseudomonas fluorescens in fresh meat at different pH values, stored under refrigeration, and temperature abuse, microbial mathematical modeling was applied. The primary Baranyi and Roberts and the modified Gompertz models were fitted to the experimental data to obtain the growth parameters. The Ratkowsky extended model was used to determine the effect of pH and temperature on the growth parameter µmax. The program DMFit 3.0 was used for model adjustment and fitting. The experimental data showed good fit for both the models tested, and the primary and secondary models based on the Baranyi and Roberts models showed better validation. Thus, these models can be applied to predict the growth of P. fluorescens under the conditions tested.

Synthesis and in vitro evaluation of peracetyl and deacetyl glycosides of eugenol, isoeugenol and dihydroeugenol acting against food-contaminating bacteria.

Essential oils, as well as their separate components, have shown promise as alternatives to synthetic preservatives. Therefore, it would be interesting to optimize the effect of these compounds and to evaluate their applicability as additives in food. To this end, six peracetyl and deacetyl glycosides were synthesized from eugenol, isoeugenol and dihydroeugenol. All of the glycosides were characterized by IR and NMR. The synthesized compounds and their aglycones were evaluated to determine their minimal bactericidal concentrations (MBC) against the spoilage food bacteria Escherichia coli, Listeria monocytogenes, Staphylococcus aureus and Salmonella enteritidis. All deacetyl glycosides were about twice as active as aglycones, and the peracetyl glycosides were, in most cases, equipotent with aglycones. The deacetyl glycoside of dihydroeugenol proved to be the most active compound against the bacteria tested, with a 0.37% MBC v/v for E. coli and 0.18% v/v for the other bacteria.

Preservative of Essential Oil Blends: Control of Clostridium perfringens Type a in Mortadella

Abstract The aim of this study was to evaluate the antimicrobial effect of the essential oils of cinnamon, cardamom, clove, oregano, and thyme and their synergism on vegetative cells and endospores of Clostridium perfringens type A inoculated in meat sausage (mortadella), as well as the influence of blends on the color, and lipid oxidation through the determination of thiobarbituric acid reactive substances (TBARS index). The anticlostridial action of the oil blends was established. The two added oil blends (Treat. 1: oregano, clove, and thyme; Treat. 2: oregano, clove, and cinnamon) in combination with reduced nitrite content (75 ppm) promoted a lower growth of C. perfringens in mortadella stored at 15 °C for 21 days in comparison to treatments containing only 75 ppm of nitrite. The essential oil blends showed antioxidant action and did not alter food color, thus possessing potential application as a preservative for the meat products industry.

Antibacterial and anti-biofilm activity of cinnamon essential oil and eugenol / Atividade antibacteriana e anti-biofilme de óleo essencial de canela e eugenol

ABSTRACT: Biofilms are responsible for most of the interference caused by microorganisms in food processing. The aim of this study was to evaluate the cinnamon (Cinnamomum zeylanicum) essential oil and eugenol sanitizer and anti-biofilm activity against biofilms. Concentrations used of essential oil were 0.0% (control) 0.12%; 0.48%; 0.96% and 1.92%; the amount of eugenol was 0.76%. Concentrations were determined from other published studies. Number of viable cells and quantification the bacterial biomass were determined. Anti-biofilm treatment was effective in preventing the formation of biofilms. The 1.92% concentration was the most satisfactorily with Escherichia coli reduction of 5.91log CFUcm-2 and Staphylococcus aureus reduction of 5.17log CFUcm-2 (P<0.05) biomass of the two bacteria. Sanitizing treatment was not effective in reducing biomass. Seen this, the cinnamon and eugenol essential oil may be promising alternatives for controlling biofilms.

RESUMO: Os biofilmes são responsáveis pela maior parte da interferência causada pelos micro-organismos no processamento de alimentos. O objetivo deste estudo foi avaliar a atividade anti-biofilme do óleo essencial de canela (Cinnamomum zeylanicum) e do composto majoritário eugenol. As concentrações utilizadas de óleo essencial foram de 0,0% (controle), 0,12%; 0,48%; 0,96% e 1,92%; a concentração de eugenol foi de 0,76%. As concentrações foram determinadas a partir de outros estudos publicados. Determinou-se o número de células viáveis e quantificou-se a biomassa bacteriana. O tratamento anti-biofilme foi eficaz na prevenção e formação de biofilmes. A concentração de 1,92% foi satisfatória, com redução de 5,91log CFUcm-2 de células viáveis em biofilme de Escherichia coli e redução de 5,17log CFU cm-2 de Staphylococcus aureus. A biomassa de ambas bactérias foi reduzida significativamente (P<0,05), entretanto, o tratamento sanitizante não foi eficaz na redução da biomassa. Diante dos resultados, o óleo essencial de canela e eugenol podem ser alternativas promissoras no controle de biofilmes.

A Weibull model to describe antimicrobial kinetics of oregano and lemongrass essential oils against Salmonella Enteritidis in ground beef during refrigerated storage.

The antimicrobial effect of oregano (Origanum vulgare L.) and lemongrass (Cymbopogon citratus (DC.) Stapf.) essential oils (EOs) against Salmonella enterica serotype Enteritidis in in vitro experiments, and inoculated in ground bovine meat during refrigerated storage (4±2 °C) for 6 days was evaluated. The Weibull model was tested to fit survival/inactivation bacterial curves (estimating of p and δ parameters). The minimum inhibitory concentration (MIC) value for both EOs on S. Enteritidis was 3.90 µl/ml. The EO concentrations applied in the ground beef were 3.90, 7.80 and 15.60 µl/g, based on MIC levels and possible activity reduction by food constituents. Both evaluated EOs in all tested levels, showed antimicrobial effects, with microbial populations reducing (p≤0.05) along time storage. Evaluating fit-quality parameters (RSS and RSE) Weibull models are able to describe the inactivation curves of EOs against S. Enteritidis. The application of EOs in processed meats can be used to control pathogens during refrigerated shelf-life.

Essential oils of thyme and Rosemary in the control of Listeria monocytogenes in raw beef.

This study was developed in order to evaluate two alternatives for the control of Listeria monocytogenes in raw bovine meat pieces, both based on the use of Thymus vulgaris and Rosmarinus officinalis essential oils (EOs). The antilisterial activity of different concentrations of the EOs was tested in vitro using agar dilution and disk volatilization techniques. In addition, L. monocytogenes was inoculated in meat pieces, which were submerged in edible gelatin coatings containing 2% (v/v) EOs or submitted to the vapor of EOs (0.74 µL.cm(-3)). L. monocytogenes was quantified after one, 48 and 96 hours of storage (7 °C). In the in vitro tests, the EO of T. vulgaris presented higher activity. The two options used (edible gelatin coating and vapor activity), in spite of exercising effects with differentiated behaviors, presented antibacterial activity against L. monocytogenes inoculated in raw bovine meat (p < 0.05). Greatest antibacterial activity were obtained in the experiment that used edible coatings containing EOs, at 48 hours of storage reductions in bacterial counts between 1.09 and 1.25 Log CFU.g(-1) were obtained. In the vapor effect experiment, the EO of T. vulgaris caused the highest reduction in the population of bacteria inoculated in raw bovine meat (p < 0.05), 0.40 Log CFU.g(-1) at 96 hours of storage. This study supplied important information regarding new and promising natural alternatives, based on the concept of active packaging, for the control of L. monocytogenes in the meat industry.

Inhibitory activity of Syzygium aromaticum and Cymbopogon citratus (DC.) Stapf. essential oils against Listeria monocytogenes inoculated in bovine ground meat.

This research evaluated the antimicrobial effect of the clove (Syzygium aromaticum) and lemongrass (Cymbopogon citratus (DC.) Stapf.) essential oils (EOs) against Listeria monocytogenes ATCC 19117 growth added to bovine ground meat stored under refrigeration (5 ± 2 °C) for three days. The EOs, extracted by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS), were tested in vitro using an agar well diffusion methodology for determination of Minimum Inhibitory Concentration (MIC). The MIC concentrations for both essential oils on culture tested of L. monocytogenes were 1.56%. The EOs concentrations applied in contaminated ground beef were 1.56, 3.125 and 6.25% (w/v) based on MIC levels and possible activity reductions by food constituents. The bacteria populations were significantly reduced (p ≤ 0.05) after one day of storage in ground meat samples treated with clove and lemongrass EOs at concentrations of 1.56%. There were no significant counts of L. monocytogenes in samples at the other concentrations of the two oils applied after the second day of storage. The sensory acceptability evaluation of the bovine ground meat samples treated with EOs showed that the addition at concentrations higher than 1.56% promote undesirable alterations of taste, odor and characteristic color. The application of EOs at low concentrations in food products can be used in combination with other preservation methods, such as refrigeration, to control pathogens and spoilage bacteria during shelf-life; which goes according to current market trends, where consumers are requesting natural products.

Predictive modeling of Pseudomonas fluorescens growth under different temperature and pH values

Abstract Meat is one of the most perishable foods owing to its nutrient availability, high water activity, and pH around 5.6. These properties are highly conducive for microbial growth. Fresh meat, when exposed to oxygen, is subjected to the action of aerobic psychrotrophic, proteolytic, and lipolytic spoilage microorganisms, such as Pseudomonas spp. The spoilage results in the appearance of slime and off-flavor in food. In order to predict the growth of Pseudomonas fluorescens in fresh meat at different pH values, stored under refrigeration, and temperature abuse, microbial mathematical modeling was applied. The primary Baranyi and Roberts and the modified Gompertz models were fitted to the experimental data to obtain the growth parameters. The Ratkowsky extended model was used to determine the effect of pH and temperature on the growth parameter µmax. The program DMFit 3.0 was used for model adjustment and fitting. The experimental data showed good fit for both the models tested, and the primary and secondary models based on the Baranyi and Roberts models showed better validation. Thus, these models can be applied to predict the growth of P. fluorescens under the conditions tested.

Sensibilidade de bactérias patogênicas em alimentos a óleos essenciais de plantas medicinais e condimentares / Sensitivity of pathogenic bacteria in food to essential oils of medicinal and spice plants

Os óleos essenciais (OEs), também chamados de óleos voláteis ou etéreos, são produtos do metabólismo secundário dos vegetais. Tanto os óleos como os seus componentes são utilizados como produtos nas indústrias de alimentos, pois possuem comprovada atividade antimicrobiana. As Concentrações Mínimas Inibitórias (CMI) desses óleos para diversas bactérias devem ser determinadas. As CMI variam de acordo com o óleo utilizado, dos compostos majoritários e da fisiologia da bactéria em estudo. Neste trabalho, os OEs das plantas Melaleuca alternifolia, Cinnamomum zeylanicum e Cymbopogon martini foram testados quanto à atividade antimicrobiana (através da CMI) contra as bactérias patogênicas Escherichia coli e Staphylococcus aureus. Neste estudo, verificamos que E. coli e S. aureus foram sensíveis aos três OEs em todas as concentrações. Os resultados in vitro sugerem que os três OEs possuem potencial para utilização, como uma alternativa aos antimicrobianos e conservantes sintéticos.

Antimicrobial activity of Satureja montana L. essential oil against Clostridium perfringens type A inoculated in mortadella-type sausages formulated with different levels of sodium nitrite.

This research evaluated the antimicrobial effect of the winter savory (Satureja montana L.) essential oil (EO) against Clostridium perfringens type A (ATCC 3624) inoculated in mortadella-type sausages formulated with different levels of sodium nitrite (NaNO2: 0 ppm, 100 ppm and 200 ppm) in addition to EO at concentrations of 0.0%, 0.78%, 1.56% and 3.125% stored at 25°C for 30 days. The EO extracted by hydrodistillation and analyzed by gas chromatography-mass spectrometry (CG-MS) was tested in vitro using an agar well diffusion method for determination of minimum inhibitory concentration (MIC) on C. perfringens. According to compositional analysis of the winter savory EO, 26 chemical compounds were identified, and the major constituents were thymol (28.99%), p-cymene (12.00%), linalool (11.00%) and carvacrol (10.71%). The results obtained showed that EO applied at a concentration of 1.56%, which was defined as the MIC, exhibited antimicrobial activity against C. perfringens in the in vitro assays, and the transmission electron microscopy (TEM) revealed structural damage and cell lysis of C. perfringens caused by EO treatment. A synergistic effect between NaNO2 and EO was observed. In mortadella-type sausages formulated with 100 ppm of NaNO2 and EO at all concentrations tested, the population of target microorganisms was reduced (p≤0.05) compared to control samples during all storage period. This data suggests the potential combined use of savory EO and minimal amounts of the synthetic additive, NaNO2 to control C. perfringens in mortadella, which goes according to current market trends, where consumers are requesting natural products.