Investigating the effects of conventional and unconventional edible parts of red beet (Beta vulgaris L.) on target bacterial groups and metabolic activity of human colonic microbiota to produce novel and sustainable prebiotic ingredients.

This study investigated the effects of freeze-dried red beet root (FDBR) and freeze-dried red beet stem and leaves (FDBSL) on target bacterial groups and metabolic activity of human colonic microbiota in vitro. The capability of FDBR and FDBSL to cause alterations in the relative abundance of different selected bacterial groups found as part of human intestinal microbiota, as well as in pH values, sugar, short-chain fatty acid, phenolic compounds, and antioxidant capacity were evaluated during 48 h of in vitro colonic fermentation. FDBR and FDBSL were submitted to simulated gastrointestinal digestion and freeze-dried prior to use in colonic fermentation. FDBR and FDBSL overall increased the relative abundance of Lactobacillus spp./Enterococcus spp. (3.64-7.60%) and Bifidobacterium spp. (2.76-5.78%) and decreased the relative abundance of Bacteroides spp./Prevotella spp. (9.56-4.18%), Clostridium histolyticum (1.62-1.15%), and Eubacterium rectale/Clostridium coccoides (2.33-1.49%) during 48 h of colonic fermentation. FDBR and FDBSL had high positive prebiotic indexes (>3.61) during colonic fermentation, indicating selective stimulatory effects on beneficial intestinal bacterial groups. FDBR and FDBSL increased the metabolic activity of human colonic microbiota, evidenced by decreased pH, sugar consumption, short-chain fatty acid production, alterations in phenolic compound contents, and maintenance of high antioxidant capacity during colonic fermentation. The results indicate that FDBR and FDBSL could induce beneficial alterations in the composition and metabolic activity of human intestinal microbiota, as well as that conventional and unconventional red beet edible parts are candidates to use as novel and sustainable prebiotic ingredients.

A review on bioactive compounds of beet (Beta vulgaris L. subsp. vulgaris) with special emphasis on their beneficial effects on gut microbiota and gastrointestinal health.

This review discusses the available literature concerning the bioactive compounds of beet (Beta vulgaris L.) and their ability to modulate the gut microbiota and parameters indicative of gastrointestinal health. Data of published literature characterize beet as a source of a variety of bioactive compounds (e.g. diet fiber, pectic-oligosaccharides, betalains and phenolics) with proven beneficial effects on human health. Beet extracts and pectin and pectic-oligosaccharides from beet have shown able to modulate positively gut microbiota composition and activity, with noticeable bifidogenic effects, in addition to stimulate the growth and metabolism of probiotics. Beet betalains and phenolics seem to increase the production of metabolites (e.g. short chain fatty acids) by gut microbiota and probiotics, which are linked with different beneficial effects on host health. The outstanding contents of betalains and phenolics with antioxidant, anti-inflammatory and anti-carcinogenic properties have been linked to the positive effects of beet on gastrointestinal health. Beet should be a healthy choice for use in domestic meal preparations and a source of ingredients to formulate added-value functionalized food products.

Development and in vitro evaluation of novel nutraceutical formulations composed of Limosilactobacillus fermentum, quercetin and/or resveratrol.

This study developed and carried out an in vitro evaluation of nutraceutical formulations composed of potentially probiotic Limosilactobacillus fermentum (L. fermentum 139, L. fermentum 263 or L. fermentum 296), quercetin and/or resveratrol. L. fermentum strains had counts of >9 log CFU/g and contents of QUE and RES of >200 µg/mg in formulations after freeze-drying. Formulations with QUE and RES protected L. fermentum during exposure to in vitro acidic stomach conditions. L. fermentum strains had counts of >6 log CFU/g on day 60 and/or 90 of refrigeration storage. Contents of QUE (>29%) and RES (>50%) in formulations were potentially bioaccessible. Higher counts of L. fermentum and higher contents of QUE and RES were found in formulations stored under refrigerated rather than under room temperature. All nutraceutical formulations had antioxidant properties. Combinations of probiotic L. fermentum and QUE and/or RES should be an innovative strategy to develop added-value nutraceutical formulations.

Combined chitosan and Cympobogon citratus (D.C. ex Nees) Stapf. essential oil to inhibit the fungal phytopathogen Paramyrothecium roridum and control crater rot in melon (Cucumis melo L.).

This study evaluated the efficacy of combined chitosan (Chi) and Cymbopogon citratus (DC) Stapf. essential oil (CCEO) to inhibit the fungal phytopathogen Paramyrothecium roridum L. Lombard & Crous and control crater rot in melon (Cucumis melo L.). Effects of several Chi and CCEO concentrations to inhibit the growth of four P. roridum isolates in vitro, as well as the type of interaction of some combined concentrations of Chi and CCEO was evaluated. Effects of coatings with combined concentrations of Chi and CCEO on development of crater rot lesions in melon artificially inoculated with P. roridum during storage (15 days, 25 °C) were measured. Chi (2.5, 3.75, 5, and 6.75 mg/mL) and CCEO (0.3 and 0.6 µL/mL) led to growth inhibition of the four examined P. roridum isolates. Combinations of Chi (5 mg/mL) and CCEO (0.15 and 0.3 µL/mL) had additive interaction to inhibit P. roridum. Coatings with additive combined concentrations of Chi and CCEO decreased the development and severity of carter rot lesions in melon during room storage regardless of the inoculated P. roridum isolate. Therefore, application of coatings formulated with combined concentrations of Chi and CCEO could be alternative strategies to control crater rot caused by P. roridum in melon and decrease synthetic fungicide use in this fruit.

Chitosan nanoemulsions of cold-pressed orange essential oil to preserve fruit juices.

Sweet orange essential oil is obtained from the peels of Citrus sinensis (CSEO) by cold pressing, and used as a valuable product by the food industry. Nanoencapsulation is known as a valid strategy to improve chemical stability, organoleptic properties, and delivery of EO-based products. In the present study we encapsulated CSEO using chitosan nanoemulsions (cn) as nanocarrier, and evaluated its antimicrobial activity in combination with mild heat, as well as its sensorial acceptability in orange and apple juices. CSEO composition was analyzed by GC-MS, and 19 components were identified, with limonene as the predominant constituent (95.1%). cn-CSEO was prepared under low shear conditions and characterized according to droplet size (<60 nm) and polydispersity index (<0.260 nm). Nanoemulsions were stable for at least 3 months at 4 ± 2 °C. cn-CSEO were compared with suspensions of CSEO (s-CSEO) (0.2 µL of CSEO/mL) in terms of antibacterial activity in combination with mild heat (52 °C) against Escherichia coli O157:H7 Sakai. cn-CSEO displayed a greater bactericidal activity than s-CSEO at pH 7.0 and pH 4.0. The validation in fruit juices showed an improved bactericidal effect of cn-CSEO in comparison with s-CSEO when combined with mild heat in apple juice, but not in orange juice. In both juices, the combination of CSEO and mild heat exerted synergistic lethal effects, reducing the treatment time to cause the inactivation of up to 5 Log10 cycles of E. coli O157:H7 Sakai cells. Finally, the sensory characteristics of both juices were acceptable either when using s-CSEO or CSEO nanoemulsified with chitosan. Therefore, as a promising carrier for lipophilic substances, the encapsulation of EOs with chitosan nanoemulsions might represent an advantageous alternative when combined with mild heat to preserve fruit juices.

Coatings with chitosan and phenolic-rich extract from acerola (Malpighia emarginata D.C.) or jabuticaba (Plinia jaboticaba (Vell.) Berg) processing by-product to control rot caused by Lasiodiplodia spp. in papaya (Carica papaya L.) fruit.

This study evaluated if coatings with chitosan (Chi) and phenolic-rich extract from acerola (Malpighia emarginata D.C., PEA) or jabuticaba (Plinia jaboticaba (Vell.) Berg, PEJ) processing by-products are effective to control the development of rot caused by Lasiodiplodia pseudotheobromae, L. viticola, L. euphorbicola, L. theobromae and L. hormozganensis in papaya (Carica papaya L.) fruit. Effects of formulated coatings on some physicochemical parameters indicative of postharvest quality of papaya were investigated. Twenty-six different phenolics were found in PEA and PEJ, including flavonoids, stilbenes, tannins and phenolic acids. Chi (1-5 mg/mL), PEA and PEJ (25-100 mg/mL) separately caused mycelial growth inhibition on all isolates. Combinations of Chi (3 and 4 mg/mL) and PEA (50 and 75 mg/mL) or PEJ (75 and 100 mg/mL) had additive interactions. Coatings with Chi (4 mg/mL) and PEA (50 or 75 mg/mL) or PEA (75 or 100 mg/mL) inhibited rot development in papaya fruit infected with Lasiodiplodia isolates during 8 days of room temperature storage. Coatings with 4 mg/mL Chi and 75 mg/mL PEA or 100 mg/mL PEJ were the most effective to control rot development. These coatings did not affect negatively physicochemical parameters indicative of postharvest quality of papaya fruit during storage. Coatings with combined Chi and PEA or PEJ could be novel strategies to control postharvest rot caused by Lasiodiplodia in papaya fruit.

Mentha piperita L. essential oil inactivates spoilage yeasts in fruit juices through the perturbation of different physiological functions in yeast cells.

This study evaluated the efficacy of the essential oil from Mentha piperita L. (MPEO) to inactivate cells of the potentially spoilage yeasts Candida albicans, Candida tropicalis, Pichia anomala and Saccharomyces cerevisiae in cashew, guava, mango and pineapple juices during 72 h of refrigerated storage. Damage in different physiological functions caused by MPEO in S. cerevisiae in cashew and guava juices were investigated using flow cytometry (FC). The effects of the incorporation of an effective anti-yeast MPEO dose on sensory characteristics of juices were also evaluated. MPEO displayed minimum inhibitory concentration of 1.875 µL/mL against all tested yeasts. A >5 log reduction in counts of C. albicans, P. anomala and S. cerevisiae was observed in cashew and guava juices with 7.5 and 3.75 µL/mL MPEO. Tested MPEO concentrations (1.875, 3.75 and 7.5 µL/mL) were not effective to cause >5 log reduction in counts of target yeasts in mango and pineapple juices during 72 h of exposure. Incorporation of 1.875 µL/mL MPEO in cashew and guava juices strongly compromised membrane permeability, membrane potential, enzymatic activity and efflux pump activity in S. cerevisiae cells. This same MPEO concentration did not affect appearance, odor and viscosity in fruit juices, but negatively affected their taste and aftertaste. These results show the efficacy of MPEO to inactivate potentially spoilage yeasts in fruit juices through disturbance of different physiological functions in yeast cells. However, the combined use of MPEO with other technologies should be necessary to decrease its effective anti-yeast dose in fruit juices and, consequently, the possible negative impacts on specific sensory properties of these products.

Control of Autochthonous Spoilage Lactic Acid Bacteria in Apple and Orange Juices by Sensorially Accepted Doses of Citrus Spp. Essential Oils Combined with Mild Heat Treatments.

This study assessed the compromised acceptance threshold (CAT) and rejection threshold (RT) of Citrus lemon (CLEO) and Citrus reticulata essential oil (CREO) in apple and orange juices. The efficacy of CLEO and CREO concentrations below the RT were evaluated alone and combined with mild heat treatment (MHT) (54 °C, up to 12 min) to inactivate the autochthonous spoilage bacteria Lactobacillus brevis, Lactobacillus plantarum, and Leuconostoc mesenteroides in apple and orange juices. The CAT of CLEO and CREO varied from 0.15 to 0.17 µL/mL in orange and apple juices. The RT of CLEO was approximately 0.58 µL/mL in apple and orange juices, and the RT of CREO was 0.68 µL/mL in both juices. When CLEO and CREO were assayed alone, the highest concentration (0.50 µL/mL) decreased counts of all strains approximately 2 log10 CFU/mL after 12 min of exposure to 54 °C. All concentrations of CLEO or CREO in combination with MHT acted synergistically against L. brevis, L. plantarum, and L. mesenteroides. Decreases in counts varied with the strain, CLEO and CREO concentrations, juice type, and exposure time to the combined treatment. CREO was more effective than CLEO in combination with MHT against the strains in apple and orange juices. Effective combinations of CLEO or CREO with MHT to control the autochthonous spoilage bacteria did not compromise the quality parameters (°Brix, pH, and titratable acidity) that characterize unsweetened juices. These results indicate CLEO or CREO at concentrations below the sensory RT in combination with MHT as a feasible technology to control autochthonous spoilage bacteria in fresh fruit juices. PRACTICAL APPLICATION: The present study provides novel information concerning the efficacy of sensorially accepted doses of CLEO and CREO combined with MHT against autochthonous spoilers in fruit juice. The valuable synergistic effects that can be observed when combining CLEO and CREO with MHT reveal a feasible preservation technology and alternative to traditional treatments that are successful because they help reduce treatment intensity, thereby avoiding adverse effects on the sensory, physicochemical, and nutritional properties of these products.

Investigation of damage to Escherichia coli, Listeria monocytogenes and Salmonella Enteritidis exposed to Mentha arvensis L. and M. piperita L. essential oils in pineapple and mango juice by flow cytometry.

The effects of Mentha arvensis L. (MAEO; 0.625 µL/mL) and M. piperita L. (MPEO; 1.25 µL/mL) essential oils on viable cell counts and physiological functions in Escherichia coli, Listeria monocytogenes and Salmonella enterica Serovar Enteritidis in pineapple and mango juice after a 15 min-exposure under refrigeration were evaluated in this study. The physiological functions of the bacterial cells were assessed by flow cytometry using the fluorochromes thiazole orange, propidium iodide, bis-1,3-dibutylbarbutiric acid, ethidium bromide, and 5-cyano-2,3-ditolyl tetrazolium chloride to investigate membrane integrity, membrane potential, efflux activity, and respiratory activity. MAEO and MPEO sharply reduced (>5 log10 CFU/mL cycles) the counts of E. coli, L. monocytogenes and Salmonella Enteritidis in pineapple juice, and caused smaller reductions (0.61-1.58 log10 CFU/mL cycles) in mango juice. Bacterial cells exposed to MAEO and MPEO in pineapple and mango juice showed increased membrane permeability, membrane depolarization and changes in efflux pump and respiratory activity. More physiological damage occurred in bacterial cell populations exposed to MAEO or MPEO in pineapple juice than in mango juice. These results indicate that MAEO and MPEO inactivate E. coli, L. monocytogenes and Salmonella Enteritidis cells in pineapple and mango juice through a multi-target action mode that disrupts cytoplasmic membranes, increases permeability and potential depolarization, as well as inhibits efflux pump and respiratory activity.

Effects of honey from Mimosa quadrivalvis L. (malícia) produced by the Melipona subnitida D. (jandaíra) stingless bee on dyslipidaemic rats.

This study assessed the effects of supplementation with honey from Mimosa quadrivalvis L. (malícia) (MH) produced by jandaíra stingless bees (Melipona subnitida D.) on the lipid metabolism, antioxidant status and some intestinal health parameters of rats with diet-induced dyslipidaemia. Rats were randomly divided into four groups: healthy control (HC), dyslipidaemic control (DC), healthy experimental (EHH) and dyslipidaemic experimental (EDH). Malícia honey (MH) was administered (1000 mL kg-1) via orogastric feeding for 35 days. Dyslipidaemic rats supplemented with MH showed lower food consumption, increased glucose tolerance and superoxide dismutase (SOD) activity, and decreased total cholesterol, LDL and AST blood levels. Counts of Bifidobacterium spp. and Lactobacillus spp. and excretion of organic acids in faeces increased in dyslipidaemic rats supplemented with MH. MH supplementation protected the colon and liver from tissue damage induced by the dyslipidaemic diet. These results show the beneficial effects of MH on the lipid metabolism, antioxidant status and intestinal health of rats with diet-induced dyslipidaemia.

Beneficial effects of consumption of acerola, cashew or guava processing by-products on intestinal health and lipid metabolism in dyslipidaemic female Wistar rats.

This study assessed the effects of diet supplementation with industrial processing by-products of acerola (Malpighia emarginata D.C.), cashew (Anacardium occidentale L.) and guava (Psidium guajava L.) fruit on the intestinal health and lipid metabolism of female Wistar rats with diet-induced dyslipidaemia. Female rats were randomly divided into five groups: healthy control, dyslipidaemic control and dyslipidaemic experimental receiving acerola, cashew or guava processing by-products. Fruit processing by-products were administered (400 mg/kg body weight) via orogastric administration for 28 consecutive days. Acerola, cashew and guava by-products caused body weight reduction (3·42, 3·08 and 5·20 %, respectively) in dyslipidaemic female rats. Dyslipidaemic female rats receiving fruit by-products, especially from acerola, presented decreased faecal pH, visceral fat, liver fat and serum lipid levels, as well as increased faecal moisture, faecal fat excretion, faecal Bifidobacterium spp. and Lactobacillus spp. counts and amounts of organic acids in faeces. Administration of the tested fruit processing by-products protected colon and liver from tissue damage (e.g. destruction of liver and colon cells and increased fat deposition in hepatocytes) induced by dyslipidaemic diet. Dietary fibres and phenolic compounds in tested fruit by-products may be associated with these positive effects. The industrial fruit processing by-products studied, mainly from acerola, exert functional properties that could enable their use to protect the harmful effects on intestinal health and lipid metabolism caused by dyslipidaemic diet.

Synergistic mixtures of chitosan and Mentha piperita L. essential oil to inhibit Colletotrichum species and anthracnose development in mango cultivar Tommy Atkins.

This study assessed the efficacy of chitosan (CHI) and Mentha piperita L. essential oil (MPEO) alone or in combination to control the mycelial growth of five different Colletotrichum species, C. asianum, C. dianesei, C. fructicola, C. tropicale and C. karstii, identified as potential anthracnose-causing agents in mango (Mangifera indica L.). The efficacy of coatings of CHI and MPEO mixtures in controlling the development of anthracnose in mango cultivar Tommy Atkins was evaluated. CHI (2.5, 5, 7.5 and 10 mg/mL) and MPEO (0.3, 0.6, 1.25, 2.5 and 5 µL/mL) alone effectively inhibited mycelial growth of all tested Colletotrichum strains in synthetic media. Mixtures of CHI (5 or 7.5 mg/mL) and MPEO (0.3, 0.6 or 1.25 µL/mL) strongly inhibited mycelial growth and showed additive or synergistic inhibitory effects on the tested Colletotrichum strains based on the Abbott index. The application of coatings of CHI (5 or 7.5 mg/mL) and MPEO (0.6 or 1.25 µL/mL) mixtures that presented synergistic interactions decreased anthracnose lesion severity in mango artificially contaminated with either of the tested Colletotrichum strains over 15 days of storage at 25 °C. The anthracnose lesion severity in mango coated with the mixtures of CHI and MPEO was similar or lower than those observed in mango treated with the synthetic fungicides thiophanate-methyl (10 µg a.i./mL) and difenoconazole (0.5 µg a.i./mL). The application of coatings containing low doses of CHI and MPEO may be an effective alternative for controlling the postharvest development of anthracnose in mango cultivar Tommy Atkins.

The efficacy of Mentha arvensis L. and M. piperita L. essential oils in reducing pathogenic bacteria and maintaining quality characteristics in cashew, guava, mango, and pineapple juices.

This study evaluated the ability of the essential oil from Mentha arvensis L. (MAEO) and M. piperita L. (MPEO) to induce ≥5-log reductions in counts (CFU/mL) of E. coli, L. monocytogenes, and Salmonella enterica serovar Enteritidis in Brain-Heart Infusion broth (BHIB) and cashew, guava, mango, and pineapple juices during refrigerated storage (4±0.5°C). The effects of the incorporation of these essential oils on some physicochemical and sensory parameters of juices were also evaluated. The incorporation of 5, 2.5, 1.25, or 0.625µL/mL of MAEO in BHIB caused a ≥5-log reduction in counts of E. coli and Salmonella Enteritidis after 24h of storage; but only 5µL/mL was able to cause the same reduction in counts of L.monocytogenes. The incorporation of 10µL/mL of MPEO in BHIB caused a ≥5-log reduction in counts of E. coli, Salmonella Enteritidis, and L. monocytogenes after 24h of storage; smaller reductions were observed in BHIB containing 5, 2.5, and 1.25µL/mL of MPEO. Similar reductions were observed when the MAEO or MPEO was incorporated at the same concentrations in mango juice. The incorporation of MAEO or MPEO at all tested concentrations in cashew, guava, and pineapple juices resulted in a ≥5-log reduction in pathogen counts within 1h. The incorporation of MAEO and MPEO (0.625 and 1.25µL/mL, respectively) in fruit juices did not induce alterations in °Brix, pH, and acidity, but negatively affected the taste, aftertaste, and overall acceptance. The use of MAEO or MPEO at low concentrations could constitute an interesting tool to achieve the required 5-log reduction of pathogenic bacteria in cashew, guava, mango, and pineapple fruit juices. However, new methods combining the use of MAEO or MPEO with other technologies are necessary to reduce their negative impacts on specific sensory properties of these juices.

Inactivation of Escherichia coli, Listeria monocytogenes, and Salmonella Enteritidis by Cymbopogon citratus D.C. Stapf. Essential Oil in Pineapple Juice.

In the present study, the efficacy of Cymbopogon citratus D.C. Stapf. essential oil (CCEO) to provoke a 5-log CFU/ml (5-log) inactivation in a mixed composite of Escherichia coli, Listeria monocytogenes, and Salmonella enterica serovar Enteritidis in pineapple (Ananas comosus (L.) Merril) juice (4°C) was assessed. Moreover, the effects of CCEO on the physicochemical and sensory quality parameters of pineapple juice were evaluated. The MIC of CCEO was 5 µl/ml against the composite mix examined. For L. monocytogenes and E. coli inoculated in juice containing CCEO (5, 2.5, and 1.25 µl/ml), a ≥5-log reduction was detected after 15 min of exposure. This same result was obtained for Salmonella Enteritidis incubated alone in pineapple juice containing CCEO at 5 and 2.5 µl/ml. Overall, Salmonella Enteritidis was the most tolerant and L. monocytogenes was the most sensitive to CCEO. The physicochemical properties (pH, titratable acidic [citric acid per 100 g], and soluble solids) of pineapple juice containing CCEO (2.5 and 1.25 µl/ml) were maintained. Juice containing CCEO (2.5 and 1.25 µl/ml) exhibited similar scores for odor, appearance, and viscosity compared with juice without CCEO. However, unsatisfactory changes in taste and aftertaste were observed in juices containing CCEO. These results suggest that CCEO could be used as an alternative antimicrobial compound to ensure the safety of pineapple juice, although CCEO at the tested concentrations negatively impacted its taste. Therefore, further studies are needed to determine the balance between microbial safety and taste acceptability of pineapple juice containing CCEO.

Comparative inhibitory effects of Thymus vulgaris L. essential oil against Staphylococcus aureus, Listeria monocytogenes and mesophilic starter co-culture in cheese-mimicking models.

In the present study, we assessed the effects of Thymus vulgaris L. essential oil (TVEO) on Staphylococcus aureus and Listeria monocytogenes, pathogenic bacteria frequently associated with fresh or low-ripened cheeses (e.g., Brazilian coalho cheese), and on a starter co-culture comprising Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris, which are commonly used for the production of different cheeses. To measure these effects, we determined the minimum inhibitory concentration (MIC) and assessed bacterial cell viability over time in (coalho) cheese-based broth and in a semi-solid (coalho) cheese model at 10 °C. The MIC for TVEO was 2.5 µL/mL against S. aureus and L. monocytogenes, while the MIC was 1.25 µL/mL against the starter co-culture. The TVEO (5 and 2.5 µL/mL) sharply reduced the viable counts of all assayed bacteria in cheese broth over 24 h; although, at 5 µL/mL, TVEO more severely affected the viability of the starter co-culture compared with pathogenic bacteria. The addition of 1.25 µL/g of TVEO in the semi-solid cheese model did not reduce the viable counts of all assayed bacteria. At 2.5 µL/g, TVEO slightly decreased the viable counts of S. aureus, L. monocytogenes and Lactococcus spp. in the semi-solid cheese model over 72 h. The final counts of Lactococcus spp. in a semi-solid cheese model containing 2.5 µL/mL TVEO were lower than those of pathogenic bacteria under the same conditions. These results suggest that the doses of TVEO used to control pathogenic bacteria in fermented dairy products, especially in low-ripened cheeses, should be cautiously considered for potential negative effects on the growth and survival of starter cultures.

Sublethal amounts of Origanum vulgare L. essential oil and carvacrol cause injury and changes in membrane fatty acid of Salmonella Typhimurium cultivated in a meat broth.

This study aimed to evaluate whether sublethal concentrations of the essential oil of Origanum vulgare L. (OVEO) and its major compound carvacrol (CAR) cause injury to the cell membrane and outer membrane of Salmonella enterica serovar Typhimurium ATCC 14028 grown in a meat broth and to assess the effect of these substances on membrane fatty acid (FA) composition. Exposure of Salmonella Typhimurium ATCC 14028 to sublethal concentrations of OVEO or CAR caused damage to the cytoplasmic membrane and outer membrane. OVEO- and CAR-treated cells showed lower amounts of saturated FA than nontreated cells. Changes in membrane FA composition were mainly related to an increase of C16:1ω7c, C16:1ω7t, and C18:2ω6c, and to a decrease of C16:0, C17:0 cyclo, and C19:0 cyclo. These results indicate that exposure to sublethal concentrations of OVEO or CAR caused sublethal injury Salmonella Typhimurium ATCC 14028 and suggest that an adaptive response to these stresses is related to increased synthesis of unsaturated FA and cis-trans isomerization.

Rosmarinus officinalis L. essential oil and its majority compound 1,8-cineole at sublethal amounts induce no direct and cross protection in Staphylococcus aureus ATCC 6538.

In this study, the inhibitory efficacy of Rosmarinus officinalis essential L. (ROEO) and 1,8-cineole (CIN) in inhibiting the growth and survival of Staphylococcus aureus ATCC 6538 and the induction of direct and bacterial cross protection (lactic acid pH 5.2; NaCl 100 g/L; high temperature 45°C) were evaluated following exposure to sublethal and increasing amounts of these treatments in meat broth. All of the concentrations of the ROEO and CIN examined in this study (minimum inhibitory concentration [MIC], 1/2 MIC, and 1/4 MIC) inhibited the viability of S. aureus throughout the 120 min of exposure. The overnight exposure of S. aureus to sublethal amounts of both ROEO or CIN in meat broth did not result in direct or cross protection. Cells progressively subcultured (24-h cycles) in meat broth with increasing amounts of ROEO or CIN showed no increased direct tolerance. These results reveal the antimicrobial efficacy of ROEO and CIN for use in food conservation systems as anti-S. aureus compounds given their efficacy at inhibiting bacterial growth, in addition to their lack of induction for the development of homologous and heterologous resistance.

Efficacy of the application of a coating composed of chitosan and Origanum vulgare L. essential oil to control Rhizopus stolonifer and Aspergillus niger in grapes (Vitis labrusca L.).

This study evaluated the efficacy of the combined application of chitosan (CHI) and Origanum vulgare L. essential oil (OV) in the inhibition of Rhizopus stolonifer URM 3728 and Aspergillus niger URM 5842 on laboratory media and on grapes (Vitis labrusca L.) and its influence on the physical, physicochemical and sensory characteristics of the fruits during storage (25 °C, 12 days and 12 °C, 24 days). The application of mixtures of different CHI and OV concentrations (Minimum Inhibitory Concentration - MIC, 1/2 MIC and 1/4 MIC) inhibited the mycelial growth of the test fungi. The application of CHI and OV at sub-inhibitory concentrations (CHI 1/2 MIC + OV 1/4 MIC; CHI 1/2 MIC + OV 1/2 MIC) inhibited spore germination and caused morphological changes in fungal spores and mycelia, in addition to inhibiting the growth of the assayed fungi strains in artificially infected grapes as well as the autochthonous mycoflora of grapes stored at both room and cold temperature. In general, the application of a coating composed of CHI and OV at sub-inhibitory concentrations preserved the quality of grapes as measured by their physical and physicochemical attributes, while some of their sensory attributes improved throughout the assessed storage time. These results demonstrate the potential of the combination of CHI and OV at sub-inhibitory concentrations to control post-harvest pathogenic fungi in fruits, in particular, R. stolonifer and A. niger in grapes.