Cereus jamacaru DC. (mandacaru) fruit as a source of lactic acid bacteria with in vitro probiotic-related characteristics and its protective effects on Pediococcus pentosaceus during lyophilization and refrigeration storage

This study isolated and identified autochthonous lactic acid bacteria (LAB) from mandacaru fruit and evaluated their potential probiotic and technological aptitudes in vitro, as well as the protective effects of freeze-dried mandacaru fruit on the most promising LAB isolate during lyophilization and refrigeration storage. Initially, 212 colonies were isolated from mandacaru fruit, and 34 were preliminarily identified as LAB. Thirteen isolates identified by 16S-rRNA sequencing as Pediococcus pentosaceus were negative for DNase, gelatinase, hemolytic, and biogenic amine production. The selected isolates showed proteolytic activity, diacetyl and exopolysaccharide production, and good tolerance to different NaCl concentrations while having low cellular hydrophobicity and antagonistic activity against pathogens. The survival of isolates sharply decreased after 3 h of exposure to pH 2 and had a good tolerance to 1 % bile salt. A principal component analysis selected P. pentosaceus 57 as the most promising isolate based on the examined technological and probiotic-related physiological properties. This isolate was lyophilized with mandacaru fruit and stored under refrigeration for 90 days. P. pentosaceus 57 lyophilized with mandacaru fruit had high viable cell counts (9.69 ± 0.03 log CFU/mL) and >50 % of physiologically active cells at 90 days of refrigeration storage. The results indicate that mandacaru fruit is a source of P. pentosaceus with aptitudes to be explored as potential probiotic and technological characteristics of interest for the food industry, besides being a good candidate for use in lyophilization processes and refrigeration storage of LAB due to its cryoprotective effects.

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.

Spontaneous fermentation improves the physicochemical characteristics, bioactive compounds, and antioxidant activity of acerola (Malpighia emarginata D.C.) and guava (Psidium guajava L.) fruit processing by-products

This study aimed to investigate the effects of spontaneous fermentation on physicochemical characteristics, bioactive compounds, and antioxidant activity of acerola and guava fruit industrial by-products. Viable cell counts of lactic acid bacterial (LAB) in acerola and guava by-products were ≥ 5.0 log CFU/mL from 24 h up to 120 h of fermentation. Fermented acerola and guava by-products had increased luminosity and decreased contrast. Contents of total soluble solids and pH decreased, and titrable acidity increased in acerola and guava by-products during fermentation. Ascorbic acid contents decreased in acerola by-product and increased in guava by-product during fermentation. Different phenolic compounds were found in acerola and guava by-products during fermentation. Fermented acerola and guava by-products had increased contents of total flavonoids, total phenolics, and antioxidant activity. The contents of total flavonoids and total phenolics positively correlated with antioxidant activity in fermented acerola and guava by-products. These results indicate that spontaneous fermentation could be a strategy to improve the contents of bioactive compounds and the antioxidant activity of acerola and guava by-products, adding value and functionalities to these agro-industrial residues.

Predicting and Modelling the Growth of Potentially Pathogenic Bacteria in Coalho Cheese

Coalho is a semihard medium- to high-moisture cheese produced in various states in the northeastern region of Brazil. This study was conducted to predict the growth kinetics (maximum growth rate, Grmax) of Escherichia coli, Listeria monocytogenes, Salmonella, and Staphylococcus aureus using the ComBase predictor with various combinations of temperature, pH, and water activity (a_w) in commercial Coalho cheese samples. The growth of two antibiotic-resistant derivative strains of L. monocytogenes (parental strains ATCC 19115 and ATCC 7644) and S. aureus (parental strains ATCC 13565 and ATCC 19095) was measured in commercial Coalho cheese samples during 14 days of storage as a function of the initial contamination level (3 and 5 log CFU/g) and storage temperature (7.5 and 12°C). The highest Grmax values predicted by ComBase under the various conditions of temperature, pH, and a_w were for L. monocytogenes (0.006 to 0.065 log CFU/g/h) and S. aureus (0.003 to 0.048 log CFU/g/h). The Grmax values predicted by ComBase for E. coli and Salmonella were 0.007 to 0.026 and 0.008 to 0.041 log CFU/g/h, respectively. An experimental challenge in Coalho cheese revealed that the populations of all tested antibiotic-resistant derivative strains of L. monocytogenes and S. aureus increased (>0.5 log CFU/g) by day 14 of storage at 7.5 or 12°C. L. monocytogenes and S. aureus had higher Grmax values in cheese samples stored at 12°C than those stored at 7.5°C. The ComBase growth predictions under the temperature, pH, and a_w conditions in commercial Coalho cheese samples were generally fail-safe for predicting the growth of L. monocytogenes and S. aureus in the actual product. These results indicate that Coalho cheese has pH and a_w characteristics that allow the growth of E. coli, L. monocytogenes, Salmonella, and S. aureus. These cheeses are typically stored at temperatures that do not prevent the growth of these bacteria.

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.

Assessment of Nutrient Value and Microbiological Safety of Pomacea lineata

Pomacea lineata is a fresh water shellfish that is utilized as food, medicinal portions, or licking remedies. The objective of this study was to evaluate the nutritional and microbiological aspects of P. lineata and spawning. The samples were collected in the Jaguaribe River (Paraíba, Brazil) during the rainy and dry seasons. The biochemical composition, mineral composition, total mesophilic bacteria (TMB), total coliforms (TC), fecal coliforms (FC), Salmonella sp., Staphylococcus aureus, and Vibrio presence were determined. Each 100 g of P. lineata presented 3.1 g of ashes; 9.4 g of proteins; 2.7 g of lipids; 0.6 g of carbohydrates; 1800.0 mg of calcium; 78.0 mg of phosphorus, and 58.4 mg of iron. Each 100 g of spawning presented 10.4 g of ashes; 4.5 g of proteins; 2.8 g of lipids; 1.3 g of carbohydrates; 3633.0 mg of calcium; 39.4 mg of phosphorus; and 4.6 mg of iron. Each 100 g of P. lineata provided 65.7 kcal and spawning 48.3 kcal. In the dry season P. lineata and spawning showed no TMB and TC, FC, S. aureus, Salmonella, or Vibrio. In the rainy season P. lineata and spawning presented increase in TMB and TC, FC, S. aureus, and Salmonella. The presence of Vibrio was not detected. P. lineata presented proteins, low lipid, and carbohydrate content, energy values close to those of lean meats, high contents of calcium and iron, and presented low contamination level with pathogenic bacteria. Since P. lineata substances may be useful in the treatment of respiratory and gastrointestinal diseases without presenting toxic or cytotoxic effects already described in the literature, it may be considered as a potential functional food.

Biofilm formation by Staphylococcus aureus from food contact surfaces in a meat-based broth and sensitivity to sanitizers

This study assessed the capacity of adhesion, the detachment kinetic and the biofilm formation by Staphylococcus aureus isolated from food services on stainless steel and polypropylene surfaces (2 × 2 cm) when cultivated in a meat-based broth at 28 and 7 °C. It was also to study the efficacy of the sanitizers sodium hypochlorite (250 mg/L) and peracetic acid (30 mg/L) in inactivating the bacterial cells in the preformed biofilm. S. aureus strains adhered in high numbers regardless the assayed surface kind and incubation temperature over 72 h. Cells detachment of surfaces revealed high persistence over the incubation period. Number of cells needed for biofilm formation was noted at all experimental systems already after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered on polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacity to adhere and form biofilm on polypropylene and stainless steel surfaces under different growth conditions. Moreover, the cells in biofilm matrix were resistant for total removal when submitted to the exposure to sanitizers.

Adhesion and biofilm formation by Staphylococcus aureus from food processing plants as affected by growth medium, surface type and incubation temperature

This study assessed the effect of different growth media [BHI broth, BHI broth plus glucose (10 g/100 mL) and BHI broth plus NaCl (5 g/100 mL)] and incubation temperatures (28 or 37 ºC) on the adherence, detachment and biofilm formation on polypropylene and stainless steel surfaces (2 x 2 cm coupons) for a prolonged period (24-72 h) by some strains of Staphylococcus aureus (S3, S28 and S54) from food processing plants. The efficacy of the sanitizers sodium hypochlorite (250 mg/mL) and peracetic acid (30 mg/mL) in reducing the number of viable bacterial cells in a preformed biofilm was also evaluated. S. aureus strains adhered in highest numbers in BHI broth, regardless of the type of surface or incubation temperature. Cell detachment from surfaces revealed high persistence over the incubation period. The number of cells needed for biofilm formation was noted in all experimental systems after 3 days. Peracetic acid and sodium hypochlorite were not efficient in completely removing the cells of S. aureus adhered onto polypropylene and stainless steel surfaces. From these results, the assayed strains revealed high capacities to adhere and form biofilms on polypropylene and stainless steel surfaces under the different growth conditions, and the cells in biofilm matrixes were resistant to total removal when exposed to the sanitizers sodium hypochlorite and peracetic acid.

Combination of Origanum vulgare L. essential oil and lactic acid to inhibit Staphylococcus aureus in meat broth and meat model

This study assessed the occurrence of an enhancing inhibitory effect of the combined application of Origanum vulgare L. essential oil and lactic acid against Staphylococcus aureus by the determination of Fractional Inhibitory Concentration (FIC) index and cell viability in meat broth and meat model. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of the oil was 0.6 and 1.25 µL.mL^-1, respectively. Lactic acid showed MIC and MBC of 2.5 and 5µL.mL^-1, respectively. FIC indices of the combined application of the oil and lactic acid were 0.5 showing a synergic interaction. The essential oil and lactic acid showed similar (p>0.05) anti-S. aureus effect in meat broth over 96 h of exposure. Treatment with essential oil or lactic acid presented a smaller anti-staphylococcal effect in meat in comparison to meat broth. No significant difference (p>0.05) was found for the microbial counts in meat treated with each antimicrobial alone or in mixture. These results could arise as an interesting approach for the improvement of food preservation using more natural procedures, considering the current demand of consumer and sensory quality of foods.

Combined application of origanum vulgare l. essential oil and acetic acid for controlling the growth of staphylococcus aureus in foods

This study evaluated the occurrence of an enhancing inhibitory effect of the combined application of Origanum vulgare L. essential oil and acetic acid against Staphylococcus aureus by the determination of Fractional Inhibitory Concentration (FIC) index and kill-time assay in nutrient broth, meat broth and in a food model (meat pieces). Acetic acid showed MIC and MFC of 0.6 and 1.25 μL.mL^-1, respectively. For O. vulgare essential oil MIC and MBC were 1.25 and 2.5 μL.mL^-1, respectively. FIC indexes of the mixture of essential oil and acetic acid at MIC x ½ were ≤ 1.0, showing an additive effect. No synergy was found at kill-time study. Anti-staphylococcal effect of the antimicrobials alone or in mixture (MIC x ½) was lower in meat than in nutrient and meat broths. The effective combination of essential oils and organic acids could appear as an attractive alternative for the food industry, as the doses to inhibit the microbial growth in foods can be lowered.