Probability of growth modelling to optimise the use of biopreservation technologies to control the development of Staphylococcus aureus in goat’s raw milk soft cheeses

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Effects of essential oils on escherichia coli inactivation in cheese as described by meta-regression modelling

Publication . Silva, Beatriz Nunes; Cadavez, Vasco; Teixeira, José; Gonzales-Barron, Ursula

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). The growing intention to replace chemical food preservatives with plant-based antimicrobials that pose lower risks to human health has produced numerous studies describing the bactericidal properties of biopreservatives such as essential oils (EOs) in a variety of products, including cheese. This study aimed to perform a meta-analysis of literature data that could summarize the inactivation of Escherichia coli in cheese achieved by added EOs; and compare its inhibitory effectiveness by application method, antimicrobial concentration, and specific antimicrobials. After a systematic review, 362 observations on log reduction data and study characteristics were extracted from 16 studies. The meta-regression model suggested that pathogenic E. coli is more resistant to EO action than the non-pathogenic type (p 0.0001), although in both cases the higher the EO dose, the greater the mean log reduction achieved (p 0.0001). It also showed that, among the factual application methods, EOs’ incorporation in films render a steadier inactivation (p 0.0001) than when directly applied to milk or smeared on cheese surface. Lemon balm, sage, shallot, and anise EOs showed the best inhibitory outcomes against the pathogen. The model also revealed the inadequacy of inoculating antimicrobials in cheese purposely grated for performing challenge studies, as this non-realistic application overestimates (p 0.0001) the inhibitory effects of EOs.

2020Journal article

Open access

Lactic acid bacteria from artisanal raw goat milk cheeses: technological properties and antimicrobial potential

Publication . Silva, Beatriz Nunes; Fernandes, Nathália; Carvalho, Laís; Faria, Ana Sofia; Teixeira, José António; Rodrigues, Carina; Gonzales-Barron, Ursula; Cadavez, Vasco

In cheese-making, a starter culture composed of adequately chosen lactic acid bacteria (LAB) may be suitable to ensure the rapid acidification of milk, improve textural and sensory characteristics, and avoid pathogen proliferation. In this work, 232 LAB isolates collected from artisanal goat’s raw milk cheeses produced in Portugal were evaluated for their antimicrobial capacity (at 10 and 37°C), as well as their acidifying and proteolytic properties. Among the 232 isolates, at least 98% of those isolated in De Man- Rogosa-Sharpe (MRS) agar presented antagonism against Listeria monocytogenes, Salmonella Typhimurium, or Staphylococcus aureus, whereas less than 28.1% of M17-isolated LAB showed antagonism against these pathogens. M17-isolated LAB displayed better results than MRS ones in terms of acidifying capacity. As for the proteolytic assay, only 2 MRS isolates showed casein hydrolysis capacity. Principal component analyses and molecular characterization of a subset of selected isolates were conducted to identify those with promising capacities and to correlate the identified LAB genera and species with their antimicrobial, acidifying, and/or proteolytic properties. Lactococcus strains were associated with the highest acidifying capacity, whereas Leuconostoc and Lacticaseibacillus strains were more related to antimicrobial capacities. Leuconostoc mesenteroides, Lactococcus lactis, and Lacticaseibacillus paracasei were the predominant organisms found. The results of this work highlight various strains with pathogen inhibition capacity and suitable technological properties to be included in a customized starter culture. In future work, it is necessary to appropriately define the starter culture and implement it in the cheese-making process to evaluate if the in-vitro capacities are observable in a real food system.

2023Journal article

Open access

Technological potential of lactic acid bacteria isolated from Portuguese goat’s raw milk cheeses

Publication . Silva, Beatriz Nunes; Faria, Ana Sofia; Cadavez, Vasco; Teixeira, José António; Gonzales-Barron, Ursula

In this work, a total of 97 MRS-grown and 135 M17-grown lactic acid bacteria strains were isolated from 20 goat’s raw milk cheeses, and their antimicrobial, acidifying, and proteolytic activities were determined in vitro. Principal component analyses adjusted to a subset of 84 promising isolates evidenced that, for MRS isolates, antagonism against Staphylococcus aureus correlated well with higher acidification potential, whereas for M17 isolates, the antagonisms against S. aureus and Listeria monocytogenes were more correlated. The outcomes highlighted various strains with pathogen inhibition ability and satisfactory technological properties that may be useful for the development of a customised starter culture.

2021Conference object

Open access

In vitro antimicrobial activity of extracts and essential oils of Cinnamomum, Salvia, and Menthaspp. against foodborne pathogens: a meta‐analysis study

Publication . Ezzaky, Youssef; Elmoslih, Abdelkhaleq; Silva, Beatriz Nunes; Bonilla‐Luque, Olga María; Possas, Arícia; Valero, Antonio; Cadavez, Vasco; Gonzales-Barron, Ursula; Achemchem, Fouad

Essential oils (EOs) are a class of natural products that exhibit potent antimicrobial properties against a broad spectrum of bacteria. Inhibition diameters (IDs) and minimum inhibitory concentrations (MICs) are the typical measures of antimicrobial activity for extracts and EOs obtained from Cinnamomum, Salvia, and Mentha species. This study used a meta-analytical regression analysis to investigate the correlation between ID and MIC measurements and the variability in antimicrobial susceptibility tests. By utilizing pooled ID models, this study revealed significant differences in foodborne pathogens’ susceptibility to extracts, which were dependent on both the plant species and the methodology employed (p < .05). Cassia showed the highest efficacy against Salmonella spp., exhibiting a pooled ID of 26.24 mm, while cinnamon demonstrated the highest efficacy against Bacillus cereus, with a pooled ID of 23.35 mm. Mint extract showed the greatest efficacy against Escherichia coli and Staphylococcus aureus. Interestingly, cinnamon extract demonstrated the lowest effect against Shiga toxin-producing E. coli, with a pooled ID of only 8.07 mm, whereas its EOs were the most effective against this bacterial strain. The study found that plant species influenced the MIC, while the methodology did not affect MIC measurements (p > .05). An inverse correlation between ID and MIC measurements was identified (p < .0001). These findings suggest that extracts and EOs obtained from Cinnamomum, Salvia, and Mentha spp. have the potential to inhibit bacterial growth. The study highlights the importance of considering various factors that may influence ID and MIC measurements when assessing the effectiveness of antimicrobial agents.

2023Journal article

Open access

Extraction, chemical characterization, and antioxidant activity of bioactive plant extracts

Publication . Silva, Beatriz Nunes; Cadavez, Vasco; Ferreira-Santos, Pedro; Teixeira, José António; Gonzales-Barron, Ursula

Natural extracts have been proposed as preservatives to increase the safety of various food products. In this work, the phytochemical and antioxidant profiles of French lavender (Lavandula stoechas), lemon balm, basil, tarragon, salvia, and spearmint extracts were studied. The results show that hydroethanolic extracts may be more effective as biopreservatives if moderate temperatures are used in the extraction process, as they revealed higher phenolic content. More specifically, the results also show that lemon balm extracts present a great potential to be used as biopreservatives, due to their high-level phenolic and flavonoid contents and antioxidant activity.

2020Conference object

Open access