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Abstract(s)
Os extratos obtidos a partir das sementes de Bixa orellana L. (urucum) são amplamente utilizados na indústria alimentar como um corante natural. Além disso, a composição química destas sementes tem sido associada à capacidade de retardar a deterioração de alimentos propícios a contaminação microbiana. Assim, a presente tese teve por objetivo geral avaliar o efeito antimicrobiano dos extratos de urucum, em um alimento muito propício à contaminação microbiana, a carne fresca, sobre Staphylococcus aureus, o qual é um patógeno de alta relevância nesta matriz alimentar. Este objetivo foi alcançado pela realização de duas experiências que visaram: (1) realizar uma síntese meta-analítica da capacidade antimicrobiana in vitro dos diversos extratos de urucum sobre S. aureus; e (2) caracterizar, mediante modelos de microbiologia preditiva, a cinética de sobrevivência do S. aureus, durante o período de refrigeração, em bifes de carne bovina revestidos com extrato de sementes de urucum em óleo de coco, embalados em atmosfera normal e a vácuo.
Para a modelação meta-analítica do diâmetro de inibição e da concentração mínima inibitória (MIC), referente à capacidade antimicrobiana in vitro destes extratos sobre o patógeno em questão, foi realizada uma revisão sistemática seguida da extração de dados de 17 artigos com informações consideradas relevantes. Para os dados de diâmetro de inibição encontrados nos artigos, aplicaram-se três modelos meta-analíticos com moderadores, e para o MIC realizou-se uma meta-análise de subgrupos sem moderadores.
O Modelo 1 que testou os efeitos do solvente, da concentração do extrato e da parte da planta, demonstrou um efeito significativo da concentração do extrato (p<0,001) no diâmetro de inibição, bem como permitiu evidenciar diferenças entre solventes (p<0,001) na sua eficácia na extração de compostos antimicrobianos. Para uma concentração fixa de extrato de folhas de 1,0 mg/ml, a extração em éter de petróleo produz maior diâmetro de inibição (12,71 mm) enquanto a extração em álcali produz o menor diâmetro de inibição (8,954 mm). O Modelo 2 mostrou que para uma concentração de 1,0 mg/ml, o diâmetro de inibição provocado pelo extrato de folhas foi de 10,97 mm e pelo extrato de sementes foi de 8,725 mm. Desta forma, S. aureus possui maior susceptibilidade aos extratos obtidos a partir de folhas. O Modelo 3 mostrou que os extratos metanólicos produziram halos de inibição 4,823 mm superiores (p<0,001) aos dos extratos etanólicos, e demonstrou que para um mesmo incremento na concentração do extrato, o extrato metanólico produz um incremento superior (+0,734 mm) no diâmetro de inibição do que o extrato etanólico (p=0,004). Os modelos meta-analíticos dos MIC evidenciaram que os extratos metanólicos e etanólicos de urucum têm maior efeito bacteriostático que os extratos obtidos com clorofórmio. O MIC global para os extratos de folhas (1,145 mg/ml; IC 95% 0,334 – 3,921 mg/ml) foi inferior ao MIC global para os extratos de sementes (1,383 mg/ml; IC 95% 0,179 – 10,70 mg/ml).
A caracterização da cinética de sobrevivência do S. aureus em bifes refrigerados revestidos com extrato de sementes de urucum em óleo de coco ao 0%, 10%, 20% e 30%, e armazenados sob atmosfera normal ou a vácuo, foi realizada mediante o ajuste do modelo Weibull(σ, β) a cada uma das curvas experimentais obtidas após inoculação superficial do patogênico nos bifes (~5.3 log CFU/cm2). Em termos gerais, quanto maior foi a concentração de urucum extraído, maior foi seu poder bactericida. Exceto para o extrato de urucum a 30%, todas as curvas do S. aureus inoculado nos bifes mantidos em atmosfera normal apresentaram uma fase inicial de resistência à inativação, pelo que os parâmetros de forma β quantificaram a convexidade da curva de inativação com valores maiores a 1,0. Comprovou-se uma maior inativação quando os bifes foram embalados a vácuo, mediante o decréscimo imediato do S. aureus em todas as curvas de sobrevivência, agora côncavas (β<1,0). Uma transformação dos parâmetros Weibullianos σ e β permitiu estimar o tempo necessário para atingir a primeira redução decimal do S. aureus em bifes revestidos com óleo de urucum extraído ao 0%, 10%, 20% e 30%, o qual foi ∞, 14,4 dias (IC 95%: 8,1 – 20,8 dias), 8,3 dias (IC 95%: 6,6 – 10,1 dias) e 2,5 dias (IC 95%: 0,24 – 4,8 dias), respectivamente, quando embalados em atmosfera normal; e significativamente e gradativamente menores quando embalados a vácuo: 10,6 dias (IC 95%: 0,80 – 22 dias), 7,2 dias (IC 95%: 0,11 – 14,3 dias), 2,9 dias (IC 95%: 2,2 – 3,7 dias) e 0,43 dias (IC 95%: 0,05 – 0,81 dias), respectivamente. Este trabalho de investigação permitiu concluir que o extrato de sementes de urucum em óleo de coco apresenta-se como um antimicrobiano promissor que pode ser aplicado como cobertura de carnes de bovino in natura para o controle do S. aureus.
The extracts obtained from the seeds of Bixa orellana L. (annatto) are widely used in industry as a natural food colorant. In addition, the chemical composition of these seeds has been associated with the ability to delay microbiological deterioration. Thus, the present thesis had the general objective of evaluating the antimicrobial effect of annatto extracts in a food commodity highly susceptible to microbial contamination – fresh bovine meat – against Staphylococcus aureus, which is a highly incident pathogen in this food matrix. This objective was achieved through two experiments aimed at: (1) performing a meta-analytical synthesis of the in vitro antimicrobial capacity of different annatto extracts against S. aureus; and (2) to characterise, using predictive microbiology models, the survival kinetics of S. aureus in refrigerated beef steaks coated with annatto seed oil extract, packed under normal atmosphere and vacuum condition. For the meta-analytical modelling of the inhibition diameter and the minimum inhibitory concentration (MIC), referring to the in vitro antimicrobial capacity of annatto extracts against the pathogen in question, a systematic review was first undertaken followed by data extraction of 17 articles with relevant information. Three meta-analytical models with moderators were adjusted to the inhibition diameter data, and a subgroup meta-analysis model was adjusted to the MIC data. Model I that tested the effects of the solvent, extract concentration and part of the plant demonstrated a significant effect of the extract concentration (p<0.001) on the inhibition diameter, and allowed to find differences between solvents (p <0.001) in their effectiveness to extract antimicrobial compounds. For a fixed concentration of leaf extract of 1.0 mg/ml, extraction in petroleum ether is expected to produce the largest diameter of inhibition (12.71 mm) while extraction in alkali the smallest diameter of inhibition (8.954 mm) against S. aureus. Model II summarised that, for a concentration of 1.0 mg ml, the inhibition diameter caused by the leaf extract is 10.97 mm and by the seed extract 8.725 mm, so that S. aureus is more susceptible to leaf extracts. Model III estimated that methanolic extracts produced, on average, inhibition halos 4.823 mm larger than ethanolic extracts (p<0.001), and demonstrated that for the same increase in extract concentration, methanolic extracts produce a greater increase in the diameter of inhibition (in 0.734 mm) than ethanolic extracts (p=0.004). The meta-analytical models of MIC showed that the methanolic and ethanolic extracts of annatto have a greater bacteriostatic effect than the extracts in chloroform. The overall MIC for leaf extracts (1.145 mg/ml; 95% CI 0.334 - 3.921 mg/ml) was numerically lower than the overall MIC for seed extracts (1.383 mg/ml; 95% CI 0.179 - 10.70 mg/ml). The characterisation of the survival kinetics of S. aureus in refrigerated beef steaks coated with coconut oil extract of annatto seeds at 0%, 10%, 20% and 30%, and stored under normal atmosphere or under vacuum, was carried out by adjusting the Weibull (σ, β) model to each of the experimental curves that were obtained after surface inoculation of the pathogen on the steaks (~ 5.3 log CFU/cm2). In general terms, the greater the concentration of annatto extracted, the greater its bactericidal effect. Except for the annatto extract at 30%, all S. aureus curves from steaks in normal atmosphere showed an initial phase of resistance to inactivation, so the β shape parameters quantified this convexity with values greater than 1.0. Greater effectiveness of the extract was verified when the steaks were vacuum-packed, by means of the immediate decrease of S. aureus in all survival curves, now of concave shape (β <1.0). A transformation of the Weibullian parameters σ and β made it possible to estimate the time needed to reach the first decimal reduction of S. aureus on steaks coated with annatto oil extracted at 0%, 10%, 20% and 30%, which was ∞, 14.4 days (95% CI: 8.1 - 20.8 days), 8.3 days (95% CI: 6.6 - 10.1 days) and 2.5 days (95% CI: 0.24 - 4.8 days), respectively, when packaged under normal atmosphere; and significantly and gradually lower when vacuum-packed: 10.6 days (95% CI: 0.80 - 22 days), 7.2 days (95% CI: 0.11 - 14.3 days), 2.9 days (95% CI: 2.2 - 3.7 days) and 0.43 days (95% CI: 0.05 - 0.81 days), respectively. This research work concluded that the extract of annatto seeds in coconut oil emerges as a promising antimicrobial that can be applied as a coating on fresh beef to control S. aureus.
The extracts obtained from the seeds of Bixa orellana L. (annatto) are widely used in industry as a natural food colorant. In addition, the chemical composition of these seeds has been associated with the ability to delay microbiological deterioration. Thus, the present thesis had the general objective of evaluating the antimicrobial effect of annatto extracts in a food commodity highly susceptible to microbial contamination – fresh bovine meat – against Staphylococcus aureus, which is a highly incident pathogen in this food matrix. This objective was achieved through two experiments aimed at: (1) performing a meta-analytical synthesis of the in vitro antimicrobial capacity of different annatto extracts against S. aureus; and (2) to characterise, using predictive microbiology models, the survival kinetics of S. aureus in refrigerated beef steaks coated with annatto seed oil extract, packed under normal atmosphere and vacuum condition. For the meta-analytical modelling of the inhibition diameter and the minimum inhibitory concentration (MIC), referring to the in vitro antimicrobial capacity of annatto extracts against the pathogen in question, a systematic review was first undertaken followed by data extraction of 17 articles with relevant information. Three meta-analytical models with moderators were adjusted to the inhibition diameter data, and a subgroup meta-analysis model was adjusted to the MIC data. Model I that tested the effects of the solvent, extract concentration and part of the plant demonstrated a significant effect of the extract concentration (p<0.001) on the inhibition diameter, and allowed to find differences between solvents (p <0.001) in their effectiveness to extract antimicrobial compounds. For a fixed concentration of leaf extract of 1.0 mg/ml, extraction in petroleum ether is expected to produce the largest diameter of inhibition (12.71 mm) while extraction in alkali the smallest diameter of inhibition (8.954 mm) against S. aureus. Model II summarised that, for a concentration of 1.0 mg ml, the inhibition diameter caused by the leaf extract is 10.97 mm and by the seed extract 8.725 mm, so that S. aureus is more susceptible to leaf extracts. Model III estimated that methanolic extracts produced, on average, inhibition halos 4.823 mm larger than ethanolic extracts (p<0.001), and demonstrated that for the same increase in extract concentration, methanolic extracts produce a greater increase in the diameter of inhibition (in 0.734 mm) than ethanolic extracts (p=0.004). The meta-analytical models of MIC showed that the methanolic and ethanolic extracts of annatto have a greater bacteriostatic effect than the extracts in chloroform. The overall MIC for leaf extracts (1.145 mg/ml; 95% CI 0.334 - 3.921 mg/ml) was numerically lower than the overall MIC for seed extracts (1.383 mg/ml; 95% CI 0.179 - 10.70 mg/ml). The characterisation of the survival kinetics of S. aureus in refrigerated beef steaks coated with coconut oil extract of annatto seeds at 0%, 10%, 20% and 30%, and stored under normal atmosphere or under vacuum, was carried out by adjusting the Weibull (σ, β) model to each of the experimental curves that were obtained after surface inoculation of the pathogen on the steaks (~ 5.3 log CFU/cm2). In general terms, the greater the concentration of annatto extracted, the greater its bactericidal effect. Except for the annatto extract at 30%, all S. aureus curves from steaks in normal atmosphere showed an initial phase of resistance to inactivation, so the β shape parameters quantified this convexity with values greater than 1.0. Greater effectiveness of the extract was verified when the steaks were vacuum-packed, by means of the immediate decrease of S. aureus in all survival curves, now of concave shape (β <1.0). A transformation of the Weibullian parameters σ and β made it possible to estimate the time needed to reach the first decimal reduction of S. aureus on steaks coated with annatto oil extracted at 0%, 10%, 20% and 30%, which was ∞, 14.4 days (95% CI: 8.1 - 20.8 days), 8.3 days (95% CI: 6.6 - 10.1 days) and 2.5 days (95% CI: 0.24 - 4.8 days), respectively, when packaged under normal atmosphere; and significantly and gradually lower when vacuum-packed: 10.6 days (95% CI: 0.80 - 22 days), 7.2 days (95% CI: 0.11 - 14.3 days), 2.9 days (95% CI: 2.2 - 3.7 days) and 0.43 days (95% CI: 0.05 - 0.81 days), respectively. This research work concluded that the extract of annatto seeds in coconut oil emerges as a promising antimicrobial that can be applied as a coating on fresh beef to control S. aureus.
Description
Mestrado de dupla diplomação com o Centro Federal de Educação Tecnológica Celso Suckow da Fonseca - CEFET/RJ
Keywords
Antimicrobiano Achiote Óleo de coco Revestimento Meta-análise Weibull