Browsing by Author "Sant'Ana, Anderson S."
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- An extend bigelow-type meta-regression model descring the heat resistance of neosartorya sporesPublication . Gonzales-Barron, Ursula; Cadavez, Vasco; Alvarenga, Verônica O.; Prado-Silva, Leonardo; Sant'Ana, Anderson S.A meta-regression based on an extended-Bigelow equation was adjusted to 326 D-values of Neosartorya spp., taken from the literature, in order to summarise its heat resistance parameters. As the meta-regression accommodated relevant study characteristics, it was possible to estimate D*-values and z-values of temperature, pH and °Brix for the various beverages, inactivation methods, fruits and preservative use/no use.
- Anti-listerial activity of lactic acid bacteria isolated from artisanal cheeses produced in the State of Minas Gerais, BrazilPublication . Campagnollo, Fernanda B.; Margalho, Larissa P.; Kamimura, Bruna A.; Alvarenga, Verônica O.; Cadavez, Vasco; Gonzales-Barron, Ursula; Sant'Ana, Anderson S.Introduction: Brazilian artisanal cheeses, among them Minas cheeses, are highly appreciated by consumers. Nonetheless, some cheeses have been regularly found to harbour high-risk pathogens, such as Listeria monocytogenes, mainly arising from their elaboration with raw milk and informal production. However, cheese matrices are complex systems whose microbial competing factors (i.e., indigenous lactic acid bacteria (LAB)) and intrinsic properties (acidity, temperature, and water activity) can act as effective hurdles against L. monocytogenes proliferation. Purpose: The aim of this study was to evaluate the capacity of LAB strains isolated from Minas artisanal cheeses as anti-listerial agents. Methods: A total of 891 LAB strains were isolated from 244 Minas artisanal cheese samples (466 using MRS agar (MRSLAB) and 425 using M17 agar (M17LAB)), which were tested qualitatively for anti-listerial activity by the deferred antagonism assay at 30oC (24 h). Two L. monocytogenes strains, serotypes 1/2b and 4b, isolated from cheese and crude milk, respectively, were used. LAB strains with positive anti-listerial activity at 30oC were further tested at 7oC (10 days). Results: MRSLAB strains presented significantly better anti-listerial activity at 30oC (73.0% and 70.8% for serotypes 1/2b and 4b, respectively) compared to M17LAB strains (21.2% and 23.1%, respectively), and there was no significant difference between listeria serotypes (P<0.05). Selected MRSLAB and M17LAB strains were able to keep anti-listerial activity at 7oC, with no significant differences between MRSLAB (96.8% and 97.2% for listeria 1/2b and 4b, respectively) and M17LAB (95.2% and 96.8%, respectively) or between Listeria serotypes (P<0.05). Significance: These results suggested that LAB isolated from Minas cheeses using MRS agar present a better inhibitory effect against L. monocytogenes at different temperatures. These strains can be used as starter cultures in order to inhibit pathogen survival.
- Behavior of Listeria monocytogenes in the presence or not of intentionally-added lactic acid bacteria during ripening of artisanal Minas semi-hard cheesePublication . Gonzales-Barron, Ursula; Campagnollo, Fernanda B.; Schaffner, Donald W.; Sant'Ana, Anderson S.; Cadavez, VascoThe fate of Listeria monocytogenes during ripening of artisanal Minas semi-hard cheese, as influenced by cheese intrinsic properties and by autochthonous (naturally present) or intentionally-added anti-listerial lactic acid bacteria (LAB) was modeled. Selected LAB strains with anti-listerial capacity were added or not to raw or pasteurized milk to prepare 4 cheese treatments. Counts of LAB and L. monocytogenes, pH, temperature and water activity were determined throughout cheese ripening (22 days, 22±1ᵒC). Different approaches were adopted to model the effect of LAB on L. monocytogenes: an independent approach using the Huang primary model to describe LAB growth and the linear decay model to describe pathogen inactivation; the Huang-Cardinal [pH] model using the effect of pH variation in a dynamic tertiary approach; and the Jameson-effect with Nmax tot model which simultaneously describes L. monocytogenes and LAB fate. L. monocytogenes inactivation occurred in both treatments with added LAB and inactivation was faster in raw milk cheese (−0.0260 h−1) vs. pasteurized milk cheese (−0.0182 h−1), as estimated by the linear decay model. Better goodness-of-fit was achieved for the cheeses without added LAB when the Huang primary model was used. A faster and great pH decline was detected for cheeses with added LAB, and the Huang-Cardinal [pH] model predicted higher pathogen growth rate in cheese produced with raw milk, but greater L. monocytogenes final concentration in pasteurized milk cheese. The Jameson-effect model with Nmax tot predicted that LAB suppressed pathogen growth in all treatments, except in the treatment with pasteurized milk and no LAB addition. The Huang-Cardinal [pH] model was more accurate in modeling L. monocytogenes kinetics as a function of pH changes than was the Jameson-effect model with Nmax tot as a function of LAB inhibitory effect based on the goodness-of-fit measures. The Jameson-effect model may however be a better competition model since it can more easily represent L. monocytogenes growth and death. This study presents crucial kinetic data on L. monocytogenes behavior in the presence of competing microbiota in Minas semi-hard cheese under dynamic conditions.
- A comparison of dynamic tertiary and competition models for describing the fate of Listeria monocytogenes in Minas fresh cheese during refrigerated storagePublication . Cadavez, Vasco; Campagnollo, Fernanda B.; Silva, Rosicléia A.; Duffner, Clara M.; Schaffner, Donald W.; Sant'Ana, Anderson S.; Gonzales-Barron, UrsulaThis study compares dynamic tertiary and competition models for L. monocytogenes growth as a function of intrinsic properties of a traditional Brazilian soft cheese and the inhibitory effect of lactic acid bacteria (LAB) during refrigerated storage. Cheeses were prepared from raw or pasteurized milk with or without the addition of selected LAB with known anti-listerial activity. Cheeses were analyzed for LAB and L. monocytogenes counts, pH and water activity (aw) throughout cold storage. Two approaches were used to describe the effect of LAB on L. monocytogenes: a Huang-Cardinal model that considers the effect of pH and aw variation in a dynamic kinetic analysis framework; and microbial competition models, including Lotka-Volterra and Jameson-effect variants, describing the simultaneous growth of L. monocytogenes and LAB. The Jameson-effect with γ and the Lotka-Volterra models produced models with statistically significant coefficients that characterized the inhibitory effect of selected LAB on L. monocytogenes in Minas fresh cheese. The Huang-Cardinal model [pH] outperformed both competition models. Taking aw change into account did not improve the fit quality of the Huang-Cardinal [pH] model. These models for Minas soft cheese should be valuable for future microbial risk assessments for this culturally important traditional cheese
- Meta-analysis of the effects of sanitizing treatments on Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes inactivation in fresh producePublication . Prado-Silva, Leonardo; Cadavez, Vasco; Gonzales-Barron, Ursula; Rezende, Ana Carolina B.; Sant'Ana, Anderson S.The aim of this study was to perform a meta-analysis of the effects of sanitizing treatments of fresh produce on Salmonella spp., Escherichia coli O157:H7 and Listeria monocytogenes. From 55 primary studies found to report on such effects, 40 were selected based on specific criteria, leading to more than 1000 data on mean log reduction of these three bacterial pathogens impairing the safety of fresh produce. Data were partitioned to build three meta-analytical models that could allow the assessment of differences in mean log reductions among pathogens, fresh produce and sanitizers. Moderating variables assessed in the meta-analytical models included type of fresh produce, type of sanitizer, concentration, treatment time and temperature. Further, a proposal was done to classify the sanitizers according to their bactericidal efficacy by means of a meta-analytical dendrogram. The results indicated that both time and temperature significantly affected the mean log reductions of the sanitizing treatment (p<0.0001). In general, sanitizer treatments led to lower mean log reductions when applied to leafy greens (for example, 0.68 log-reductions [0.00-1.37] achieved in lettuce) as compared to other non-leafy vegetables (for example, 3.04 mean log-reductions [2.32-3.76] obtained for carrots). Among the pathogens, E. coli 0157:H7 was more resistant to ozone (1.6 mean log reductions), while L. monocytogenes and Salmonella presented high resistance to organic acids such as, citric acid, acetic acid and lactic acid (∼3.0 mean log reductions). With regards to the sanitizers, it has been found that slightly acidic electrolysed water, acidified sodium chlorite and the gaseous chlorine dioxide clustered together, indicating they possessed the strongest bactericidal effect. The results reported seem to be an important achievement for advancing the global understanding of the effectiveness of sanitizers for microbial safety of fresh produce.
- Modeling the effects of temperature and pH on the resistance of Alicyclobacillus acidoterrestris in conventional heat-treated fruit beverages through a meta-analysis approachPublication . Silva, Leonardo P.; Gonzales-Barron, Ursula; Cadavez, Vasco; Sant'Ana, Anderson S.In this work, all publicly-accessible published findings on Alicyclobacillus acidoterrestris heat resistance in fruit beverages as affected by temperature and pH were compiled. Then, study characteristics (protocols, fruit and variety, °Brix, pH, temperature, heating medium, culture medium, inactivation method, strains, etc.) were extracted from the primary studies, and some of them incorporated to a meta-analysis mixed-effects linear model based on the basic Bigelow equation describing the heat resistance parameters of this bacterium. The model estimated mean D* values (time needed for one log reduction at a temperature of 95°C and a pH of 3.5) of Alicyclobacillus in beverages of different fruits, two different concentration types, with and without bacteriocins, and with and without clarification. The z T (temperature change needed to cause one log reduction in D-values) estimated by the meta-analysis model were compared to those ('observed' z T values) reported in the primary studies, and in all cases they were within the confidence intervals of the model. The model was capable of predicting the heat resistance parameters of Alicyclobacillus in fruit beverages beyond the types available in the meta-analytical data. It is expected that the compilation of the thermal resistance of Alicyclobacillus in fruit beverages, carried out in this study, will be of utility to food quality managers in the determination or validation of the lethality of their current heat treatment processes.
- Quantitative risk assessment of Listeria monocytogenes in traditional Minas cheeses: the cases of artisanal semi-hard and fresh soft cheesesPublication . Campagnollo, Fernanda B.; Gonzales-Barron, Ursula; Cadavez, Vasco; Sant'Ana, Anderson S.; Schaffner, Donald W.This study estimated the risk of listeriosis from Brazilian cheese consumption using quantitative microbial risk assessment (QMRA). Risks associated to consumption of two cheese types were assessed: artisanal ripened semihard cheese (produced with raw milk) and refrigerated fresh soft cheese (produced with pasteurized milk). The semi-hard cheese model predicted Listeria monocytogenes growth or decline during ripening, while the soft cheese model predicted pathogen growth during refrigerated storage. Semi-hard cheese modeling scenarios considered L. monocytogenes starting concentration from −2.4 to 6 log CFU/mL in raw milk and three ripening times (4, 22 and 60 days). Soft cheese modeling scenarios considered L. monocytogenes starting concentration from −2.4 to 4 log CFU/mL in milk. The inclusion of anti-listerial lactic acid bacteria (LAB) in cheeses was also examined. Risk of listeriosis due to consumption of soft cheese was 6000 and 190 times greater than that of semi-hard cheese, for general and vulnerable populations, respectively. Aging semi-hard cheese reduced risk, and risk was influenced by L. monocytogenes starting concentration. Aging cheese with inhibitory LAB for 22 days reduced risk over 4 million-fold when L. monocytogenes was assumed to be 6 log CFU/mL in raw milk. The inclusion of inhibitory LAB also reduced risk of listeriosis due to soft cheese consumption, but not as much as for semi-hard cheese. QMRA results predicted that consumption of contaminated cheeses can carry a high risk of listeriosis, especially for vulnerable populations. Scenario analyses indicated that aging of semi-hard cheese and inclusion of antimicrobial LAB mix in semi-hard and soft cheeses are effective risk mitigation measures.
- Selection of indigenous lactic acid bacteria presenting anti-listerial activity, and their role in reducing the maturation period and assuring the safety of traditional Brazilian cheesesPublication . Campagnollo, Fernanda B.; Margalho, Larissa P.; Kamimura, Bruna A.; Feliciano, Marcelo D.; Freire, Luisa; Lopes, Letícia S.; Alvarenga, Verônica O.; Cadavez, Vasco; Gonzales-Barron, Ursula; Schaffner, Donald W.; Sant'Ana, Anderson S.Artisanal raw milk cheeses are highly appreciated dairy products in Brazil and ensuring their microbiological safety has been a great need. This study reports the isolation and characterization of lactic acid bacteria (LAB) strains with anti-listerial activity, and their effects on Listeria monocytogenes during refrigerated shelf-life of soft Minas cheese and ripening of semi-hard Minas cheese. LAB strains (n ¼ 891) isolated from Minas artisanal cheeses (n ¼ 244) were assessed for anti-listerial activity by deferred antagonism assay at 37 C and 7 C. The treatments comprised the production of soft or semi-hard Minas cheeses using raw or pasteurized milk, and including the addition of selected LAB only [Lactobacillus brevis 2-392, Lactobacillus plantarum 1-399 and 4 Enterococcus faecalis (1-37, 2-49, 2-388 and 1-400)], L. monocytogenes only, selected LAB co-inoculated with L. monocytogenes, or without any added cultures. At 37 C, 48.1% of LAB isolates showed anti-listerial capacity and 77.5% maintained activity at 7 C. Selected LAB strains presented a bacteriostatic effect on L. monocytogenes in soft cheese. L. monocytogenes was inactivated during the ripening of semi-hard cheeses by the mix of LAB added. Times to attain a 4 log-reduction of L. monocytogenes were 15 and 21 days for semi-hard cheeses produced with raw and pasteurized milk, respectively. LAB with anti-listerial activity isolated from artisanal Minas cheeses can comprise an additional barrier to L. monocytogenes growth during the refrigerated storage of soft cheese and help shorten the ripening period of semi-hard cheeses aged at ambient temperature.
- Using extended Bigelow meta-regressions for modelling the effects of temperature, pH, °Brix on the inactivation of heat resistant mouldsPublication . Alvarenga, Verônica O.; Gonzales-Barron, Ursula; Silva, Leonardo P.; Cadavez, Vasco; Sant'Ana, Anderson S.The management of Heat Resistant Moulds (HRMs) is considered a great challenge for the juice fruit industry. Neosartorya, Byssochlamys and Talaromyces are three out of the main genera isolated from fruit juices that show great resistance to heat treatments. Several inactivation parameters can be found in the literature, however all of them were carried out in specific food matrices and using diverse inactivation methods. Thus, this meta-analysis study synthesizes the thermal resistance parameters of the three HRMs by adjusting extended Bigelow-based meta-regression models to data on inactivation experiments conducted in different liquid media. The meta-analytical data, extracted from publications between 1969 and 2017, was composed of decimal reduction time (D), inactivation method, temperature of inactivation, pH, °Brix, age of spores, and type of medium (model, juice, concentrates). Pooled D* values (D at 90 °C, pH 3.5 and 12° Brix) were estimated for B. fulva (1.95 min; 95% CI: 1.21–3.11 min), Talaromyces (4.03 min; 95% CI: 3.43–4.74 min), Neosartorya (0.5.35 min; 95% CI: 4.10–7.08 min), and B. nivea (10.32 min; 95% CI: 5.81–18.4 min). It was found that increasing the soluble solids in concentrates tends to cause a lower decrease in the heat resistance of Neosartorya and Talaromyces than increasing the soluble solids in model liquid or juices (p = 0.001; 0.012). In general, the screw-capped tubes and three neck round inactivation methods render higher D* values (p lt 0.05) than the thermal death tubes, the polyethylene bag and the capillary methods. Spores of Talaromyces (overall zpH = 7.56; 95% CI: 5.13–13.5) and Neosartorya (overall zpH = 7.07; 95% CI: 5.04–10.8) appear to be more thermal sensitive to a decrease in medium pH than spores of Byssochlamys (overall zpH = 4.34; 95% CI: 3.20–6.73). The meta-regression models presented in this study can be valuable for estimating pooled inactivation kinetic parameters to be used by the fruit juice industry in the management of thermal processes and in the determination of shelf-life.