Growth of Byssochlamys nivea in pineapple juice under the effect of water activity and ascospore age

The study of thermal resistant mould, including Byssochlamys nivea, is of extreme importance since it has been associated with fruit and fruit products. The aim of this work is to analyze the influence of water activity (a w) and ascospore age (I) on the growth of Byssochlamys nivea in pineapple juice. Mold growth was carried out under different conditions of water activity (a w) (0.99, 0.96, 0.95, 0.93, 0.90) and ascospore age (I) (30, 51, 60, 69, 90 days). Growth parameters as length of adaptation phase (λ), maximum specific growth rate (µmax) and maximum diameter reached by the colony (λ) were obtained through the fit of the Modified Gompertz model to experimental data (measuring radial colony diameter). Statistica 6.0 was used for statistical analyses (significance level α = 0.05). The results obtained clearly showed that water activity is statistically significant and that it influences all growth parameters, while ascospore age does not have any statistically significant influence on growth parameters. Also, these data showed that by increasing a w from 0.90 to 0.99, the λ value substantially decreased, while µmax and λ values rose. The data contributed for the understanding of the behavior of B. nivea in pineapple juice. Therefore, it provided mathematical models that can well predict growth parameters, also helping on microbiological control and products' shelf life determination.

Growth of byssochlamys nivea in pineapple juice under the effect of water activity and ascospore age.

The study of thermal resistant mould, including Byssochlamys nivea, is of extreme importance since it has been associated with fruit and fruit products. The aim of this work is to analyze the influence of water activity (aw) and ascospore age (I) on the growth of Byssochlamys nivea in pineapple juice. Mold growth was carried out under different conditions of water activity (aw) (0.99, 0.96, 0.95, 0.93, 0.90) and ascospore age (I) (30, 51, 60, 69, 90 days). Growth parameters as length of adaptation phase (λ), maximum specific growth rate (µmax) and maximum diameter reached by the colony (A) were obtained through the fit of the Modified Gompertz model to experimental data (measuring radial colony diameter). Statistica 6.0 was used for statistical analyses (significance level α = 0.05). The results obtained clearly showed that water activity is statistically significant and that it influences all growth parameters, while ascospore age does not have any statistically significant influence on growth parameters. Also, these data showed that by increasing aw from 0.90 to 0.99, the λ value substantially decreased, while µmax and A values rose. The data contributed for the understanding of the behavior of B. nivea in pineapple juice. Therefore, it provided mathematical models that can well predict growth parameters, also helping on microbiological control and products' shelf life determination.

Alicyclobacillus acidoterrestris in pasteurized exotic Brazilian fruit juices: isolation, genotypic characterization and heat resistance.

In this study, the population of Alicyclobacillus spp. was estimated in pasteurized exotic Brazilian fruit juices using the most probable number (MPN) technique followed by biochemical tests. Pasteurized passion fruit (n = 57) and pineapple (n = 50) juices were taken directly from Brazilian manufacturers. While Alicyclobacillus spp. was isolated from passion fruit juice, the microorganism was not found in any pineapple juice samples. A higher incidence of Alicyclobacillus was observed in samples taken in June and July (dry months in Brazil) in comparison to the other months (March, April, May and August), and the highest Alicyclobacillus counts were recovered from these samples(>23 MNP/100 mL). Sixteen (n = 16) Alicyclobacillus strains were typed using the randomly amplified polymorphic DNA method (RAPD-PCR). RAPD-PCR revealed great genetic similarity between the passion fruit juice strains and Alicyclobacillus acidoterrestris DSM 2498. The heat resistance of three isolates was determined, and the mean D(95°) (1.7 min) and z (7.6 °C) values in the passion fruit juice were not significantly different (p > 0.05) from those obtained for the DSM 2498 strain (D(95°) = 1.5 min and z = 7.1 °C). This is the first report on the isolation of A. acidoterrestris from exotic fruit juices such as passion fruit juice. It is worth pointing out the importance of applying good agricultural practices in the field and applying controls for the fruit selection and washing steps, as well as controlling the time/temperature conditions for pasteurization so as to reduce the incidence and chances of A. acidoterrestris spoilage in these juices.

Modelling the lag time and growth rate of Aspergillus section Nigri IOC 4573 in mango nectar as a function of temperature and pH.

AIMS: To assess the behaviour of Aspergillus section Nigri IOC 4573 in mango nectar as affected by temperature and pH. METHODS AND RESULTS: A central composite design (2(2)+2*2+3) was used to estimate the influence of temperature (17·2-22·8°C) and pH (3·28-4·7) on A. section Nigri growth (λ, lag time; µ, growth rate). Secondary models (polynomial and Arrhenius-Davey) describing the effects of temperature and pH on λ and µ were constructed. A decrease in temperature from 22·8°C to 17·2°C resulted in an a 16-fold increase in λ. The increase in temperature from 20°C to 22·8°C at pH=4·0 led to a fourfold increase in µ. The polynomial model was the best in fitting the data and the pH (linear), temperature (linear and quadratic terms) significantly influenced λ. For µ, there was a significant influence by the pH (linear), temperature and pH (quadratic terms). CONCLUSIONS: The storage of mango nectar at <15°C and reduced pH could completely inhibit the growth of A. section Nigri. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to show how storage temperature and seasonal variability (pH) between harvests may affect mould growth in mango nectar.

Heat resistance and the effects of continuous pasteurization on the inactivation of Byssochlamys fulva ascospores in clarified apple juice.

AIMS: To determine thermal resistance, the effect of pasteurization temperature variations (c. 2 degrees C) in a continuous system in the number of decimal reductions (n) of a Byssochlamys strain in clarified apple juice (CAJ). METHODS AND RESULTS: Thermal destruction kinetics of Byssochlamys fulva IOC 4518 in thermal death tubes were determined at 85 degrees , 90 degrees , 92 degrees and 95 degrees C by using Weibull distribution frequency model. Three processes with different heating and holding temperatures (A: 94 degrees , 92 degrees C; B: 95 degrees , 93 degrees C; C: 96 degrees , 94 degrees C, respectively) were performed in a continuous system. Process time was 30 s. delta (time of first decimal reduction) values were: 42.98, 8.10, 3.62 and 1.81 min. Variable n ranged from 0.16 to >4.78 for process B (equivalent to industrial). Variable n (0.95-2.66 log CFU ml(-1)) were obtained in CAJ bottles processed under condition B, while process A resulted in total heat-resistant mould (HRM) survival and process C in total HRM destruction. CONCLUSIONS: This study demonstrates that small variations in temperature during the CAJ pasteurization could result in elimination or survival of HRM due to its nonlogarithmic behaviour. SIGNIFICANCE AND IMPACT OF THE STUDY: This was the first study to use Weibull frequency method to model inactivation of HRM in fruit juices. Temperature variations could culminate in the presence of HRM in pasteurized juices even when low counts (<10 spores per 100 ml) were present in the raw materials.

Estudio epidemiologico e microbiologico de um surto de intoxicacao alimentar. / Epidemiological and microbiological study of an outbreak of food intoxication

O estudo de um surto de toxi-infeccao alimentar que ocoreu simultaneamente em dois restaurantes de uma mesma instituicao, indicou a carne cozida condimentada ou a maionese de batata, ambas preparadas de vespera, como a causa da toxi-infeccao. A mediana do tempo de incubacao correspondeu a doze horas e meia, a duracao dos sintomas foi inferior a vinte e quatro horas em quase todos os casos e a diarreia foi o sintoma predominante. Embora as contagens de Clostridium prefringens nas fezes dos doentes tenha sido elevada, nao se pode deixar admitir tambem Bacillus cereus, como possivel causa do surto