Modeling Botrytis Cinerea Spores Growth in Carbon Dioxide Enriched Atmospheres
ABSTRACT This study simulates the conditions in which Botrytis may appear in a modified atmosphere packed horticulture product, such as strawberry, so as to elaborate a predictive model that could allow us to estimate the shelf-life of a contaminated food product in such atmosphere conditions (0 to 40% CO2). The estimated shelf-lives obtained at 18 °C were 92, 164, and 236 h in storage atmospheres of 0, 10, and 20% CO2, respectively, very close to observed values; no growth was observed above 30% CO2. The elaborated predictive model allows us to: (a) control development of this fungi if the food product is maintained in an atmosphere containing more than 20% CO2 and (b) predict the time taken for potential colonies to become visible (3 mm dia) and, thus, cause immediate rejection by consumers.
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ABSTRACT: The application of models of microbial growth to the design of food safety systems requires consideration of the effect of arbitrary changes in external variables on growth of bacteria. In particular, the effect of changes in external variables, such as temperature, on the probability that the microbial population size will not exceed acceptable levels at a given time needs to be predicted. This paper presents a method of calculating the time-dependent probability distribution of the microbial population size under arbitrary changes of temperature through time. To illustrate this method, the effect of a sudden temporary increase in temperature on the evolution of the probability distribution of Lactobacillus plantarum population size is presented. The effect of this change in temperature on the time taken for the population to reach a critical size, with a given probability, is also calculated and the application of this calculation to the design of HACCP protocols is discussed.International Journal of Food Microbiology 04/2001; 64(3):317-23. · 3.43 Impact Factor
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ABSTRACT: The growth responses of salmonellae (mixed inoculum of Salmonella thompson, S. stanley and S. infantis) as affected by NaCl concentration, pH level and storage temperature were studied in laboratory medium. Growth curves were obtained at 5 concentrations of NaCl (0.5-4.5%, w/v), 5 pH levels (5.6-6.8) and 5 storage temperatures (10-30 degrees C). Sigmoid curves (Gompertz form) were fitted to the data and the curve parameters used to produce a polynomial model from which predicted growth curves could be generated for any combination of NaCl, pH and storage temperature within the limits studied. From those growth curves values for growth rate, generation time, lag time and other values such as time to a 1000-fold increase in numbers were derived. Such a model offers a cost-effective approach to understanding the microbial growth response in foods, and forms a data-base against which other controlling factors could be evaluated. Some problems of fitting curves to microbial growth data and of modelling such data are discussed.International Journal of Food Microbiology 04/1988; 6(2):155-78. · 3.43 Impact Factor
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ABSTRACT: The effects of elevated O2 alone or in combination with elevated CO2 atmospheres for postharvest decay control on strawberry fruit (Fragaria×ananassa Duch.) were assessed. In vitro and in vivo growth of Botrytis cinerea Pers.:Fr. and the effects on fruit quality were determined under eight atmospheres: air, 40, 60, 80, 90 and 100 kPa O2, 40 kPa O2+15 kPa CO2 and air+15 kPa CO2. The commercially-used CO2 level of 15 kPa in air and its combination with 40 kPa O2 were most effective in suppressing mycelial growth in vitro following 7 days at 5°C under the atmospheres. However, after 14 days of treatment at 5°C, 100 kPa O2 inhibited mycelial growth more than either of the CO2 treatments. In all treatments, the growth rate increased immediately upon removal from the atmosphere, indicating that there was no residual inhibitory effect. The 100 kPa O2 treatment was also the most effective in controlling decay on the fruit during 14 days of storage. Although the quality parameters of respiration, ethylene production, firmness, soluble solids, titratable acidity and external color were only mildly affected by the superatmospheric O2 treatments, volatile content (acetaldehyde, ethanol and ethyl acetate) increased greatly. While the fruit treated with 15 kPa CO2 had the highest volatile concentrations after 14 days at 5°C, after an additional 2 days in air at 20°C, volatile concentrations in fruit treated with 100 kPa O2 equaled or surpassed those of fruit treated with CO2. The volatile concentration in fruit treated with 15 kPa CO2 generally decreased during 2 days in air, while the volatile content increased in fruit treated with high O2, with greater increases with increasing O2 level. The fruit treated with 40 kPa O2+15 kPa CO2 achieved an intermediate level between the O2 and CO2 treatments. Although the 100 kPa O2 treatment reduced decay, both in vitro and in vivo, increased production of fermentative metabolites that impart a negative organoleptic property to the fruit makes this a doubtful alternative for decay control on strawberry.Postharvest Biology and Technology. 01/2000;