ABSTRACT
This study estimates the shelf life of vacuum packed beef meat (three muscles: striploin (longissimus thoracis et lumborum, LTL), tenderloin (psoas major, PM) and outside chuck (trapezius thoracis, TT)) at refrigeration temperatures (0 °C-10 °C) based on modelling the growth of two relevant groups of spoilage microorganisms: lactic acid bacteria (LAB) and Enterobacteriaceae. The growth models were developed combining a two-step and a one-step approach. The primary modelling was used to identify the parameters affecting the growth kinetics, guiding the definition of secondary growth models. For LAB, the secondary model included the effect of temperature and initial pH on the specific growth rate. On the other hand, the model for Enterobacteriaceae incorporated the effect of temperature on the specific growth rate and the lag phase; as well as the effect of the initial pH on the specific growth rate, the lag phase and the initial microbial count. We did not observe any significant effect of the type of muscle on the growth kinetics. Once the equations were defined, the models were fitted to the complete dataset using a one-step approach. Model validation was carried out by cross-validation, mitigating the impact of an arbitrary division between training and validation sets. The models were used to estimate the shelf life of the product, based on the maximum admissible microbial concentration (7 log CFU/g for LAB, 5 log CFU/g for Enterobacteriaceae). Although LAB was the dominant microbiota, in several cases, both LAB and Enterobacteriaceae reached the critical concentration practically at the same time. Furthermore, in some scenarios, the end of shelf life would be determined by Enterobacteriaceae, pointing at the potential importance of non-dominant microorganisms for product spoilage. These results can aid in the implementation of effective control measures in the meat processing industry.
Subject(s)
Enterobacteriaceae , Food Microbiology , Animals , Cattle , Vacuum , Uncertainty , Colony Count, Microbial , Temperature , Meat/microbiology , Food Packaging/methods , Food Preservation/methodsABSTRACT
One of the main current challenges in Educational Data Mining and Learning Analytics is the portability or transferability of predictive models obtained for a particular course so that they can be applied to other different courses. To handle this challenge, one of the foremost problems is the models' excessive dependence on the low-level attributes used to train them, which reduces the models' portability. To solve this issue, the use of high-level attributes with more semantic meaning, such as ontologies, may be very useful. Along this line, we propose the utilization of an ontology that uses a taxonomy of actions that summarises students' interactions with the Moodle learning management system. We compare the results of this proposed approach against our previous results when we used low-level raw attributes obtained directly from Moodle logs. The results indicate that the use of the proposed ontology improves the portability of the models in terms of predictive accuracy. The main contribution of this paper is to show that the ontological models obtained in one source course can be applied to other different target courses with similar usage levels without losing prediction accuracy.
ABSTRACT
In this study, we developed predictive models describing the growth of Staphylococcus aureus on cooked broccoli florets. A pool of 3.5 log CFU/g of five S. aureus strains were inoculated on 10 g broccoli portions. The samples were then stored at 10, 20, 30 and 37 °C, and colonies were enumerated at different time intervals. Baranyi and Roberts model was fitted to the data using a Bayesian Adaptive Markov Chain Monte Carlo for estimation of the growth parameters. S. aureus showed low growth at 10 °C on broccoli samples and at 20-37 °C interval, Baranyi and Roberts model fitted well to the experimental data (R2>0.97). Estimated growth parameters were correlated with the possibility of toxin production and indicate the potential presence of these biological hazards on contaminated broccoli after heat treatment. Additionally, linear regression was performed for growth rate as storage temperature function. This secondary model followed a linear tendency with R2=0.997 and was compared with two tertiary models (ComBase Predictor and Pathogen Modeling Program) and literature data, demonstrating similar growth rate values of both. These results can be helpful for food services and managers to establish food safety standards for S. aureus growth on cooked broccoli.
Subject(s)
Brassica , Food Microbiology , Staphylococcus aureus/growth & development , Vegetables/microbiology , Bayes Theorem , Brassica/microbiology , Colony Count, Microbial , Markov Chains , Monte Carlo Method , TemperatureABSTRACT
It is well known that intake of probiotic brings health benefits. Lactic bacteria with probiotic potential have aroused the interest of the industry in developing food products that incorporate such benefits. However, incorporating probiotic bacteria into food is a challenge for the industry, given the sensitivity of probiotic cultures to process conditions. Therefore, the objective of this study is to evaluate gelatin- and inulin-based filmogenic solutions as a potential vehicle for incorporating probiotics into food products and to model the fermentation kinetics. L. salivarius (Lactobacillus salivarius) growth in filmogenic solutions was analyzed under the influence of a variety gelatin concentrations (1.0-3.0%) and inulin concentrations (4.0-6.0%) and fermented under the effect of different temperatures (25-45 °C). A full 23 factorial plan with three replicates at the central point was used to optimize the process. The impacts of process conditions on cell development are fundamental to optimize the process and make it applicable by the industry. The present study showed that the optimal conditions for the development of probiotic cells in filmogenic solutions are a combination of 1.0% gelatin with 4.0% inulin and fermentation temperature of 45 °C. It was observed that the maximum cell growth occurred in an estimated time of about 4 h of fermentation. L. salivarius cell production and substrate consumption during the fermentation of the filmogenic solution were well simulated by a model proposed in this article, with coefficients of determination of 0.981 (cell growth) and 0.991 (substrate consumption).
ABSTRACT
AIMS: The aim of this work was to use mathematical kinetic modelling to assess the combined effects of aW, pH, O2 availability and temperature on the growth rate and time to growth of Aspergillus fumigatus strains isolated from corn silage. METHODS AND RESULTS: A full factorial design was used in which two factors were assayed: pH and aW . The aW levels assayed were 0·80, 0·85, 0·90, 0·92, 0·94, 0·96, 0·98 and 0·99. The levels of pH assayed were 3·5, 4, 4·5, 5, 6, 7, 7·5 and 8. The assay was performed at normal oxygen tension at 25 and 37°C, and at reduced oxygen tension at 25°C. Two strains of A. fumigatus isolated from corn silage were used. Kinetic models were built to predict growth of the strain under the assayed conditions. The cardinal models gave a good quality fit for radial growth rate data. The results indicate that the environmental conditions which take place during silage production, while limiting the growth of most micro-organisms, would not be able to control A. fumigatus. Moreover, pH levels in silage, far from limiting its growth, are also close to its optimum. Carbon dioxide at 5% in the environment did not significantly affect its growth. CONCLUSIONS: A need for a further and controlled acidification of the silage exists, as no growth of A. fumigatus was observed at pH 3·5, as long as the organoleptic characteristics of the silage are not much compromised. SIGNIFICANCE AND IMPACT OF THE STUDY: Aspergillus fumigatus is one of the major opportunistic pathogens able to cause illness such as allergic bronchopulmonary aspergillosis, aspergilloma and invasive aspergillosis to rural workers. Exposure of animals to A. fumigatus spores can result in infections, particularly in those organs exposed to external invasion, such as the airways, mammary gland and uterus at birth.
Subject(s)
Aspergillus fumigatus/growth & development , Silage/microbiology , Aspergillus fumigatus/isolation & purification , Hydrogen-Ion Concentration , Kinetics , Models, Biological , Temperature , Water , Zea maysABSTRACT
Mycotoxin requires special attention in public health due to pathological hazard in human and animals. Among these toxins, emphasized are the fumonisin produced mainly by Fusarium verticillioides, which is primary pathogen in corn. This study aimed the development of mathematical models in fumonisin production, as well as to evaluate the chromatography profile of secondary metabolites of Fusarium verticillioides. Corn (heat-treated or not) was adjusted to 15, 20 and 25% moisture content, and it was inoculated or not with F. verticillioides. These flasks were incubated at 20, 25 and 30º C for 20 days, and the fumonisins were quantified by high performance liquid chromatography (HPLC). The temperature affected the fumonisin production in higher extension than moisture content, and the highest fumonisin level was reached at 20º C with 25% moisture content. The chromatogram profiles showed many peaks with retention time which differed of fumonisin, suggesting diversity in compounds arisen from metabolic pathway, which were also from F. verticillioides. These metabolites were not observed in optimized condition for fumonisin production, showing decreased trend when other fungal growth was increased. The mathematical models predicted the fumonisin level trend at the 20th days performance in a real data contamination evaluated in corn, which were submitted to graphical and mathematic
As micotoxinas merecem atenção especial no contexto de saúde pública por desencadearem alterações patológicas em humanos e animais. Dentre estas toxinas, destacam-se as fumonisinas, produzidas principalmente por Fusarium verticillioides, um patógeno primário de milho. O trabalho objetivou desenvolver modelos matemáticos para produção de fumonisinas, bem como avaliar o perfil cromatográfico de metabólitos secundários de Fusarium verticillioides. Grãos de milho submetidos ou não ao tratamento térmico tiveram a umidade ajustada para 15, 20 e 25%, sendo inoculados ou não com F. verticillioides. Os grãos permaneceram incubados a 20, 25 e 30º C por 20 dias e, após este período, as fumonisinas foram quantificadas por cromatografia líquida de alta eficiência (CLAE). A temperatura exerceu maior efeito em comparação à umidade e, a maior produção da toxina ocorreu em grãos mantidos a 25% de umidade sob 20º C. Os perfis cromatográficos apontaram uma variabilidade nos picos com tempo de retenção diferente de fumonisinas, sugerindo serem compostos oriundos de atividade metabólica, principalmente de F. verticillioides. Estes compostos não foram observados nas condições ótimas para produção de fumonisinas e, reduziram com o crescimento de outros gêneros fúngicos. Os modelos matemáticos possibilitaram a predição dos níveis de fumonisinas no 20º dia subseqüente a partir de dados reais de grãos d
ABSTRACT
Mycotoxin requires special attention in public health due to pathological hazard in human and animals. Among these toxins, emphasized are the fumonisin produced mainly by Fusarium verticillioides, which is primary pathogen in corn. This study aimed the development of mathematical models in fumonisin production, as well as to evaluate the chromatography profile of secondary metabolites of Fusarium verticillioides. Corn (heat-treated or not) was adjusted to 15, 20 and 25% moisture content, and it was inoculated or not with F. verticillioides. These flasks were incubated at 20, 25 and 30º C for 20 days, and the fumonisins were quantified by high performance liquid chromatography (HPLC). The temperature affected the fumonisin production in higher extension than moisture content, and the highest fumonisin level was reached at 20º C with 25% moisture content. The chromatogram profiles showed many peaks with retention time which differed of fumonisin, suggesting diversity in compounds arisen from metabolic pathway, which were also from F. verticillioides. These metabolites were not observed in optimized condition for fumonisin production, showing decreased trend when other fungal growth was increased. The mathematical models predicted the fumonisin level trend at the 20th days performance in a real data contamination evaluated in corn, which were submitted to graphical and mathematic
As micotoxinas merecem atenção especial no contexto de saúde pública por desencadearem alterações patológicas em humanos e animais. Dentre estas toxinas, destacam-se as fumonisinas, produzidas principalmente por Fusarium verticillioides, um patógeno primário de milho. O trabalho objetivou desenvolver modelos matemáticos para produção de fumonisinas, bem como avaliar o perfil cromatográfico de metabólitos secundários de Fusarium verticillioides. Grãos de milho submetidos ou não ao tratamento térmico tiveram a umidade ajustada para 15, 20 e 25%, sendo inoculados ou não com F. verticillioides. Os grãos permaneceram incubados a 20, 25 e 30º C por 20 dias e, após este período, as fumonisinas foram quantificadas por cromatografia líquida de alta eficiência (CLAE). A temperatura exerceu maior efeito em comparação à umidade e, a maior produção da toxina ocorreu em grãos mantidos a 25% de umidade sob 20º C. Os perfis cromatográficos apontaram uma variabilidade nos picos com tempo de retenção diferente de fumonisinas, sugerindo serem compostos oriundos de atividade metabólica, principalmente de F. verticillioides. Estes compostos não foram observados nas condições ótimas para produção de fumonisinas e, reduziram com o crescimento de outros gêneros fúngicos. Os modelos matemáticos possibilitaram a predição dos níveis de fumonisinas no 20º dia subseqüente a partir de dados reais de grãos d