ETHYLENE OXIDE AS A STERILISING AGENT OF MEDICAL DEVICES: LETHALITY ESTIMATION BY DEVELOPMENT OF KINETIC MODELLING STUDIES

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Simulation of solar drying of grapes using an integrated heat and mass transfer model

Publication . Ramos, Inês N.; Brandão, Teresa R. S.; Silva, Cristina L. M.

A mathematical model was developed to simulate solar drying of grapes, integrating heat and mass transfer models solved by an explicit finite differences method, considering changing boundary conditions. The model simultaneously incorporated shrinkage of the product, changes in effective moisture diffusivity and dependence of thermal properties on water content and temperature. Field experiments were carried out in a mixed mode solar dryer located in the North of Portugal, with pre-blanched grapes. A good prediction of experimental solar drying curves was attained. The mathematical model can be applied for simulating solar drying of different foods, once known their specific thermo-physical properties. Simulations obtained with the developed model can be valuable for predicting accurate drying times and consequently to design, control and optimise the production of dried foods.

2015Journal article

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Antilisterial active compound from lactic acid bacteria present on fresh iceberg lettuce

Publication . Ramos, Bárbara; Ferreira, Vânia; Brandão, Teresa R. S.; Teixeira, Paula; Silva, Cristina L. M.

Pediococcus pentosaceus DT016, a bacteriocin producing strain, was isolated from fresh lettuce. A protein with antilisterial activity (bacDT016), between 11 to 17 kDa, was identifi ed and characterized as the bioactive substance from the LAB culture. Highest bacteriocin production was noted after 15 h of growth. Antibacterial activity was affected by some enzymes and detergents, as well as by temperatures equal or above 80 ºC. DT016 strain contains an 1110 bp DNA fragment with homology to pediocin AcH/PA-1.

2016Journal article

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Biopreservation approaches to reduce Listeria monocytogenes in fresh vegetables

Publication . Ramos, Bárbara; Brandão, Teresa R. S.; Teixeira, Paula; Silva, Cristina L. M.

Two biopreservation approaches for fresh lettuce, rocket salad, parsley and spinach were studied. The potential of Pediococcus pentosaceus DT016, as a protective culture, to suppress Listeria monocytogenes in vegetables during storage was evaluated. The pathogen numbers in the vegetables inoculated with P. pentosaceus DT016 were significantly (p < 0.01) lower throughout the storage period and, at the last storage day, a minimum difference of 1.4 log CFU/g was reported when compared with the vegetables without the protective culture. Moreover, by using two levels of L. monocytogenes (about 6 and 4 log CFU/g), it was observed that the antagonist effect of P. pentosaceus was higher for the lower pathogen numbers. The second approach evaluated a pediocin DT016 solution to inactivate and control L. monocytogenes proliferation. The pathogen load was studied after washing with: water, chlorine and the pediocin solution and along storage at 4  °C. Comparing the various washing solutions, the vegetables washed with pediocin presented significantly (p < 0.01) lower pathogen numbers throughout storage, by a minimum of 3.2 and 2.7 log CFU/g, than in vegetables washed with water and chlorine, respectively. The proposed methodologies are promising alternatives to maintain the safety of fresh vegetables during extended storage at refrigeration temperature.

2020Journal article

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A review on ozone-based treatments for fruit and vegetables preservation

Publication . Miller, Fátima A.; Silva, Cristina L. M.; Brandão, Teresa R. S.

The development and application of efficient methods for the preservation of food products have always been industrial concerns. The search for new technologies that assure safety and quality of the products is an ever-growing challenge. In this context, ozone has emerged, presenting a set of characteristics that makes it highly suitable for fruits and vegetables. Ozone properties and ozone applications to fruits and vegetables industries are included in this work. Due to the potential of ozone-based treatments for obtaining safe products with extended shelf life, several researchers have been focusing on this topic. A compilation of those works is presented in this review, with emphasis on the ozone impact on microbial inactivation and quality aspects of processed fruits and vegetables, and fruit juices as well. This review can be a helpful tool for finding process conditions of ozone-based treatments and subsequent impacts on quality and safety attributes of already studied products, opening further areas of research.

2013Journal article

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Application of optimal experimental design concept to improve the estimation of model parameters in microbial thermal inactivation kinetics

Publication . Gil, Maria M.; Miller, Fátima A.; Silva, Cristina L.M.; Brandão, Teresa R. S.

The estimation of model parameters with high precision is of major importance in mathematical predictions. If a mathematical model is properly chosen and if the primary objective is to improve parameter estimation, underlying statistical theories can be applied. Precision increases with the number of experimental points. However, and in many situations,maximum precision is attained when sampling consists of replicates of specific experimental points. Experimental conditions can be optimized using the Doptimal design concept based on minimization of the generalized variance of the parameter estimates. The objective of this work was to use this methodology for the design of experiments for microbial inactivation processes described by a Gompertz-based model under isothermal and non-isothermal conditions. The application of D-optimal design concept considerably improved parameters precision, when compared to the commonly used heuristic designs.

2014Journal article

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