Browsing by Author "Vieira, M. M. C."
Now showing 1 - 10 of 23
Results Per Page
Sort Options
- Effect of antioxidant and optimal antimicrobial mixtures of carvacrol, grape seed extract and chitosan on different spoilage microorganisms and their application as coatings on different food matricesPublication . Rubilar, Javiera F.; Cruz, R. M. S.; Khmelinskii, Igor; Vieira, M. M. C.There is growing interest in the use of natural agents with antimicrobial (AM) and antioxidant (AOX) properties. Optimization of the AM capacity for mixtures containing carvacrol, grape seed extract (GSE) and chitosan, against gram-negative (Pseudomonas aeruginosa), gram-positive bacteria (Staphylococcus aureus, Listeria innocua and Enterococcus faecalis) and yeast (Saccharomyces cerevisiae) at 106 cfu mL−1 was studied. To observe the synergistic or antagonistic effect and find optimal combinations between the three agents, a simplex centroid mixture design was run for each microorganism, combining carvacrol (0-300 ppm, X1)X, GSE (0-2000 ppm, X2) and chitosan (0-2% w/v, X3). Results of the response surface analysis showed several synergistic effects for all microorganisms. Combinations of 60 ppm-400 ppm-1.2% w/v (carvacrol-GSE-chitosan; optimal AM combination 1, OAMC-1); 9.6 ppm-684 ppm-1.25% w/v (OAMC-2); 90 ppm-160 ppm-1.24% w/v (OAMC-3) were found to be the optimal mixtures for all microorganisms. Radical scavenging activity (RSA) of the same agents was then compared with a standard AOX (butylated hydroxytoluene; BHT) at different concentrations (25, 50 and 100 ppm; as well as the optimal AM concentrations) by the 1,1-diphenyl-2- picrylhydrazyl (DPPH) method. RSA increased in the following order: chitosan< carvacrol< BHT< GSE and for the OAMC: OAMC-2< OAMC-1< OAMC-3. The best RSA (OAMC-3) was applied as a coating in two different food matrices (strawberries and salmon). For strawberries, P. aeruginosa was more sensitive to the action of OAMC-3 than S. cerevisiae. For salmon, S. aureus was more resistant to the action of OAMC-3 than E. faecalis and L. innocua.
- Effect of cold chain temperature abuses on the quality of frozen watercress (Nasturtium officinale R. Br.)Publication . Cruz, R. M. S.; Vieira, M. M. C.; Silva, C. L. M.The objective of this work was to study the effect of temperature abuses on the colour and vitamin C content of a new frozen vegetable, watercress (Nasturtium officinale R. Br.). The vitamin C content, expressed as ascorbic (AA) and dehydroascorbic (DHAA) acids, and colour, expressed in the Hunter Lab parameters, were evaluated along a plan of temperature abuses, based on a real situation for a four month frozen storage period. A comparison between the hue angle and AA experimental data and prediction models, using kinetic parameters determined under isothermal conditions, was also run. The colour showed some variation, namely on the parameters L, a, TCD (Total Colour Difference) and hue angle. Although, during the temperature abuses, some fluctuation was observed, no vitamin C degradation or major colour changes occurred. A zero-order and a first-order prediction models fitted well the experimental data for the hue angle and AA behaviour with temperature abuses, respectively. In general, the frozen watercress colour and vitamin C content were not impaired by the imposed temperature abuses. This work will help to predict and understand the sensory and nutritional quality changes of frozen watercress that might occur during frozen storage and distribution in the cold chain under the used conditions.
- Effect of heat and thermosonication treatments on peroxidase inactivation kinetics in watercress (Nasturtium officinale)Publication . Cruz, R. M. S.; Vieira, M. M. C.; Silva, C. L. M.The effect of heat and the combined heat/ultrasound (thermosonication) treatment on the inactivation kinetics of peroxidase in watercress (Nasturtium officinale) was studied in the temperature range of 40-92.5 degrees C. In the heat blanching processes, the enzyme kinetics showed a first-order biphasic inactivation model. The activation energies and the rates of the reaction at a reference temperature for both the heat-labile and heat-resistant fractions were, respectively, E(a1) = 421 +/- 115 kJmol(-1) and E(a2) = 352 +/- 81 kJmol(-1), k(184.6 degrees C) = 18 +/- 14min(-1) and k(284.6 degrees C) = 0.24 +/- 0.14min(-1). The initial relative specific activity for both isoenzyme fractions were also estimated, being C(01) = 0.5 +/- 0.08 mu mol min(-1)mg protein(-1) and C(02) = 0.5 +/- 0.06 mu mol min(-1)mg protein(-1), respectively. The application of thermosonication was studied to enable less severe thermal treatments and, therefore, improving the quality of the blanched product. In this treatment the enzyme kinetics showed a first-order model. The activation energy, the rate of reaction at a reference temperature and the initial relative specific activity were, respectively, E(a3) = 496 +/- 65 kJmol(-1), k(387.5 degrees C) = 10 +/- 2min(-1) and C(03) = 1 +/- 0.05 mu mol min(-1)mg protein(-1), proving that the enzyme became more heat labile. The present findings will help to design the blanching conditions for the production of a new and healthy frozen product, watercress (Nasturtium officinale), with minimized colour or flavour changes along its shelf life. (c) 2004 Elsevier Ltd. All rights reserved.
- Effect of heat and thermosonication treatments on watercress (Nasturtium officinale) vitamin C degradation kineticsPublication . Cruz, R. M. S.; Vieira, M. M. C.; Silva, C. L. M.The use of ultrasound in food processing creates novel and interesting methodologies, which are often complementary to classical techniques. In this work, the effect of heat and the combined treatment heat/ultrasound (thermosonication) on the thermal degradation kinetics of vitamin C in watercress (Nasturtium officinale) was studied in the temperature range of 82.5 to 92.5 °C. First order reaction kinetics adequately described the vitamin C losses during both blanching processes. The activation energies and the reaction rates at 87.5 °C for heat (H) and thermosonication (Ts) treatments were, respectively, EavitCH = 150.47 ± 42.81 kJ mol− 1 and EavitCTs = 136.20 ± 60.97 kJ mol− 1, and k87.5 °CvitCH = 0.75 ± 0.10 min− 1 and k87.5 °CvitCTs = 0.58 ± 0.11 min− 1. No significant differences (P > 0.05) were detected between both treatments. The thermosonication treatment was found to be a better blanching process, since it inactivates watercress peroxidase at less severe blanching conditions and consequently retains vitamin C content at higher levels. The present findings will help to optimise the blanching conditions for the production of a new and healthy frozen product, watercress, with heat and a new blanching process methodology.
- Enterococcus faecalis and Pseudomonas aeruginosa behaviour in frozen watercress (Nasturtium officinale) submitted to temperature abusesPublication . Oliveira, S. R.; Cruz, R. M. S.; Vieira, M. M. C.; Silva, C. L. M.; Gaspar, M. N.Watercress is an herb traditionally consumed fresh. If frozen, would be readily available to consumers. However, pathogenics resistant to frozen storage are a safety concern in this new product. in this study watercress was artificially contaminated with Pseudomonas aeruginosa ATCC 27853 and Enterococcus faecalis ATCC 29212. Their survival was evaluated after blanching, frozen storage and temperature fluctuations of the frozen product. The blanching caused a reduction of about 2 log cfu per gram of product of total viable count (TVC) and about 1.7 and 1.3 log cfu per gram of product of P. aeruginosa and E. faecalis, respectively. P. aeruginosa seemed to be more sensitive to temperature abuses than E. faecalis. After 3 months, TVC was still observed with a reduction of about 3 log cfu per gram of product. At the end of the study, exposure to freeze-thaw cycles resulted in death or injury of the microorganisms. These findings on the behaviour of two microorganisms of concern in frozen watercress will help improving the safety and cold chain settings for this product. (C) 2008 Elsevier Ltd and IIR. All rights reserved.
- Food science and technology students self-evaluate soft and technical skillsPublication . Flynn, Katherine M.; Ho, Peter; Vieira, M. M. C.; Rosa, Marco DallaFood Scientists and Technologists (FS&T) need diverse skills in the globalized food and drink sector: Food-specific or scientific / technical skills and generic or intuitive soft skills. This study determined how satisfied FS&T students were with overall improvement, and in key technical and soft skills, based on their university work; and if satisfaction was linked to geography, degree in progress, anticipated degree, anticipated work place or anticipated job responsibility. An on-line survey was completed by 267 students in over 20 countries using a 5-point Likert scale to evaluate satisfaction. Responses were analyzed by the Friedman or Kruskal Wallis tests for more than two groups, otherwise by the Wilcoxon Signed Rank or Mann-Whitney tests. There were no differences in Overall Satisfaction with technical and soft skills training. Among soft skills, training in Working with Others and Being Responsible were more often rated “Excellent” and students were more satisfied with their training than with Solving Problems, Communication and Positive Attitude. Students anticipating a job with high responsibility were more satisfied with overall soft skill training and with 3 of the 5 specific soft skills. Among technical skills, students were more satisfied with improvement in basic sciences (Microbiology, Chemistry, Processing, Safety), and those in Northern Europe were more satisfied with overall technical training. These data show variations in perception and/or efficacy of technical and soft skill training in Food Science programmes and underline the need for separate attention to the incorporation of soft skill training into the design of FS&T courses
- Garum: recovering of the production process of an ancestral condimentPublication . Vieira, M. M. C.The objective of the present work was to study the shelf life of a recipe of a fish sauce Garum originated in the roman empire.
- Impact of thermal blanching and thermosonication treatments on watercress (Nasturtium officinale) quality: thermosonication process optimisation and microstructure evaluationPublication . Cruz, R. M. S.; Vieira, M. M. C.; Fonseca, Susana C.; Silva, C. L. M.The objectives of the present work were to optimise watercress heat and thermosonication blanching conditions, in order to obtain a product with better quality for further freezing, and to evaluate the effects of thermosonication on the microstructure of watercress leaves. In a chart of optimal time–temperature conditions for a 90% peroxidase inactivation (imposed constraint), vitamin C (objective function) and a-value (improvement toward green) were mathematically predicted for both heat and thermosonication blanching treatments. Two optimal thermosonication combinations were selected: 92°C and 2 s, retaining 95% of vitamin C content and 5% a-value improvement, and a better condition in terms of practical feasibility, 86°C and 30 s, allowing a 75% vitamin C retention and 8% a-value improvement. The experimental values, for each thermosonication optimal time–temperature zone, were in good agreement with the models' predicted responses. In terms of microstructure, thermosonicated watercress at 86 and 92°C showed similar loss of turgor and release of chloroplasts. The proposed optimal thermosonication blanching conditions allow the improvement of the blanched watercress quality and consequently contribute for the development of a high-quality new frozen product. However, a suitable scale-up is mandatory for industrial implementation.
- Inactivation kinetics of peroxidase in zucchini (Cucurbita pepo L.) by heat and UV-C radiationPublication . Neves, Filipa I. G.; Vieira, M. M. C.; Silva, C. L. M.The effect of traditional thermal water blanching, or its combination with a UV-C radiation pre-treatment (11 J/m2), on the inactivation kinetics of peroxidase in zucchini (Cucurbita pepo L.) was carried out in the temperature range of 80 to 98 °C, and up to 3 min of processing time. Peroxidase inactivation started being noticed only at temperatures around 85 °C. For both treatments, the inactivation kinetics followed a first order reaction with the Arrhenius model describing the temperature dependence of the reaction rate. The obtained kinetic parameters (kHeat 89.6 °C = 7.37 × 10− 7 ± 3.47 × 10− 7 min− 1 and Ea Heat = 925 ± 69 kJ mol− 1; kHeat 89.6 °C + UV-C = 2.42 × 10− 5 ± 6.58 × 10− 6 min− 1 and Ea Heat + UV-C = 596 ± 48.8 kJ mol− 1) showed that UV-C radiation had a significant contribution to increase the peroxidase degradation rate. These results will help to design new pre-processing conditions for the production of frozen zucchini, using less severe thermal treatments and attempt to minimize quality losses.
- Kinetic parameters estimation for ascorbic acid degradation in fruit nectar using the partial equivalent isothermal exposures (PEIE) method under non-isothermal continuous heating conditionsPublication . Vieira, M. M. C.; Teixeira, A. A.; Silva, C. L. M.With the purpose of testing the Paired Equivalent Isothermal Exposures (PEIE) method to determine reaction kinetic parameters under non-isothermal conditions, continuous pasteurizations were carried out with a tropical fruit nectar [25% cupuacu (Theobroma grandiflorum) pulp and 15% sugar] to estimate the ascorbic acid thermal degradation kinetic parameters. Fifteen continuous thermal exposures were studied, with seven being cycled. The experimental ascorbic acid thermal degradation kinetic parameters were estimated by the PEIE method (E-a = 73 +/- 9 kJ/mol, k(80 degreesC) = 0.017 +/- 0.001 min(-1)). These values compared very well to the previously determined values for the same product under isothermal conditions (E-a = 73 +/- 7 kJ/mol, k(80 degreesC) = 0.020 +/- 0.001 min(-1)). The predicted extents of reaction presented a good fit to the experimental data, although the cycled thermal treatments presented some deviation. In addition to being easier and faster than the Isothermal method, the PEIE method can be a more reliable method to estimate first-order reaction kinetic parameters when continuous heating is considered.
- «
- 1 (current)
- 2
- 3
- »