Browsing by Author "Silva, C. L. M."
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- Accelerated life testing of frozen green beans (Phaseolus vulgaris, L.) quality loss kinetics: colour and starchPublication . Martins, R. C.; Lopes, I. C.; Silva, C. L. M.This study uses the information derived from a computational research for the design of accelerated life testing (ALT) to implement experimentally the step stress methodology for the quantification of frozen green beans (Phaseolus vulgaris, L.) colour and starch degradation kinetics. Colour loss and starch degradation were successfully modelled, respectively, by a first-order reversible and apparent first-order kinetics, under dynamic temperature fluctuations. Results show that the step stress produces models with lower regression standard errors than the conventional isothermal methodology, increasing the accuracy of the estimated kinetic parameters. The ALT methodology, produces however, higher confidence intervals for the estimated kinetic parameters, than the isothermal methodology (e.g. colour b-coordinate by the: (i) isothermal methodology: k₋₁₅ ºC=22.189±0.349 day⁻¹·10⁻³; and (ii) ALT methodology: k₋₁₅ ºC=22.189±0.349 day⁻¹·10⁻³). Furthermore, as expected, higher Arrhenius activation energies (Ea) were estimated by the ALT step-stress methodology, than by the isothermal methodology (e.g. Hunter total colour difference (TCDH): (i) isothermal methodology: Ea=106.272±18.67 kJmol⁻¹; and (ii) ALT methodology: Ea=140.344±18.670 kJmol⁻¹). Accelerated tests are valuable tools, that can aid the study of quality losses in frozen foods. Although ALT tests increase the complexity of data analysis, they produce satisfactory results, when applied to frozen green beans kinetics of starch and colour losses.
- Advances in ISEKI_Mundus networkPublication . Ribotta, P.D.; Silva, C. L. M.
- Apiculate wine yeasts: growth kinetics and aroma compounds productionPublication . Moreira, N. E. O.; Silva, C. L. M.; Vasconcelos, I. M.; Mendes, F.; Hogg, T.
- Application of optimal experimental design concept in microbial inactivation studiesPublication . Gil, M. M.; Brandão, Teresa R. S.; Silva, C. L. M.
- Author Correction: Emerging challenges and opportunities in innovating food science technology and engineering education (npj Science of Food, (2024), 8, 1, (5), 10.1038/s41538-023-00243-w)Publication . Saguy, I. S.; Silva, C. L. M.; Cohen, E.Correction to: npj Science of Foodhttps://doi.org/10.1038/s41538-023-00243-w, published online 13 January 2024 In the article, incorrect in-text numbered citations were provided in the third paragraph in the section titled “Internships”. The correct text should have appeared as below: “Bridging the academia-industry gap in the food sector through collaborative courses and internships was recently studied. More than fifteen years of university extension diplomas in food technology Diplomas demonstrated how collaborative courses strengthen academia-industry bonds, and employability was boosted thanks to internships and the network created22. Internships could support students in developing their identity, which is achieved by close contact with their future working tasks34, enhancing familiarity with and nearness to their future profession35 and industry-based projects and governance36. Also, student projects in collaboration with the industry make the students face a reality37. In light of these benefits, it is clear why the internship in the food industry received such a high Likert-type average. This very high importance given by the panel to industry internships coincides with their ranking, as aforementioned in the previous section, highlighting the core role of the food industry in students’ education.”
- Characterization of traditional degrees of sugar boiling: hydroxymethylfurfural (hmf), 5-methylfurfural and 2-furaldheydePublication . Quintas, M.; Silva, C. L. M.
- Colour and chlorophyll's degradation kinetics of frozen green beans (Phaseolus Vulgaris, L.)Publication . Martins, R. C.; Silva, C. L. M.Colour changes and chlorophyll's degradation of frozen green beans (Phaseolus vulgaris, L., variety bencanta) were studied during 250 days of storage at -7, -15 and -30°C. Chlorophyll's a and b losses were modelled by a first order reaction kinetics. Colour Hunter a and b coordinates and total colour difference were successfully described by a first order reversible model. The temperature effect was well mathematically described by the Arrhenius law, for both quality parameters.
- Computational design of accelerated life testing applied to frozen green beansPublication . Martins, R. C.; Silva, C. L. M.Three different accelerated life tests (ALT) were designed by computer simulation to investigate their practical applicability to quantify kinetics of quality loss in frozen stored foods. Heat transfer and quality degradation inside a green bean were simulated, using a spectral finite element method (SFEM), to develop pseudo-experimental data. Temperature fluctuations inside a refrigerator were simulated, by a piecewise linear stochastic differential equation, and integrated into the SFEM program. Thereafter, the simulated data was treated by non-linear regression analysis to estimate the kinetic parameters. The different ALT tests were then compared in terms of precision and accuracy. This study shows that temperature fluctuations, inside a refrigerator, influence the accuracy of the kinetic estimates, and if the temperature spectrum is used to derive kinetic estimates, it is possible to apply accurately ALT methodologies to frozen foods.
- Critical evaluation of restrictions used to optimize sterilization processing conditionsPublication . Silva, C. L. M.; Korczak, K.A computer program, using a finite differences method, was developed to model the heat sterilization for cylindrical packaged conduction heating foods. This program was introduced into an optimization routineto calculate optimum processing conditions, maximizing the surface or the volume average quality, using different restrictions. Depending on the pack dimensions and the heating rate of the product the least-lethality point is at the geometric center or along the radius or the vertical axis. Therefore, sterility values specified at the center and at the least-Iethality point were used as sterility criteria for calculating optimum conditions. The effect of an integrated sterility value constraint on optimal temperature was also investigated. Depending on the product thermal properties, processing conditions and target lethality the optimum temperature calculated using the sterility value at the center as restriction can overestimate the correet valueby as much as 4°C.
- Design and optimization of food processing conditionsPublication . Silva, C. L. M.The main research objectives of the group are the design and optimization of food processing conditions. Most of the work already developed is on the use of mathematical modeling of transport phenomena and quantification of degradation kinetics as two tools to optimize the final quality of thermally processed food products. Recently, we initiated a project with the main goal of studying the effects of freezing and frozen storage on orange and melon juice pectinesterase activity and quality. The main criterion to adequately pasteurize orange juice is a two decimal reduction of the activity of the enzyme. Preliminary experiments with orange and melon juices and previously published work for march white grapefruit pulp indicated that freezing storage is effective in reducing the pectinesterase activity. The final objective is to determine if the freezing storage of these juices, before pasteurization, can offer advantages in terms of the final product quality and total energy consumption. Finally, we have also been developing computer programs to model the heat transfer during the freezing process of solid foods. We have plans to further improve these models in order to have the possibility of predicting the effect of storage medium temperature fluctuations on the product temperature and quality.