João Noronha - Academia.edu (original) (raw)
Papers by João Noronha
Food and Bioproducts Processing
In this article, mathematical models for the design and evaluation of in-pack sterilization proce... more In this article, mathematical models for the design and evaluation of in-pack sterilization processes, including the evaluation of process deviations consisting of drops in the ambient temperature, are discussed. Models for simulating conduction heating, broken heating and convection heating are considered and the methodologies used in the determination of the empirical parameters associated with the proposed methods are briefly discussed. The methods are validated against experimental data obtained by processing three different canned foods in a retort simulator. Results for beans in tomato sauce, cream of chicken soup and peas in brine, processed in A1 metal cans (65mm diameter x 102mm height), meat chunks in gravy processed in UT cans (73 mm diameter x 115mm height) and fish processed in Dingley cans (105 mm x 17 mm x 15 mm) were used in the validation trials. f h, values ranged from 4.5 min to 38.8 minutes. Both 'normal' and 'deviant' processes were considered. A...
Journal of Food Science, 1997
A procedure was developed for theoretical calculation of internal product temperatures during in-... more A procedure was developed for theoretical calculation of internal product temperatures during in-container sterilization of foods. Experimental product temperatures were determined through traditional heat penetration tests (processing in a retort with come-up time of increasing temperature and holding time at constant temperature). These were used to produce, through a proposed inverse superposition solution, a ''standardized,'' normalized, dimensionless product temperature curve corresponding to the response of product temperature to a constant retort temperature profile. This ''standardized'' curve was then used, through Duhamel's superposition theorem, to calculate product temperatures for time-varying retort temperature profiles. Limitations associated with the application of Duhamel's theorem were also transferred to the proposed methodology. Theoretical, for perfect mixing, and experimental, for conduction heating, data were used in example calculations.
Journal of Food Processing and Preservation, 1993
Optimal variable retort temperature profiles (VRT) for the sterilization of conduction heded fd w... more Optimal variable retort temperature profiles (VRT) for the sterilization of conduction heded fd were calculared using a quasi-Newton multivariable optimization algorithm considering both the maximization of Surface quality and the minimization of total process time. When the maximization of su#ace quality was the objective, an increase up to 20% in quality retention was predicted for optimal VRT profiles as compared to optimal constant retort temperature profiles (CRT). When considering the minimization of total process time, the use of VRT projles allowed reduction in the total process time of up to 45 % while still providing the same surface quality as optimal CRT. Since the results could not be generalized, it was concluded that optimal VRTprofiles should be calculated on a case-by-case basis.
Journal of Food Processing and Preservation, 1996
Journal of Food Processing and Preservation, 1996
An existing semi-empirical model for simulating product temperature profiles during thermal proce... more An existing semi-empirical model for simulating product temperature profiles during thermal processing of conduction or convection heating foods under time varying boundary conditions (variable retort temperatures) was extended for the case of broken-line heating products. The use of the method for determination of the empirical heat penetration parameters for broken-line heating curves as defined by Ball oh, fh, fM. xJ was evaluated. Starch solutions, showing broken-line heating behavior, were used as a food simulant. To investigate the consistency of the determined broken-line heating parameters, and to test the applicability of the method when boundary conditions are time dependent, process deviations consisting of drops on the heating medium temperature during the holding phase of a process were evaluated. The model is a promising approach, i f the correct empirical parameters are used.
Food Research International, 1994
The performance of an enzyme-based Time Temperature Integrator (TTI) in monitoring the spatial di... more The performance of an enzyme-based Time Temperature Integrator (TTI) in monitoring the spatial distribution of processing values was evaluated. After proper kinetic calibration, processing values calculated from the response of free a-amylase (z = 7"C, 90-115°C) were found to match processing values obtained from a variable temperature history with the general method in laboratory heating experiments where 'ITIs were embedded in a spherical teflon food model particle. These systems were then applied as wireless monitors of processing value distributions under various processing conditions (viscosity of the brine, End-Over-End rotation, headspace) in a pilot retort. The particle-toparticle variation in processing values for an in-pack heat treated food model system could readily be determined with this TII. The possibilities of such wireless systems in heat penetration studies, design and optimization for processing conditions which are not readily accessible to physical experimentation are indicated.
Food Control, 1994
Possibilities for and restrictions to the combined use of a multi component timetemperature integ... more Possibilities for and restrictions to the combined use of a multi component timetemperature integrator (TTI) and the equivalent point method (EPM) to quantify the impact of a thermal process were considered in this theoretical study. The impact on Clostridium botulinurn spores, chosen as target quality attribute in this study can be represented fairly by an 'equivalent point' when the activation energies of the constituents making up the multicomponent TTI are close to the activation energy of the target quality attribute (error Sl 70) but substantial errors (up to 60%) may arise when the activation energies of target and multicomponent TTI constituents differ largely. By reconsidering the temperature histories with three different reference temperatures (~0, 423 K, 394.1 K). the importance of this resealing parameter was found to be negligible. The combined use of a multicomponent TTI and the EPM to quantify the impact of a thermal process will require careful verification.
Food Science and Biotechnology in Developing …, 2004
Guimarães: Forvisão, 2003
Produção apoiada pelo Programa Operacional Formação Profissional e Emprego, co-financiado pelo Es... more Produção apoiada pelo Programa Operacional Formação Profissional e Emprego, co-financiado pelo Estado Português e União Europeia, através do Fundo Social Europeu. ... Ministério do Trabalho e da Solidariedade - Secretaria de Estado do Emprego e Formação.
Journal of Food Engineering, 1996
Tuking into account the similarities of broken-line heating curves and heatpenetration curves obt... more Tuking into account the similarities of broken-line heating curves and heatpenetration curves obtained when a product undergoes a drop in rotational speed during thermal processing in a rotary water cascading retort. a .semiempirical method used for handling broken-line heating behaviour is suggested as a method of dealing with this type of process deviation. For this purpose, the possibility of extrapolating the empirical heating rate parameter fl,, determined on the heat-penetration curve of white beans in brine processed in a still retort, to the 'still' conditions associated with a rotational speed drop in a rotary water cascading retort, was investigated. Following this upproach, safe product temperature predictions were obtained. The main criterion influencing the quality of the evalution was the determination of the correct empirical parametric value to be used. This means, when determining this parametric value, cure is required when selecting the correct temperature interval on the heat-penetration curve.
Journal of Food Engineering, 1995
Semi-empirical methods for the prediction of time-temperature histories in conductive and non-con... more Semi-empirical methods for the prediction of time-temperature histories in conductive and non-conductive (convective and mixed mode) heating foods subjected to a time-variable processing temperature are proposed. Four alternatives are considered: (i) Hayakawa's method (Duhamel's theorem and Hayakawa's formulae); 60 Duhamel's theorem with analytical solution; (iiO numerical solution with apparent time (time shift); (iv) numerical solution with apparent position. The incorporation of the empirical heating characteristics f and j in conductive models was accomplished by evaluating the existing analogies with thermophysical properties in the solutions of the Fourier equation. Approaches using Duhamel's theorem or finite difference solutions were used to handle variable boundary conditions. The application of the models in the calculation of processing values for thermal processes with different come up times and different boundary conditions during come up time and thermal processes with process deviations is discussed. The numerical solution with apparent position was preferred because it combines accuracy and flexibility. NOTATION a D f F J Rate of change of the heating medium temperature (in eqns (13) and (14)) Time required to decrease the concentration by 90% (mini Time required to reduce the difference between the heating medium temperature and the product temperature to one-tenth of its value (mini Processing value (total lethality)(rain) Lag factor in heat penetration curves 249
Critical Reviews in Food Science and Nutrition, 1995
In this review, current methods used to evaluate the integrated impact of time and temperature up... more In this review, current methods used to evaluate the integrated impact of time and temperature upon preserving a food product by a heat treatment are considered. After identifying the basic premise any preservation scheme shall meet, the central role of a feasible description for the heat activation kinetics of microorganisms, their spores, and other quality attributes are stressed. Common concepts to quantify a thermal process are presented. Shortcomings of the prevalent evaluation methods are highlighted and attention is given to the development, restrictions, and possibilities of time-temperature-integrators as "new" evaluation tools to measure the impact of a "classical" in-pack heat treatment and more modern heating techniques such as continuous processing of solid/liquid mixtures on foods.
Journal of Food Engineering, 1996
The dij$erences in temperature dependence between spore inucti\'ution a~tl degradation of quality... more The dij$erences in temperature dependence between spore inucti\'ution a~tl degradation of quality fcrctoncs allow the optimisation of thermal processes ill terms of maxjmisation of quality retention by choosing an optimum heatinS pr@ile. While the maximisation of the retention ,for a single quality f&or has recei\?cd considerable attention in research, the possibilities of simultLlneolr s!\' maximising the retention qf' different qua& ,factors hurt up to now not been addressed. In this article the possibilities of the simultaneous optimisation for more than one qua& factor were thcoretical!y assessed. The LLW of both constant and variable retort temperature profiles was considered. A special emphusis was given to the formulation of uppropriate objective functions for the simrr1tancorr.s optimisation qf the su$ace retention of quality factors. For the simultaneous optimisation of quulity factors the objective ,fimc.tions should be form&ted in terms of maximising final retention and not, as in the case of single component optimisation, in terms qf minimisation of cook \!alutrs. The use of variable retort temperature prc$iles was shown to be particularl_\ interesting for the simultaneous optimisation of more than one quality f2ctol; as the final retention calculated compared well with the maximum retention achieved using individual calculated optimum constant retort temperature control for each of the components.
In this communication we will describe the steps taken for the identification and selection of de... more In this communication we will describe the steps taken for the identification and selection of descriptive terms for the establishment of a sensory profile for Requeijão (curd cheese). The developed profile will be used to create an assessment grid for the sensory evaluation of a traditional curd cheese produced in centre region of Portugal: Requeijão Serra da Estrela. For the establishment of the sensory profile the methodology described in ISO 11035:1994(E) was closely followed. For the identification of descriptive terms a mix of Requeijão bought directly from local traditional producers and in supermarkets was used. The panel was comprised of 18 assessors, with diversified experience on descriptive sensory analysis. A final list of 37 descriptors for Requeijão was obtained. Terms were identified and selected for the evaluation of the outer (7) and inner (3) appearance; aroma (7); flavour (7); oral texture (7) and after feel (6).
Food security has been a target of attention of governments and their organisations. This is due,... more Food security has been a target of attention of governments and their organisations. This is due, in part, to the pressure made by more and more well informed, attentive and worried consumers. To guarantee security in the food chain and to respond to the consumer worries, the European Union set up a series of legal mechanisms, which were then transposed to the member states. These legal mechanisms frequently clash with traditional practices of food production. This clash happens, in part, due to diverging conceptions regarding food quality and security (technical-scientific conceptions versus cultural-local conceptions). This paper reports the reflections made at the beginning of the Portuguese project "Application of HACCP methodology in the dairy sector: from milk production to the production of cheese and curd cheese". The main objective of this Project is the setting up of a common language among the producers responsible for putting into practice the HACCP systems and...
Food and Bioproducts Processing
In this article, mathematical models for the design and evaluation of in-pack sterilization proce... more In this article, mathematical models for the design and evaluation of in-pack sterilization processes, including the evaluation of process deviations consisting of drops in the ambient temperature, are discussed. Models for simulating conduction heating, broken heating and convection heating are considered and the methodologies used in the determination of the empirical parameters associated with the proposed methods are briefly discussed. The methods are validated against experimental data obtained by processing three different canned foods in a retort simulator. Results for beans in tomato sauce, cream of chicken soup and peas in brine, processed in A1 metal cans (65mm diameter x 102mm height), meat chunks in gravy processed in UT cans (73 mm diameter x 115mm height) and fish processed in Dingley cans (105 mm x 17 mm x 15 mm) were used in the validation trials. f h, values ranged from 4.5 min to 38.8 minutes. Both 'normal' and 'deviant' processes were considered. A...
Journal of Food Science, 1997
A procedure was developed for theoretical calculation of internal product temperatures during in-... more A procedure was developed for theoretical calculation of internal product temperatures during in-container sterilization of foods. Experimental product temperatures were determined through traditional heat penetration tests (processing in a retort with come-up time of increasing temperature and holding time at constant temperature). These were used to produce, through a proposed inverse superposition solution, a ''standardized,'' normalized, dimensionless product temperature curve corresponding to the response of product temperature to a constant retort temperature profile. This ''standardized'' curve was then used, through Duhamel's superposition theorem, to calculate product temperatures for time-varying retort temperature profiles. Limitations associated with the application of Duhamel's theorem were also transferred to the proposed methodology. Theoretical, for perfect mixing, and experimental, for conduction heating, data were used in example calculations.
Journal of Food Processing and Preservation, 1993
Optimal variable retort temperature profiles (VRT) for the sterilization of conduction heded fd w... more Optimal variable retort temperature profiles (VRT) for the sterilization of conduction heded fd were calculared using a quasi-Newton multivariable optimization algorithm considering both the maximization of Surface quality and the minimization of total process time. When the maximization of su#ace quality was the objective, an increase up to 20% in quality retention was predicted for optimal VRT profiles as compared to optimal constant retort temperature profiles (CRT). When considering the minimization of total process time, the use of VRT projles allowed reduction in the total process time of up to 45 % while still providing the same surface quality as optimal CRT. Since the results could not be generalized, it was concluded that optimal VRTprofiles should be calculated on a case-by-case basis.
Journal of Food Processing and Preservation, 1996
Journal of Food Processing and Preservation, 1996
An existing semi-empirical model for simulating product temperature profiles during thermal proce... more An existing semi-empirical model for simulating product temperature profiles during thermal processing of conduction or convection heating foods under time varying boundary conditions (variable retort temperatures) was extended for the case of broken-line heating products. The use of the method for determination of the empirical heat penetration parameters for broken-line heating curves as defined by Ball oh, fh, fM. xJ was evaluated. Starch solutions, showing broken-line heating behavior, were used as a food simulant. To investigate the consistency of the determined broken-line heating parameters, and to test the applicability of the method when boundary conditions are time dependent, process deviations consisting of drops on the heating medium temperature during the holding phase of a process were evaluated. The model is a promising approach, i f the correct empirical parameters are used.
Food Research International, 1994
The performance of an enzyme-based Time Temperature Integrator (TTI) in monitoring the spatial di... more The performance of an enzyme-based Time Temperature Integrator (TTI) in monitoring the spatial distribution of processing values was evaluated. After proper kinetic calibration, processing values calculated from the response of free a-amylase (z = 7"C, 90-115°C) were found to match processing values obtained from a variable temperature history with the general method in laboratory heating experiments where 'ITIs were embedded in a spherical teflon food model particle. These systems were then applied as wireless monitors of processing value distributions under various processing conditions (viscosity of the brine, End-Over-End rotation, headspace) in a pilot retort. The particle-toparticle variation in processing values for an in-pack heat treated food model system could readily be determined with this TII. The possibilities of such wireless systems in heat penetration studies, design and optimization for processing conditions which are not readily accessible to physical experimentation are indicated.
Food Control, 1994
Possibilities for and restrictions to the combined use of a multi component timetemperature integ... more Possibilities for and restrictions to the combined use of a multi component timetemperature integrator (TTI) and the equivalent point method (EPM) to quantify the impact of a thermal process were considered in this theoretical study. The impact on Clostridium botulinurn spores, chosen as target quality attribute in this study can be represented fairly by an 'equivalent point' when the activation energies of the constituents making up the multicomponent TTI are close to the activation energy of the target quality attribute (error Sl 70) but substantial errors (up to 60%) may arise when the activation energies of target and multicomponent TTI constituents differ largely. By reconsidering the temperature histories with three different reference temperatures (~0, 423 K, 394.1 K). the importance of this resealing parameter was found to be negligible. The combined use of a multicomponent TTI and the EPM to quantify the impact of a thermal process will require careful verification.
Food Science and Biotechnology in Developing …, 2004
Guimarães: Forvisão, 2003
Produção apoiada pelo Programa Operacional Formação Profissional e Emprego, co-financiado pelo Es... more Produção apoiada pelo Programa Operacional Formação Profissional e Emprego, co-financiado pelo Estado Português e União Europeia, através do Fundo Social Europeu. ... Ministério do Trabalho e da Solidariedade - Secretaria de Estado do Emprego e Formação.
Journal of Food Engineering, 1996
Tuking into account the similarities of broken-line heating curves and heatpenetration curves obt... more Tuking into account the similarities of broken-line heating curves and heatpenetration curves obtained when a product undergoes a drop in rotational speed during thermal processing in a rotary water cascading retort. a .semiempirical method used for handling broken-line heating behaviour is suggested as a method of dealing with this type of process deviation. For this purpose, the possibility of extrapolating the empirical heating rate parameter fl,, determined on the heat-penetration curve of white beans in brine processed in a still retort, to the 'still' conditions associated with a rotational speed drop in a rotary water cascading retort, was investigated. Following this upproach, safe product temperature predictions were obtained. The main criterion influencing the quality of the evalution was the determination of the correct empirical parametric value to be used. This means, when determining this parametric value, cure is required when selecting the correct temperature interval on the heat-penetration curve.
Journal of Food Engineering, 1995
Semi-empirical methods for the prediction of time-temperature histories in conductive and non-con... more Semi-empirical methods for the prediction of time-temperature histories in conductive and non-conductive (convective and mixed mode) heating foods subjected to a time-variable processing temperature are proposed. Four alternatives are considered: (i) Hayakawa's method (Duhamel's theorem and Hayakawa's formulae); 60 Duhamel's theorem with analytical solution; (iiO numerical solution with apparent time (time shift); (iv) numerical solution with apparent position. The incorporation of the empirical heating characteristics f and j in conductive models was accomplished by evaluating the existing analogies with thermophysical properties in the solutions of the Fourier equation. Approaches using Duhamel's theorem or finite difference solutions were used to handle variable boundary conditions. The application of the models in the calculation of processing values for thermal processes with different come up times and different boundary conditions during come up time and thermal processes with process deviations is discussed. The numerical solution with apparent position was preferred because it combines accuracy and flexibility. NOTATION a D f F J Rate of change of the heating medium temperature (in eqns (13) and (14)) Time required to decrease the concentration by 90% (mini Time required to reduce the difference between the heating medium temperature and the product temperature to one-tenth of its value (mini Processing value (total lethality)(rain) Lag factor in heat penetration curves 249
Critical Reviews in Food Science and Nutrition, 1995
In this review, current methods used to evaluate the integrated impact of time and temperature up... more In this review, current methods used to evaluate the integrated impact of time and temperature upon preserving a food product by a heat treatment are considered. After identifying the basic premise any preservation scheme shall meet, the central role of a feasible description for the heat activation kinetics of microorganisms, their spores, and other quality attributes are stressed. Common concepts to quantify a thermal process are presented. Shortcomings of the prevalent evaluation methods are highlighted and attention is given to the development, restrictions, and possibilities of time-temperature-integrators as "new" evaluation tools to measure the impact of a "classical" in-pack heat treatment and more modern heating techniques such as continuous processing of solid/liquid mixtures on foods.
Journal of Food Engineering, 1996
The dij$erences in temperature dependence between spore inucti\'ution a~tl degradation of quality... more The dij$erences in temperature dependence between spore inucti\'ution a~tl degradation of quality fcrctoncs allow the optimisation of thermal processes ill terms of maxjmisation of quality retention by choosing an optimum heatinS pr@ile. While the maximisation of the retention ,for a single quality f&or has recei\?cd considerable attention in research, the possibilities of simultLlneolr s!\' maximising the retention qf' different qua& ,factors hurt up to now not been addressed. In this article the possibilities of the simultaneous optimisation for more than one qua& factor were thcoretical!y assessed. The LLW of both constant and variable retort temperature profiles was considered. A special emphusis was given to the formulation of uppropriate objective functions for the simrr1tancorr.s optimisation qf the su$ace retention of quality factors. For the simultaneous optimisation of quulity factors the objective ,fimc.tions should be form&ted in terms of maximising final retention and not, as in the case of single component optimisation, in terms qf minimisation of cook \!alutrs. The use of variable retort temperature prc$iles was shown to be particularl_\ interesting for the simultaneous optimisation of more than one quality f2ctol; as the final retention calculated compared well with the maximum retention achieved using individual calculated optimum constant retort temperature control for each of the components.
In this communication we will describe the steps taken for the identification and selection of de... more In this communication we will describe the steps taken for the identification and selection of descriptive terms for the establishment of a sensory profile for Requeijão (curd cheese). The developed profile will be used to create an assessment grid for the sensory evaluation of a traditional curd cheese produced in centre region of Portugal: Requeijão Serra da Estrela. For the establishment of the sensory profile the methodology described in ISO 11035:1994(E) was closely followed. For the identification of descriptive terms a mix of Requeijão bought directly from local traditional producers and in supermarkets was used. The panel was comprised of 18 assessors, with diversified experience on descriptive sensory analysis. A final list of 37 descriptors for Requeijão was obtained. Terms were identified and selected for the evaluation of the outer (7) and inner (3) appearance; aroma (7); flavour (7); oral texture (7) and after feel (6).
Food security has been a target of attention of governments and their organisations. This is due,... more Food security has been a target of attention of governments and their organisations. This is due, in part, to the pressure made by more and more well informed, attentive and worried consumers. To guarantee security in the food chain and to respond to the consumer worries, the European Union set up a series of legal mechanisms, which were then transposed to the member states. These legal mechanisms frequently clash with traditional practices of food production. This clash happens, in part, due to diverging conceptions regarding food quality and security (technical-scientific conceptions versus cultural-local conceptions). This paper reports the reflections made at the beginning of the Portuguese project "Application of HACCP methodology in the dairy sector: from milk production to the production of cheese and curd cheese". The main objective of this Project is the setting up of a common language among the producers responsible for putting into practice the HACCP systems and...