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Food Process Design / Z.B. Maroulis, G.D. Saravacos.
Abstract
Contenido: Diseño de procesos en la ciencia alimenticia; Diseño de procesos en principios alimenticios; Diseño de procesos por computadora; Procesos de calentamiento; Refrigeración y congelamiento; Evaporación; Deshidratación; Procesos térmicos en alimentos; Procesos de transferencia de masa; Procesos de separación por membrana; Apéndices.
... The recommended flow for whole milk in PHE 1-1 is 0.5 < v m, PHE 1-1 < 1.5 m s À1 [21] and turbulent flow (Re > 4000). [24][25][26] The Reynolds number of milk in PHE 1-1 (Re PHE 1-1 ) is given by [12] Re ...
... Re > 4000). [24][25][26] The Reynolds number of milk in PHE 2-3 (Re PHE 2-3 ) is given by [12] Re ...
... The advantage of Eqn (26) is that for all values of p 1 > 0, the outlet temperature of milk from PHE 1-1 will be less than the required 72°C plus a practical tolerance, highlighting a failure to heat the milk stream correctly. ...
A novel Friday 13th (Fr 13) risk analysis of the vulnerability to surprise (unexpected) failure of a global milk pasteurizing plant consisting of heating, holding and cooling unit operations is developed and illustrated. We define two or more interconnected unit operations as a global model. The aim was to gain new insight into the effects of accumulating random (stochastic) changes that could lead to overall failure in an otherwise well-operated and well-maintained pasteurizing plant. The methodology is a development of the work of Davey and co-workers (Food Control 29, 1 (2015) 248–253, CES 127 (2015) 133–142). Failure is defined in terms of criteria that must be met to ensure safe operation. Realistic data for large-scale pasteurization are used. Results reveal that the overall global model is vulnerable to failure in 12.5% of all cases over the long term. If each simulation can be considered a daily process, this translates to some 46 failures each year to meet the design pasteurization criteria. This new process insight cannot be obtained using traditional risk and hazard approaches. How this new Fr 13 methodology can be used to simulate design changes to the physical system to minimize vulnerability to failure is discussed. The finding should be of immediate interest to milk processors. © 2015 Curtin University of Technology and John Wiley & Sons, Ltd.
... The recommended flow for whole milk in PHE 1-1 is, 0.5 < v m,PHE1-1 < 1.5 m s À1 (Kessler, 2002), with turbulent flow (Re > 4000) (Hayhurst, 1997;Lewis and Heppell, 2000;Maroulis and Saravacos, 2003). The Reynolds number of the milk in PHE 1-1 (Re PHE1-1 ) is given by Sinnott (2005) ...
... The recommended flow for whole milk in PHE 2-3 is the same as that for PHE 1-1 i.e. 0.5 < v m,PHE2-3 < 1.5 m s À1 (Kessler, 2002) with turbulent flow (i.e. Re > 4000) (Hayhurst, 1997;Lewis and Heppell, 2000;Maroulis and Saravacos, 2003). The Reynolds number of the milk in ...
Here an integrated three-step microbiological Fr 13 risk assessment (Chem. Eng. Sci. 152 (2016) 213-226) is synthesised for the first time. It is applied to vulnerability to failure of a batch-continuous pasteurizer for raw milk containing viable Mycobacterium avium subsp. paratuberculosis (MAP) - a chronic enteric pathogen linked to Crohn’s disease in humans. Pasteurization of raw milk is therefore globally important. The aim was to advance the Fr 13 risk framework to an integrated 3-step microbiological failure synthesis to study how naturally occurring fluctuations in processing can be transmitted and impact multi-step processes. The 3-steps of the pasteurizer are the heat-up of raw milk, holding for thermal inactivation of contaminant MAP, and; cool-down of the heat-treated milk. Overall pasteurizer failure is defined as unwanted survival of MAP following holding and is characterised by a risk factor (p2) for milk leaving this step. Realistic large-scale pasteurization is simulated using a refined Monte Carlo (with Latin Hypercube) sampling. Results show that for a (Regulatory) design reduction of log10 = 5.5 (> 99.999%) in viable MAP on a heat-up to 72 °C with 15 s holding, and a design safety margin of 2%, p2 = 5.75%. This equates to up to ∼ 21 failures with unwanted MAP survival each year - averaged over an extended period of daily batch-continuous operations. We show these microbiological failures can be mitigated by installing precise safety-integrity-level (SIL) mass flow control on the input raw milk and by ensuring a holding time of ≥ 15 s. Results appear generalizable and therefore could be applied to a range of integrated 3-step microbiological processes. Findings will be of direct interest to risk analysts and milk processors and manufactures of equipment. The work is part of an investigation and development of Fr 13 as a new risk assessment and process design tool.
... The destruction of microorganisms is usually well described as a first order reaction, although the mechanism may be more complex, resulting in non-log-linear curves (Kessler, 2002;Maroulis & Saravacos, 2003). In a first order reaction, the integration of the change in microorganism concentration, at a given temperature, can be expressed as shown in Eq. (1) where N 0 is the initial spore population, N t is the surviving spore population at time t, and k, the velocity constant which can be obtained by linear regression when plotting the logarithmic reduction as a function of time. ...
... In a first order reaction, the integration of the change in microorganism concentration, at a given temperature, can be expressed as shown in Eq. (1) where N 0 is the initial spore population, N t is the surviving spore population at time t, and k, the velocity constant which can be obtained by linear regression when plotting the logarithmic reduction as a function of time. D θ Eq. (2) is the time necessary at a specific temperature to reduce the number of microorganism to a tenth of the original value and is temperature (θ) dependent (Kessler, 2002;Maroulis, et al., 2003). The effect of the absolute temperature on the inactivation velocity constant k, and thus on the D θ , is given by the Arrhenius Eq. (3) where E a is the energy of activation in J/mol, R is the universal gas constant = 8.314 J/mol.K, k 0 is the velocity constant in s −1 for 1/ T = 0 and T is the temperature in Kelvin. ...
A new generation of high pressure homogenizers reaching up to 400 MPa offers opportunities for spore inactivation and high pressure sterilization of foods. A Stansted Fluid Power ultra-high pressure homogenization (UHPH) unit was tested to inactivate bacterial spores in a model buffer system. Bacillus subtilis PS832 and Geobacillus stearothermophilus ATCC7953 spores’ thermal resistances were assessed (D, z-value and Ea). The pressure and valve temperature were monitored during UHPH. Residence times under pressure and high temperature were estimated and enabled comparison with thermal inactivation, indicating the estimated thermal contribution to inactivation. Spore germination was also assessed but no germination was observed. Up to five log10B. subtilis and two log10G. stearothermophilus spores were inactivated by the harshest treatments (> 300 MPa –Tvalve > 145 °C for ~ 0.24 s). The inactivation profiles were similar to the predicted thermal inactivation suggesting that the valve temperature might be a dominant parameter leading to bacterial spore inactivation.
... The volume reduction in the brine concentrator in ZLD system is assumed to be 90% [45]. The mass and energy balances of the multiple-effect evaporator and the crystallizer for the fourth scenario are calculated using the methods presented by Zacharias et al. [46] and Bennett et al. [47]. The energy consumption rates of the components of the tertiary treatment systems are shown in Table 2. ...
The study analyzes a potential to improve the local waste and wastewater management in a Finnish community. The Lappeenranta wastewater treatment plant (WWTP) is used as a case study. Two different technological setups are considered for improving the wastewater treatment plant. These are used to construct four alternative wastewater reclamation scenarios. The mass and energy balances for the considered scenarios are developed and used as input for the profitability evaluation. The utilization of the sewage sludge from the WWTP and municipal solid waste fraction that cannot be recycled for the generation of heat and electricity at the CHP plant is investigated with the aim to improve the economic performance of the wastewater treatment facility. The studied scenarios are initially compared based on their investment and operational costs. The cost of water treatment increases significantly in the case of the investigated tertiary treatment systems: higher amounts of chemicals and electricity are needed to improve the water quality. At the same time, the study indicates that the profitability of a WWTP integrated with a CHP plant can be reasonably high in a wide range of likely price scenarios for alternative wastewater purification systems. The results of the analysis showed a significant potential for the investigated wastewater reclamation systems to improve the efficiency of solid waste and wastewater management in the community.
... Their direct correlation with the experimental data and the relatively small number of used parameters is the main advantage of the empirical models. Moreover, empirical models do not require large computing infrastructure, they have low running costs and do not require specialized personnel for their operation (Karoglou et al., 2005;Maroulis and Saravacos, 2003;Moropoulou et al., 2014). ...
Water capillary absorption is one of the main water uptake mechanisms in building materials, affecting their overall durability. Thus, the investigation of their capillary rise kinetics can be very useful as regards understanding buildings behavior, contributing to the increase of their durability and their service life. For this reason, a first-order mathematical model was used describing the capillary water uptake under dynamic environmental conditions (different air velocity, air temperature, and relative air humidity) for various natural and artificial building materials. This model successfully fits the experimental data.
From the results, it was found that both building materials’ intrinsic characteristics and environmental conditions influence the capillary rise kinetics. In order to assess the validity of the proposed model, a comparison with a similar model was performed. The fitting of the utilized model was more accurate because of the incorporation of the environmental parameters into it. Finally, the proposed model was utilized in order to predict the capillary water uptake under hypothetical extreme weather real-case scenarios. It was found that the proposed model can successfully predict the capillary water uptake under different real-case environmental conditions. The applicability of this semiempirical model, using parameters with physical meaning, could make it suitable for use in building simulators. This model can contribute to risk assessment tools, dealing with various challenges related to climate change and its effect upon built environment.
... Their direct correlation with the experimental data and the relatively small number of used parameters is the main advantage of the empirical models. Moreover, empirical models do not require large computing infrastructure, they have low running costs and do not require specialized personnel for their operation (Karoglou et al., 2005;Maroulis and Saravacos, 2003;Moropoulou et al., 2014). ...
Water capillary absorption is one of the main water uptake mechanisms in building materials, affecting their overall durability. Thus, the investigation of their capillary rise kinetics can be very useful as regards understanding buildings behavior, contributing to the increase of their durability and their service life. For this reason, a first-order mathematical model was used describing the capillary water uptake under dynamic environmental conditions (different air velocity, air temperature, and relative air humidity) for various natural and artificial building materials. This model successfully fits the experimental data. From the results, it was found that both building materials’ intrinsic characteristics and environmental conditions influence the capillary rise kinetics. In order to assess the validity of the proposed model, a comparison with a similar model was performed. The fitting of the utilized model was more accurate because of the incorporation of the environmental parameters into it. Finally, the proposed model was utilized in order to predict the capillary water uptake under hypothetical extreme weather real-case scenarios. It was found that the proposed model can successfully predict the capillary water uptake under different real-case environmental conditions. The applicability of this semi-empirical model, using parameters with physical meaning, could make it suitable for use in building simulators. This model can contribute to risk assessment tools, dealing with various challenges related to climate change and its effect upon built environment.
... For this purpose, any optimization method should consider the entire lifecycle of the process. In food process design, the product quality is a basic objective and often includes sanitarian, nutritional and organoleptic aspects (Maroulis and Saravacos, 2003). However, one can consider other aspects of the product related to consumer acceptance such as the homogeneity of production or ergonomics of the final product package. ...
Cassava (Manihot esculenta) is the most important staple food in sub-Saharan Africa. However, the shelf-life of the crop is short and, for this reason, the roots are usually processed into more stable products like cassava flour by village-based enterprises. Most of these enterprises use small-scale locally built pneumatic dryers, but such dryers still need further development, so the objective of this research was to improve their energy performance. Experiments were conducted at two cassava processing centres, one in Tanzania and one in Nigeria. Sensors were installed on the dryers, product samples were collected and the mass and energy balance of the equipment analysed, allowing the dryers' minimum air mass flow rates to be calculated. The air mass flow rates of both dryers were then reduced to a level approximating the minimum value. In Tanzania, the air mass flow rate of the dryer was reduced by 24%, while in Nigeria it was reduced by 14%. In both locations, the modifications decreased the dryers' heat input without jeopardising evaporation rates, and so not affecting the final moisture content of the dry products. Air temperatures at the dryer outlets decreased and relative humidity increased, while enthalpy remained unchanged. The energy required to evaporate 1 kg of water decreased by 20% in Tanzania and by 13% in Nigeria. The modification also improved energy efficiency by 25% in Tanzania and by 14% in Nigeria. However, in Nigeria, where yellow cassava flour was being used, the dryer modifications resulted in greater product colour losses.
... Notwithstanding, only processing of foods packaged in cans or plastic containers and continuous aseptic processing (without containers) have been studied in depth for the heat transfer point of view. Almost no attention has been devoted to food processing in glass containers (Maroulis and Saravacos 2003). During the last years there has been in Argentina a steady increase in the processing of low volumes of vegetable and fruit preserves at commercial level (home-made, organic, specialties, etc.), due to their much higher value. ...
A sigmoid model is proposed for the simulation of food temperature evolution during the processing of preserves in low capacity sterilizers. Predicted results are compared against a formula method (exponential), widely used in the simulation and control of industrial processes. The proposed model resulted to be simple and accurate for the prediction of thermal histories of foods of different shapes and sizes sterilized in glass jars, and may be very useful for low volume processors. The exponential model did not provide accurate predictions for these processing conditions.
... These properties are of great importance in the simulation and design of food processes and in the Computer-Aided Process Engineering (CAPE). [1,2] Their influence is even greater in problems of conceptual design, in which a wrong estimation of a property can lead to an infeasible design plan. Physical properties of food materials can be categorized as follows [3,4] : ...
The requirement of reliable data on transport properties of foods has emerged in the last decade due to their importance in the design and simulation of food processing operations. An international effort to obtain and analyze the published data has been made recently, due to the lack of reliable theoretical predictive models. In this framework, a user-friendly database system for the storage and maintenance of the transport properties of foodstuffs is proposed and developed in a Microsoft Access environment. The system allows the end-user to input and retrieve data, as well as to view diagrams with single or comparative data and predict values via a fully featured user-friendly interface. Currently the database has registered over 250 articles, which correspond to approximately 1200 records for the thermal conductivity and 1780 records for moisture diffusivity. Due to its flexibility, the system can be used as an universal template for developing similar database systems.
... Recent studies show that the moisture content of food waste is between 75 and 95 % w/w [17] indicating and verifying the fact that a large amount of water has been effectively removed from food waste in the participating households. The recorded weight loss of the substrate corresponds to the least attracted bound water, which may be the multilayer and free water, whereas the remaining water is mainly non-free water, meaning that it is directly attached to surface solids by strong attractive molecular forces [10]. The increased deviation of moisture content from the mean values can be attributed to the different characteristics (e.g., size and shape) of the input waste in each household. ...
This paper introduces a new approach for domestic food waste management and pretreatment through the dehydration of food waste separated at source. An innovative domestic waste dryer was used in order to carry out the research performed. This work presents the methodology and the results of the first pilot scale demonstration of a new technique for the separation and dehydration of food waste separated at source. The system was installed in 25 selected households in Papagos-Cholargos Municipality in Athens, Greece, and operated on a daily basis for a total period of 8 months. The hygienic dehydration of food waste at source resulted to its significant mass reduction, about 70 % w/w, due to the removal of its moisture content during the drying process, while the energy requirements are sustained at economically viable levels. The low water content of the produced biomass prevents the biological decomposition, restricts odor emissions, and thus reduces the frequency at which domestic waste needs to be collected. Additionally, the dried biomass can be handled much easier compared to wet food waste. Also, the examined physicochemical characteristics of the dried waste show that it has the potential to be used in alternative and environmental friendly ways to produce high value-added products such as bioethanol, biogas, thermal energy, and compost.
... This procedure is based on the principle of selective permeation of the solute molecules through semi-permeable, polymeric or inorganic membranes. The driving force for mass transfer across the membrane in most membrane processes, such as a microfiltration, ultrafiltration, nanofiltration and reverse osmosis is mechanical pressure (Maroulis and Saravacos, 2003). Nanofiltration is a unit operation that permits many applications, such as solvent recovery from filtered oil, exchange of solvents in the chemical industry (Geens et al., 2006), concentration and purification of ethanolic extracts of xantophylls, which is important in both the pharmaceutical and food industries (Tsui and Cheryan, 2007) and in wine concentration (Banvolgyi et al., 2006), as well as in juice concentration (Vincze et al., 2006) in the food industry. ...
Propolis is a natural product with a variable and complex chemical composition associated with its high concentration on polyphenolic compounds. The effect of pH variation (2.0, 3.0, 4.3, 6.0 and 8.0) during aqueous and ethanolic propolis extraction was studied for up to 10 days. Total phenols and flavonoids contents were measured for the extracts by spectrophotometric assays. Antioxidant activity was measured by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and ferric thiocyanate (FTC) methods. The best time of extraction was up to 5 days for all samples. Basic aqueous extracts (pH 8.0) resulted in a higher concentration of compounds than the extract without pH modification, reaching an increase of 160% in flavonoids and 25% in phenols. Ethanolic extracts with pH variation resulted in an extract with 50% less polyphenols and 6% less flavonoids than extract without pH modification. The antioxidant activity was highest for ethanolic extract at pH 4.3 and aqueous extract at pH 8.0 – almost 90% and 45%, respectively, in DPPH method – and was related to the level of polyphenols by Pearson's correlations.
... Although sterilization is widely used for food preservation, only processing of foods packaged in cans or plastic containers and continuous aseptic processing (without containers) have been studied in depth from the heat transfer point of view. Almost no attention has been devoted to food processing in glass containers (Maroulis and Saravacos, 2003). ...
A sigmoid model is proposed for the simulation of food temperature evolution during the processing of preserves in batch low capacity sterilizers. Predicted results are compared against experimental data and a formula method (exponential) widely used in the simulation and control of industrial processes. The proposed model result to be simple and accurate for the prediction of thermal histories of foods of different shapes and sizes sterilized in glass jars of different sizes, and may be very useful for low volume processors. The exponential model did not provide accurate predictions for these processing conditions.
... This procedure is based on the principle of selective permeation of the solute molecules through semi-permeable, polymeric or inorganic membranes. The driving force for mass transfer across the membrane in most membrane processes, such as a microfiltration, ultrafiltration, nanofiltration and reverse osmosis is mechanical pressure (Maroulis and Saravacos, 2003). Nanofiltration is a unit operation that permits many applications, such as solvent recovery from filtered oil, exchange of solvents in the chemical industry (Geens et al., 2006), concentration and purification of ethanolic extracts of xantophylls, which is important in both the pharmaceutical and food industries (Tsui and Cheryan, 2007) and in wine concentration (Banvolgyi et al., 2006), as well as in juice concentration (Vincze et al., 2006) in the food industry. ...
Propolis has a variable and complex chemical composition with high concentration of flavonoids and phenolic compounds present in the extract. The extract varies with the solvent used in extraction. Ethanol extracts more phenolic acid and polar compounds than water. Before their use in industry, extracts must be concentrated but the use of high temperatures can degrade some compounds. Membrane processes is an option that allows concentration at low temperatures. Nanofiltration was carried out with aqueous and ethanolic extracts and each extract results in two distinct fractions: permeate and retentate. The capacity of the membrane to retain the compounds was verified by spectrophotometric analysis: for aqueous solution, the membrane retained around 94% of the phenolic compounds and 99% of the flavonoids, while for the ethanolic solution these values were 53% and 90%, respectively. Ferulic acid retention index was 1.00 and 0.88 to aqueous and ethanolic solutions, respectively. Thus, the nanofiltration process showed high efficiency in the concentration of propolis extracts.
Introducción La evaporación es una operación unitaria que se emplea en la industria alimenticia para concentrar una solución consistente de un solvente volátil y un soluto no volátil, lo cual se logra por la diferencia de volatilidades entre el solvente y el soluto. Esto incrementa el contenido de sólidos de los alimentos y permite conservarlos por una reducción de la actividad de agua. La evaporación es también utilizada a fin de reducir peso y volumen, lo cual permite reducir los costos de almacenamiento, transporte y distribución. Los cambios en la calidad de los alimentos que resultan de éste tratamiento térmico son minimizados por el diseño óptimo y la correcta operación de los equipos de evaporación (evaporadores). Básicamente un evaporador consiste en un equipo de intercambio de calor, en el cual el medio de calentamiento, generalmente vapor de agua a baja presión, condensa entregando calor latente de condensación a la solución que hierve, y que separa las fases líquida y vapor de la solución en ebullición. En un evaporador de película ascendente, los tubos del intercambiador se calientan con el vapor existente en el exterior de tal forma que el líquido asciende por el interior de los tubos, debido al arrastre que ejerce el vapor formado, el cual genera una película que se mueve rápidamente hacia arriba.
RESUMO: Os alimentos submetidos ao processo de fritura apresentam características sensoriais muito agradáveis e conferem ao alimento cor dourada e uniforme, melhorando sua apresentação e intensificando sabores e aromas. A conservação do produto pelo processo de fritura decorre da destruição de microrganismos e inativação de enzimas presentes nos alimentos e sua palatabilidade é incrementada como conseqüência a perda de umidade e ganho de gordura. O estudo da transferência de massa faz-se necessário para expressar a absorção de óleo em função do tempo de fritura em contraposição à umidade perdida pelo alimento. Objetiva-se com este trabalho elucidar o mecanismo difusional de transferência de massa dos óleos comestíveis nos alimentos em contradifusão com a perda de umidade. Correlacionar também, parâmetros matemáticos de estudos utilizados na transferência de massa com o que ocorre no processo de fritura de alimentos concomitante à transferência de calor. As variáveis levantadas que interferem no processo de fritura foram: tempo, temperatura de fritura, tamanho, forma e composição dos alimentos sólidos imersos no óleo. Além disso, o estudo da transferência de massa no processo de fritura e difusão do óleo na superfície dos produtos alimentícios forneceu dados significativos sobre algumas das variáveis que interferem no processo.
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