No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
A model of heat and mass transfer inside a pressure cooker
Abstract
A model has been developed to describe steam cooking in a pressure cooker. The physical and thermal characteristics of commercial pressure cookers and of the food cooked in them, heat and mass transfer laws and various phenomena (conduction in solids, liquid and gas free convection, undercooled and emitted steam boiling, condensation and also valve opening laws) were all taken into account. Gas and water were considered to be two homogeneous fluid compartments. The hot plate was also modelled. This model enabled the prediction of heat and mass fluxes and pressures, the composition of gas, the temperature in the fluid compartment and temperature pattern in food under non-steady conditions during the three periods of cooking (pressure increase, pressure regulation and pressure decrease). The model was validated experimentally using an instrumented device containing a model foodstuff (PTFE cube). The fluxes generated by the model enabled the description of pressure and temperature increases, and allowed us to suggest better methods for energy-saving and rapid steam cooking.
... Unlike ordinary cooking pot (CP), a pressure cooker is an appliance that is used to cook foods at high pressure and temperature to reduce the cooking time. The use of saturated steam and reduction in cooking time are the two methods of preserving vitamins (Rocca-Poliméni et al., 2011). Pressure cookers have many nutritional, organoleptic and sanitary advantages however the literature does not have sufficient studies to explain these traits (Koca and Anıl, 1996;Rocca-Poliméni et al., 2011). ...
... The use of saturated steam and reduction in cooking time are the two methods of preserving vitamins (Rocca-Poliméni et al., 2011). Pressure cookers have many nutritional, organoleptic and sanitary advantages however the literature does not have sufficient studies to explain these traits (Koca and Anıl, 1996;Rocca-Poliméni et al., 2011). Rocca-Poliméni et al. (2011) developed a model which includes the physical and thermal characteristics of a commercial pressure cooker and of the food cooked in it based on the energy balance and heat and mass transfer relations. ...
... Pressure cookers have many nutritional, organoleptic and sanitary advantages however the literature does not have sufficient studies to explain these traits (Koca and Anıl, 1996;Rocca-Poliméni et al., 2011). Rocca-Poliméni et al. (2011) developed a model which includes the physical and thermal characteristics of a commercial pressure cooker and of the food cooked in it based on the energy balance and heat and mass transfer relations. ...
The main contribution of this study is to present a novel thermal model for analyzing the wheat cooking process and to propose a design procedure for an energy-efficient cooking pot. A small-scale cooking pot was designed and an experimental setup was installed to verify the model under various operating conditions. The developed model was solved using the Engineering Equation Solver software. Results were compared with those of the experiments and good agreement was obtained. Additionally, a computational fluid dynamics model was developed to verify the thermal model and have a useful design tool for large-scale cooking pots. It was found that the energy efficiency of the cooking process can be enhanced by initiating nucleate boiling (at ~5 °C minimum temperature difference between the heating element surface and saturation) which will supply the minimum heat flux on the helicoidal heat exchanger of the cooking pot. Lessening the energy demand but preserving the final product quality has decreased the 5-day biological oxygen demand of wastewater at least 50%. It is proposed that the wheat to water ratio can be reduced to 1.0−1.2 once the energy optimization and water recovery practices are satisfied. The estimated average specific energy consumption rate lies between 400‒475 ±5% W/kg (thermal power supplied for one kilogram of wheat) which can be reduced ~25% further by reducing the wheat to water ratio to 1.0. The results reported in the present study are expected to guide thermal and food engineers for the design applications of industrial cooking pots, energy optimization with less harmful wastewater and process control strategies for cooking of wheat.
... The aim of this study was, therefore, to firstly develop a kinetic model of the evolution of carrot texture as a function of time-temperature history. Then, this model was coupled with a previously developed heat and mass transfer model (Rocca-Poliméni et al. 2011) in order to predict the evolution of texture as a function of cooking time in a pressure cooker. Finally, global criteria of the degree of cooking were calculated and these criteria could be used to compare cooking in a pressure cooker with another cooking method objectively. ...
... This equipment supplies considerable heating power (up to 2500 W) with very low thermal inertia. This cooking device had previously been described in detail by Rocca-Poliméni et al. (2011). Figure 1 presents a schematic view of the instrumented device. ...
... Constant heat transfer coefficients were used for each transfer and were obtained from different correlations (Rohsenow et al. 1998;Incropera et al. 2007) for typical temperature differences except the heat transfer coefficients between the bottom wall of the pressure cooker and liquid water and between the external lateral walls and ambient air which were individually and experimentally determined by measurement of temperature under steady state. The heat transfer coefficients concerning the hot plate, dependent on its design and geometry, were also identified by specific experiments described in Rocca-Poliméni et al. (2011). Boiling was taken into account with two transitions. ...
This study deals with changes to the food texture of carrot (Daucus carota) during steam cooking in a pressure cooker. A previously developed thermal pressure cooker model was used to predict the temperature evolution of the product from core to surface. This compartment model took into account heat and mass transfer laws and various phenomena to adequately describe pressure cookers’ mode of operation. In addition, a model predicting texture evolution as a function of the time-temperature history was proposed and its parameters were determined from experimental measurements in a standard Kramer cell after homogeneous cooking in a water bath. Combining the two models enabled an estimate of the degree of cooking from core to surface of the product as a function of cooking time. A volume averaged value for the degree of cooking was generated and permitted a good prediction of texture by comparison with the Kramer cell measurements. The combined model can be used to compare different cooking conditions reaching the same final texture.
... This method assures the attainment of the pasting or gelatinization temperature of starch in the ceramic slurry as compared with the conventional heating process. However, the issue of long heating time was partially solved because it relied on the heat transfer of the materials and the pre-heating of the pressure cooker and the load to cause pressurized steam heating [15]. Thus, the present study demonstrates a simultaneous pressure cooking and microwave irradiation to consolidate red clay-based ceramic suspension loaded with the starch powder. ...
... This can be conveniently carried out inside a microwave pressure cooking system that speeds up the gelatinization of starch and shortens the heating time. This new system operates with the same heating principle as the conventional pressure cooker [15,16]. The difference with this new system is that the whole assembly is made up of microwave transparent materials [17]. ...
This study presents a simultaneous application of pressure cooking and microwave irradiation to consolidate ceramic slurry as a rapid shaping technique. The ceramic slurry, composed of red clay, feldspar, quartz and water, was solidified with the gelatinization of starch under varying heating conditions inside a domestic microwave pressure cooker. It was found out that, for a small amount of ceramic slurry, a shortest heating time of 2.52 min was achieved at microwave pressure cooking conditions of 50% power level and target temperature of 60 °C. Based on these conditions, large shaped ceramic prototypes of different shapes were successfully formed using proposed empirical equations to determine a desired heating time at any power levels. The physical characterizations revealed that the physical properties of dried and fired ceramic bodies formed under microwave pressure cooking were better than that of the conventional counterpart. Microstructural investigation into the fired samples revealed larger void spaces in conventional sample than that in microwave pressure-cooked sample.
... Its originality lies in the possibility to connect the power consumption of the furnace to the temperature field in the cavity, and to allow access to the heat flux received by a test material. As done by [9], we used a Polytetrafluoroethylene (PTFE) cylinder to simulate a model foodstuff. ...
... This action is therefore not taken into account in our numerical simulations. In this study, the developed methodology is applied to a model foodstuff (PTFE cylinder), as has been done in previous studies [9]. ...
... Steam undergoes a change phase from liquid to gas, an energy-intensive process. It has been reported that steam evaporation accounts for 90%, whereas conventional losses account for 10% of the total heat losses in a cookpot [22]. To overcome heat losses through evaporation, a study used sunflower oil in one of the vessels [23]. ...
... There is a high energy demand in the now days due to population growth, and as a result, most households still use traditional cooking methods such as burning charcoal and firewood [8]. Traditional cookstoves have negative effects on the natural environment, deforestation, global warming, and poverty, with time-and labor-intensive tasks on women, which are also harmful to their health [3,[8][9][10][11][12]. According to [13] Tanzania is one of the majority of African nations, in which access to clean cooking technology is a severe and developing issue. ...
Traditional cooking techniques prevalent contribute to deforestation, indoor air pollution, and associated health issues. This study explores the transformative potential limitations for improved biomass cookstoves (ICS) uptake among the rural households in Kilimanjaro. ICS offer a faster, more efficient cooking process, reducing cooking time, minimizing heat loss, preserving nutrients, fostering healthier eating habits, and enhancing the flavor of meals. Data were gathered from 300 families in two districts through a crosssectional study, employing both quantitative and qualitative analysis, a binary regression analysis model was used to analyze data collected. The findings indicate that firewood is the major cooking fuel source in the region, where preferred by 83.0% of all respondents and 91.70% of population utilize traditional cookstoves while only 13.0% utilize ICS. The results show that income, education level, occupation and awareness of the household head have greater effect on the uptake of ICS, result indicates that the probability of utilize ICS would increase by 63.173 for every unit increase in monthly household income. Furthermore, households with higher education are more likely to utilize ICS technology by 4.579 times higher compared to those with lower education level. Therefore, the study suggests initiating on public campaign to raise the public awareness and encourage the uptake and utilization of improved cookstoves in rural households. The study's insights can guide policymakers, businesses, and stakeholders in promoting realistic cooking solutions, addressing and overcoming financial barriers of energy challenges, and tackling environmental issues in rapidly growth population in Tanzania.
... A complete rice cooker was modeled by [102], with the objective of simulating variations in behavior according to different energy profiles, as saving energy is an important factor in food processing, along with the final quality of the products. ...
In recent years, modelling techniques have become more frequently adopted in the field of food processing, especially for cereal-based products, which are among the most consumed foods in the world. Predictive models and simulations make it possible to explore new approaches and optimize proceedings, potentially helping companies reduce costs and limit carbon emissions. Nevertheless, as the different phases of the food processing chain are highly specialized, advances in modelling are often unknown outside of a single domain, and models rarely take into account more than one step. This paper introduces the first high-level overview of modelling techniques employed in different parts of the cereal supply chain, from farming to storage, from drying to milling, from processing to consumption. This review, issued from a networking project including researchers from over 30 different countries, aims at presenting the current state of the art in each domain, showing common trends and synergies, to finally suggest promising future venues for research.
... Degree of starch gelatinization to be taken into account. Some researchers including Rocca-Polimeni et al. (2011) have modeled a full rice cooker for energy saving purposes. ...
... (b) The reduction of the heat transfer coefficient h 3,w due to the presence of air, which does not condensate, can be taken into account accordingly to [48][49] where y a is the ratio between the air mass and the total mass (air and steam). (c) The food product arrangement into the processing tank, reducing the overall food surface involved in the heat exchange due to overlapping layers, can be taken into account with the corrective coefficient n -0.25 [50][51]. ...
Many industrial processes require high amounts of steam. Design and operation of steam plants are particularly complex when the steam supply is required for short periods and with a varying time schedules. To fulfil the discontinuous needs of steam users, avoiding the steam boiler oversizing to the peak value of the steam request, a thermal energy storage (TES) system can be adopted. The proper sizing of TES systems, which, in this application, is constituted by a steam accumulator vessel installed between the steam generator and the consumer, cannot be based on the sole initial and final state conditions of the steam storage, since a performance prediction of the process time-evolution is also required.
... It is commonly used for cooking food faster than conventional cooking methods, which presents a significant saving of energy. The heating sequence taking place inside the pressure cooker involves three successive events 17 . The first and second periods involve heating of liquid and elevation of interior pressure due to rise in temperature and water vaporization. ...
The consolidation of red clay-based slurry by gelatinization of starch in a domestic pressure cooker was presented. Aqueous ceramic slurries were prepared consisting of a ternary powder mixture of red clay, quartz, feldspar, and different starch types. The starch slurries with and without the presence of ceramic particles demonstrated the same gelling mechanism and heating time inside the pressure cooker. The gel strengths of pressure-cooked samples were higher than samples heated conventionally. Subsequently, the shaping of large ceramic prototypes is possible using a calculated heating time based on best pressure cooking conditions. The physical characterizations disclosed that the pressure-cooked ceramic samples in dried and fired states exhibited better physical properties depending upon the type of starch added in the ceramic slurry. Specifically, the compressive strengths of fired ceramic bodies shaped in the pressure cooker ranged from 82 ± 2 to 255 ± 9 MPa with bulk porosities of 29.0 ± 0.8-18.7 ± 0.2%, whereas the conventionally shaped bodies possessed compressive strengths ranging from 138 ± 8 to 164 ± 11 MPa with bulk porosities of 25.6 ± 0.1-28.5 ± 0.2%.
Save in energy is the motto each & every country due to the problem of availability of natural resources. So researchers has been focused their directions to overcome energy crises. Among these, they are also in search of saving cooking food in pressure cookers. They suggested new design & modifications in lid of various pressure cookers. Elliptical shape is for ease of opening & closing of lid with vessel. But we saw to the rural community, the peoples are not having exact skill of locking & unlocking. Because of which, there are difficulties for easier handling of pots, which carries spilling of food and hence the burning to kitchen people. These difficulties are overcame by modified inner lid, which is the combination of merits of circularity & elliptical of shapes. It gives 14.54 % increase in heat transfer, easy locking & unlocking by reducing angle by 50°-60° and thermal stresses by 0.43 × 10⁸N/mm².
The concept architecture presented in this paper is about Creating Human Experience through Food (CHEF) in Space. It is part of promoting Commercial Human Spaceflight Expeditions (CHASE), a USC Fall 2021 team project. The overall plan proposes the early transition of the International Space Station (ISS) operations away from NASA core human spaceflight projects to an university consortium and the private sector. The plan comprises adding private labs experimental and manufacturing modules, and includes a hotel that accommodates space tourists in the future, as mandated by US space policy. The goal of CHEF is to serve freshly prepared gourmet food that provides space travelers with an exceptional dining experience. It addresses the challenges of creating a more palatable meal, providing nutritious and tasty food, and catering to individual's caloric needs. CHEF strategy tailors to individual's cravings of the day, on-orbit. It proposes a food technology system that prepares, cooks, and serves the food in an automated fashion. The use of a pressure cooker concept is introduced to cook food per the space travelers' request in short turnaround cycle, from order to delivery. A mixture of preserved food, raw ingredients and spices are processed to go into an ISS, space-compliant pressure cooker system that uses solar energy. With the use of existing technologies, such as 3-D printing of food, robotic chef, tele-robot arms, and Astrobees, integrated together, an automated kitchen service is made possible to implement the end-to-end, fresh restaurant-style gourmet food experience. Because of the US space tourism mandates for ISS, and the Gateway and Artemis mission plan for returning astronauts to the Moon, there is now an economic opportunity to build a robotic kitchen in space that caters to space travelers in the future. Together with water and breathable air, good nutrition is critical for human spaceflight. CHEF in Space project's goal is to serve gourmet food in their short or long journeys to space. Food is the vital fuel to support humans and it is imperative that their needs are addressed with the highest priority along with crew safety and wellbeing. For any successful and productive human space exploration or space activity, great tasting fresh meals are a prerequisite for the space traveler, especially as we plan endurance-class missions and tours-of-duty lasting months to years to the Moon, Mars and beyond. Evolving from the ISS, CHEF systems can progress to serve the crew on Gateway and Artemis, followed by endurance-class missions to the Moon, Mars and beyond.
Frying is one of the most common units in food processing and catering worldwide, which involves simultaneous physicochemical and structural changes. However, the problems of traditional frying technology, such as low thermal utilization and poor processing efficiency, have been gradually exposed to industrial production. In this paper, strategies of applying physical fields, such as pressure field, electromagnetic field, and acoustic field in frying technology separately or synergistically with improved efficiency and quality attributes are reviewed. The role of physical fields in the frying process was discussed with modifications in heat and mass transfer and porous structures. The effects of physical fields and their processing parameters on moisture loss kinetics, oil uptake, texture, color, and nutrients retention of fried food are introduced, respectively. Recent advances in multi-physical field-based frying techniques were recommended with synergistic benefits. Furthermore, the trends and challenges that could further develop the multi-physical field-based frying techniques are proposed, showing further commercial prospects for the purpose. The application of physical fields has brought new inspiration to the exploitation of efficient and high-qualified frying technologies, while higher technical levels and economic costs need to be taken into consideration.
• Highlights
• The role of physical fields in pretreatments and frying process were reviewed.
• The mechanism of physics fields on frying efficiency and quality was summarized.
• The physicochemical and microstructure changes by physics fields were discussed.
• The synergy of physical fields in frying technology were outlined.
• The trends for further multi-physical field-based frying techniques were proposed.
Indonesia has a typical rice processing method as part of the nation’s culture, namely ketupat. Ketupat is typical food made of rice wrapped in diamond shaped-woven coconut leaves and boiled in water. This article reviewed the variety of processing ketupat as well as changes in ketupat during storage of ketupat according to the results of research and related references. Traditionally, ketupat is cooked in boiling water for 5 hours. This is considered inefficient in terms of cooking fuel and time required for cooking. The efforts of modifying ketupat cooking method have been done to shorten processing time, such as cooking ketupat in pressure cooker for 30 minutes. The development of ready-to-cook ketupat or quick-cooking product in attractive package becomes a promising opportunity. Quick-cooking ketupat was made by immersing ketupat in salt, steaming, freezing and drying. The package of quick-cooking ketupat was designed using HDPE plastics made square shape that requires boiling period for 30 minutes. Ingredients and the amount of rice, the size of coconut leaves, immersion process and cooking technic affected the texture of ketupat produced. Ketupat is normally stored for 2 days in room temperature and 4-7 day if it is refrigerated. Spoilage of ketupat is due to microbiological and physical changes during storage. Starch retrogradation and increase in RS III may occur when ketupat is stored at low temperature.
Increasing of fluid pressure in phase change applications is an important area for research, as it requires high grade energy. Low grade energy (heat energy) may be employed to develop fluid pressure in selective applications with isochoric heating in a non-flow process. Pressure vessel is a common example working on isochoric heating process to develop steam pressure. Experiments are conducted in this vessel to analyze the characteristics of isochoric heating process. Some of the characteristics investigated are (i) mass of the steam leaving the vessel for a given volume ratio (mass of water contained in the vessel to volume of the vessel), ratio of time taken to release steam to heating time, ratio of enthalpy of the steam leaving the vessel to useful enthalpy rise of water and steam mixture for different volume ratio. The effect of insulating the circumference of the vessel on the above mentioned characteristics are also investigated in this paper. Further experiments using any liquid refrigerant as working medium can lead this research to attain a remarkable development of using low grade energy for refrigeration applications.
Steam sterilisation using autoclaves or retorts is a widely used thermal process in the food processing and pharmaceutical industries. Unfortunately, sterilisation, using steam, consumes a significant amount of energy and is known to cause unwanted peak energy demand when a number of autoclaves operate in parallel. The objective of this paper is to extend the previously published numerical methodology developed to simulate in detail the thermal energy consumption of an industrial sized empty autoclave used for steam sterilisation, to include products, in this case, intravenous solution packed in plastic pouches and a steam flow controller. The external parameters supplied to the numerically modelled controller are the maximum steam flow rate and the autoclave temperature as a function of time which it needs to maintain. The numerical model is then used to predict the actual transient temperature and pressure profiles and the details of the mass transfers in the autoclave during a sterilisation cycle, the transient temperature distribution within the products as well as details of the transient thermal energy consumption. The results from numerical modelling were validated with measurements obtained under actual operating conditions. The simulated total steam consumption was within 3% of the measured data. A reduction of 8% in steam consumption was obtained due to insulation on the outer walls.
A numerical model has been developed to simulate heat and mass transfer phenomena during a steam air sterilisation cycle of an operating industrial autoclave. The objective of this paper is to present a practical methodology applicable for evaluating transient heat and mass transfer phenomena by assuming quasisteady state conditions. As a first step, an empty autoclave was considered. The developed model utilises measured steam flow rates as input parameters and predicts the transient temperature and pressure profiles. The numerical results are validated against two measured on-site data sets, one obtained in summer and the other in winter. The detailed numerical results allow the major heat losses within the process were identified to be determined, thus presenting the importance of having such a numerical model when conducting analyses for evaluating potential thermal energy savings in thermal processes. It is shown, that in any cyclic operation involving the heating and cooling of the containing walls, the insulation should be placed on the heated side.
Chickpea is a leguminous that can be consumed both fresh and baked, and must be hydrated in both cases. The objective of this study was to discuss mathematical and numerical models, and also experimentally evaluate the process of water uptake in chickpea (Cicer arietinum) under different temperatures and pressures, determining the diffusion coeffcient of water in the grains and the activation energy of the hydration process. The values for the diffusion coeffcient ranged from 7.38 x 10-11 to 5.21 x 10-10 m2 s-1. The activation energy was determined at 36.040kJ mol-1, the activation volume
at -7.724 x 1000 cm3 mol-1 and the constant value was 2.185 x10-4. By comparing the experimental results with those obtained from the analytical solution of the theoretical model, there was a satisfactory fit of the model to the experimental data, and the hydration curves were plotted. A good adjustment of the numerical model, the model of Abu-Ghannam and the Peleg model was made to the experimental data. The Arrhenius-Eyring type equation was used to explain the dependency of the diffusion coeffcient with the temperature and pressure in the hydration process.
A food property is a particular measure of the food’s behavior as a matter or its behavior with respect to energy, or its interaction with the human senses, or its efficacy in promoting human health and well-being. An understanding of food properties is essential for scientists and engineers who have to solve the problems in food preservation, processing, storage, marketing, consumption, and even after consumption. Current methods of food processing and preservation require accurate data on food properties; simple, accurate, and low-cost measurement techniques; prediction models based on fundamentals; and links between different properties. The first edition was well received,
secured bestseller from the publisher, and received an award. Appreciation from scientists, academics, and industry professionals around the globe encouraged me to produce an updated version. This edition has been expanded with the addition of some new chapters and by updating the contents of the first edition. The seven chapters in the first edition have now been expanded to 24 chapters. In this edition, the definition of the terminology and measurement techniques are clearly presented. The theory behind the measurement techniques is described with the applications and limitations of the methods. Also, the sources of errors in measurement techniques are compiled. A compilation of the experimental data from the literature is presented in graphical or tabular form, which would be very useful for food engineers and scientists. Models can reduce the numbers of experiments, thereby reducing time and expenses of measurements. The empirical and theoretical prediction models are compiled for different foods with processing conditions. The applications of the properties are also
described, mentioning where and how to use the data and models in food processing.
Chapter 1 provides an overview of food properties including its definition, classification, and predictions. Chapters 2 through 4 present water activity and sorption isotherm including its terminology, measurement techniques, data for different foods, and its prediction models. Chapters 5 through 12 present thermodynamic and structural characteristics including freezing point, glass transition, gelatinization, crystallization, collapse, stickiness, ice content, and state diagram. Chapters 13 through
15 discuss the density, porosity, shrinkage, size, and shape of foods. Chapters 15 through 23 present the thermophysical properties including specific heat, enthalpy, thermal conductivity, thermal diffusivity, and heat transfer coefficient. Chapter 24 provides the acoustic properties of foods.
This second edition will be an invaluable resource for practicing and research food technologists, engineers, and scientists, and a valuable text for upper-level undergraduate and graduate students in food, agriculture and biological science, and engineering. Writing such a book is a challenge, and any comments to assist in future compilations will be appreciated. Any errors that remain are entirely mine. I am confident that this edition will prove to be interesting, informative, and enlightening.
Potatoes were cooked in a combination-steam oven by two traditional cooking treatments, forced convection (FC) and steaming (S) and four combined treatments (FC/S, FC–FC/S, S–FC, FC–FC/S–FC). Weight loss, shear force, crust hardness, texture profile analysis (TPA), colour (L*, a*, b*), surface and center cook values were evaluated. S, FC/S and FC–FC/S treatments were faster (∼17min) than the others (45, 36 and 41min for FC, S–FC and FC–FC/S–FC), showing significantly lower cook values both at the center (1.7–3.0min for S, FC/S, FC–FC/S and 3.7–5.2min for FC, S–FC, FC–FC/S–FC) and at the surface (4.4-7.3min for S, FC/S, FC–FC/S and 15.3–18.4min for FC, S–FC, FC–FC/S–FC).Potatoes cooked with FC and FC–FC/S–FC were characterized by the formation of a dry crust significantly harder than in the other products. FC/S and FC–FC/S cooking treatments resulted in a very hard and pale product. S–FC treatment showed a limited weight loss accompanied by a soft texture and surface browning that make it the recommended treatment for home and food service cooking of potato (cv. Agata).
A thermal treatment is an intrinsic part of most food processing procedures and may be employed to inactive enzimes and toxic '• factors, to change texture and flavour or to preserve. The vitamin degree of transformation or destruction in cooking methods depends on the temperature and on the time of exposure to this temperature. Oxigen, light and transition metals frequently play an active role in accelerating or promoting vitamin losses. Both chemical change and difussion proceed more rapidly as the temperature is raised. An advantage of deep frying consists of the fact that the temperature within the food does not exceed the temperature of the steam under the crust, and that frying times are in general very short compared to other cooking procedures. Another advantages may be the low content of dissolved oxygen in frying fats, and also in its high tocopherol content. There is no leaching of water-soluble vitamins in deep-frying. Speaking of vitamin stability we have to keep in mind that the concept of vitamins is a more physiological concept than a chemical one. The stability itself is not a property of the various vitamins but rather of the various chemical compounds sometimes called vitamers, of which a certain vitamin group consists. For practical purposes, vitamin losses should be considered only in foods wich substantially contribute to the vitamin supply of single people or population groups. There is little data in the literature about vitamin changes in deep-frying of food. However published experimental data on vitamin loses show that deep-frying is one of the most protective cooking procedures. For example, in ours results the vitamin C losses of stewed vegetable foods were twice higher than that of fried ones, (raw potatoes containing 19 mg/100g fresh weight, 13 mg/100 fried in olive oil, and 5 mg/100g stewed in the same oil).
The effect of pressure cooking on aflatoxin residues in polished rice was conducted to determine reduction of aflatoxin and mutagenic potentials. Three rice lots consisting of naturally contaminated, A. parasiticus-infested, and aflatoxin-spiked rice were steamed by ordinary and pressure cookers after they were washed with water. They were chemically analyzed for aflatoxins using a silica solid phase extraction tube and high-performance liquid chromatography (HPLC)-fluorescence detection (FD), and the presence of aflatoxin residues was confirmed using HPLC-electrospray ionization (ESI)-mass spectrometry (MS). An in vitro mutagenicity test with Salmonella typhimurium TA100 was employed to verify the results based on chemical analyses. The aflatoxin loss (78-88%) was notable after pressure cooking, and the reduction of aflatoxin-induced mutagenic potential (68-78%) was in good agreement with the HPLC results. It can be concluded that Koreans are safe from the aflatoxin-related risk if a pressure cooker is employed for cooking rice. The average Korean daily intake of aflatoxin through the consumption of staple rice would fall to 0.15 ng/kg bw/day, which would not exceed the established tolerable daily intake (0.40 ng/kg bw/day).
The study of “Heat Balance ” in a domestic pressure cooker is an important investigation for energy conservation. In the present study, experiments were conducted on a domestic pressure cooker to measure Input Heat, Utilized Heat and Heat Lost for different volumes of water filled in a pressure cooker. Experiments were conducted on 0.008m3 (8litre) pressure cooker filled with water at 12.5%, 25%, 37.5% and 46.25% of its capacity, respectively 1.0kg, 2.0kg, 3.0kg and 3.7kg of water. Two approaches were adopted to determine an optimum condition of the pressure cooker. In first approach, the pressure cooker was insulated and the other in non-insulated. In both cases, cookers of similar capacity, make and design were used. Outer surface of the cooker was insulated with asbestosrope, clay and cow-dung bindings. Interesting results were arrived during the study that, there was not having much difference in heat input, heat utilization for insulated and non insulated cookers when the water level was only about 12.5% volume. In other cases the insulated cooker consumes more heat input than the non-insulated cooker. The reason was found that thermal mass capacity of the insulated cooker was more and stores heat energy. When the pressure cooker is filled with 46.25% of its volume by water, it utilizes a maximum of 30% of total heat supplied. On reducing the volume of water filled in the cooker, the heat loss increased and consumes more thermal energy.
Processing and cooking conditions cause variable losses of vitamins. Losses vary widely according to cooking method and type of food. Degradation of vitamins depends on specific conditions during the culinary process, e.g., temperature, presence of oxygen, light, moisture, pH, and, of course, duration of heat treatment. The most labile vitamins during culinary processes are retinol (vegetable boiling, 33% retention), vitamin C (the most damaging factors are cooking and oxidation), folate (leaching into the cooking water, 40% retention), and thiamin (cooking, retention 20-80%). Niacin, biotin, and pantothenic acid are quite stable, but information on some vitamins, especially vitamins D and K, is incomplete. The percentage losses of some nutrients in foods after cooking treatment were frequently reported: not continual changes during heat treatment, only modifications at the beginning and after heat treatment. Changes of nutrients in food during the culinary process have not yet been sufficiently investigated. A few authors have attempted to summarize the kinetic data which can be used to describe the time-temperature effect on nutrients. (c) 2005 Elsevier Inc. All rights reserved.
A wide-ranging analytical investigation of laminar film condensation is presented. The situation under study is an isothermal vertical plate with steam as the condensing vapor and air as the noncondensable gas. In addition to the noncondensable gas, the analytical model includes interfacial resistance, superheating, free convection due to both temperature and concentration gradients, mass diffusion and thermal diffusion, and variable properties in both the liquid and the gas-vapor regions. Heat-transfer results are obtained for a wide range of parameters including bulk concentration of the noncondensable gas, system pressure level, wall-to-bulk temperature difference, and degree of superheating. It is demonstrated that small bulk concentrations of the noncondensable gas can have a decisive effect on the heat-transfer rate. For instance, for a bulk mass fraction of air equal to 0.5 per cent, reductions in heat transfer of 50 per cent or more are sustained. The influence of the noncondensable gas is accentuated at lower pressure levels. It is shown that the aforementioned reductions in heat transfer are due entirely to the diffusional resistance of the gas-vapor boundary layer. The interfacial resistance is shown to be a second order effect. A similar finding applies to thermal diffusion and diffusion thermo. The effect of superheating, which is very small in the case of a pure vapor, becomes much more significant in the presence of a noncondensable gas. A reference temperature rule is deduced for extending the Nusselt model to variable-property conditions.
The kinetics of vitamin C destruction during the cooking of a potato dish were measured. Five domestic cooking apparatuses, including a superheated steam oven, a free convection oven, a forced convection oven, a microwave oven and a pressure cooker, were compared. Whatever the cooking condition, when the residence time was equal to the cooking time, the reduced quantity of vitamin C remaining in the potato dish was approximately 0.7. A model considering the thermal and the enzymatic destruction of vitamin C and the thermal deactivation of enzymes was proposed. The parameters of the model were identified using the results of the cooking experiments and isothermal kinetics of vitamin C destruction in potato extracts. The simulations showed that the loss of vitamin C at the cooking time was mainly due to the enzymatic destruction. A prolonging of the residence time resulted in additional losses by thermal destruction. A low water content and the presence of air in the cooking atmosphere further increased the destruction rate.
During underground coal gasification (UCG), a cavity is formed in the coal seam when coal is converted to gaseous products. This cavity grows three dimensionally in a nonlinear fashion as gasification proceeds. The cavity shape is determined by the flow field, which is a strong function of various parameters such as the position and orientation of the inlet nozzle and the temperature distribution and coal properties such as thermal conductivity. In addition to the complex flow patterns in the UCG cavity, several phenomena occur simultaneously. They include chemical reactions (both homogeneous and heterogeneous), water influx, thermomechanical failure of the coal, heat and mass transfer, and so on. Thus, enormous computational efforts are required to simulate the performance of UCG through a mathematical model. It is therefore necessary to simplify the modeling approach for relatively quick but reliable predictions for application in process design and optimization. The primary objective of this work is to understand the velocity distribution and quantify the nonideal flow patterns in a UCG cavity by performing residence time distribution (RTD) studies using computational fluid dynamics (CFD). The methodology of obtaining RTD by CFD is validated by means of of representative laboratory-scale tracer experiments. Based on the RTD studies, the actual UCG cavity at different times is modeled as a simplified network of ideal reactors, called compartments. The compartment model thus obtained could offer a computationally less expensive and easier option for determining UCG process performance at any given time, when used in a reactor-scale model including reactions. The network of ideal reactors can be easily simulated using a flowsheet simulator (e.g., Aspen Plus). We illustrate the proposed modeling approach by presenting selected simulation results for a single gas-phase second-order water−gas shift reaction.
The great progress in the energy efficiency of household appliances is primarily generated by the improved design of refrigerators, freezers, washing machines and dishwashers. In the long term, a positive effect on household electricity consumption is expected with increasing numbers of old appliances being replaced by new and more energy-efficient ones. Studies of electricity consumption in private households show that energy efficiency can also be improved by changes in consumer behaviour, in addition to improvements in the technical design of appliances. Consumer studies on behavioural aspects of electricity consumption related to large household appliances have already been conducted, but little information is available about cooking. However, the influence of consumer behaviour on energy consumption is particularly interesting where cooking is concerned. The most important processes of manual and machine food preparation shall therefore be investigated regarding performance and energy efficiency. This provides a basis for attempting to estimate the energy-saving potential of optimized cooking processes in order to obtain sound scientific information about the energy-saving potentials for the most typical and relevant cooking processes in European households, which are:
The study shows that the energy consumption of typical household cooking processes varies greatly according to the chosen method. In the tests carried out for this study, the method making most sense in terms of energy consumption saved between 50% and 70% energy compared with the least favourable method. Based on the results, the authors provide recommendations on energy-saving cooking methods.
The expression Y = (1 + Zn)1/n where Y and Z are expressed in terms of the solutions for asymptotically large and small values of the independent variable is shown to be remarkably successful in correlating rates of transfer for processes which vary uniformly between these limiting cases. The arbitrary exponent n can be evaluated simply from plots of Y versus Z and Y/Z versus 1/Z. The expression is quite insensitive to the choice of n and the closest integral value can be chosen for simplicity. The process of correlation can be repeated for additional variables in series. Illustrative applications are presented only for flow, conduction, forced convection, and free convection, but the expression and procedure are applicable to any phenomenon which varies uniformly between known, limiting solutions.
The quantity of heat transmitted from a metal surface to boiling water increases as the temperature difference ΔT is increased, but after the ΔT has reached a certain limit, quantity Q decreases with further increase in ΔT. This turning point is the maximum value of heat transmitted. The existence of this point was actually observed in the experiment. Under atmospheric pressure, ΔT corresponding to the maximum value of heat transfer for water at 100°C falls between 20 degC to 40 degC, and Q is between 1080000 and 1800000 kcal/m2 h (i.e. between 2000 and 3000 kg/m2h, if expressed in constant evaporation rate at 100°C) ; this figure is larger than the maximum value of heat transfer as was previously considered. Also, the minimum value of heat transfer was obtained, and in the Q-ΔT curve for the high temperature region, the burn-out effect is discussed.
The effects of four culinary treatments (steaming and boiling in a covered pot, a pressure cooker or a microwave oven) on the chlorophyll a and b, all-trans-lutein, phaeophytin a and b and all-trans-β-carotene (provitamin A) contents of green beans (Phaseolus vulgaris, L.) were evaluated. The pigments in the fresh and treated beans were determined by gradient elution reverse-phase HPLC with UV detection. Boiling the beans in a covered pot, pressure cooking or microwaving them caused smaller losses of pigments than steamed cooking. Since pressure cooking also generally leads to smaller losses of nutritious components (e.g. vitamin C), it is recommended over the traditional method of boiling beans in a covered pot.
In many rural areas, poor people still depend on wood and other biomass fuels for most of their household and income-generating activities. The difficult, time-consuming work of collecting and managing traditional fuels is widely viewed as women's responsibility, which is a factor in women's disproportionate lack of access to education and income, and inability to escape from poverty. Therefore, it is important for energy access programs to have a special focus on women. New options for energy access and sustainable livelihoods, like small-scale biofuels production, can have dramatic benefits for rural women, and their families and communities. Energy development, as both a driving force and a consequence of such tremendous changes, has had profound impact on economic, social, and environmental development. Rural energy has always been a critical issue due to years of energy shortage for both households and industries. Biomass, for long time, has been the only available fuel in many rural areas. The situation in rural areas is even more critical as local demand for energy outstrips availability and the vast majority of people depend on non-commercial energy supplies. Energy is needed for household uses, such as cooking, lighting, heating; for agricultural uses, such as tilling, irrigation and post-harvest processing; and for rural industry uses, such as milling and mechanical energy and process heat. Energy is also an input to water supply, communication, commerce, health, education and transportation in rural areas.
The kinetics of riboflavin degradation in green gram whole (Vigna radiata L.), as well as in pure riboflavin solutions, at initial concentrations present in green gram were studied over a temperature range of 50–120 °C (steady state temperature process). Riboflavin degradation followed first order kinetics, where the rate constant increased with an increase in the temperature. The temperature-dependence of degradation was adequately modelled by the Arrhenius equation. The degradation kinetics of riboflavin, in normal open pan cooking, pressure-cooking and a newly developed and patented fuel-efficient `Eco-cooker', were also studied (unsteady state heating process). A mathematical model, to predict the losses of riboflavin from the time–temperature data of the unsteady state heating/cooking process, has been developed using the steady state kinetic parameters obtained. The results indicate riboflavin degradation of a similar magnitude in all three modes of cooking used in the study.
Mathematical simulation studies for thermal food processes require knowledge of thermal diffusivity and convective heat transfer coefficient. There have been different experimental and empirical approaches reported in the literature for determination of these parameters where different approximations were applied. One of the most applied approaches is to assume an infinite convective heat transfer coefficient at the surface boundary when analytical solutions for infinite slab, infinite cylinder and sphere are used for further determinations. Since this approach results in certain errors in results, it would be an important task to determine thermal diffusivity and convective heat transfer coefficient simultaneously.Therefore, the objective of this study was to review the literature for determination of thermal diffusivity and mathematically apply optimization methodologies for simultaneous determination of heat transfer coefficient. For this purpose, constrained optimization methodologies, based on analytical solutions of infinite slab, infinite cylinder and sphere were defined, and results were discussed intensively. The results showed that a precise determination of thermal diffusivity and convective heat transfer coefficient is a difficult task, but knowing the location where the experimental time–temperature was obtained would really simplify this problem.
Data for thermodynamic quantities. Find in the library at 540 C
Compound dH dG S
CuCl -137.2 -119.9 86.2
CuCl2 -220.1 -175.7 108.09
CuO -157.3 -129.7 42.6
Cu2O -168.6 -149.0 93.1
Energy conservation in cooking rice is an important area for scientific investigation. Experiments were conducted to measure the energy consumption during normal and controlled cooking of both unsoaked and presoaked rice using two types of domestic cooking appliance, namely, an electric rice cooker and a pressure cooker. Cooking rice with controlled energy input, under pressure and with presoaking were the three approaches, which resulted in saving of energy. Electric rice cooker was found to be the most energy-efficient among the different combinations of cooking appliance and the types of heat source used in the study. The energy consumption was much less (23–57%) compared to other methods. Prior soaking of rice generally reduced energy consumption as well as cooking time, more prominently during normal cooking. Controlled cooking offered more savings in energy compared to presoaking rice. Considering the energy consumption and cooking time, controlled cooking of presoaked rice was found to be the best among the several approaches investigated. Measurement of water evaporation loss appears to be a good indirect method of assessing the efficiency of heat utilization. Controlled energy input is another useful method that optimizes the energy utilization for cooking, besides presoaking and pressure cooking. Controlled cooking is desirable in all types of rice cooking.
Cooking rate was examined for excess-water and optimal-water cooking of unsoaked and presoaked rice. The linear relationship between the logarithmic moisture gain ratios of cooked rice and the time of cooking showed that cooking rate followed the equation of a first-order chemical reaction. During excess-water cooking of presoaked rice a single rate constant was observed, while in the case of unsoaked rice two rate constants were observed. Interestingly, optimal-water cooking in electric rice cooker showed that the number of rate constants increased by one as compared to excess-water cooking for both unsoaked and presoaked rice. Controlled cooking, an energy saving method proposed earlier by the authors behaved similar to the normal method of cooking under otherwise identical conditions. Present evaluation of cooking rate constants under commonly practiced conditions of cooking would be useful in designing more efficient rice cookers.
Modelling fluid flow, heat transfer and water condensation in a pressure cooker In: Proceedings of CHT-08: Aavances in Computational Heat Transfer, Marrakech, Morocco. Idel'cik, I.E., 1996. Handbook of Hydraulic Resistance Fundamentals of heat and mass transfer
- D Flick
- R Rocca
- C Doursat
- J Vasseur
- G Trystram
Flick, D., Rocca, R., Doursat, C., Vasseur, J., Trystram, G. (2008). Modelling fluid flow, heat transfer and water condensation in a pressure cooker. In: Proceedings of CHT-08: Aavances in Computational Heat Transfer, Marrakech, Morocco. Idel'cik, I.E., 1996. Handbook of Hydraulic Resistance, third ed. Begell House Inc., Redding. Incroprera, F.P., DeWitt, D., 2002. Fundamentals of heat and mass transfer, fifth ed. John Wiley & Sons, Hoboken.
The effect of liquid viscosity on bubble formation and heat transfer in boiling Heat Transfer in Boiling
- F Hollborn
, F., Hollborn, E., 1977. The effect of liquid viscosity on bubble formation and heat transfer in boiling. In: Hahne, E., Grigull, U. (Eds.), Heat Transfer in Boiling. Hemisphere Publishing, Washington, pp. 391–423.
Numerical Heat Transfer and Fluid Flow Effect of pressure cooking on aflatoxin B1 in rice
- Patankar Taylor
- Francis
- London
- J W Park
- Y.-B Kim
Patankar, 1980. Numerical Heat Transfer and Fluid Flow. Taylor and Francis, London. Park, J.W., Kim, Y.-B., 2006. Effect of pressure cooking on aflatoxin B1 in rice. Journal of Agricultural and Food Chemistry 54, 2431–2435.