Academic literature on the topic 'Food simulation'

There is an increasing interest in dynamical food web modeling, and recent advances of computational biology provide new algorithms and tools for modern systems ecology. In this work stochastic individual-based models are used for simulating food web dynamics in two case studies: the Kelian river, in Borneo, Indonesia and a marine ecosystem in Gulf of Guinea. The two cases present effects from human perturbations. In both cases, we constructed food webs, based on real databases. We parameterized the stochastic dynamical model for the system models and performed sensitivity analysis (and community response indicators) in order to quantify the relative importance of system components. The main aims are to understand the importance of functional diversity of aquatic ecosystems and relations between the dynamics of species and the whole community in perturbed ecosystems due to human activities (pollution due to gold mining activity and human settlements in the case of the Kelian river ecosystem and the impact of Fish Aggregation Devices on skipjack tuna communities in the case of the Gulf of Guinea ecosystem). In Kelian river case, our results suggest that invertebrate shredders are indicators of human impact on the river. In downstream sites our results show that the river is more polluted and the relative importance of grazers and shredders decrease. The primary producers disappear downstream as consequence of mine activity and human waste. In the marine system case study, we analyzed the effects of association between tunas and FADs, and compared this to the behavior of free tuna individuals. The results suggest that skipjack tuna is affected by the use of FADs as fishing strategy on them. Some individual species show more sensibility to variation of population size of tuna. These two studies contribute to better understand how functional diversity is related to human impact. This kind of approach may help in shaping systems-based conservation and marine fisheries management strategies. Keywords: food web, aquatic ecosystems, stochastic model, sensitivity analysis

There is an increasing interest in dynamical food web modeling, and recent advances of computational biology provide new algorithms and tools for modern systems ecology. In this work stochastic individual-based models are used for simulating food web dynamics in two case studies: the Kelian river, in Borneo, Indonesia and a marine ecosystem in Gulf of Guinea. The two cases present effects from human perturbations. In both cases, we constructed food webs, based on real databases. We parameterized the stochastic dynamical model for the system models and performed sensitivity analysis (and community response indicators) in order to quantify the relative importance of system components. The main aims are to understand the importance of functional diversity of aquatic ecosystems and relations between the dynamics of species and the whole community in perturbed ecosystems due to human activities (pollution due to gold mining activity and human settlements in the case of the Kelian river ecosystem and the impact of Fish Aggregation Devices on skipjack tuna communities in the case of the Gulf of Guinea ecosystem). In Kelian river case, our results suggest that invertebrate shredders are indicators of human impact on the river. In downstream sites our results show that the river is more polluted and the relative importance of grazers and shredders decrease. The primary producers disappear downstream as consequence of mine activity and human waste. In the marine system case study, we analyzed the effects of association between tunas and FADs, and compared this to the behavior of free tuna individuals. The results suggest that skipjack tuna is affected by the use of FADs as fishing strategy on them. Some individual species show more sensibility to variation of population size of tuna. These two studies contribute to better understand how functional diversity is related to human impact. This kind of approach may help in shaping systems-based conservation and marine fisheries management strategies. Keywords: food web, aquatic ecosystems, stochastic model, sensitivity analysis

The development of a simulation strategy and modelling algorithm with potential application to a variety of food process operations, particularly to thermal processing of canned foodstuffs has been undertaken. A review of published work identified previous efforts in the development of mathematical models for thennal process operations, including their limitations. The review showed that Finite Difference methods have found wide application in modelling conduction heating of canned foods. A similar model would be a useful numerical yardstick for validating any developments in this work. The great diversity of food handling operations have been grouped into a more manageable small number of classes. Such classification recognised that sets of related operations share common characteristics and functions which are the basis for the development of mathematical models for each class of operations. The strategy developed involved hierarchical decomposition of unit operations into assemblies of basic modules and mathematical modelling of these basics. A model of the operation can then be constructed simply by selecting and arranging the required basic units with due consideration to the boundary conditions of the physical problem. For transient operations with positional variation, these elementary modules have been termed "zones". The range of basic zones to model representative units have been identified. This hierarchical zone-model simulation has been demonstrated for heat transfer in a cylindrical container and for batch retort operation. The repeated use of the same unit modules for different operations makes this a flexible and robust strategy. The mathematics of zone-modelling has been developed for heat conduction in foodstuffs in cylindrical containers. To ensure accuracy, the numerical integration steps were rigorously monitored using mathematical procedures well-established for this purpose. The validity of the model has been tested against the analytical and implicit finite difference solutions. Generally, zone models agreed within 1 % of these standard yardsticks with the difference becoming negligible when sufficiently small integration steps or zone sizes were used. The effectiveness of zone-modelling as a simulation tool has been established using experimental data and the various sources of discrepancy between the model and experimental data accounted for. Thermocouple measurement errors have been found to have contributed most significantly to this discrepancy. Detailed analysis and modelling of thermocouple measurement errors has been carried out using zone-modelling to simulate the true experimental system which accounted for the presence of a thermocouple. The result has been an improved agreement between experiment and the zonemodel, and it also demonstrated the flexibility of the modelling technique. Further resuhs have shown that the discrepancy varied with thermocouple size and type. The contributions to error of temperature variability of, and of uncertainty in, thermophysical properties of the food were discussed. , The flexibility and robustness of zone-modelling have been further demonstrated using some practical situations including heat transfer to foodstuff in flexible packaging - such as sausage rolls, heat transfer in a food container with varying headspaces and the consequence of steam interruption during processing. Examples have been discussed of other transient processes that could similarly be modelled using this technique. The main achievements of this work include the application of hierarchical simulation and zonemodelling techniques to food processing and the development of a novel mathematical modelling technique which is more flexible than finite differences. Moreover, the applications of zonemodelling to the study of thermocouple errors, to the study of the consequences of steam interruption during thermal processing, and to heat transfer in foods in flexible containers, are developments of interest in food processing. It is concluded that the hierarchical simulation and zone modelling algorithm are robust and flexible techniques with potential applications in food process simulation .

Drying is a unit operation where water is removed from a material by means of evaporation and mass transfer. It is widely used in industrial manufacturing processes. Many of these processes involve drying of porous materials. Porous media are, in general, heterogeneous systems. The microstructure of the pore space influences transport properties and hence, drying rates. Thus, a quantitative geometrical characterization of the pore space is crucial for accurate prediction of porous media drying rates. Simulation of porous media structure, given a specific size distribution of constituent particles, followed by pore-space characterization is a powerful as well as economical predictive tool for product design. Realistic unconsolidated porous media were reconstructed through Monte Carlo gravitational particle packing simulation. The porous media simulation was validated by comparison with extracted transport related micro-structural parameters from x-ray micro-CT (computed tomographic) images. A mathematical morphology based three-dimensional image processing algorithm was developed to characterize the pore space in the simulated porous media. This realistic pore-throat network information was utilized in an invasion percolation based simulation of porous media drying and showed satisfactory agreement with quantitative data extracted from in-situ NMR (nuclear magnetic resonance) imaging experiments.

The aim of this study was to investigate drying characteristics (temperature gradient, rate of drying and temperature change, drying time, diffusivity values, shrinkage) of isotropic and anisotropic foods by observing the changes in temperatures at four different locations and moisture contents and to build an appropriate model for simulation of temperature and moisture distribution using finite element method. The lean meat samples (anisotropic) with three fiber configurations (v<br>flow normal to fiber, drying along the fiber, h1<br>flow normal to fiber, h2<br>flow along to fiber) and minced meat (isotropic) were dried at two different temperatures (48

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.<br>The fast food industry, specifically the service department, has experienced sustainable economic growth and has evolved in the application of substantial methods, however, it has presented a slowdown due to deficient operation level provided in the customer service area. A large number of customers do not make the purchase owing to a series of unmet trends that face the consumer behaviour which leads to significant economic losses and inefficient service. They have therefore focused their efforts on finding impulse mechanisms through allowing them to migrate to less costly processes and/or to achieve better utilisation of available resources without success. This research inquires into the effectiveness of the Lean Thinking Simulation (LTS) model, which consists in the development of a set of methodological phases and the adaptation of the technological support termed as Digital Change to improve the performance of customer service in Peruvian fast food. The main result of this practical study was defined by a Dashboard in real-time, and as a first approximation of the model, a 17.03% improvement can be shown in the performance of customer service on the fast food selected.<br>Revisión por pares

Atmospheric freeze drying (AFD) is the lyophilization of a product at atmospheric pressure conditions and temperatures ranging generally between -15 and -5 ◦C (avoiding, thereby, ice melting). The quality of the obtained dried products is quite similar to the quality of products dried by vacuum freeze drying (VFD), but without the need of generating vacuum, maintaining temperatures around -50 ◦C in the condenser, or defrosting it. There are several ways to carry out AFD, such as the use of a fluidized bed or a tunnel conveyor. Nevertheless, AFD involves considerably longer drying times than VFD, and the process must be modified in some way in order to shorten them without loss of product quality at the same time. Moreover, since this process is usually carried out with air at very low temperatures, it can saturate rapidly. This situation leads to a reduction of the gradient of water concentration between air and product surface, and consequently, a diminution of the mass transfer rate. The use of an adsorbent material compatible with the food product (i.e., not toxic for human consumption) in a fluidized bed, could constitute an alternative for using other extra energy supplies (such as IR application, or heat pump). At the same time, the use of the adsorbent medium presents two additional advantages: the first, as the heat of adsorption of water vapour is of the same order of magnitude than sublimation heat of ice, no additional energy supply is necessary; second, it acts as adsorbent medium for generated water vapour, allowing air recirculation, which means an additional reduction of operative costs. In particular, non-food wheat bran is an interesting material to be applied as adsorbent in this process; this adsorbent is not only compatible with foodstuff, but also, since it is a by-product of the cereal processing industry, it is cheap and can be easily discarded (and reused, for example, in compost) without recovering it by means of a thermal treatment. Nonetheless, as it is the hard outer layer of cereals consisting of combined aleurone and pericarp, its particles exhibit a very irregular plane shape, with rests of grain brush and, in some cases, broken pericarp. These characteristics confer to the particle a rough surface and, as undesired consequence, the possibility of mechanical interaction during fluidization. However, when two different materials are fluidized in a fluidized bed, the mixture may undergo segregation, causing a poor contact between the adsorbent and the food particles. Thus, instead of using a traditional fluidized bed, a spout-fluid bed (an apparatus similar to the spouted bed, with lateral air injectors beside the main jet) may be utilized, and thereby enhancing mixing. On the other hand, CFD simulation would offer a great potential for simulating the AFD process, its optimization from the fluid dynamic point of view, and the design of new equipment. Various investigators have been working on the application of CFD models for simulating AFD in fluidized bed. However, in general, they simulated a single piece of foodstuff, but not the complete system with air, food material, and adsorbent (when it is applied). The general objectives of the PhD work are to determine the hydrodynamic conditions under which AFD in adsorbent fluidized bed is feasible, and to obtain a first approach to a CFD model of the process. Particularly, the study of the hydrodynamics of the process (non-food wheat bran fluidization behaviour, and mixing of binary mixtures) in a fluidized bed as well as in a spout-fluid bed is aimed from the experimental point of view, while the evaluation of the possibility of simulation by means of a CFD code of the AFD process by immersion in adsorbent medium in a fluidized bed is intended in the theoretical field. Unlike sand or other materials in which regular bubbles are formed, non-food wheat bran exhibits canalization or preferential air paths formation, and bed does not expand after overcoming minimum fluidization velocity. In addition, bran particle diameter is represented by a population distribution whose majority is Geldart B. Therefore, considering other bran particles physical characteristics such as rough surface and rest of grain brushes, it can be said that this "pseudo-cohesive" behaviour is caused principally by mechanical interactions rather than electrostatic forces as occurs in cohesive powders. In general terms, it can be observed a cyclical behaviour of channels generation and collapse. The number of channels and their shape depend on air superficial velocity as well as the bed position where they are formed. Anyway, in general they follow the Channel Generation and Collapse Cycle where two main stages are represented: I, generation, and II, collapse. Experiments emulating different stages of the AFD process with adsorbent application (using fresh food, partially lyophilized material, and completely lyophilized foodstuff) were done employing different food particles (peas, carrot discs, and potato slabs). Experiments were carried out in a 35 cm squared base fluidized bed and in a 20x10 rectangle base fluid-spout bed. The effects on segregation of air superficial velocity, product volumetric fraction, and particle shape were evaluated. For evaluating the segregation, segregation indexes form literature were evaluated, but some difficulties were found using them, besides it is not possible to obtain information about the segregation profiles with them. Thus, a novel way for characterizing segregation was proposed (the Three Thirds Segregation Indexes Set, TTSIS), consisting of three numbers that evaluate the distribution profile of a material of interest (food product, for the current case) and a fourth one that gives an idea of the segregation level. TTSIS was found the best tool for quantifying the segregation phenomenon, as it allows not only to measure the segregation level, but also classify the segregation pattern. As it was expected from the theory, it was evidenced that, even for a binary mixture composed by a pseudo-cohesive powder and a solid whose particles are considerably greater than the powder ones, the air superficial velocity plays a very important role in mixing. Particularly, at high air flows (2.6 umf-adsorbent for the analysed cases) uniform distribution of the material of interest are reached when dried foodstuff is used. Nonetheless, product density plays a fundamental role, since disuniform segregation profiles were obtained when fresh or partially lyophilized food material was used. Uniform mixing profiles were reached in the fluid-spout bed with a good circulation of the food particles along the bed during the fluidization. These results shown to be independent of the product density. Thus, this kind of bed should be used if an uniform mixing between adsorbent and food product is desired. Segregation phenomenon in channelling fluidized beds and the mixing process in fluid-spout beds might be explained by means of two food particle transport mechanisms (passive and active) and two movement blocking effects (floor and roof effects) observed during experimentation (video analysis), and the Channel Generation and Collapse Cycle. Regarding to CFD simulations, relatively reasonable results were obtained from the hydrodynamic point of view only at high air superficial velocity. However, specific models for cohesive or pseudo-cohesive powders are required if an accurate simulation of this kind of solids or binary mixtures integrated by them is intended. In sum, from the experimental results, emerged that the fresh product completely segregates toward the bed bottom in fluidized bed when mixtures containing food material without drying were used. Thus, a good contact between the material to be dried and the adsorbent (desirable for utilizing the adsorption heat for ice sublimation) would be not possible for AFD with use of adsorbent in fluidized bed applications. In contrast, using a fluid-spout bed maintains a very good mixing even if fresh food particles are used. Thus, beside the already known applications of this kind of beds for catalytic processes, its utilization for AFD with adsorbent medium seems to be an interesting and novel option for this process. Nevertheless, CFD simulation might be performed only for non-cohesive powders since the simulation of pseudo-cohesive materials fluidization is currently limited because of the lack of hydrodynamic models for this kind of solids.