The invention pertains to system and method for controlled and measurable cooking of meat items. Particularly, the invention pertains to method and system for modeling, calculating and monitoring temperature in a meat item and issuing instructions for timing the cooking stages, such as flipping the item, for obtaining optimal cooking.
Monitoring a cooking process is necessary for optimizing the cooking of food items to obtain best results, customizing the cooking to any particular food item and saving investment of energy resources. Several apparatuses and methods are offered in this field, but none of them fully analyzes and models the cooking process itself, which leads to non-repetitive, non-controlled results as well as reduction in consumption of energy.
It is, therefore, an object of the present invention to provide a method and apparatus for resolving the shortcomings of those in the prior art.
It is yet another object of the present invention to provide a method for profiling, modeling and monitoring temperature and heat flow in meat pieces or food times in general in a cooking process.
It is yet another object of the present invention to provide a continuous profiling, modeling and monitoring method for optimizing the cooking process with dynamic, of the cooking of meat pieces and food items.
It is yet another object of the present invention to provide such a method for minimizing energy consumption in the cooking process.
It is yet another object of the present invention to provide an apparatus for profiling, modeling and monitoring temperature and heat flow in meat pieces or food times in general in a cooking process.
This and other objects of the present invention will become apparent as the description proceeds.
In one aspect, the present invention pertains to method and system for controlled and calculated cooking of meat items such as cattle, fish and poultry meat and the like. In one embodiment, the invention also pertains to controlled, measurable and/or calculated cooking temperature of other relatively flat and homogeneous food items. Particularly, the invention pertains to a method for measuring the initial conditions that characterize a food item and cooking appliance before start of the cooking, and calculating the spatially differential temperature of the item as it changes in real time.
In one embodiment, such calculation is done with a mathematical model that models the meat or food item as a three dimensional, 3D, body sliced horizontally relative to the cooking surface according to the temperature gradient from bottom to top. A heat flow equation with a finite element method is used to calculate the spatial temperature of any defined slice of the food item and the differential change between neighbor slices. Hands and sensor free monitoring of the food item is essential for automatic cooking. Sensors such as thermometers plugged into the item or manual intervention with kitchenware should no longer be required to provide real-time information on the cooking of the item and for obtaining optimal results. Instead, the method of the present invention enables real-time decisions such as when to flip the food item on the hot surface without the need for human or sensor intervention. In turn, this allows building robotic means that carries out an automatic cooking process.
In still another embodiment, the model is dynamic, time dependent and continuously updated. The values of different parameters of the system surroundings are measured by the sensors of the apparatus and updated in real-time. Then the parameters values are fed to the model for recalculating the temperature profile of the food item, particularly the temperature at its core, Tcore, and dynamically reevaluating its temporal cooking state. Such dynamic and continuous variable value updating, recalculation and reevaluation improve the temperature modeling of the food item at any given time, especially Tcore and ΔTcore, which is the temporal change in the temperature of Tcore, and eventually optimizes the cooking process and the cooking of the food item.
In still another embodiment, the system is configured to simultaneously scan, monitor and cook a plurality of pieces of meat and/or food items or a plurality of pieces of meat of different types, cattle, poultry, fish and the like. At the same time, the system is configured to model every piece or item separately from other pieces/items and independently set their individual cooking plans as they dynamically change in the cooking process.
The following drawing describes the cooking scheme of the meat/food item on a flat hot surface:
An objective of the invention is to calculate the temporal ΔTcore, namely the differential of the temperature with time in a central slice as defined by the 3D model of the meat or food item 200 and horizontally oriented relative to the cooking surface 400. Tcore is the temperature of a modeled central slice of the meat or food item 200, where the slice is horizontally equithermal with Tcore at every point in the slice. On the other hand, the temperature of the item is perpendicularly non-equithermal, with a gradient of temperature from the bottom surface that interfaces the cooking surface 400 to the top exposed surface of the item 200.
Tcore is calculated based on measurements done with an externally located 3D sensor that monitors the cooking apparatus and item 200 it cooks. ΔTcore is calculated relative to measured parameters of the cooking apparatus and surrounding conditions at any given change of temperature, ΔT, during cooking. An example of such surrounding conditions may be the temperature of the cooking surface. The non-equithermal and anisotropic characteristics of the meat or food item 200 in the perpendicular direction applies to the method of the invention for continuous monitoring and differential calculation of the temperature with time.
The method involves solving the heat flow equation of meat in real time. In first order, one can assume that a flat piece of meat is an isotropic 3D object. Heat flows into the meat bulk through the hot lower surface, and is conducted and released out through the exposed surfaces of the piece of meat or item, namely its upper and side surfaces. The first order approximation of the heat and temperature profile within the meat/item can be derived from solving a one dimensional heat flow equation, shown below, with a constant diffusion parameter of the meat/food:
where—
The interpretation of this equation is that heat flows through the meat along the X coordinate at a rate that is proportional to the diffusion constant D and to the local second derivative of the temperature along the X direction. In general, this partial differential equation cannot be solved analytically, for most real life boundary conditions. We, therefore, solve it numerically using standard known methods for finite element calculations. Such methods may be the Crank-Nicolson method, forward and backward Euler and/or other known methods, all relevant to the method described here. Common to all these methods is the need to build a grid in space and time, where the calculation for the X axis is done in dx and dt steps, where dx and dt are small relative to the size of the object and dx=L/N where L is the height of the object and N the number of steps to calculate along the X axis. The Crank-Nicolson method, given that dt and dx are the calculation steps, can be represented in the following equation:
Where i represents the number of slices, each having a thickness of dx, and n represents the nth time step of the calculation. After introducing a new constant:
One can rearrange the equation in the following way:
In this representation, the left side of the equation contains components of the temperature in various locations in the meat or food item but in a single time step n+1. The right side of the equation is a combination of temperatures in the time step n. Since we assume certain boundary and initial conditions at n=0 and n=N, the right side of the equation is known and therefore the left side can be developed to a set of equations that can be solved for any n for all the x values from i=0 to i=N.
The meat/item is placed on a hot surface with a known temperature of 100° C. in this case. The temperature in the modeled inner slices is in equilibrium with the ambient room temperature of 25° C. in this case. Therefore, all the Tis of the right side of the equation at n=0 are known and can be replaced with a constant vector, Ai. On the left side of the equation, all the Th+1 values can be replaced with a new representation for simplicity, Ui. Now the new set of equations will look like this:
Developing this set of equations and placing number value to the index i we get:
In the first equation, U−1 is the temperature of the hot surface at the bottom that is measured by the sensor head that continuously, remotely monitors the cooking process. Therefore, we can replace it with the measured value and move it to the right side of the first equation. We then get the following equation:
Where Co is a known value. We can, therefore, express U1 only as a function of U0:
We can then introduce this U1 expression into the second equation instead of the U1 on its left side and get a second equation as follows:
We can now express U2 as a function of U0 and introduce the expression of U1 and U2 into the third equation. Again we get an equation that involves only U3 and U0.
Repeating this process of replacement along the whole group and down to the last equation, we end up with the last equation that contains only expressions of U0 and UN. We now remember that UN=TNn+1, which represents the temperature of the upper surface of the meat/item at a given time n+1, as remotely measured by the sensor head above the cooking plate. This value is measured in real time by the sensor head and can give the correct value for time n+1 for any n. Introducing this value into the last equation enables to calculate and solve U0.
After solving for U0, one can go back to the first equation, introduce the calculated value of U0 and calculate U1. Similarly, all the Uis from U1 to UN−1 are calculated in an iterative way. This basically gives us an accurate temperature profile of the meat/item in a time step n=1, from its lower surface up to its upper surface. This profile is a combination of heat flow calculations for the internal part of the meat/food item and measurements of the surface temperatures and the height profile of the meat, taken by the sensor head in real time.
We can now repeat this process to calculate the temperatures at n=2, n=3 etc. after substituting the results of the temperature profile for n=1, n=2 in the right side of the equation. This iterative process sets a method for predicting the internal temperature of the meat/food item while cooking on hot surface and monitoring with a sensor head as described above. This method is indifferent to exchanging positions between the top and bottom surfaces of the meat or food item, particularly flipping the meat if and when done in the cooking process. This is because the sensor head measures the top and bottom temperatures of the meat/item, and their values are introduced into the model in realtime. Therefore, flipping will not change the model progress and result. Rather the model will give a good fit to the core temperature with or without flipping throughout the process.
Based on its measurement and calculation capabilities, the system of the present invention is configured to re-evaluate calculated temperature values according to measured values, thereby more accurately predicting the core temperature value of the meat or food item. Thus, for example, when flipping a piece of meat, the system is configured to measure the actual temperature of the current top surface, compare it to its previous one which is used to calculate Tcore and introduce the measured value into the set of equations to obtain a more accurate calculated core temperature value.
D, the diffusion constant in the heat flow equation, is composed of the following parameters:
where—
The density and specific heat capacity are distinguished for the different components that may be part of a slice of meat. Such components may include bones, fat, water and proteins. Typically, D will be selected to represent water that takes 70% on average of the mass of any meat that is cooked. D for lean meat, namely with low fat content, would be in the area of 0.12-0.14 mm2/sec. Using this value provides accurate temperature calculations. Based on https://www.tandfonline.com/doi/pdf/10.1271/bbb.58.1942, meat fat has lower diffusion value around 0.1 mm2/sec. Therefore, it is important to try and estimate the percentage of fat in the cooked meat to improve the accuracy of the model. Further, bones in the meat should be excluded from calculation, since they behave differently from meat and do not contribute for attributing a proper core temperature to the meat slice. Based on Heldman, https://meatscience.org/docs/default-source/publications-resources/rmc/1975/heat-transfer-in-meat.pdf?sfvrsn=e308bbb3_2, in the reference mentioned above, a 10% difference in thermal conductivity may also exist between directions parallel or perpendicular to the fibers of the meat, so cutting the meat may be important to set the proper D value.
It is, therefore, suggested in the method of the present invention to use the visual and thermal sensors of the system, which are part of the sensing head, to identify the areas of the meat before cooking, which are not to be controlled or measured in the process. Focusing on meat only areas will give better results of the model in predicting the core temperature of the meat.
A visible region image of the meat from the sensor head-detecting bone area (lighter line) 220, pure fat area (white line) 230 and meat area (black line) 210. In this case, the cooking model will run only on the area surrounded by the black line and will result with the most accurate core temperature estimation.
The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Quantitatively, emissivity is the ratio of the thermal radiation from a surface to the radiation from an ideal black surface at the same temperature as given by the Stefan-Boltzmann law. The ratio varies from 0 to 1. Most organic materials have relatively high emissivity, but this parameter is no way constant and changes with the surface temperature, content and shape of the surface, of the monitored object. In order to accurately measure the temperature of a surface of an object one has to be able to estimate or measure its emissivity. The relation between temperature, emissivity and emitted thermal power is given by the Stefan-Boltzmann equation:
where—
The thermal sensor that is part of the scanning optical head that measures the meat from above, is measuring the parameter P/A (the emitted power per unit area of the meat, displayed on each pixel of the thermal sensor). For a known emissivity of the meat one can, therefore, use the equation above to calculate the accurate temperature of the upper surface of the meat. The ambient temperature may be measured by a simple thermometer or scanning optical head at certain pre-defined locations that are in equilibrium with the environment.
There are several methods that are suggested to estimate or measure the emissivity:
The scanning optical head 100 that is located above the cooking plate measures all the meat and cooking tool parameters that are important for solving the heat flow equation and heat flow model described above in real time. One suggested structure of such an optical head is given in
The scanning optical head contains the following components:
The capabilities and functionalities of the scanning optical head combined with the modeling and mathematical calculations in the CPU enable to obtain accurate cooking temperatures and a finely cooked piece of meat or any other food item. The scanning optical head provides realtime data on the cooked item, its parts and content, the boundaries of the meat/item part that is monitored, its surroundings and cooking appliance. These can be used to reevaluate the diffusion constant that depends on the thermal conductivity of the meat/item, its density and specific heat capacity. The new value of the diffusion constant can be fed back to the set of equations to obtain a more accurate value of Tcore.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/IL2023/050170 | 2/16/2023 | WO |