HK1138163B - Low oil volume frying device and method - Google Patents

Description

Low oil frying device and method

Technical Field

The present invention relates to systems and methods for frying food suitable for restaurants, and more particularly to apparatus and methods for optimizing product quality and cooking oil usage in commercial restaurant operations employing a fry vat.

Background

Fryers are widely used in restaurants for cooking a variety of food products such as french fries, fried chicken nuggets, fried fish and the like. A typical fryer includes one or more fryer vats containing cooking oil, each vat having a burner or heating element for heating the oil to a cooking temperature. Typically, the vat is adapted to receive a fry basket containing food products so that the food products can be immersed in hot oil and cooked, and then removed, drained of excess oil and used for serving guests. During cooking, the food product absorbs a large amount of oil. The absorbed or ingested oil is compensated by periodically adding replacement or supplemental oil to the vat to cook a subsequent batch of food.

During the cooking of food products by frying, the oil is contaminated with particulate food matter and other debris. The cooking process results in an increase in the degradation of the oil due to an increase in the amount of impurities that accumulate in the oil over time, such as, for example, an increase in the content of free fatty acids and total polar compounds in the oil. Furthermore, cooking oil degrades over a period of time due to being subjected to elevated cooking temperatures. The oil may also absorb taste and odour from the food, especially when cooking strong tasting foods such as fish. When cooking continues with degraded vat oil, undesirable off-flavors are added to the food product and affect the quality of the cooked food product. Most importantly, the taste and texture of the final food product is reduced below acceptable quality standards. Therefore, to optimize food quality, it is necessary to periodically replace the oil in the fry vat with fresh oil. The combined cost of replacement oil and waste oil for commercial restaurant frying operations can account for a significant percentage of the total cost of the cooked food product. Another cost consideration in connection with the use of oil is that oil changes are labor intensive and therefore constitute a time consuming and expensive operation.

To extend the useful life of cooking oil and reduce the need for time consuming and expensive oil changes, it is known to filter particulate matter from the oil. A conventional method is batch filtration, where the cooking oil is drained from the vat and then manually filtered before returning it to the vat. After the trough is drained, it may also be wiped clean manually to remove any debris that may have accumulated at the bottom of the trough. This approach has several disadvantages. First, the tank must be taken out of service and then drained thoroughly. Once the oil has been filtered and returned to the tank, it must be reheated to cooking temperature. This is time consuming and inefficient and in practice it means that the oil can only be filtered after the end of the restaurant's business day. In addition, manually filtering the oil tends to be a messy and inconvenient task.

To address these drawbacks, various semi-automatic filtration methods have been proposed. These methods eliminate manual filtration by providing an oil outlet that directs used oil from the vat directly to a filter and a pump or other mechanism for returning filtered oil to the fry vat. Typically, the number of batches of food product is counted and the oil is filtered when a predetermined number of batches is reached. However, depending on the type of food product to be cooked, the temperature of the oil and other factors, it is not possible by the number of batches themselves to provide an accurate indication of whether the oil needs to be filtered. When cooking food in hot oil, the oil deteriorates due to the increased content of free fatty acids and total polar compounds in the oil. In the case of using only batch counts, it is only possible to filter the oil once a day, for example, if the number of batches cooked that day is relatively small, but other factors can adversely affect the quality of the oil, so if the oil is not filtered often, the food quality deteriorates. Also, it is a practical situation that restaurant employees may choose to perform semi-automatic filtering only at the end of a business day, which may also result in a degradation of food quality between filtering cycles.

Accordingly, there is a need for an improved apparatus and method for automatically filtering cooking oil in a fryer.

Further, there is a need for a system and method for monitoring the elapsed time since the last filtration of cooking oil in a fryer and the number of batches or quality of food products cooked and automatically filtering the oil based on the elapsed time since the last filtration and the batch or quality count.

There is also a need to reduce the amount of oil used to fry food products to reduce the oil usage cost and the amount of labor associated with performing a vat oil change.

Disclosure of Invention

According to one aspect of the present invention, a commercial method of efficiently frying discrete batches of food includes providing a fry vat containing a quantity of cooking oil and subsequently separately and sequentially cooking the discrete batches of uncooked food. The amount of food in each discrete batch is in the range of from about 0.0375 to about 0.1 by weight relative to the amount of cooking oil, while the total amount of food to be cooked in the fry vat at any one time relative to the amount of oil in the fry vat is less than or equal to about 0.1 by weight. The food to be cooked in the cooking oil typically results in an oil absorption by the food of from about 5.5% to about 13% by weight of the uncooked food, and the oil turnover rate of the oil in the fry vat is from about 0.0026 to about 0.007 per discrete batch based on the weight of oil absorbed per batch versus the amount of oil present in the fry vat. Each discrete batch was removed from the fry vat after cooking. Replacement oil is periodically added to the fry vat to replace the absorbed oil of the food. Cooking a sufficient number of batches over an extended period of time without changing the oil while achieving an oil turnover equal to the amount of oil in the vat in less than about 60 hours of operation of the fry vat.

According to another aspect of the invention, the discrete batch size is about 0.05 on a weight basis relative to the amount of cooking oil.

In another aspect of the invention, the cooked food is french fries and the oil drawn by the food is about 7% by weight of the food on a frozen uncooked basis.

According to another aspect of the invention, the oil change time is about 16 hours of operation of the fry vat.

According to another aspect of the invention, the oil is used for at least 112 hours of operation of the fry vat before the oil is discarded and replaced with fresh oil.

According to another aspect of the invention, oil consumption is minimized. The amount of oil consumed per pound of food cooked is about 0.1 or less, and in another embodiment about 0.087 pounds or less of oil per pound of french fries cooked. Typically, this can be achieved while employing an oil turnover rate of from about 0.0026 to about 0.007 while maintaining a high quality of the final cooked food product.

According to another aspect of the invention, the oil in the fry vat is periodically filtered.

In accordance with another aspect of the invention, replacement oil is added to the vat at a flow rate of from about 0.008 to about 0.08 gallons of replacement oil per minute per gallon of oil in the fry vat.

According to yet another aspect of the present invention, the method may further include periodically and frequently filtering the fry vat's oil after frying a predetermined amount of food and/or after a predetermined period of time after cooking has begun. Typically, frequent periodic filtration according to the present invention refers to rapid filtration of vat oil (typically without any further frying of additional batches of food in the fry vat) after frying a quantity of food in the oil when the ratio of the quantity of food fried to the quantity of oil in the fry vat is about 0.7 (e.g., after frying about 21 pounds of food fried using a fry vat having about 30 pounds of oil), and more preferably about 0.4 (e.g., after frying about 12 pounds of food using a fry vat having about 30 pounds of oil) or less, and most preferably about 0.33 or less. In addition, alternate periodic filtering may occur after about 2 hours or less after cooking the initial food product in the oil, and more preferably after about 1 hour or less after cooking the initial food product in the oil.

According to another aspect of the present invention, a commercial method is provided for efficiently frying discrete batches of food. The method includes providing a fry vat containing a quantity of cooking oil, separately and sequentially cooking discrete batches of uncooked food, the quantity of food in each discrete batch by weight relative to the quantity of cooking oil being in the range of from about 0.0375 to about 0.1, wherein the total quantity of food to be cooked in the fry vat relative to the quantity of oil in the fry vat at any one time is less than or equal to about 0.1, the food to be cooked in the cooking oil resulting in an oil absorption by the food of from about 5.5% to about 13% by weight of the uncooked food, and an oil turnover rate of from about 0.0026 to about 0.007 per discrete batch. Removing each discrete batch from the fry vat after cooking; and frequently periodically filtering the oil in the fry vat and returning the filtered oil to the fry vat.

According to another aspect of the invention, the filtering occurs rapidly after frying food in the fry oil, wherein the ratio of the amount of food fried to the amount of oil in the fry vat is about 0.7 or less, more preferably about 0.4 or less, and most preferably about 0.33 or less. The method may further include cooking a sufficient number of batches over an extended period of time without changing the oil to achieve an oil turnover equal to the amount of oil in the vat in less than about 60 hours of operation of the fry vat. In addition, the method may further comprise periodically adding replacement oil to the fry vat to replace the absorbed oil of the food.

According to another aspect of the present invention, there is provided an improved method for frying food products in cooking oil, the method comprising monitoring the elapsed time since the most recent filtration of the cooking oil, monitoring the number of batches of cooking food products in the oil, and filtering the oil when a predetermined threshold is reached based on the elapsed time since the most recent filtration and the number of batches cooked.

According to yet another aspect of the invention, providing a prompt to an operator before filtering when a predetermined threshold is reached is provided.

According to another aspect of the invention, the oil is filtered based on a formula defining a threshold as a function of the number of batches of food cooked and the elapsed time since the last filtering.

According to another aspect of the invention, a method of treating cooking oil used in cooking food products includes monitoring a time elapsed since a last filtration of the cooking oil, monitoring an amount of food product cooked in the oil, and filtering the oil when a predetermined threshold is reached based on the time elapsed since the last filtration and the amount of food product cooked in the oil.

According to another aspect of the invention, a method of treating cooking oil used in cooking food products includes monitoring a time elapsed since a last filtration of the cooking oil, weighing the food products before cooking to monitor an amount of food products cooked in the oil, and filtering the oil when a predetermined threshold is reached based on the time elapsed since the last filtration and the amount of food products cooked in the oil.

According to another aspect of the invention, a system for filtering oil in a fryer pot includes a fry vat, an oil outlet and an oil return inlet in the fry vat, an oil filter, a valve for allowing oil to flow from the outlet to the filter, a pump for returning oil from the filter to the fry vat through the oil return inlet, means for monitoring elapsed time since a last filtration of the cooking oil, means for monitoring a number of batches of food cooked in the oil, and means for controlling the valve and the pump to filter the oil when a predetermined threshold is reached based on the elapsed time since the last filtration and the number of batches of food cooked.

According to another aspect of the invention, an apparatus for monitoring elapsed time since a recent filtration of oil comprises a batch sensor and a computer.

According to another aspect of the invention, the computer is programmed to calculate the threshold value using a formula, wherein the formula defines the threshold value as a function of the amount of food cooked and the elapsed time since the last filtration of the oil.

In accordance with another aspect of the invention, the system includes a baffle adjacent the return oil inlet for establishing a flow of filtered oil for flushing the tank.

In accordance with another aspect of the present invention, an automated method for maintaining an amount of oil in a fry vat having a volume includes automatically monitoring the amount of oil in a fry vat device and sensing the amount of oil in the fry vat. Automatically adding oil to the fry vat at a low average flow rate relative to the amount of oil in the fry vat when the sensed amount of oil in the vat is less than or equal to a first predetermined amount. The low average flow rate is in the range of about 0.008 to about 0.08 pounds per minute per pound of oil present in the fry vat at the first predetermined amount. As a result of the addition of oil, the addition of oil at a low average flow rate avoids a temperature drop of more than about 15 ° F and preferably more than about 10 ° F or 5 ° F of the bulk oil present in the fry vat.

According to another aspect of the invention, the method includes causing oil to enter the fry vat at a desired location, such as a side wall of the fry vat.

In accordance with another aspect of the invention, adding oil at a low average flow rate avoids the overall temperature of the oil in the fry vat dropping more than about 15 ° F, preferably about 10 ° F and more preferably about 5 ° F when oil is added.

In accordance with another aspect of the invention, the supplemental oil is added to the fry vat at a low average flow rate in the range of from about 0.008 to about 0.08 gallons per minute per gallon of oil present in the vat at the first predetermined amount.

According to another aspect of the invention, the addition of oil at the low average flow rate is continued until the amount of oil in the fry vat reaches a second predetermined amount.

Drawings

FIG. 1 is a front view of one embodiment of a fryer pot including a filter device;

FIG. 2 is a schematic diagram of an automatic oil filtration system according to the present invention;

FIG. 3 is a flow chart for an intermittent automatic oil filtration process according to the present invention;

FIG. 4 is a flow diagram of a request filtering based filtering method according to the present invention; and

FIG. 5 is a front view of the fry vat of the fry pan.

Detailed Description

Referring to the drawings in general and to FIGS. 1 and 2 in particular, a fryer 10 according to the present invention is illustrated. Fryer 10 includes a housing 12 and two fryer vats 14A, 14B, as shown. Each fry vat 14A, 14B is configured to simultaneously accommodate two fry baskets 16. Frying basket 16 may be manually or automatically placed in the frying position and removed from vat 14A, 14B as is well known in the art. Each basket 16 is held in a holding position above the oil in the vat 14A, 14B by a respective bracket 17. Such arrangements are well known in the art. Other configurations of fryer vats for a fryer including a single vat, two vats as shown, three vats, or four or more vats are also possible, as desired. Each tank 14A, 14B is provided with a suitable heating element 15, which may be a gas burner or an electric heating element as known in the art. The housing 12 of fryer 10 has a front panel 18 that includes a control and display panel 20 for the fry vat 14A, 14B. Control and display panel 20 includes input keys or buttons and an alphanumeric display (e.g., an LED or LCD display) for controlling various functions and monitoring the status of fryer pot 10, as described in more detail below.

The lower portion of the housing 12 has one or more doors 22 for providing access to the interior of the lower portion of the housing 12. An oil pan 24 is disposed inside the lower portion of the housing 12 behind the door 22. The oil pan 24 is preferably secured in a slide-out drawer 26 for easy access and removal for cleaning. A filter screen 28 and filter element 30 are provided above or in an upper position of the oil pan 24 for periodically screening and filtering the fry vat oil to remove undesirable food debris from the frying of food products.

Referring to fig. 1, 2 and 5, each tank 14A, 14B has its oil outlet or drain 32 at a bottom 33 that is inclined toward oil outlet 32 and an electromagnetically controlled valve 34 located below oil outlet 32. Bottom 33 of each trough 14A, 14B is preferably a substantially flat surface including a surface inclined to oil outlet 32 to facilitate drainage of oil and debris from troughs 14A, 14B. When oil in one of the tanks 14A, 14B is to be filtered, the associated valve 34 is opened so that oil drains from tank 14A through oil outlet 32 and is directed through pipe 36 to filter screen 28 for removal of larger residue particles and then through filter element 30 for removal of smaller particles. The filter element 30 may comprise a stainless steel mesh or other suitable filter material. Alternatively, a disposable filter paper or tray (not shown) may be placed on top of the filter screen 28 or filter element 30 and, if desired, a filter powder such as one containing diatomaceous earth may be dusted onto the paper, as is well known in the art. A similar arrangement is provided for the sump 14B, for example using the same oil pan 24, filter screen 28, filter element 30, and other components shown in fig. 2.

After passing through the filter element 30, the filtered oil is returned to the tank 14A or 14B by the pump 38 through the return line 40. Valve 41 directs the filtered oil through pipes 40 and 43 to tank 14A or 14B. Oil is returned to sump 14A via return oil inlet 42. Preferably, as shown in fig. 5, a deflector 44 is provided in each of the sumps 14A and 14B adjacent the return oil inlet 42 to deflect the flow of oil into a wider flow or spray it to flush out any remaining debris from the bottom of the sumps 14A and 14B.

Referring to fig. 2 and 5, a basket sensor 50 may optionally be located in each of the slots 14A and 14B to detect each time a basket 16 is placed into and removed from one of the slots 14A and 14B. The basket sensor 50 may be, for example, an optical or electromechanical device. A temperature sensor 52, such as a thermocouple or RTD (resistance temperature detector), and a fuel level sensor 54 may also be provided in each of the tanks 14A and 14B. An oil auto-fill system 55 may also be provided to fill, refill, or fill the tanks 14A, 14B with fresh oil that is pumped by a pump 68 from an oil source 66 through a solenoid controlled valve 80 and a tube 72 to flow to a desired location in the tank 14A. The oil used in fryer 10 may be any suitable type of cooking oil commonly used for cooking food products. In general use, each batch of food to be fried is substantially identical and predetermined or pre-measured, so the total amount of food cooked can be calculated by weight by simply counting the number of batches cooked. Alternatively, a scale 56 is provided for weighing the food product prior to cooking the food product to monitor the amount by weight of the cooked food product.

A controller 60 is provided to control the food cooking cycle, monitor the heating history of the cooking oil (i.e., the time since the beginning of cooking the food) and the number of batches of food cooked in each vat 14A and 14B to control the filtration process, and to control the oil fill process. As shown in fig. 2, the controller 60 receives inputs from the basket sensor 50, temperature sensor 52 and fuel level sensor 54 in each of the tanks 14A and 14B, the scale 56 (if any), and operator inputs from keys or buttons on the control and display panel 20. Controller 60 outputs display signals to control and display panel 20 and control signals to burner or heating element 15, valves 34, 41 and 80, pumps 38 and 68, and other components of fryer pot 10. The controller 60 may be, for example, a PC (personal computer), a specialized microcontroller (e.g., for each slot as needed), a microprocessor, or a custom logic device.

FIG. 3 is a flow chart of an Automatic Intermittent Filtration (AIF) method according to the present invention. The tank 14 is filled with oil and heated to a suitable cooking temperature. The food product is placed in the basket 16 and the basket 16 is lowered into the hot oil in the vat 14. In embodiments with an optional basket sensor 50, when the basket 16 enters the slot 14, it triggers the basket sensor 50 to send a signal to the controller 60. For example, without a basket sensor, the operator presses a produce key of the control and display panel 20 to initiate a programmed cooking cycle for a food product such as french fries. The programmed cooking cycle includes an appropriate cooking time and temperature for the selected food product.

In response to the activation of the production key, the system checks to see if a particular type of key on the control and display panel 20 has been selected. For example, since fish production has different characteristics than many other food products, it is desirable to use tanks that are only directed to fish production and to filter cooking oil only on demand when the operator deems filtering desirable (which may be more frequent than for lighter tasting foods such as french fries). Thus, if the "fish" production key is selected, the system disables the AIF mode and only filters when manually instructed to do so.

If the particular type key is not actuated, the batch counter is set and incremented. Each time the operator presses a key on the control and display panel 20, the batches are counted to initiate a cooking cycle for a batch of food. Alternatively, batches are counted as the basket 16 descends into the trough 14 as the basket 16 passes the basket sensor 50. The current lot number may be displayed on the control and display panel 20 if desired. The system also monitors the elapsed time since the oil was heated to cooking temperature. The filter procedure is initiated when the counter reaches a predetermined number, such as 10 (indicating that 10 batches of food product have been cooked), and/or when the oil is at a cooking temperature or other predetermined temperature for a predetermined time, such as one hour.

The controller 60 stores time and batch information to determine when to initiate the filter routine. The elapsed time since the last filtration of the oil, plus the number of batches and/or the amount by weight of food cooked in the oil, provides a more purposeful indication than the number of batches alone of when the oil should be filtered for optimizing cooking performance and extending the useful life of the oil.

As noted above, in a typical restaurant, the total amount of food cooked can be calculated by weight, usually by simply counting the number of batches cooked, since each batch of food to be fried is pre-measured. For example, a batch of french fries may be standardized to about 1.5 pounds.

The threshold for triggering filtering may be expressed as a formula, where the threshold F is defined_thAs a function of the amount of food cooked and the elapsed time, e.g. b + kt ═ F_thWhere b is the number of batches of food cooked k is a constant selected to achieve the desired filtering frequency t is the unit time elapsed since the most recent filtering in an exemplary embodiment, the unit time t may be expressed as a fraction of an hour. For example, one unit t may be defined as 1/10(6 minutes) of 1 hour and the constant k may be 1. The threshold F may be set at 10. In this example, the filter procedure is triggered when the sum of the number of batches since the most recent filtration, b, and the number of 1/10 hour intervals equals 10. It has been found that excellent oil quality and consistency can be maintained during more or less continuous cooking periods (e.g., busy periods in restaurants) where each batch of food is cooked in about 3 minutes, with oil being filtered once every 10 batches (i.e., about every 30 minutes), thereby providing improved and more consistent cooking results as compared to infrequent filtering, such as filtering at the end of a day when the food is fried. During more intermittent cooking (e.g., during cold refreshment in a restaurant), when only a few batches are cooked in an hour, it has been found that the oil quality decreases over time because some food debris (e.g., debris from the wrapped breading) remains in the hot oil and continues to carbonize. The elapsed time unit t combined with the number of batches b is used to ensure that the oil is filtered at the appropriate time intervals, even during intermittent cooking, so that the oil quality is maintained. Thus, the system and method of the present invention takes into account and provides improved oil and food quality during continuous and intermittent cooking. The formula and constant k may be programmed into the controller 60 using the data from the control and display panel 20, basket sensor 50 (if used) andand/or scale 56.

During the filtration process, the burner or heating element 15 for the tank 14 to be filtered is switched off. The solenoid controlled valve 34 at the bottom 33 of the tank 14 is opened and the oil flows through the outlet or discharge opening 32 and the pipe 36 to the filter screen 28 and the filter element 30 where debris is removed from the oil.

Pump 38 is then turned on to deliver filtered oil through return oil inlet 42 to tank 14 to flush tank 14. In this manner, food, remaining debris and other debris may be removed from the trough 14 prior to filling with filtered oil. Valve 34 is still open. After a predetermined flush time, such as one minute, valve 34 is closed and pump 38 may remain open to refill valve 14, or alternatively pump 38 is closed and flush oil is drained from tank 14 back to the filter removing debris, repeating the flush cycle before refilling tank 14, if desired. In one embodiment, when the oil reaches the level of the heating element 15, the heating element is activated to reheat the oil in the sump 14.

Alternatively, at the completion of the filtration and flush cycle, valve 31 is closed and pump 38 is turned on. The filtered oil is pumped back into the tank 14 and fresh oil is added, if necessary, by a manual or automatic oil filling system 55 to achieve the appropriate oil level as detected by the oil level sensor 54. The burner or heating element 15 is turned back on (e.g., when the oil level covers the heating element 15) and heats the oil back to cooking temperature. Regardless of the particular filtering embodiment, all of the foregoing steps are automatically controlled by software running on the controller 60.

Alternatively, before starting the filtration program, the operator may be prompted or asked if he desires to filter the oil at that time. He may choose to delay filtering, for example if there is a busy hour at a restaurant, and he does not want to stop using the slot. If the operator presses the "NO" button on the control panel 20, filtering will be delayed and cooking will be allowed to continue. However, the production count is divided by 2 and the counter is reset so that the next cue for filtering occurs as soon as possible. Optionally, a red light or LED or other indicator on the control panel 20 may be triggered when the count reaches 1 to alert the operator of the filtering to the next cooking cycle. Alternatively, the system may prompt the operator about being or not responding to information such as "do you ok" after the operator enters a command about whether to filter at that time.

As seen in fig. 4, a manual filtering method is also provided. The manual filtering process is initiated when the operator presses and holds the "filter" key on the control and display panel 20. Preferably, the operator must depress or hold the key for a defined time, such as 5 seconds, to avoid accidentally triggering the filtration cycle. The system prompts the operator to confirm that he desires filtration and, if he confirms, shuts down the burner or heating element for the selected tank 14. The system then prompts the operator by asking if the operator desires to pour oil. If he responds by pressing the "yes" key, valve 34 is opened and oil is drained from sump 14 to oil pan 24 for filtering as previously described. If the operator selects "no" in response to the prompt at any point, the burner or heating element 15 is turned back on and the system returns to the cooking mode.

The system then prompts the operator whether flushing of the tank 14 is desired. If so, valve 34 is opened and pump 38 is turned on to flush sump 14 with clean oil. After a predetermined flush time (e.g., 1 minute), valve 34 is closed and pump 38 is turned on to refill tank 14. As shown in fig. 4, the flush cycle may be repeated if desired. After the final flush is completed, the burner or heating element 15 is turned on to warm the oil back to cooking temperature and the system returns to cooking mode. This flushing operation flushes food debris and other food debris from the trough through the drain 32.

In one embodiment, monitoring the combination of elapsed time since the most recent filtering of the oil and the number of batches of food products cooked provides a more accurate determination of the oil quality and ensures that the filtering is performed at an optimal point in time. It has been found that an automatic filtration process performed in this manner can be accomplished very quickly, for example, for a typical size fry vat, filtration can be accomplished in only about 3 or 4 minutes, depending on the size of the fry vat, such as a 15 or 30 pound oil vat. Thus, even during business days restaurant operators can filter the oil more often and more conveniently, thereby extending the useful life of the oil and resulting in substantial cost savings and reducing the volume of waste oil.

Turning now to other aspects of the present invention, it is noted that prior to initiating a cooking operation, vat 14 is filled to a predetermined nominal level of cooking oil 64 to provide a predetermined oil weight and/or depth. As discussed in detail below, the present invention provides an optimized oil usage to achieve at least one change in cooking oil 64 by selecting a predetermined amount of oil based on the type of food to be cooked, the discrete batch size of typical food, the maximum amount of food cooked in the vat 14 at any given time, the amount of oil absorbed by the food product during cooking, the rate of change of oil for a batch of cooked food, and the number of batches participating in cooking over an extended period of time for a given operation. By operating in accordance with this aspect of the invention, oil usage is minimized over an extended period of time for commercial operation of fryer 10, while maintaining high quality for the finished cooked food product.

During the process of cooking food, much of the oil is absorbed by the food. The amount of oil absorbed is referred to as oil ingestion. In order to maintain the level of oil 64 in the tank at or near the predetermined nominal level selected in accordance with the present invention, replacement oil needs to be periodically added to tank 14. As noted previously, in order to automatically compensate for oil intake, an oil source 66, an oil level sensor 54 and a pump 68 are provided for pumping oil from the oil source 66 to the sump 14. The oil level sensor 54 may be any suitable device for sensing oil level, including, by way of example, sensing based on light sensing, weight sensing, or oil level sensing based on a temperature difference between a temperature measured proximate the oil level sensor 54 and a temperature of the heated cooking oil 64. With regard to the latter sensing method, it is noted that when the level of heated cooking oil 64 drops below the position of oil level sensor 54, the temperature at sensor 54 also drops. This temperature differential may be a basis for controller 60 to initiate the addition of replacement oil to vat 14 until oil level sensor 54 indicates a desired temperature at sensor 54 when cooking oil 64 returns to a desired predetermined oil level.

The oil supply 66 may be held in any suitable container, such as a cartridge oil can (jug-in-box) container 70 or a bulk source (not shown) that stores oil at a remote location. The container 70 may be stored within the housing 12 or remotely. Oil replacement pipe 72 provides a fluid path from oil reservoir 70 to sump 14 and may have heating element 73 associated therewith to heat replacement oil, as described below. In the exemplary embodiment, tube 72 terminates at an oil inlet 74 on one of the side walls 76 of tank 14, such as a rear side wall 78 shown in FIG. 5. It is understood that the oil inlets may be located at any desired location so that replacement or supplemental oil may be poured into the fry vat 14. Whenever the oil level sensor 54 senses that the oil level in the sump 14 has dropped from the nominal oil level by a predetermined amount, the controller 60 activates the pump 68 to cause replacement oil to be pumped from the oil reservoir 70 to the sump 14 via the pipe 72. As shown in fig. 1 and 2, a single oil reservoir 70 and a single oil pump 68 may be used to provide replacement oil to tanks 14A and 14B by directing oil through a solenoid controlled valve 80 or other suitable valve. Valve 80 is controlled by controller 60 and is movable between different valve positions to direct replacement oil to either slots 14A and 14B or to slot 14A only or slot 14B only via tube 82, depending on the need for replacement oil as sensed by sensor 54. If replacement oil is not required in tank 14A or 14B, valve 80 is closed to prevent flow through valve 80. Alternatively, tanks 14A and 14B have their own dedicated oil supply 66, valve 80, and/or pump 68.

The pumping of replacement or top-up oil is performed at a low average flow rate and continues until the oil level in the sump 14 has been replenished to a full or nominal oil level. Once the oil level sensor 54 senses that the process has been completed, the controller 60 stops the pump 68 to stop further flow of replacement oil. Replacement oil may be added in a continuous flow, or alternatively in an intermittent flow, for example by pumping individual doses, such as a dose of about 1/2 pounds of sleg or even, of replacement oil dispensed at the oil inlet 74 every 60 seconds or more until a full or rated oil volume is reached.

The addition of replacement oil at ambient temperature (and oil at a temperature below the nominal cooking oil temperature) will cause the temperature of the heated cooking oil 64 in the sump 14 to drop. To avoid unacceptable temperature drops and to produce consistent high quality food products, it is advantageous to maintain a relatively consistent cooking temperature for cooking oil 64 during the cooking cycle of food product production. Thus, in accordance with the present invention, the addition of replacement oil is accomplished in a manner to avoid a temperature drop that adversely affects the cooking capability of the heated overall sump oil. Preferably, the introduction of replacement oil is accomplished in a manner that avoids a temperature drop of the heated bulk oil in the fry vat that exceeds about 10 ° F, and more preferably is less than or equal to about 5 ° F. When the replacement oil is added in this way, the frying performance is not adversely affected. In particular, during the addition of replacement oil, the batch of food to be fried is not adversely affected, nor is the fryer's ability to accept a new batch of food adversely affected.

The temperature drop experienced depends essentially on: (1) the temperature of the cooking oil heated in the sump, (2) the temperature of the replacement oil added and (3) the relative amount of replacement oil and the amount of oil present in the sump. The present invention aims to limit the overall temperature drop of the heated sump oil by adding replacement oil at a low average flow rate relative to the sensed amount of oil present in the sump, and/or by causing the start of the addition of replacement oil each time a relatively low amount of oil level drop from the nominal level is experienced or detected.

In regard to the latter, the controller 60 initiates a flow of replacement oil by activating the pump 68 whenever the amount of oil drop reaches a predetermined set point. Preferably, this set point is selected to cause operation of the flow of replacement oil when the oil drop represents a drop of about 0.02 pounds or less of replacement oil per pound of rated oil for the fry vat. More preferably, for replacement oil at about ambient temperature, the set point is about 0.015 pounds per pound of nominal oil for the fry vat. Thus, a nominal amount of cooking oil 64 is, for example, 30 pounds, and preferably this set point for initiating addition of replacement oil at ambient temperature may be at about 0.6 pounds or less of oil level drop; and a more preferred set point to initiate flow of replacement oil at ambient temperature may be at an oil level that drops about 0.45 pounds or less from a nominal oil level for cooking.

In another embodiment of the invention, when supplemental replacement oil is added, replacement oil is added to sump 14 at a low average flow rate relative to the amount of oil present in the sump. For oil added at ambient temperature, the average flow rate is preferably in the range of about 0.008 pounds per minute for each pound of sump oil to an upper limit of about 0.08 pounds per minute or less for each pound of sump oil. For example, for a sump 14 having 30 pounds of sump oil therein when replacement oil is added, the average flow rate of replacement oil may be in the preferred range of about 0.24 pounds of replacement oil per minute to about 2.4 pounds of replacement oil per minute or less at the upper limit. When the replacement oil is heated above ambient temperature, oil may be added at a higher rate of average flow rate, and a set point for starting the flow of replacement oil may be set where the sump oil drops more.

In yet another embodiment of the present invention, the replacement or supplemental oil may be heated by a suitable heating source, such as a resistive heating element 73 associated with replacement oil tube 72. The oil may be heated to a desired temperature, such as, for example, about 100 ° F, 200 ° F, 300 ° F or more, typically up to the cooking temperature of the oil, and anywhere within a temperature range of about 100 ° F up to about the cooking oil temperature of the sump 14. A higher replacement oil temperature (typically up to the nominal cooking oil temperature) allows for a higher flow rate of replacement oil without causing an excessive temperature drop of the oil in the fry vat (preferably a drop of up to 10 ° F temperature, and most preferably a drop of 5 ° F or less).

Note that the flow rate mentioned above is an average flow rate, and therefore the actual flow rate in a short time such as 5 seconds may sometimes be higher than the average flow rate of the replacement oil in a longer time such as 1 minute. For example, adding 0.5 pounds of seleger or an aliquot of replacement oil in 6 seconds followed by no addition of replacement oil for a duration of 54 seconds is considered to be an average flow rate of 0.5 pounds per minute, or for a sump 14 having 30 pounds of sump oil in sump 14 when replacement oil is added, is considered to be 0.016 pounds per minute for sump oil present per pound. Similarly, the continuous flow of replacement oil at 2.5 pounds per minute was stopped after 1/4 minutes, which was considered to be an average flow rate of 0.625 pounds per minute, or 0.0208 pounds per minute for a sump having 30 pounds of oil when replacement oil was added, which was considered to be replacement oil per pound of sump oil present.

It is also noted that since the temperature of the heated cooking oil 64 drops when replacement oil at ambient temperature is added, the controller 60 may be programmed to activate it if addition of replacement oil is desired and/or during which the heating element 15 has not been activated. Controller 60 may also be programmed to stop the flow of replacement oil when a temperature drop of cooking oil 64 greater than about 5 degrees due to the addition of replacement oil is detected; and resuming the addition of the replacement oil when the temperature of the sump oil is restored by increasing by at least a predetermined amount.

In commercial cooking operations, such as large volume quick service restaurants, special consideration also needs to be made on the quality variations of the cooking oil. This may result in degradation of the oil during cooking because of an increased amount of impurities that accumulate in the cooking oil 64 over a period of time. For example, as noted previously, cooking of food products increases the content of free fatty acids and total polar compounds in the oil. In addition, cooking oil may deteriorate over time as the oil is subjected to elevated cooking temperatures. Regardless of the cause, after prolonged use, the quality of the oil drops to a point where the degraded oil begins to significantly affect the quality of the cooked food product. Most importantly, the taste and texture of the final food product drops below acceptable quality. Therefore, in order to maintain high quality food products, cooking oil 64 needs to be replaced periodically. Replacement of cooking oil 64 is typically accomplished by retrieving or draining substantially all of cooking oil 64 and then refilling tank 14 with fresh oil to a predetermined level of oil. Draining the cooking oil 64 may be conveniently accomplished by opening the valve 34 to drain the cooking oil 64 through the outlet 32, the tube 36, and into the oil pan 24, and thereafter discarding the oil from the pan 24. Any residue or debris and/or degraded oil on the surface of the sump 14 may also be removed manually or otherwise during the process of replacing the oil. Refilling the tank 14 with cooking oil 64 may be accomplished by manually refilling fresh oil to the tank 14, or by pumping fresh oil from a bulk oil source or from the oil source 66 at the oil inlet 74 and into the tank 14.

The point in time when the oil of the tank 14 needs to be replaced can be determined by different test methods as is well known to a person skilled in the art. Briefly, these tests include testing the taste of the food being cooked, checking the characteristics of the oil during cooking, observing the amount of smoke emitted during cooking, and comparing the color of the cooking oil 64 used to a known color spectrum. In the taste test, the cooked food is tested for burnt, bitter or rancid taste. If any such taste is experienced, the oil needs to be replaced. When cooking with oil of acceptable quality, active bubbles (rise relatively quickly) leave the food as it cooks. Observing a slow and dull bubble (rising relatively slowly) indicates that the oil has decomposed and that cooking oil 64 needs to be discarded. In addition, any oil that produces too much yellow foam needs to be replaced. Furthermore, excessive smoke, which is often accompanied by yellow foam and off-flavors during cooking, is a signal that the oil is deteriorated to the extent that it should be discarded and replaced.

A colorimetric test may also be employed to determine if the oil needs to be replaced. The oil naturally darkens as it ages and is used for cooking. The oil colour of the used sump oil can be tested and compared with a chromatogram of acceptable quality. Typically, color testing involves taking a small sample of the bath oil using an eye dropper or other suitable device, and then holding the bath sample close to the color spectrum of the oil to compare the color and color spectrum of the bath sample. The oil color spectrum may be selected to have the color of fresh oil or the color of oil that has been used for an extended period of time but has not yet reached the point where it needs to be discarded. It is noted that since the color of the bath oil varies depending on the type of food cooked, each food type may have its own guide criteria for comparison with the color of the bath sample tested. If the oil sample retrieved from the well is significantly lighter in color than the darker color of the chromatogram, no oil change is indicated. If the oil is close to or slightly above the darker color of the chromatogram, such a result will suggest further scrutiny in the quality of the oil, for example by further testing using the aforementioned test methods. If the sample color is much darker than the standard color, oil change is usually approved.

According to one aspect of the present invention, the need to sample and test the quality of the oil may be reduced or eliminated by replacing the oil after the food being cooked and/or the time of use reaches a predetermined amount.

In addition to the amount of labor and expense involved in monitoring the quality of the oil in order to maintain the quality of the food cooked, the cost of the cooking oil used over a period of time is also of considerable importance in commercial restaurant frying operations. This is particularly true when considering the large amounts of cooking oil consumed in restaurants due to large volume cooking applications. In frying food such as french fries and chickens, for example, the cost of cooking oil is a very large proportion of the total cost of producing the cooked product, and thus the amount spent annually on cooking oil is considerable. Thus, an important objective achieved by the present invention is to reduce oil costs by increasing the amount of food that can be cooked over the time for a given cooking oil usage without having to sacrifice the quality of the product cooked.

The reduced oil usage is essentially achieved by performing the cooking operation according to the invention. Preferably, the food product is cooked in discrete predetermined batch sizes or batch sizes that are substantially predetermined and of consistent weight, with a relatively low amount of sump oil relative to the weight of food cooked in each batch or basket. Typically, these amounts are predetermined as a ratio of the weight of the precooked food to the weight of the oil. Other aspects are the periodic addition of replacement oil to the vat to compensate for oil ingestion during cooking, providing relatively high oil turnover (oil turnover rate) per batch of cooked food within a specified range, and cooking a sufficient number of batches to achieve at least one oil turnover during a specified period of operation. As will be discussed in detail later, oil turnover is considered to have occurred when the weight of oil drawn in by the total amount of food cooked over a period of time is equal to the weight of the nominal oil weight of the fry vat. Thus, for a tank holding 30 pounds of oil during frying, 30 pounds of oil has been consumed or absorbed by the food being cooked. The amount of oil that evaporates or is otherwise lost, such as by splashing out of the sump, is relatively small and can generally be neglected.

The present invention can achieve a high quality food production and provide a high quality method for cooking quick serve food products including french fries and chicken nuggets, sticks, chests, chips and the like. For quick service restaurants in accordance with the present invention, high quality french fries are typically cooked in discrete batches of frozen french fries weighing between about 1.125 pounds to 3.0 pounds per batch, which may be, for example, 1.5 pounds per batch. The french fries are cooked in a bath oil that is heated to a desired temperature, typically in the range of about 320 to about 335 ° F (168 ℃) or other temperature as desired. The controller 60 may operate the heating element 15 to maintain the temperature within this range or other temperatures as desired. Note that when simultaneously cooking frozen french fries in an amount that weighs more than 1.5 pounds total, it is preferred that the vat 14 (configured to hold 30 pounds of cooking oil during operation) be equipped with two fry baskets 16. Thus, if, for example, 3 pounds of french fries are to be cooked simultaneously, a batch of french fries of about 1.5 pounds size is preferably placed in each of the two fry vats 16. It is also noted that when multiple fry baskets 16 are used, it is desirable to lower the fry baskets 16 into the vat sequentially, at least 30 seconds apart. This is done so that the oil temperature can be restored from the temperature drop caused by submerging the frozen french fries in the first basket 16 before submerging the next batch contained in the second basket 16. Typically, when cooking high quality french fries, the depth of the oil is preferred so that the frozen french fries batch can be submerged when it is initially placed in the oil, so that the highest portion of the batch is preferably submerged below the surface of the oil. In exemplary 1¹/₂The depth of the sump oil in a pound batch is typically on the order of about 3.8 or about 4 inches. As the french fries cook, the fries lose moisture and gradually tend to float on the oil. Preferably each batch is cooked for a predetermined periodDepending on the type and size of the food product. For example, cooking one type of french fries for about 3 minutes. Setting the cooking time is well known in the art and may vary depending on the type of food, the configuration of the food product including the surface area of the food relative to the food bulk, the temperature of the food product when placed in the trough, and other factors.

In practicing the present invention to reduce the amount of oil used, the amount of cooking oil used in the vat 14 is optimized relative to the discrete batches of uncooked food and the total amount of food to be cooked at any given time. For example, if fryer 10 is to be used to cook batches of frozen french fries weighing about 1.125 pounds to 3.0 pounds, then a predetermined nominal amount of cooking oil 64 is placed in vat 14 such that the desired uncooked batch weighs about 0.0375 to about 0.1 of the weight of cooking oil 64 in vat 14. Thus, for a batch of about 1.5 pounds, it is preferred that about 15 to 40 pounds of sump oil be in sump 14 for cooking. It is further noted that the maximum total amount of food cooked in vat 14 at any given time is preferably less than or equal to 0.1 times the weight of cooking oil 64. For example, if the amount of cooking oil 64 is 30 pounds, no more than about 3 pounds of frozen french fries or other food items are cooked at the same time. This can be achieved, for example, by: there is room in the 30 pound flume to accommodate two fry baskets, each containing 1.5 pounds of french fries or other food.

Cooking of frozen french fries typically results in oil imbibed by the food in the range of about 5.5% to about 8% by weight of the uncooked french fries. Cooking of proteinaceous foods such as chicken and fish filets results in oil ingested by the food in the range of about 5.5% to about 13% by weight of the uncooked food.

Depending on the type of food being cooked, a single vat 14 may be used to cook more than a single type of food. For example, in one type of operation, the vat may be dedicated to cooking only frozen french fries or only chicken slices. In other examples, the trough may be used for cooking french fries and chicken slices. With such an elapsed period of time, the resulting oil uptake during cooking ranges from about 5.5% to about 13% by weight of the precooked food. Thus, in cooking different types of food, a typical rate of change achieved by the absorbed or oil-absorbed amount during cooking is in the range of about 0.0026 to 0.007 per 1.5 pound batch in a discrete step with about 30 pounds of cooking oil in the vat being used. By cooking a sufficient number of batches over the duration of the operating time during which the cooking oil is subjected to elevated cooking temperatures, a sufficiently high rate of change of cooking oil 64 is achieved to enable the efficient oil usage of the present invention, thereby resulting in a high oil life before oil change is needed or desired. For example, a sufficient number of batches are cooked over an operating time, such as about 60 hours, to provide at least one replacement of cooking oil 64. This may occur, for example, after 6 10 hour work shifts are completed. As a more specific alternative example, when cooking 1.5 pound batches of frozen french fries, which have an average oil uptake of about 7% of the uncooked french fries weight, cooking about 285 batches will achieve one change of cooking oil 64 (30 pounds of oil).

As illustrated by the following example, by cooking and operating fry vat 10 in accordance with the present invention, a substantial reduction in total oil usage can be achieved without a significant reduction in food quality.

Example I-conventional frying of food

The fry vat of the frying apparatus is filled to a conventional initial nominal cook level of about 50 pounds of cooking oil. The oil was heated to a target cooking temperature of about 335 ° F (168 ℃) during about 10 consecutive hours of daily operation each day. The fry vat is used to fry a plurality of batches of frozen french fries in succession, each batch weighing about 1.5 pounds prior to cooking. The batch weight of frozen french fries was 0.030 relative to the weight of the bath oil. At least a 30 second delay is provided between submerging a first basket having a first batch and a second basket having a second batch of frozen fries so long as two 1.5 pound batches of fries are simultaneously being cooked. For a total of about 3lbs of frozen french fries, no more than two batches were cooked simultaneously. Thus, the maximum weight of food cooked at any given time is 0.06 times the weight of 50 pounds of cooking oil in the vat. The donut is lowered into the fry vat and cooked for a cooking period of about 3 minutes. Other batches were cooked sequentially in the same manner to cook about 100 pounds of frozen french fries per day. Each day of operation consists of the duration of the operation during the restaurant's work. The oil is continuously maintained in the range of about 320 ° F to about 335 ° F during daily operations, including periods when food cooking is not occurring. At the end of the daily operating period, the heating was turned off and the tank oil was filtered and allowed to cool to room temperature until the next day during which restaurant operations began. During cooking, the frozen french fries absorb an average amount of cooking oil that weighs about 7% of the weight of the uncooked frozen french fries. The average rate of change per 1.5 pound batch of cooked french fries is about 0.0021. As the oil level dropped, makeup oil was periodically added to the sump to maintain approximately 50 pounds of oil in the sump. The frying apparatus was used in the same manner for 6 consecutive business days. About 100 pounds of frozen french fries are cooked per working day, thus totaling about 600 pounds of french fries. During this time, the cooked french fries were periodically tasted and determined to have acceptable taste and quality levels. The quality of the oil was also monitored. After 6 days of frying, the quality of the cooking oil has degraded to the point where it is necessary to replace the entire approximately 50 pounds of cooking oil in the vat with fresh oil. During 6 days of operation, about 42 pounds of supplemental cooking oil was added to the tank to maintain the level of cooking oil in the tank at about 50 pounds. During this 6 day period, about 84% change of the nominal 50 pound tank cooking oil was achieved, which equates to an average 14% daily change rate. The total oil used was about 92 pounds over a 6 day period, which included an initial amount of about 50 pounds of cooking oil and about 42 pounds of added make-up oil. The average weight of cooking oil used to fry 100 pounds of french fries was calculated to be 15.33 pounds.

Example II frying of food according to the invention

The fry vat of the frying apparatus is filled to an initial nominal cooking level of about 30 pounds of cooking oil. The oil is heated during operation to a target cooking temperature of about 335 ° F (168 ℃). The fry vat is used to fry multiple batches of frozen french fries in succession, each batch weighing about 1.5 pounds prior to cooking. The batch weight of frozen french fries was 0.05 relative to the weight of the vat oil. When two 1.5 pound batches of fry are to be cooked at the same time, at least a 30 second delay is provided between submerging a first basket having a first batch and a second basket having a second batch of frozen fry. For a total of about 3lbs of frozen french fries, no more than two batches were cooked simultaneously. Thus, the maximum weight of food cooked at any given time is 0.1 times the weight of 30 pounds of cooking oil in the vat. The donut is lowered into the fry vat and cooked for a cooking time of about 3 minutes. Other batches were cooked sequentially in the same manner to cook about 100 pounds of frozen french fries per day. Each day of operation as in example I consists of a duration of operation. During operation, the oil is continuously maintained in the range of about 320 ° F to about 335 ° F and heated as needed to maintain the oil temperature in the desired range, including during periods when food cooking is not occurring. The heating was turned off at the end of the 10 hour operating period and the sump oil was cooled to room temperature until the next day during restaurant operations. During cooking, the frozen french fries absorb an average amount of cooking oil that weighs about 7% of the weight of the uncooked frozen french fries. The average rate of replacement per 1.5 pound batch of frozen french fries is about 0.0035((1.5 pound batch x. 07)/30 pounds of oil in the tank). As the oil level dropped, makeup oil was periodically added to the sump to maintain approximately 30 pounds of oil in the sump. The frying apparatus was used in the same manner for 12 consecutive business days. About 100 pounds of frozen french fries were cooked each day, thus totaling about 1200 pounds of french fries. During this time of operation, cooked french fries are periodically tasted and determined to have acceptable taste and quality levels. The quality of the oil was also monitored. After an operating period of 12 days or about 120 hours of frying, the quality of the cooking oil is still good enough to allow continued cooking. About 84 pounds of supplemental cooking oil was added to the tank over a 12 day period to maintain the level of cooking oil in the tank at about 30 pounds. During this 12 day period, approximately 280% of the 30 pound rated vat cooking oil turnover was achieved, which equates to an average 23.33% daily turnover rate. Stated another way, one change was achieved over a tank operation on the order of about 43 hours in which 429 batches weighing 1.5 pounds were cooked. The total oil used over the 12 day period was approximately 114 pounds, which included an initial nominal amount of cooking oil of approximately 30 pounds and additional oil of approximately 84 pounds. The average weight of cooking oil used to fry 100 pounds of french fries was calculated to be 9.50 pounds.

Comparing the results of examples I and II, the average amount of cooking oil used to fry 100 pounds of frozen french fries in accordance with the present invention dropped from about 15.33 pounds to about 9.50 pounds. The oil usage was reduced by 5.80 pounds per 100 pounds of cooked frozen french fries, resulting in a very significant reduction of at least 38%. In a quick service restaurant cooking 100 pounds of frozen french fries per day, the inventive method of example II will use about 3467 pounds of cooking oil over a one year period. On the other hand, the conventional cooking method of example I would use about 5595 pounds of oil per year to cook an equivalent amount of french fries. This indicates a reduction in planned annual cooking oil usage of at least about 2128 pounds or at least about 38 percent.

In the example shown above, the time between required oil changes is extended from 6 days for conventional cooking methods to 12 days for cooking by means of the cooking according to the invention. On a one year basis, this would reduce 30 necessary oil changes and further substantially reduce the labor costs associated with performing oil changes. In addition to reducing labor and oil costs, the present invention reduces environmental impact. Not only is the oil used and the degraded oil discarded reduced, but a corresponding reduction in the packaging of the oil container is also achieved. This thereby reduces waste in discarding cans and cardboard packaging from the can-in-box containers.

It is believed that the primary factor in increasing the service period between required oil changes is due to the improved oil turnover rate provided by the optimized cooking oil method used in example II, which is 23.33% versus 14% achieved by the conventional cooking method of example I. It is again noted that the term 100% change as used herein refers to the amount of cooking oil 64 that is added in an amount equal to 100% of the predetermined nominal amount initially placed in vat 14 to compensate for oil ingestion. When a 100% oil change is achieved, the exact original nominal oil volume in the groove 14 in the starting phase, which remains after the 100% oil change, can vary slightly, since it depends onIncluding various factors of how the makeup oil is added and whether it is completely mixed. For example, if replacement oil is added 60 times, 0.5 pounds each time, the original amount of oil remaining in the sump will be about (29.5/30)⁶⁰Or about 36%. However, the increased turnover rate results in relatively less time for cooking oil 64 to remain in sump 14 before being absorbed as intake oil and removed from sump 14 than for a lower turnover rate.

Thus, with the improved turnover rate achieved with the method of the present invention, the cooking oil remains in the vat 14 for a substantially shorter period of time. It is also true that a smaller percentage of cooking oil 64 remains in vat 14 for a longer period of time, causing such oil to substantially degrade. Stated another way, the improved oil turnover rate of the present invention reduces the average life of the sump oil as compared to conventional cooking. Thus, when compared to conventional cooking methods, the method of the present invention provides a sump oil having a higher percentage of relatively recently added replacement oil and a smaller percentage of relatively aged oil, including a smaller percentage of substantially aged and deteriorated oil.

As such, the operating time between necessary oil changes is extended when practicing the present invention, for example, the time between oil changes can be as long as 12 to 17 days, depending on the type of food being cooked, the throughput of food being cooked, and other cooking conditions. For example, about 112 hours of operation, such as 8 hours day operation in about 14 days, can be achieved by the optimized oil usage method of the present invention to cook about 1750 pounds or more of food product before an oil change typically should occur. It is noted that the method of optimizing oil usage of the present invention is particularly beneficial for high volume cooking operations, such as those having a throughput of 50 pounds or more of precooked food product per vat. In large volume cooking, the time to achieve one replacement occurs relatively quickly, such as, for example, in the range of about 16 to 60 hours of operation. For example, when cooking and cooking a 1.5 pound batch of frozen french fries using a nominal amount of vat oil of about 30 pounds, wherein oil uptake is about 7% of the weight of the frozen french fries, one change can be achieved within 16 hours, 24 hours, 35 hours, or 60 hours of operation, respectively, by cooking at an average rate of 17.9, 11.9, 8.2, or 4.8 batches per hour.

It is noted that all of the oil filtration methods, low average flow rate oil substitution methods, and methods of optimizing oil usage of the present invention can be used simultaneously to cook food products. However, corresponding advantages can also be achieved by implementing one such method independently of one or both of the other methods of the present invention.

While the invention has been described with reference to certain preferred embodiments, as will be appreciated by those skilled in the art, numerous modifications, improvements or substitutions may be made to the invention and such modifications, improvements or substitutions are intended to be covered by the appended claims.

Claims (23)

1. A commercial method of efficiently frying discrete batches of food comprising:

providing a fry vat containing a quantity of cooking oil;

separately and sequentially cooking discrete batches of uncooked food, the amount of food in each discrete batch by weight relative to the amount of cooking oil being in the range of from 0.0375 to 0.1, wherein the total amount of food to be cooked in the fry vat at any time relative to the amount of oil in the fry vat is less than or equal to 0.1, the food to be cooked in the cooking oil resulting in an oil absorption by the food of from 5.5% to 13% by weight of the uncooked food and an oil turnover rate of from 0.0026 to 0.007 per discrete batch;

removing each discrete batch from the fry vat after cooking;

periodically adding replacement oil to the frying tank to replace the absorbed oil of the food; and

a sufficient number of batches are cooked over an extended period of time without changing the oil to achieve an oil turnover equal to the amount of oil in the vat in less than 60 hours of operation of the fry vat.

2. The method of claim 1 wherein the discrete batch size by weight is 0.05 relative to the amount of cooking oil.

3. The method of claim 1 wherein the food is french fries and the oil ingested by the food is 7% by weight of the uncooked food.

4. The method of claim 1 wherein the oil turnover rate is 0.0035 per discrete batch.

5. The method of claim 1, wherein the oil turnover time is 35 hours or less of operation of the fry vat.

6. The method of claim 1, wherein the oil turnover time is 24 hours or less of operation of the fry vat.

7. The method of claim 1, wherein the oil turnover time is 16 hours of operation of the fry vat.

8. The method of claim 1, further characterized by: the oil is replaced after at least 112 hours of operation of the fry vat.

9. The method of claim 1 wherein the amount of oil consumed per pound of food cooked, including make-up oil and replacement oil, is 0.087 pounds of oil per pound of french fries cooked.

10. The method of claim 1 wherein the cooked food is french fries.

11. The method of claim 1, further comprising periodically filtering the oil in the tank.

12. The method of claim 1 wherein the replacement oil is added to the fry vat at an average flow rate of 0.008 to 0.08 gallons per minute per gallon of oil in the fry vat.

13. The method of claim 1 wherein the amount of oil consumed per pound of food cooked, including make-up oil and replacement oil, is from 0.087 pounds of oil per pound of french fries cooked to 0.1 pounds of oil per pound of french fries cooked.

14. The method of claim 1 further comprising periodically filtering oil in the fry vat and returning the filtered oil to the fry vat.

15. The method of claim 14 wherein the filtering occurs rapidly after frying food in the fry oil, wherein the ratio of the cumulative amount of fried food to the amount of oil in the fry vat is 0.7.

16. The method of claim 14 wherein the filtering occurs rapidly after frying food in the fry oil, wherein the ratio of the cumulative amount of fried food to the amount of oil in the fry vat is 0.4.

17. The method of claim 14 wherein the filtering occurs rapidly after frying food in the fry oil, wherein the ratio of the cumulative amount of fried food to the amount of oil in the fry vat is 0.33.

18. A commercial method of efficiently frying discrete batches of food comprising:

providing a fry vat containing a quantity of cooking oil;

separately and sequentially cooking discrete batches of uncooked food, the amount of food in each discrete batch by weight relative to the amount of cooking oil being in the range of from 0.0375 to 0.1, wherein the total amount of food to be cooked in the fry vat at any time relative to the amount of oil in the fry vat is less than or equal to 0.1, the food to be cooked in the cooking oil resulting in an oil absorption by the food of from 5.5% to 13% by weight of the uncooked food and an oil turnover rate of from 0.0026 to 0.007 per discrete batch;

removing each discrete batch from the fry vat after cooking;

frequently, the oil in the fry vat is periodically filtered and the filtered oil is returned to the fry vat.

19. The method of claim 18 wherein the filtering occurs rapidly after frying food in the fry oil, wherein the ratio of the cumulative amount of fried food to the amount of oil in the fry vat is 0.7 or less.

20. The method of claim 18 wherein the filtering occurs rapidly after frying food in the fry oil, wherein the ratio of the cumulative amount of food fried to the amount of oil in the fry vat is 0.4.

21. The method of claim 18 wherein the filtering occurs rapidly after frying food in the fry oil, wherein the ratio of the cumulative amount of food fried to the amount of oil in the fry vat is 0.33.

22. The method of claim 18 further comprising cooking a sufficient number of batches over an extended period of time without changing the oil to achieve an oil turnover equal to the amount of oil in the vat in less than 60 hours of operation of the fry vat.

23. The method of claim 19, further comprising periodically adding replacement oil to the fry vat to replace the suction oil of the food.