WO2013036813A1

WO2013036813A1 - Systems and methods for monitoring quality of cooking media

Info

Publication number: WO2013036813A1
Application number: PCT/US2012/054231
Authority: WO
Inventors: Douglas A. Burkett; Craig J. Vagedes
Original assignee: Henny Penny Corporation
Priority date: 2011-09-09
Filing date: 2012-09-07
Publication date: 2013-03-14

Abstract

A cooking medium quality monitoring device includes an analog-to-digital converter for measuring a signal corresponding to conductivity of the cooking medium, and a filter unit configured to filter an output signal of the analog-to-digital converter to produce an output sample, which corresponds to a quality measurement of the cooking medium. The device further includes a controller configured to calculate a median of a plurality of consecutive, qualified output samples when a number of samples in the plurality of consecutive, qualified output samples is greater than or equal to a first predetermined value. The controller is further configured to increment a first counter when the calculated median is greater than or equal to a first predetermined threshold, and decrement the first counter when the calculated median is less than the first predetermined threshold; and determine that a first condition is true when the first counter reaches a second predetermined value.

Description

SYSTEMS AND METHODS FOR MONITORING

QUALITY OF COOKING MEDIA

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates generally to systems and methods for monitoring quality of a cooking medium, e.g., as in a fryer.

2. Description of Related Art

[0002] When preparing food in a fryer, including an open-well fryer, pressure fryer, or the like, the quality of the cooking medium, e.g., the oil, may impact the quality of the food that is cooked by the fryer. As the cooking medium is used to cook food, particles of food may contaminate the cooking medium. The flavor characteristics of each of these food products may become infused to a greater or a lesser degree in the cooking medium. This infusion may adversely affect food quality. Moreover, upon heating the cooking medium, the cooking medium may undergo chemical reactions, e.g., hydrolysis, oxidation, and

polymerization. These chemical reactions may result in compounds, such as free fatty acids, hydroperoxides, and polymerized triglycerides. In addition, such reactions may reduce the viscosity of the cooking oils, which also may adversely affect cooking performance. In some instances, such changes to the cooking medium do not become apparent until significant change has occurred.

SUMMARY OF THE INVENTION

[0003] Therefore, a need has arisen for systems and methods for reliably monitoring the quality of cooking media that overcome these and other shortcomings of the related art. In an embodiment of the invention, a device may be configured to monitor the quality of a cooking medium. The cooking medium quality monitoring device may comprise an analog-to-digital (A/D) converter for measuring a signal which corresponds to conductivity of the cooking medium; a digital filter unit configured to filter an output signal of the A/D converter to produce an output sample, which corresponds to a quality measurement of the cooking medium; and a controller. The controller may be configured to calculate a median of a plurality of consecutive, qualified output samples when a number of samples in the plurality of consecutive, qualified output samples is greater than or equal to a first predetermined value; to increment a first counter when the calculated median is greater than or equal to a first predetermined threshold and to decrement the first counter when the calculated median is less than the first predetermined threshold; and to determine that a first condition is true when the first counter exceeds a second predetermined value.

[0004] In another embodiment of the invention, a fryer system may be configured to monitor the quality of a cooking medium in a fryer. The fryer system may comprise a cooking vessel configured to store a cooking medium; an electrode unit configured to be at least partially immersed in the cooking medium; a signal conditioning circuit configured to receive a signal generated by the electrode unit; an A/D converter for measuring a signal, generated by the signal conditioning circuit, corresponding to conductivity of the cooking medium; a digital filter unit configured to filter an output signal of the A/D converter to produce an output sample, which corresponds to a quality measurement of the cooking medium; and a controller. The controller may be configured to calculate a median of a plurality of consecutive, qualified output samples when a number of samples in the plurality of consecutive, qualified output samples is greater than or equal to a first predetermined value; to increment a first counter when the calculated median is greater than or equal to a first predetermined threshold and to decrement the first counter when the calculated median is less than the first predetermined threshold; and to determine that a first condition is true when the first counter exceeds a second predetermined value. [0005] In still another embodiment of the invention, the quality of a cooking medium may be monitored by measuring a signal with an A/D converter, which corresponds to conductivity of the cooking medium; digitally filtering an output signal of the A/D converter to produce an output sample, which corresponds to a quality measurement of the cooking medium; calculating a median of a plurality of consecutive, qualified output samples when a number of samples in the plurality of consecutive, qualified output samples is greater than or equal to a first predetermined value; incrementing a first counter when the calculated median is greater than or equal to a first predetermined threshold and decrementing the first counter when the calculated median is less than the first predetermined threshold; and determining that a first condition is true when the first counter exceeds a second predetermined value. Thus, by providing a reliable measure of the quality of a cooking medium, embodiments of the invention may provide an indication of the cooking medium's continued suitability for use in cooking.

[0006] Other objects, features, and advantages of the present invention are apparent to persons of ordinary skill in the art in view of the following detailed description of the invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] For a more complete understanding of the embodiments of the present invention, needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following description taken in connection with the accompanying drawings.

[0008] Fig. 1 is a cross-sectional view of a fryer comprising an electrode unit as a system for monitoring quality of a cooking medium, according to an embodiment of the invention.

[0009] Fig. 2 is a diagram depicting one exemplary implementation of components of a system for monitoring quality of a cooking medium, according to an embodiment of the invention. [0010] Fig. 3 A is a diagram depicting one exemplary implementation of operation of a cooking medium quality monitoring device, according to an embodiment of the invention.

[0011] Fig. 3B is a diagram depicting a portion of the operation, shown in Fig. 3A, of a cooking medium quality monitoring device, according to an embodiment of the invention.

[0012] Fig. 3C is a diagram depicting a portion of the operation, shown in Fig. 3A, of a cooking medium quality monitoring device, according to another embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0013] Preferred embodiments of the present invention, and their features and advantages, may be understood by referring to Figs. 1-3C, like numerals being used for corresponding parts in the various drawings.

[0014] Fig. 1 depicts a cooking medium system, such as a fryer apparatus 100, according to an embodiment of the invention. Fryer apparatus 100 may comprise at least one cooking vessel 110, e.g., a frypot, which may be configured to hold a cooking medium, e.g., an oil, a liquid shortening, a meltable-solid shortening, a semi-solid shortening, or the like, depicted in Fig. 1 as cooking medium 115. Electrode unit 200 may be used to obtain a measurement of the conductivity of cooking medium 115. Electrode unit 200 may be positioned in cooking vessel 110 and mounted to or through wall 125 of cooking vessel 110, such that the portions of electrode unit 200 within cooking vessel 110 may be at least partially, or completely, submerged in cooking medium 115. Electrode unit 200 may comprise an electrode plate, a guard ring, and insulators to electrically isolate the electrode plate from the wall of cooking vessel 110. Fryer apparatus 100 may be configured for use in a gas or electric fryer apparatus. Although cooking vessel 110 may be suitable for an open- well fryer, fryer apparatus 100 also may be used in a pressure fryer or the like. [0015] Fig. 2 depicts components of a cooking medium quality monitoring system, according to an embodiment. With reference to Figs. 1 and 2, a voltage may be applied to electrode unit 200, causing a current to flow through cooking medium 115. A signal conditioning circuit 210 may convert this current to a voltage, which corresponds to a conductivity of cooking medium 115. The conductivity of cooking medium 115 may correspond to the quality of cooking medium 115. Further, signal conditioning circuit 210 may amplify the voltage, and may filter the amplified voltage with, for example, a low-pass filter. In other embodiments, the order of amplifying and filtering may be reversed or either may be omitted. The resulting voltage signal may be measured by an A/D converter, e.g., a 12-bit A/D converter with a sample rate of about 16.7 Hz.

[0016] The digital filtering unit may comprise two stages of digital filtering, which may be applied to remove noise from the signal. The first stage may be a three-quarter (¾) low- pass moving average filter 230, which may be applied to each A/D sample by adding three- quarters (¾) of the current value to one-quarter (¼) of the next value to create a new current value. The second stage may be an n-sample average low-pass filter 240. N-sample average low-pass filter 240 may be applied, for example, by averaging about fifty (50) samples to obtain an adequate signal-to-noise ratio. A lesser or greater sample size may be selected for n-sample average low-pass filter 240. In the case of using 50 samples, a cooking medium quality sample, Ql, may be outputted about every three (3) seconds (e.g., about 2.667 seconds). In other embodiments, a cooking medium quality sample, Ql, may be outputted at a greater or lesser frequency, e.g., about every ten (10) seconds or less.

[0017] The cooking medium quality monitor may include one or more additional stages of filtering to achieve a suitable signal-to-noise ratio. Further, other forms of low-pass filters (e.g., finite impulse response filters, infinite impulse response filters, or the like) may be used for the first stage, the second stage, or the one or more additional stages of filtering in the filtering unit. In addition, any, but not all, of the first, second, or one or more additional stages of filtering may be omitted from the filtering unit. Moreover, the filtering unit may be configured, such that the first, second, or one or more additional stages may be applied in any order.

[0018] Controller 250 may be configured to qualify each Ql sample to reject non- representative measurements if the Ql sample does not satisfy one or more constraints. The constraints may be operating conditions that cause inaccurate or non-representative measurements. For example, controller 250 may reject a Ql sample when the cooking medium temperature is not within a cooking set-point temperature range. In such a case, the Ql sample may be rejected if the cooking medium temperature, TC_M, is not within a range defined by plus or minus (+/-) a constant, T_L, of the cooking set-point temperature, Tsp. Thus, a Ql sample may be accepted when TC_M satisfies the following equation: Tsp - T_L < TCM≤ TSP + TL.

[0019] Further, for example, controller 250 may reject a Ql sample during a cooking period, during a quick filtering period, during a maintenance filtering period, for a predetermined time period after the temperature of the cooking medium reaches a ready range, or during a period in which a filter pump or auto top-off pump are running. Controller 250 also may reject a Ql sample during some combination of these periods.

[0020] A quick filtering may be one of multiple filters of the cooking medium performed periodically during a day, or other period of time, to remove crumbs, silt, cracklings, cooking medium deterioration compounds, or the like. For example, the quick filtering may comprise draining the cooking medium to a filter pan, circulating the cooking medium through the filter media and the fry vat, and pumping the cooking medium from the filter pan back into the vat. The quick filtering also may include, for example, skimming crumbs, cracklings, or the like from the cooking medium. The quick filtering period may include a period of time during quick filtering and either after filtering until the first cook cycle or after a predetermined additional period of time.

[0021] A maintenance filtering may be performed daily, or periodically at other time intervals (e.g., intervals of greater than one day or less than one day) to clean the fry pot, filter pan, or other components of a cooking apparatus. For example, the maintenance filtering may be a more thorough cleaning of the vat, which may include scraping accretion of particles from the vat walls, brushing particles from vat crevices and cavities, and soaking the vat with a cleaning solution (e.g., a detergent, a slightly high pH cleaning solution, or the like). The particles may include, for example, crumbs, silt, cracklings, cooking medium deterioration compounds, and the like. The maintenance filtering period may include a period of time during a maintenance filtering and either after filtering until the first cook cycle or after a predetermined additional period of time. Thus, Ql samples may be disqualified from the start of a maintenance filtering until a first cook cycle, for example, to allow persistent effects of a cleaning solution to substantially disappear.

[0022] A list of consecutive Ql samples that controller 250 qualifies, according to the one or more constraints, may form a Q history list. If a Ql sample is disqualified, due to a constraint not being satisfied, the Ql samples already included in the Q history list may be deleted. When the number of qualified, consecutive Ql samples in the Q history list is greater than or equal to a predetermined value, controller 250 may be configured to calculate the median, Qmedian, of the consecutive Ql samples in the Q history list.

[0023] Controller 250 may be further configured to compare the calculated median, Qmedian, to at least one threshold. For example, controller 250 may be configured to compare Qmedian to a cooking medium quality threshold at which the cooking medium should be disposed. Controller 250 may increment a counter when Qmedian is greater than or equal to the threshold, and decrement the counter when Qmedian is less than the threshold. Further, controller 250 may determine that a condition is true (e.g., disposal of the cooking medium is needed) when the counter exceeds a predetermined value and may alert a user that the condition is true or initiate an automatic response to the condition being true (e.g., an automatic disposal system). An alert may include, for example, a display, an light-emitting diode, a visual, audible or tactile alarm, or the like, and combinations thereof. An automatic response to the condition being true may include, for example, a function that: disposes the cooking medium, filters the cooking medium, or blends the cooking medium.

[0024] Controller 250 also may be configured to compare Qmedian to thresholds in addition to, or in place of, the dispose threshold. For example, such thresholds may include, but are not limited to, one or more of: a threshold at which the cooking medium should be filtered; a threshold at which the cooking medium should be blended; a threshold at a level below the dispose, filter, or blend thresholds to give warnings before those thresholds are met; and a threshold at a level above the dispose, filter, or blend thresholds at which product quality or consumer health may be compromised.

[0025] Controller 250 also may be configured to compare Qmedian to a cooking medium quality threshold at which the cooking medium is a new cooking medium. Controller 250 may increment a counter when Qmedian is less than or equal to the threshold, and decrement the counter when Qmedian is greater than the threshold. Further, controller 250 may determine that a condition is true (e.g., the cooking medium is new, or the dispose cooking medium alert may be reset) when the counter exceeds a predetermined value and may alert a user, or another monitoring operation or performance of the cooking apparatus, that the condition is true or initiate an automatic response to the condition being true.

[0026] In an embodiment, controller 250 may be configured to reset the counter to zero, disqualify the Ql sample, and clear the Q history list in response to the occurrence of at least one reset condition. An example of a reset condition may be when a fryer or similar cooking apparatus has been unpowered (e.g., has been turned off or has lost power) for a predetermined period of time. Another example of a reset condition may be when a persistent electrode fault has occurred, for example, if the electrode is shorted by a basket, cooking utensil, or cooking medium contamination. Other examples of reset conditions may be when a dispose cooking medium function is executed or when a manual reset function is executed.

[0027] The cooking medium quality monitor may also include a timer 260 that may be started when new cooking medium is detected. When timer 260 reaches a predetermined time limit, controller 250 may alert the user, or another monitoring operation or performance of the cooking apparatus, that treatment of the cooking medium (e.g., disposal, filtering, or blending of the cooking medium) is needed, or may activate an automatic response (e.g., disposal system, or filtering or blending function), regardless of the status of the threshold detection component of the cooking medium quality monitor. The predetermined time limit may vary based upon operating conditions and preset preferences, but may be, for example, from about four (4) days to about twenty (20) days.

[0028] Figs. 3A-C depict a method of monitoring quality of a cooking medium, according to an embodiment. A voltage is applied to an electrode at S300, which causes a current to flow through the cooking medium. At S310, the current is converted to a voltage, the voltage is amplified, and the amplified voltage is filtered, for example, with a low-pass filter. This voltage is measured by an A/D converter at S320.

[0029] At S330, a three-quarter (¾) low-pass moving average filter is applied to remove noise from the signal. This filter is applied to each A/D sample by adding three-quarters (¾) of the current value to one-quarter (¼) of the next value to create a new current value. At S340, an n-sample average low-pass filter is applied to obtain a more desirable signal-to- noise ratio. For example, fifty (50) samples may be averaged in the n-sample average low- pass filter such that a cooking medium quality sample, Ql, may be outputted about every three (3) seconds (e.g., about 2.667 seconds). A lesser or greater sample size may be selected for the n-sample average low-pass filter. Further, a cooking medium quality sample, Ql, may be outputted at a greater or lesser frequency, e.g., about every ten (10) seconds or less. In addition, Fig. 3A depicts an exemplary embodiment, and the digital filtering may occur in any order or at additional stages of filtering, or combinations thereof, to achieve a suitable signal-to-noise ratio.

[0030] At S350, constraints are applied to qualify each Ql sample by rejecting non- representative measurements. The constraints may be operating conditions that cause inaccurate or non-representative measurements. For example, the constraints may include disqualifying a Ql sample during at least one of the following: a period in which the cooking medium temperature is not within a predetermined range of the cooking set-point, a cooking period, a quick filtering period and until either a first cook cycle or after a predetermined period of time, a maintenance filtering period and until either a first cook cycle or after a predetermined period of time, a predetermined period of time after a cold or warm start, and a filter pump or auto top-off pump running period. When the number of qualified, consecutive Ql samples is greater than or equal to a predetermined value, a median, Qmedian, of the consecutive Ql samples may be calculated at S360.

[0031] The calculated median, Qmedian, may be compared to at least one threshold. For example, with reference to Fig. 3B, Qmedian may be compared to a predetermined threshold at S371. The predetermined threshold may be, for example, a cooking medium quality threshold at which the cooking medium should be disposed. When Qmedian is greater than or equal to the predetermined threshold, a counter may be incremented at S381. At S382, the counter may be decremented when Qmedian is not greater than or equal to the predetermined threshold. At S371, Qmedian also may be compared to additional predetermined thresholds. For example, the additional threshold may include on or more of: a threshold at which the cooking medium should be filtered; a threshold at which the cooking medium should be blended; a threshold at a level below the dispose, filter, or blend thresholds to give warnings before those thresholds are met; and a threshold at a level above the dispose, filter, or blend thresholds at which product quality or consumer health may be compromised.

[0032] With reference to Fig. 3C, Qmedian may be compared to a predetermined threshold at S372. For example, the predetermined threshold may be a cooking medium quality threshold at which the cooking medium is a new cooking medium. When Qmedian is less than or equal to the predetermined threshold, a counter may be incremented at S383. At S384, the counter may be decremented when Qmedian is not less than or equal to the predetermined threshold. The processes depicted in Figs. 3B and 3C may be performed simultaneously or serially in either order.

[0033] Referring back to Fig. 3A, at S390, a condition may be determined to be true (e.g., disposal of the cooking medium is needed, the cooking medium is new, or the dispose cooking medium alert may be reset) when the counter exceeds a predetermined value, and may alert a user that the condition is true or initiate an automatic response to the condition being true. The predetermined value of the counter may be set, such that the predetermined value simultaneously determines both the probability that the cooking medium has exceeded the threshold, and the response time to make that determination. For example, setting the predetermined value to a greater value increases the certainty that the cooking medium quality has exceeded the threshold, but also increases the response time to make that determination. Conversely, setting the predetermined value to a lesser value reduces the certainty that the cooking medium quality has exceeded the threshold, but reduces the response time to make the determination. [0034] The dispose threshold discussed above may be set to ensure that the cooking medium is disposed before the degradation of the cooking medium causes unacceptable food product quality. The dispose threshold also may be set to correspond to some chemical property of the cooking medium. For example, the dispose threshold may be set to correspond to percent of total polar materials (%TPM), or percent free fatty acids (%FFA), both of which increase as the cooking medium degrades.

[0035] The plot below shows cooking medium quality measurements taken by an embodiment of the cooking medium quality monitor over twenty (20) days of operation.

1 2 3 4 5 6 7 9 10 11 12 13 14 15 16 17 18 19 20 21

[0036] New cooking medium is in a fryer vat on day one (1). As that cooking medium is used on days one (1) through seven (7), the cooking medium quality measurement increases, indicating that the cooking medium quality is decreasing. The inverse relationship is a result of the measurement process. The fryer vat is filled with new cooking medium on day eight (8), so the quality measurement drops back down to the new cooking medium level. The used cooking medium is not replaced through day twenty (20), so the quality measurement continues to increase.

[0037] While the trend is for the cooking medium quality measurement to increase as the cooking medium degrades, the plot depicts considerable short-term variation about the long- term trend. The plot also depicts isolated measurements of much lower magnitude than the trend. This signal variability means that simply comparing the signal to a threshold at any given time does not result in a reliable indication that the cooking medium has exceeded the threshold with acceptable certainty. Through the various embodiments of the cooking medium quality monitor and process, the certainty of the threshold detection may be increased so that it can be used effectively.

[0038] While the invention has been described in connection with preferred embodiments, it will be understood by those of ordinary skill in the art that other variations and modifications of the preferred embodiments described above may be made without departing from the scope of the invention. Other embodiments will be apparent to those of ordinary skill in the art from a consideration of the specification or practice of the invention disclosed herein. The specification and the described examples are considered as exemplary only, with the true scope and spirit of the invention indicated by the following claims.

Claims

What is claimed is:

1. A method for monitoring quality of a cooking medium, comprising:

measuring a signal with an analog-to-digital converter, which corresponds to conductivity of the cooking medium;

digitally filtering an output signal of the analog-to-digital converter to produce an output sample, which corresponds to a quality measurement of the cooking medium;

calculating a median of a plurality of consecutive, qualified output samples when a number of samples in the plurality of consecutive, qualified output samples is greater than or equal to a first predetermined value;

incrementing a first counter when the calculated median is greater than or equal to a first predetermined threshold, and decrementing the first counter when the calculated median is less than the first predetermined threshold; and

determining that a first condition is true when the first counter is greater than or equal to a second predetermined value.

2. The method of claim 1, wherein the first condition is: treatment of the cooking medium is required.

3. The method of claim 2, wherein the treatment is selected from the group consisting of: disposal, filtering, blending, and combinations thereof.

4. The method of claim 1, further comprising the steps of:

incrementing a second counter when the calculated median is less than or equal to a second predetermined threshold, and decrementing the second counter when the calculated median is greater than the second predetermined threshold; and determining that a second condition is true when the second counter exceeds a third predetermined value.

5. The method of claim 4, wherein the second condition is: the cooking medium is a new cooking medium.

6. The method of claim 5, further comprising the steps of:

starting a timer; and

determining that treatment of the cooking medium is needed when the timer reaches a predetermined time limit.

7. The method of claim 1, wherein the step of digitally filtering comprises applying a filter selected from the group consisting of: a moving average low-pass filter, an n-sample average low-pass filter, and combinations thereof.

8. The method of claim 1, further comprising the step of:

resetting the first counter to zero and disqualifying the output sample when an event occurs, that is selected from the group consisting of: power off for a predetermined period of time, detection of a persistent electrode fault, execution of a dispose cooking medium function, execution of a manual reset function, and combinations thereof.

9. The method of claim 1, further comprising the step of:

disqualifying the output sample when an event occurs, that is selected from the group consisting of: a temperature of the cooking medium is outside a predetermined temperature range, a cooking period, a quick filtering period, a maintenance filtering period, a predetermined time period after the temperature of the cooking medium reaches a ready range, a filter pump running period, an auto top-off pump running period, and combinations thereof.

10. The method of claim 1, further comprising the steps of:

incrementing a third counter when the calculated median is greater than or equal to a third predetermined threshold, and decrementing the third counter when the calculated median is less than the third predetermined threshold; and

determining that a third condition is true when the third counter exceeds a fourth predetermined value.

11. The method of claim 10, wherein the third condition is: treatment of the cooking medium is required.

12. The method of claim 11, wherein the treatment is selected from the group consisting of: disposal, filtering, blending, and combinations thereof.

13. The method of claim 10, further comprising the step of generating a warning signal when the third condition is true and the third predetermined threshold is less than the first predetermined threshold.

14. The method of claim 10, further comprising the step of generating a warning signal when the third condition is true and the third predetermined threshold is greater than the first predetermined threshold.

15. A cooking medium quality monitoring device, comprising:

an analog-to-digital converter for measuring a signal which corresponds to conductivity of the cooking medium;

a digital filter unit configured to filter an output signal of the analog-to-digital converter to produce an output sample, which corresponds to a quality measurement of the cooking medium; and

a controller configured to:

calculate a median of a plurality of consecutive, qualified output samples when a number of samples in the plurality of consecutive, qualified output samples is greater than or equal to a first predetermined value;

increment a first counter when the calculated median is greater than or equal to a first predetermined threshold, and decrement the first counter when the calculated median is less than the first predetermined threshold; and

determine that a first condition is true when the first counter exceeds a second predetermined value.

16. The cooking medium quality monitoring device of claim 15, wherein the first condition is: treatment of the cooking medium is required.

17. The cooking medium quality monitoring device of claim 16, wherein the treatment is selected from the group consisting of: disposal, filtering, blending, and combinations thereof.

18. The cooking medium quality monitoring device of claim 15, wherein the controller is further configured to: increment a second counter when the calculated median is less than or equal to a second predetermined threshold, and decrement the second counter when the calculated median is greater than the second predetermined threshold; and

determine that a second condition is true when the second counter exceeds a third predetermined value.

19. The cooking medium quality monitoring device of claim 18, wherein the second condition is: the cooking medium is a new cooking medium.

20. The cooking medium quality monitoring device of claim 19, further comprising: a timer;

wherein the controller is further configured to:

determine that treatment of the cooking medium is needed when the timer reaches a predetermined time limit.

21. The cooking medium quality monitoring device of claim 15, wherein the digital filter unit comprises a digital filter selected from the group consisting of: a moving average low- pass filter, an n-sample average low-pass filter, and combinations thereof.

22. The cooking medium quality monitoring device of claim 15, wherein the controller is further configured to:

reset the first counter to zero, and disqualify the output sample in response to the occurrence of an event selected from the group consisting of: power off for a predetermined period of time, detection of a persistent electrode fault, execution of a dispose cooking medium function, execution of a manual reset function, and combinations thereof.

23. The cooking medium quality monitoring device of claim 15, wherein the controller is further configured to:

disqualify the output sample when an event occurs, that is selected from the group consisting of: a temperature of the cooking medium is outside a predetermined temperature range, a cooking period, a quick filtering period, a maintenance filtering period, a predetermined time period after the temperature of the cooking medium reaches a ready range, a filter pump running period, an auto top-off pump running period, and combinations thereof.

24. The cooking medium quality monitoring device of claim 15, wherein the controller is further configured to:

increment a third counter when the calculated median is greater than or equal to a third predetermined threshold, and decrement the third counter when the calculated median is less than the third predetermined threshold; and

determine that a third condition is true when the third counter exceeds a fourth predetermined value.

25. The cooking medium quality monitoring device of claim 24, wherein the cooking medium requires treatment when the third condition is true.

26. The cooking medium quality monitoring device of claim 25, wherein the treatment is selected from the group consisting of: disposal, filtering, blending, and combinations thereof.

27. The cooking medium quality monitoring device of claim 24, wherein the third threshold is less than the first threshold, and the controller is further configured to generate a warning signal when the third condition is true.

28. The cooking medium quality monitoring device of claim 24, wherein the third threshold is greater than the first threshold, and the controller is further configured to generate a warning signal when the third condition is true.

29. A fryer comprising the cooking medium quality monitoring device of claim 15.

30. A fryer system comprising:

a cooking vessel configured to store a cooking medium;

an electrode unit configured to be at least partially immersed in the cooking medium; a signal conditioning circuit configured to receive a signal generated by the electrode unit;

an analog-to-digital converter for measuring a signal, generated by the signal conditioning circuit, corresponding to conductivity of the cooking medium;

a controller configured to:

calculate a median of a plurality of consecutive, qualified output samples when a number of samples in the plurality of consecutive, qualified output samples is greater than or equal to a first predetermined value; increment a first counter when the calculated median is greater than or equal to a first predetermined threshold, and decrement the first counter when the calculated median is less than the first predetermined threshold; and