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Title:
DEVICE AND METHOD FOR MEASURING THE QUALITY OF FRYING OIL
Document Type and Number:
WIPO Patent Application WO/2017/002079
Kind Code:
A1
Abstract:
The present disclosure relates to a device and a method for real-time measurement of the quality of frying oil by sensing a chemical species related to the quality of the frying oil. The device comprises an optical sensor comprising at least a light source and at least a light detector; a chamber for receiving the frying oil to be measured arranged such that the light source is optically coupled through the frying oil in the chamber to the light detector; and a processing unit configured to: receive from the light detector a signal of the frying oil absorption, transmittance, reflection, scattering, or combinations thereof, of light emitted by the light source; calculate, from the received signal, an output indicative of the quality of the frying oil using a precalculated model relating chemical species and quality of the frying oil.

Inventors:
DE BRAGA DE MELO E CASTRO, Artur Elísio (Rua Tenente Valadim, Nº 252 Hab. 14, 4100-476 Porto, 4100-476, PT)
DA COSTA BARROS, Rui Sanches (Travessa das Murtas 68, 4600-109 Amarante, 4600-109, PT)
SANTANA CARMELO ROSA, Carla Susana (R. D. João I, 454 4º Dto Trás, 4450-163 Matosinhos, 4450-163, PT)
Application Number:
IB2016/053948
Publication Date:
January 05, 2017
Filing Date:
June 30, 2016
Export Citation:
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Assignee:
AMBIFOOD, LDA (Rua Dominguez Alvarez, Nº 44 4.16, 4150-801 Porto, 4150-801, PT)
International Classes:
G01N21/3577; A47J37/12; G01N21/59; G01N21/85; G01N33/03
Foreign References:
US5712165A1998-01-27
US5818731A1998-10-06
US20030147073A12003-08-07
US20100260903A12010-10-14
Other References:
None
Attorney, Agent or Firm:
TEIXEIRA DE CARVALHO, Anabela (Patentree, Edifício NetRua de Salazares 842, 4149-002 Porto, 4149-002, PT)
Download PDF:
Claims:
C L A I M S

1. Device for real-time measurement of the quality of frying oil by sensing a chemical species related to the quality of the frying oil, said device comprising:

an optical sensor comprising at least a light source and at least a light detector; a chamber for receiving the frying oil to be measured arranged such that the light source is optically coupled through the frying oil in the chamber to the light detector;

a processing unit configured to:

receive from the light detector a signal of the frying oil absorption, transmittance, reflection, scattering, or combinations thereof, of light emitted by the light source; calculate, from the received signal, an output indicative of the quality of the frying oil using a precalculated model relating chemical species and quality of the frying oil.

2. Device according to the previous claim wherein the light source is an infrared light source.

3. Device according to any of the previous claims wherein the light source comprises a light guide embedded in a wall of the chamber for optically coupling with the frying oil.

4. Device according to any of the previous claims wherein the light detector comprises a light guide embedded in a wall of the chamber for optically coupling with the frying oil.

5. Device according to any of the previous claims wherein the light source and the light detector are embedded in a wall of the chamber.

6. Device according to any of the claims 3-5 wherein the wall is a bottom wall of the device.

7. Device according to any of the previous claims wherein the sample-holding chamber is a temperature-stabilizing chamber.

8. Device according to any of the previous claims comprising a temperature-sensing detector for measuring the frying oil temperature.

9. Device according to any of the previous claims wherein the infrared light source is a near infrared laser, near infrared laser diode, near infrared light emitting diode or incandescent source filtered for near infrared light.

10. Device according to any of the previous claims comprising one or more optical filters arranged in a optical path between light source and light detector.

11. Device according to the previous claim wherein the optical filter or filters are arranged adjacently to the light detector for increasing signal sensitivity.

12. Device according to any of the previous claims wherein the light detector is arranged for converting the received light into an electrical signal.

13. Device according to the previous claim comprising a converter arranged to convert the electrical signal into a digital signal for transmitting to the processing unit.

14. Device according to the previous claim comprising a transmitter for transmitting the digital signal to the processing unit by an electrical cable or by wireless radio transmission.

15. Device according to any of the previous claims wherein the chamber is a sample- holding chamber.

16. Device according to any of the previous claims wherein the chamber is a food- frying container.

17. Device according to any of the previous claims wherein the chemical species is polar compounds.

18. Device according to any of the previous claims comprising a metallic enclosure for enclosing the optical sensor.

19. Device according to any of the previous claims comprising a display for displaying in real-time the output indicative of the quality of the frying oil.

20. Device according to any of the previous claims wherein the light detector is a photodiode, an avalanche photodiode or a mini spectrometer.

21. Food-frying container comprising the device of any of the previous claims.

22. Method for real-time measurement of the quality of frying oil in a chamber by sensing a chemical species related to the quality of frying oil, said method comprising the following steps:

irradiating the frying oil with at least a light source;

receiving, from the at least a light detector, a signal of the frying oil absorption, transmittance, reflection, scattering, or combinations thereof, of light emitted by the light source, such that the light source is optically coupled through the frying oil in the chamber to the light detector;

calculating, from the received signal, an output indicative of the quality of the frying oil using a precalculated model relating chemical species and quality of the frying oil.

23. Method according to the previous claim for operating the device of any of the claims 1-20 or the container of claim 21.

Description:
D E S C R I P T I O N

DEVICE AND METHOD FOR MEASURING THE QUALITY OF FRYING OIL

Technical field

[0001] The present disclosure relates to a device and a method for real-time measurement of the quality of frying oil by sensing a chemical species related to the quality of the frying oil. This device is useful for measuring the frying oil parameters so the user may know when the oil organoleptic properties are no longer adequate for consumption or use.

[0002] Said device comprises an optical sensor, a chamber for receiving the frying oil to be measured, an analogue signal processing module, a transmitting unit, a receiver, a processing unit, a display device and an integrated information system.

Background Art

[0003] Empirical monitoring of the quality of frying oils, by smelling the oil and/or observing its frying properties, is perhaps the most common method found in households, small dimension food industries, and restaurants. As expected, this approach can be misleading, prone to errors arising from the subjective sensitivity and experience of the operator, and, as such, it is neither reliable nor trustable.

[0004] At a first instance, the visual inspection of the colour of the oil is based on both the scattering and absorption properties of the frying oil. Fresh oil is transparent, but the frying of food may lead, in one hand, to the presence of small micro- or milli-metric particles, and on the other hand, to a colour dependent increase of light absorption, that affect the overall perceived oil colour. Dark oil is usually considered as not adequate, which is a correct assessment only if the resulting colour arises from light absorption by specific chemical species associated to toxic by-products of the frying process. Nevertheless, an acceptable oil may also appear dark if there are food particles of very small size comparable, possibly caramelized and browned by the frying process. Consequently, a colour based judgment can lead to both inappropriate oil being repeatedly used at the expenses of public health, and unneeded exchange of frying oil with ensuing reduction in profitability. Other empirical ways to evaluate the quality of cooking oils are: duration of use, smoke evolution, and foam height.

[0005] Present regulations concerning frying oils have their origin in the recommendations given by the German Society for Fat Research to limit the alteration of frying fats in human consumption. Based on the analyses of a high number of frying oil samples, the following criteria were established in 1973. A used frying fat is deteriorated if:

i) without any doubt, odour and taste are not acceptable;

ii) in case of a doubtful sensory assessment:

a) the concentration of oxidized fatty acids, insoluble in petroleum ether, is 1.0% or greater;

b) the concentration of oxidized fatty acids, insoluble in petroleum ether, is 0.7% or higher, and the smoke point is lower than 170°C.

[0006] These criteria are mainly organoleptic in nature, and show the importance of the oxidation compounds in chemical evaluation. The main problem of these initial criteria is the complexity of both analytical methodologies, laborious and time-consuming, and the need of highly skilled personnel, inappropriate for quality monitoring outside the chemistry lab. To overcome this limitation, Polar Compounds (PC) determination was proposed as an undoubted analytical solution contributing to the application of present regulations in the field.

[0007] At the laboratory, PC are determined by adsorption chromatography on silica columns, and the value obtained by this method corresponds approximately to the change of total polar compounds (TPC) during the frying process. Given that the amount of total polar compounds was found to be very well correlated to the content of oxidized fatty acids (OFA), TPC determination was recommended as a de facto standard. A maximum limiting value of 27% TPC, corresponding to 0.7% OFA, was initially advanced to qualify a frying oil as "safe". Since then, the determination of polar compounds has become the most generally accepted method for quality monitoring of frying fats, as demonstrated by its inclusion in all the present official regulations and best practices of many countries. [0008] However, due to the complexity of specialization of PC determination method, it is still necessary to develop simple rapid analytical and accurate tests to monitor oil quality in food industry, such as restaurants and fried food outlets. Some examples of commonly available commercialized kits are TESTO, Oxifrit-Test and Veri-Fry. In spite of being rapid test solutions, these are not as rigorous as the conventional analytical test procedures. The characteristic margin of error of these devices leads to a big number of false positives, in particular in the range of TPCs around the maximum limiting value. If these methods underestimate TPC, there is a potential health risk; if overestimates, it will lead to an unnecessary increase in oil consumption, and a higher cost.

[0009] Improving rapid frying oil tests, simpler than the conventional analytical techniques but more rigorous and efficient than the currently available rapid tests, is deemed as positive and of potential success.

[0010] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.

General Description

[0011] Devices for measuring the quality of frying or cooking oils are already known in the prior art. However, these devices are colorimetric-based devices that use, for example, wavelengths ranging from 645-695 nm for monitoring the colour of the oil. The colour of the oil is an unspecific way to determine the quality of a frying oil as, for example, the colour may depend on the initial composition of the frying oil or the foods being fried.

[0012] The device of the disclosure comprises an optical sensor, a signal pre-processing module, a transmitter unit, a receiver with a processing module and a display, and an integrated information system.

[0013] The device of the disclosure determines the TPCs in frying oil by measuring its optical properties. For that purpose, a numerical model was established relating these physical properties with the quantification of said chemical components in frying oil.

[0014] The present disclosure relates to a device and a method for measuring the quality of food frying oil in multiple locations, thus allowing a large scale monitoring of frying oil. [0015] The device and method of the present disclosure are hence useful for measuring frying oil parameters so that the user may know when the oil organoleptic properties are no longer adequate for consumption or use. Therefore, the present disclosure lies in the field of optical devices for measuring values or parameters.

[0016] The present disclosure relates to a device for real-time measurement of the quality of frying oil by sensing a chemical species related to the quality of the frying oil, said device comprising:

an optical sensor comprising at least a light source and at least a light detector; a chamber for receiving the frying oil to be measured arranged such that the light source is optically coupled through the frying oil in the chamber to the light detector;

a processing unit configured to:

receive from the light detector a signal of the frying oil absorption, transmittance, reflection, scattering, or combinations thereof, of light emitted by the light source; calculate, from the received signal, an output indicative of the quality of the frying oil using a precalculated model relating chemical species and quality of the frying oil.

[0017] In an embodiment, the light source may comprise a light guide embedded in a wall of the chamber for optically coupling with the frying oil.

[0018] In an embodiment, the light detector may comprise a light guide embedded in a wall of the chamber for optically coupling with the frying oil.

[0019] In an embodiment, the light source and the light detector may be embedded in a wall of the chamber, in particular said wall is a bottom wall of the device.

[0020] In an embodiment, the light source is an infrared light source, in particular a near infrared laser, a near infrared laser diode, a near infrared light emitting diode or a incandescent source filtered for near infrared light. This has the advantage, for example, of being a particularly discriminating wavelength range for discriminating oil quality.

[0021] In an embodiment, the device now disclosed may comprise one or more optical filters arranged in the optical path between light source and light detector; wherein the optical filter or filters may be arranged adjacently to the light detector for increasing signal sensitivity.

[0022] In an embodiment, the light detector may be arranged for converting the received light into an electrical signal.

[0023] In an embodiment, the device may further comprise a converter arranged to convert the electrical signal into a digital signal for transmitting to the processing unit.

[0024] In an embodiment, the device may comprise a transmitter for transmitting the digital signal to the processing unit by an electrical cable or by wireless radio transmission.

[0025] In an embodiment, the chamber may be a sample-holding chamber, in particular a temperature-stabilizing holding chamber. This has, for example, the advantage of the optical measure not being affected by different temperatures of oil or chamber, because the measurement can be calibrated for this temperature. This is even more important when infrared measures are being made, in particular when measuring frying oil in-situ, for example when the chamber is the fryer chamber or the oil is piped from the fryer, because the temperature of the chamber and oil causes significant infrared radiation.

[0026] In an embodiment, the chamber may be a food-frying container.

[0027] In an embodiment, the chemical species may be polar compounds.

[0028] In an embodiment, the device may comprise a temperature-sensing detector for measuring the frying oil temperature. This has, for example, the advantage of the optical measure not being affected by different temperatures of oil or chamber because the precalculated model may take into account this temperature when relating chemical species and quality of the frying oil.

[0029] In an embodiment, the device may also comprise a metallic enclosure for enclosing the optical sensor.

[0030] In an embodiment, the device may comprise a display for displaying in real-time the output indicative of the quality of the frying oil. [0031] In an embodiment, the light detector is a photodiode, an avalanche photodiode or a mini spectrometer.

[0032] The present disclosure also relates to a food-frying container comprising the device now disclosed.

[0033] This disclosure also relates to a method for real-time measurement of the quality of frying oil in a chamber by sensing a chemical species related to the quality of frying oil, said method comprising the following steps:

irradiating the frying oil with at least a light source;

receiving, from the at least a light detector, a signal of the frying oil absorption, transmittance, reflection, scattering, or combinations thereof, of light emitted by the light source, such that the light source is optically coupled through the frying oil in the chamber to the light detector;

calculating, from the received signal, an output indicative of the quality of the frying oil using a precalculated model relating chemical species and quality of the frying oil.

[0034] Throughout the description and claims the word "comprise" and variations of the word, are not intended to exclude other technical features, additives, components, or steps. Additional objectives, advantages and features of the solution will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the solution.

Brief Description of the Drawings

[0035] The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of disclosure.

[0036] Figure 1: Schematic representation of one possible configuration of the optical sensor device of the present disclosure.

[0037] Figure 2-3: Schematic representations of possible configurations of the in situ measuring optical sensor device of the present disclosure. [0038] Figure 4: Representation of a block diagram of a possible configuration for the optoelectronics box interfacing the possible in situ configurations described in Figs 1 to 3.

[0039] Figure 5: Representation of a possible interconnection between hardware blocks.

[0040] Figure 6: Represents processed data, establishing a metric between processed signal and reference % TPC conditions.

Detailed Description

[0041] In an embodiment, the measurement of frying oil parameters of organoleptic and health interest, such as percentage of free fatty acids, peroxide value, p-anisidine levels and total polar compounds (TPCs), preferably TPCs, can be made using its optical characteristics, through appropriate optical sensors.

[0042] Several examples of optical sensor designs are shown in Figs 1-3. Figure 1 comprises a specific configuration of the device, implemented and further characterized and tested according to the present disclosure. The optical sensor disclosed in figure 1 comprises at least one light source 101, optical filters 102, at least a light detector 103, a temperature stabilized embodiment 104, sample holder containing the oil sample to be analysed 105, an electrical connection, such as an electrical cable 106, temperature sensing device 107.

[0043] Figs 2 and 3 comprises possible implementations of an all-optical sensor implementation, with remote optoelectronic elements. The remote unit may be directly coupled to the optical sensor or, possibly, located further away from the optical sensor, interconnected by adequate optical waveguides and any eventual needed electrical interconnection, depending on intended particular implementations of frying oil quality measurement. The detailed description herein refers to the configuration used to characterize the present disclosure.

[0044] Figure 2 represents a possible configuration of the in situ measuring device of the present disclosure, wherein the following elements are disclosed: the frying oil environment to be analysed 200, optical waveguide 201 delivering the light from at least one light source located on a remote optoelectronics box (not shown), the optical waveguide 202 collecting the light transmitted across the sample environment to at least a light detector located on a remote optoelectronics box (not shown), a metallic material 203 enclosing the optical sensor and a temperature monitoring device 204.

[0045] Figure 3 represents another possible configuration of in situ device of the present disclosure, wherein some optical waveguide delivering/collecting the light from/to a remote optoelectronics box 301 and a mirror surface 302 are represented.

[0046] Figure 5 represents a possible interconnection between hardware blocks wherein the frying oil measuring box set 501 and user sphere, with the corresponding interfacing tools 502 are represented.

[0047] In an embodiment, the device now disclosed may comprise: an optical sensor/sensing head for measuring the desired electrical and/or optical parameter, said optical sensor/sensing head comprising an electrical sensor/sensing head and/or an optical sensor head having at least a light source and a detector matched with optical filters, wherein said detector may be able to convert the optical signals to electrical ones; an analogue signal processing unit, able to filter, amplify, sample and convert the electrical signs from the optical sensors/sensing heads into digital waveforms; a transmitting unit, that receives the digital signals of the previous module and converts them to suitable transmission formats; a receiver, that supplies the received signal to the processing module, converting to frames of the raw measured values, according to proprietary and standard interface protocols to the processing module; a processing unit comprising an algorithm that converts the raw sensor measurements to a value of the food quality parameter to be analysed, said algorithm comprising the resolution of mathematical equations relating the characteristic property or properties of the sensor to said quality parameter; a display device, and an integrated information system that gathers, adds and stores the information of the food quality parameter determined from individual food processing devices.

[0048] In an embodiment, the method for measuring the quality of a frying/cooking oil, said method being executed by a device as described in the previous claim, and comprising the following steps: irradiating the oil to be analysed with a light source having a given wavelength selected according to the type of cooking oil to be analysed; measuring the value of the selected food quality parameter relevant to said type of cooking oil, and comparing the obtained measured value with the respective standard value for that specific parameter.

[0049] In an embodiment, the described optical sensor/ comprises the delivery of probing light to the sample under test (SUT), and the collection of the light transmitted across the SUT into an appropriate optical detector.

[0050] In an embodiment, the measurement of the quantity of a particular chemical species present in a mixture can be made recurring to the electromagnetic spectra, be it in absorption, transmission, reflection or scattering configurations. The most rigorous analysis can be made across the entire intended spectrum with the use of a spectrometer, referenced in the literature as measuring a specific "signature".

[0051] In an embodiment, the frying oil may be rapessed oil, peanut oil, coconut oil, palm oil and combinations thereof.

[0052] In an embodiment, a frying oil sample may be irradiated with a light source having a given spectral range.

[0053] In an embodiment, the intended spectrum may be obtained using wavelengths in the near infrared spectral range, in particular 1600-1750 nm for detecting the TPCs, more preferably 1900-2200 nm for detecting the TPCs. [0054] In an embodiment, the wavelengths used may be 1600-1750 nm, and 1900- 2200nm for detecting the TPCs. Using a wavelength in the infrared range has been found to be a more specific way to determine the TPC than a colorimetric TPC determination.

[0055] The advantage of using such spectral range relies on the ability to measure specific signatures associated to specific TPC chemical bonds.

[0056] In an embodiment, the specific "signature" is determined from the absorption, transmission, reflection or scattering at characteristic wavelengths of relevant chemical species, such as those linked to the vibrational states of C-H, O-H, C-H 2 , and CH=CH- groups. Nevertheless, the process of reducing the amount of information leads inevitably and regrettably to a potential big number of wavelengths that have to be identified, and its intensity measured in relation to some known reference. The spectral measurement requires a measurement time that scales with the wavelength range extension. Further reduction in the number of measured wavelengths and overall measurement time can be obtained by identifying a reduced set of characteristic wavelengths, supported by an adequate choice of light sources, filters and light detectors. The achieved measurement resolution and accuracy aim at low number of false negatives, considering the regulatory standards and public health interest, as well as reduction of false positives with potential benefit in cost reduction.

[0057] The present disclosure may be based on such an approach. The spectra of common use frying oils were studied in real conditions, following usual frying procedures. A model was developed relating the total polar compounds with spectral features, allowing establishing an algorithm interconnecting both.

[0058] In an embodiment, the light sources (101) can be white light sources, light emitting diodes (LED), superluminescent diodes (SLD), or laser diodes (LD).

[0059] In an embodiment, the source is chosen according to match the wavelength range of frying oil signatures.

[0060] In an embodiment, some wavelength-filtering device (102) can be located close to the photodetectors (103) to enable increased signal sensitivity. [0061] In an embodiment, the photodetectors can be implemented as normal or avalanche photodiodes, or other wavelength gated photodetector, such as a mini spectrometer, sensitive to the wavelength windows of interest. The photo detectors produce an electrical signal that will be further processed by other system modules.

[0062] In an embodiment, the optical sensor may be temperature stabilized (104).

[0063] In an embodiment, the sample local temperature may be monitored by an addit ional thermal detector (107, 204).

[0064] In an embodiment, the electrical signals from the detector at the optical sensor may be filtered and amplified, sampled, and converted to digital signals, enabling its processing in the digital domain (Fig. 4). Depending upon the parameters of interest to be measured and on the regime of operation of the optical sources, the digital signals can then be processed via numerical transforms. Examples of these modules are analogue to digital converters, electrical filters, statistic operators, spectral domain transforms.

[0065] In an embodiment, the transmitting unit receives the digital signals of the previous module and converts them to suitable transmission formats (Fig.4). The options considered were by electrical cables or by wireless radio frequency transmission, namely according to market standard known as Bluetooth. Besides physical characteristics of the transmitted signal, this module also includes appropriate protocol information enabling correct transmission of the measured signal and without crosstalk from other measurement units of the same kind or other information sources in the same environment, such as as WiFi networks. This module main function is the transmission through appropriate device communication formats and protocols of the pre-processed raw signals originating from the optical sensor to the remaining system modules.

[0066] In an embodiment, the receiver decodes the information received from the transmitter according to proprietary and standard interface protocols, and passes the transcripted pre-processed digital signal values to the processing module (502), Fig.5. Standard protocol examples are BlueTooth and WiFi. A mobile phone aka smartphone, a tablet, a personal computer, or a laptop, are examples of such a receiver. [0067] In an embodiment, the processing module comprises an algorithm that operates on the received signals, to produce a value for the intended frying oil quality parameter. This module processes mathematical equations relating the pre-processed digital signal against the devised numerical model, involving theoretical modelling and experimental work, as well as statistical operations on the measured values, such as principal components analysis, or other correlation techniques. An example of such processing is shown in Fig. 6, relating the algorithm derived signal with the varying TPC of two different frying oils.

[0068] In an embodiment, the processor module can be the intrinsic processor at the receiver, and/or an algorithm running remotely on the World Wide Web cloud (502). The parameters of the devised numerical model may be stored within the receiver/processing module, or stored and processed remotely in the cloud. Such embodiment, will yield the quality parameter of the frying oil under test

[0069] In an embodiment, a display device constitutes a user-friendly interface to human operators of the measured quality parameter, such as TPC, according to the user profile and his/her professional function. The so-called display device may be the screen of a processing unit, or a dedicated display, such as a liquid crystal display (LCD).

[0070] In an embodiment, the integrated information system (502) gathers, adds and stores the information of the frying oil quality parameter as determined from measurements at individual food processing devices.

[0071] In an embodiment, other management parameters at the food-processing unit, and corporate levels, can be also stored, enabling an integrated executive management system to be implemented that includes real-time food quality parameters assessment. Examples of the individual food processing unit information, in the case of a frying device, are asset information, location, time of the measurements, human operators involved, other food components traceability information, like frying oil brand and composition. This data integration enables quality management reporting and production planning, according to legal regulations, service quality categories and actual demand.

[0072] It will be appreciated by those of ordinary skill in the art that unless otherwise indicated herein, the particular sequence of steps described is illustrative only and can be varied without departing from the disclosure. Thus, unless otherwise stated the steps described are so unordered meaning that, when possible, the steps can be performed in any convenient or desirable order.

[0073] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0074] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof.

[0075] The above-described embodiments are combinable.

[0076] The following claims further set out particular embodiments of the disclosure.