Optical food oil quality sensor

Details Optical food oil quality sensor Optical food oil quality sensor

2003-01-13

2004-04-06

Evans, F. L. (Department: 2877)

Optics: measuring and testing

By dispersed light spectroscopy

With sample excitation

C356S417000, C250S458100

Reexamination Certificate

active

06717667

ABSTRACT:

BACKGROUND OF THE INVENTION
Fast food restaurants use both vegetable shortenings and animal fats for frying purposes. Since this operation is carried out at high temperatures in the presence of water and starch, several chemical changes take place in the oil, degrading the oil quality. Heretofore, there has been no systematic or accurate way of monitoring oil quality in restaurants quickly and easily as the oil is repeatedly used in frying. The restaurant manager's decision to change or not to change the oil is typically based on a visual inspection of the colour of the oil. The appearance of used cooking oil to the naked eye is the result of light which is both scattered and absorbed by the oil. For example, bad oil appears dark because of chemical changes that cause light absorption. Good oil may also appear dark if there are particle impurities which have sizes comparable to the wavelength of light or higher (larger than about 0.3 microns). This can create a situation where bad oil is repeatedly used at the expense of the consumer's health. Conversely, oil may be prematurely changed, to the needless expense of the restaurant owner.
SUMMARY OF THE INVENTION
The present invention seeks to provide instrumentation which measures reliably and instantaneously the chemical quality of cooking oil. It can also distinguish between colour changes due to chemical changes and colour changes due to the presence of minute size food particles in various oils.
Another object of the present invention is to provide an apparatus suitable for use in restaurants, homes and other businesses for the regular monitoring of the cooking oil which is safe, user friendly and inexpensive.
In furtherance of at least some of the foregoing objects, the applicant has appreciated that the following scientific and technical conclusions may be drawn from experimental studies of cooking oil samples as disclosed hereinafter:
(i) There is on average a clear correlation between laser induced fluorescence and the concentration of polar compound and in the oil.
(ii) Data for fluorescence vs. polar compound concentration exhibits significant standard deviation from the average. This strongly suggests that fluorescence is a measure of a variety of different chemical changes in the cooking oil of which polar compound concentration is a major component. For example, a large fluorescence signal is observed if either the polar compound concentration or the percentage of Free Fatty Acids is high. This indicates that fluorescence must be regarded as a composite index for oil quality and is not limited to a single chemical change.
(iii) Each curve shows a “knee” when the polar compound concentration reaches approximately 25%. Below this knee, the fluorescence increases slowly with polar compound concentration (with significant fluctuations) and the oil is reusable. Above this knee, the fluorescence increases extremely rapidly with polar compound concentration and reuse of the oil is ill-advised. The existence of this knee in our regression curves plays a key role in the ability of an oil sensor to discriminate between usable and non-reusable oil.


REFERENCES:
patent: 5472878 (1995-12-01), Lewis et al.
patent: 5656810 (1997-08-01), Alfano et al.
Engelsen: “Explorative Spectrometric Evaluations of Frying Oil Deterioration” Journal of the American Oil Chemists' Society, vol. 74, No. 12, Dec. 1997, pp. 1495-1508.

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