Electricity: measuring and testing – Impedance – admittance or other quantities representative of... – Lumped type parameters
Reexamination Certificate
1999-04-19
2001-07-24
Brown, Glenn W. (Department: 2858)
Electricity: measuring and testing
Impedance, admittance or other quantities representative of...
Lumped type parameters
C324S693000, C436S020000, C436S021000
Reexamination Certificate
active
06265882
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to an apparatus for measuring the content of intramuscular fat in carcasses or parts thereof.
2. Description of the Prior Art
It is well known in the art that the content of intramuscular fat (fat marbling) in beef affects the taste and consistency of the meat. Muscles with a certain degree of fat in the muscles feels tender and juicy, whereas muscles without any fat give a tough and dry feeling. In order to be able to guarantee the tenderness and taste of the meat it is therefore important to be able to determine the content of intramuscular fat of muscles in carcasses or parts thereof.
It has recently been described that the fat content of beef muscles can be predicted by measuring the muscles' impedance (see article by W. D. Slanger and M. J. Marchello in J. Anim. Sci. 72 (1994), pp. 3124-3130: “Bioelectrical Impedance Can Predict Skeletal Muscle and Fat-free Skeletal Muscle of Beef Cow Primal Cuts”). The measurement is carried out by insertion of four electrodes into a muscle. Two of the electrodes are connected to an AC generator with a frequency of 50 kHz. The two other electrodes are placed between the first electrodes so that the four electrodes are aligned. The inner electrodes are connected to a circuit measuring the voltage over the electrodes and the phase in relation to the signal of the generator. On the basis of this measurement, the meat impedance can be determined (the impedance comprises a real component, which is pure ohmic resistance, and an imaginary component, which corresponds to the phase shift). The impedance correlates to the muscle's fat content and it is thus an expression of the amount of intramuscular fat in the muscle.
The reason why four electrodes are used for the measuring is that the contact resistance between electrodes and meat is very high and may vary considerably depending on the pH and liquid content of the meat. When a constant alternating current is passed through the outer electrodes, measurements can be taken over the inner electrodes by means of a phase and amplitude detector having very high input impedance. This has the effect that the fall in voltage in the transition between the inner electrodes and the meat becomes relatively small as no current is drawn in the measuring. Variations in the contact resistance are therefore insignificant.
The above-mentioned test equipment is unsuitable for on-line measuring of intramuscular fat in abattoirs or meat processing plants. It is for instance not sufficiently reliable to comply with the requirements imposed on such equipment to allow it to be used in abattoirs to determine fat marbling.
The purpose of the invention is therefore to provide an apparatus suitable for measuring intramuscular fat under the operational conditions of abattoirs or meat processing plants. Preferably the apparatus should also be able to determine the fat content of minced meat.
SUMMARY OF THE INVENTION
The apparatus according to the invention comprises:
a first pair of electrodes consisting of two parallel insertion electrodes,
an AC generator which is connected to these electrodes,
a second pair of electrodes consisting of two insertion electrodes placed parallel to the first insertion electrodes,
a measuring circuit designed to measure the voltage and phase of the second pair of electrodes after the electrodes have been inserted into a muscle in the carcass or part thereof or into the minced meat,
a third pair of electrodes consisting of two insertion electrodes which are placed parallel to the other electrodes and
means for measuring the voltage and phase of this third pair of electrodes after they have been inserted into the muscle or minced meat.
The apparatus according to the invention has important advantages compared with the above-mentioned test equipment and these advantages make it suitable for use in the conditions prevailing in abattoirs. Firstly, the third pair of electrodes permits double measuring of the impedance, and tests show that this double measuring is able to bring the accuracy to a satisfactory level. The operator's work is thereby the same as if he were to use equipment with only one pair of measuring electrodes; he just has to move the apparatus towards the carcass so that the electrodes are inserted into the muscle. When double measuring is carried out by insertion of probes or the like into meat, it is important to avoid measuring in the same hole or area, as this could result in considerable errors. Likewise, it is important that both measurements are taken within the area of the muscle where the most reliable results are obtained. With the apparatus according to the invention, both these conditions are considered. Consequently, the apparatus of the invention not only saves labour in comparison to the traditional double-measurement technique, but the operator does not have to concentrate any harder during insertion as the points of insertion are by definition different and are in advance separated by a desired distance, given by the distance between the two pairs of measuring electrodes.
An additional advantage of the use of two pairs of measuring electrodes is that the two measuring results can immediately be compared and the measurement discarded if they differ considerably from each other. This could for instance be the case if an electrode hits a fat pocket.
For measurement of the intramuscular fat content, the electrodes are inserted into a muscle in the carcass or part thereof. In the present description the designation a “muscle” may include several coherent muscles. In the broadest sense a “muscle” may be a fleshy part or a lean meat region of the carcass or part thereof.
The apparatus according to the invention can also be used for measuring the total content of fat in minced meat from a carcass or carcass part, as the electrodes are inserted into the minced meat. Preferably, this is compacted to achieve good contact between the particles of the material. Using the apparatus according to the invention, butchers and in-store butchers can for instance quickly and cheaply determine the fat content in minced meat.
It should be mentioned that the apparatus according to the invention may comprise a fourth, fifth or even more pairs of electrodes for the measuring, but preferably the apparatus only has three pairs of electrodes as these have proved to provide sufficiently accurate results, allow direct comparison of the signals and give a simple design of the apparatus.
Advantageous embodiments of the apparatus according to the invention are described below:
The insertion electrodes preferably have a tapered free end designed for insertion into the carcass, the carcass part or the minced meat to be measured and a mounting end at which they are fitted in the apparatus.
The insertion electrodes are preferably needle or bar shaped, and are equipped with an electrically insulating jacket except for a section close to the insertion end where preferably 5 to 20 mm are bare.
Preferably, the diameter of the electrodes is 2 to 5 mm and the length 25 to 150 mm.
The apparatus preferably comprises a stop device designed to limit the insertion depth of the electrodes into the carcass, the carcass part or the minced meat, usually in the form of a plate at right angles to the electrodes.
The electrodes are usually placed in a hexagonal pattern with the electrodes of the first pair of electrodes placed in opposite apexes in the hexagon, the electrodes of the second pair of electrodes placed in two other adjacent apexes and the electrodes of the third pair of electrodes placed in the two remaining apexes.
Alternatively, the second and the third pair of electrodes may be placed in the apexes on a rectangle and the first pair of electrodes be placed in the area of the rectangle on the long center line of the rectangle.
The distance between the second pair of electrodes and the third pair of electrodes is preferably between 0.2 and 1 times the distance between the two electrodes of the first pair of electrodes, prefera
Borggaard Claus
Madsen Niels T.
Nielsen Torben
Rasmussen Allan J.
Brown Glenn W.
Marshall O'Toole Gerstein Murray & Borun
Nguyen Vincent Q.
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