NZ248916A - Determining yield of meat or wool by measuring gamma radiation attenuation - Google Patents

Description

PATENTS FORM 5 Number 248916 PATENTS ACT 1953 Dated February 25, 1994 COMPLETE SPECIFICATION NON-INVASIVE MEASUREMENT OF WOOL OR MEAT YIELD We, INSTITUTE OF GEOLOGICAL & NUCLEAR SCIENCES LIMITED, a New Zealand company, of Gracefield Road, Wellington, New Zealand do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement.

FIELD OF INVENTION 1 The invention comprises a method for the non-invasive measurement of yield of wool from raw wool or lean meat from meat containing a proportion of fat.

BACKGROUND ) Broadly raw wool contains pure wool, water, grease, dirt, suint, and vegetable matter in various amounts. A bale of raw wool, for example, will contain all of the above, and the proportions will depend upon the flock from which the wool is taken, fleece position, and other factors.

Wool yield refers to the pure wool content which is present. For example, a wool buyer is obviously concerned not just with the weight of the wool bales but with the amount of pure wool that will be yielded. Presently wool yield is estimated by drilling out samples from wool bales with a long hollow drill. The samples are then tested in a laboratory where they are subjected to chemical analysis to determine wool yield, wool grease, and vegetable matter. This is time consuming and laborious.

For completeness it should be noted that even pure wool naturally contains a certain amount of water, typically about 15% and the term "wool yield" as commonly used when expressed as a weight also includes the weight of this water content of the wool as well as the weight of the "wool base" of pure wool material absent moisture. As is well known, the moisture content of wool varies somewhat with the humidity of the ambient environment.

Meat also consists of a mixture of lean meat (often referred to simply as "lean") and fat and again the fat and lean meat content of packaged meat, such as in export meat boxes for example, is typically tested in a production line situation by destructive cutting up and weighing of the fat and lean meat components.

DESCRIPTION OF INVENTION It is an object of the present invention to provide a non-invasive method for determination of wool and meat yield.

In broad terms the invention comprises a method of determining pure wool content in raw wool or lean content in meat or vice versa, comprising irradiating the raw wool or meat with g^ama ray radiation from a first source providing gamma ray radiation of higher energy and a second source providing gamma ray radiation of lower energy, measuring the extent to which the gamma ray radiation is transmitted through the raw wool or meat, and determining the analysis by reference to the known attenuation co-efficients of the components of the raw wool or meat for each energy level of the source radiation. 2 L-. 9 1 Gamma rays interact mainly with matter by being scattered or absorbed by electrons. The attenuation of a high energy gamma ray beam as it passes through matter is a measure mainly of the mass of matter in the path of the beam. Gamma rays can give a measure of the variations in mass per unit area, bulk density, or effective thickness. content (elements of mass greater than C, N and 0) relative to pure wool and that the mineral content of the non-wool component is substantial and sufficient that practical measurement in an acceptable measurement time is possible, and also that the mineral content varies systematically with wool yield. As stated, the principal components in raw wool are pure wool, water, grease, suint, dirt and vegetable matter. Suint for example, has an average potassium content of about 27%, as well as comprising about 70% water soluble acids and 4% water insoluble acids on average. The non-wool components of raw wool also contain significant concentrations of calcium and zinc plus a range of trace elements as well as mineral elements from dirt in the fleece. Similarly it has been found that lean meat has a high mineral content relative to fat. With the method of the invention, changes in the mineral content of raw wool or meat are used to indicate the content of pure wool or lean meat or vice versa fat and, as stated, a systematic relationship has been found. Also we have found that wool yield can be measured with the method of the invention to relatively high accuracy, such as It has been found that raw wool has a high mineral ±2.5% for example, notwithstanding the chemical complexity of wool.

In the method of the invention, the raw wool or meat is irradiated, preferably simultaneously, with beams from two gamma ray sources which emit gamma rays of different energy. The transmission through the material of the higher energy gamma rays can be used to determine the mass of matter in the path of the beam. The lower energy radiation is used to scan a chemical property of the material.

For gamma rays of high energy, the principal interaction of the individual gamma rays with electrons is via the Compton interaction. The energy of the gamma rays is so high that the binding of the electrons into the material lattice is of little consequence and the collision between the gamma ray and the electron is like that of two billiard balls. For this type of interaction the attenuation of the beam incret ^s with the atomic number of the media, or simply the number of electrons present per atom. If, however, the gamma ray energy is progressively reduced, the interaction of the gamma rays with electrons via an alternative process, called the photo-electro interaction, becomes important. This becomes particularly enhanced for lower energy gamma rays interacting with heavier elements in material where the importance of the chemical binding of the electrons to the chemical lattice is important. Here the attenuation of this beam is dependent on the number of electrons Z&89 16 per atom raised to the power of 5, which produces a much more severe attenuation compared to the Compton interactions.

Preferably with the method of the invention one gamma ray component is sufficiently high in energy to ensure the interaction, even with any heavy elements in the matrix, is principally by the Compton interactions. The energy level of the higher energy beam may be in the ran,ge 1000 to 100 keV and most preferably 700 to 300 keV for example. This higher energy radiation may be provided by a source such as Caesium-137 for example, or any other suitable source. The other beam is sufficiently low in energy to ensure any heavy elements strong influence the interactions, mainly by the photo-electro interactions. The energy level of the lower energy beam may be in the range 100 to 10 keV and most preferably 80 to 20 keV for example. This lower energy radiation may be provided by a source such as Americium-241 for example.

The dual gamma radiation is passed through the wool or meat and the transmitted radiation intensities are measured by a suitable detector or array of detectors. The detector is connected to electronic measuring and computing apparatus, and the analysis carried out. The components of the raw wool, and of the raw meat including fat, have a different known mass attenuation component (MAC) for the two energies of radiation. Once this has been determined, then simple solution of simultaneous equations provides a quantative determination of the 2^89 weight fraction of the components of the raw wool, and of the most including fat. Measurements will have been made of the unattentuated intensities (count rates) of the radiation when there is no object in the beam.

If higher energy and lower energy gamma rays (g) and (n) are transmitted through raw wool containing wool yield x and non-wool material y, and meat containing fat x and lean meat y, it follows that: IB = Ino exp - + jiaymy] (1) I, = Igo exp - + /JgyBly] (2) where In and I9 are the transmitted two component radiation intensities respectively, and Ino and Igo are the corresponding intensities with the sample removed. By solving the egns (1) and (2) for m, and my, one can write the weight fraction of m*, w, and the density, p, as: v = m*/ (m* + niy) (3) or w = (PgyR - liay) / i - Jiny) -R (Mgx " ^gy)] (4) and p = (m* + m^/t (5) where t is the sample thickness, and pny are the one energy level gamma ray MAC values, and /igy are the other energy level gamma ray MAC values, and R is the logarithmic ratio defined as: R = In -- / In -- (6) ^no Igo The wt% measurement, lOOw, is insensitive to thickness (see egn (3)) for constant MAC values. The method is insensitive to the way material x is distributed in material y. For example, both egns (1) and (2) can be equally derived for a sample consisting of thin alternative layers of materials x and y, or for two quite separate layers of materials x and y, stacked one on top of the other.

It will be noted that this simple calculation does not require the thickness of the wool bale or meat box to be known. Integrating the measurement over the object volume sensed by the detector or detector array will give the overall weight fraction for that volume.

DESCRIPTION OF DRAWINGS & EXAMPLE The method of the invention will be further described with reference to the accompanying drawings, wherein: Fig. 1 schematically shows one form of measuring apparatus of the invention by way of example and without intending to be limiting, Fig. 2 shows another form of measuring apparatus of the invention, £ 8 9 1 Fig. 3 is a graph of the relative mineral content of raw wool against the pure wool content, found by experimentation, Fig. 4 is a graph of wool yield measured with the method of the invention against calibrated wool yield found by experimentation, !ifig. 5 is a graph of fat; content measured with the method of the invention against calibrated fat content found by experimentation for samples of beef meat, and Fig. 6 is a graph of measured fat content against calibrated fat content similar to Fig. 5 but for mutton meat.

Referring to Fig. 1, the apparatus shown comprises a conveyor 1 of any suitable form which carries the raw wool or meat typically packed as wool bales or meat boxes 2, the wool or lean meat yield of which is to be determined.

A collimator 3 produces a beam of radiation 4 and comprises sources 5 of higher energy and lower energy gamma radiation, positioned above the conveyor 1. For example, the beam may be about 4cm in diameter. The apparatus comprises suitable radiation shielding.

A detector 6 is positioned below the conveyor 1 and is supported by detection equipment including for example photo multipliers. The detectors and the detection equipment enable the energies of the gamma radiation to be detected after transmission through the wool bales or meat boxes.

Data processing facilities such as a computer are connected to the detection unit to process the data collected by the detectors. The determined wool yield for each bale or lean meat or fat content for each meatj box may be output in any desired form such as a display used by an operator, information to disk, a printout etc. There may be an associated reader which reads off identifying detail from the wool bale or meat box such as a bar code as it enters the apparatus and a printer which prints a label for the wool bale or meat box including identifying detail such as batch or grower data, bale or box number, as well as wool yield or fat content for that bale or box.

Fig. 2 shows an apparatus similarly comprising a conveyor indicated at 7 of any suitable form which carries the wool bales or meat boxes 8. The sources are contained in a shielded housing 9 above the conveyor comprising a shutter 10 over an exit aperture 11. The shutter is pivotally mounted as shown but could be a horizontally sliding shutter for example. The aperture may allow a mixed radiation beam typically about 40° wide to exit. 2 A 8 9 1 The shutter 10 is controlled to open for example by a control system including a sensor such as a beam extending across the conveyor 7 which is broken by an approaching wool bale or meat box moving into position below the sources. The shutter may be synchronised to stepping movement of the conveyor so that the shutter opens when a wool bale is moved into position below the sources, the conveyor stops for a present period to keep the wool bale beneath the sources while measurement is carried out, and so that the shutter closes as the conveyor moves again to convey the wool bale on, until the next wool bale is open when the shutter again opens etc.

A bank of detectors 12 is positioned below the conveyor. The detectors may comprise scintillation detectors composed of Nal (Tl) or BGO crystals, mounted on photomultipliers such as Phillips type XP4512B photomultipliers.

Fig. 3 shows relative mineral content of wool against pure wool content, referred to as wool base, found by experimentation and it can be seen that there is a generally systematic relationship of increasing mineral content with decreasing wool base. In Fig. 2 the data points show mineral content found by experimentation while the curve show the known wool base for the wool under test.

Fig. 4 shows wool yield measured with the method of the invention against calibrated wool yield found by experimentation. ^8 9 1 The line shows calibrated wool yield while the plotted data points shows the experimentally measured wool yield for a number of wool bales. Figs 5 and 6 are similar graphs, plotting measured fat content against calibrated fat content, found from measurements on boxes of frozen beef meat and mutton meat.

The following examples further illustrate the invention. t Example 1 Mini wool bales of approximate dimensions 0.5 x 0.3 x 0.2 metres containing raw wool were measured using an apparatus generally as shown in Fig. 1.

The source comprised a 241Am and 137Cs source in a housing which produced a well colliminated beam on the average about 2cm wide. The collimated path of gamma rays was defined by a lead block, with a hole 4 cm long and 0.5 cm in diameter. It is estimated that the beam entering the wool bale was about 0.5 cm in diameter and leaving the wool bale at the detector at about 4 cm in diameter.

The detector used was an Nal (Tl) Scintillation unit. The detector was positioned about 30 cm below the collimated gamma ray beam as shown in Fig. 1. The beam was intercepted by 2^8 9 a 7.5 x 7.5 cm Nal (Tl) crystal which constituted the senslxi volume of the detector.

The output from the detector was fed to a 113 Ortec preamplifier, then to an Ortec 671 main amplifier. A window was set on the photo-peak for the relevant gamma ray (60keV for 241Am and 660keV for 137Cs) using a timing single channel analyser (TSCA) . The pulses from the TSCA were fed to a Tenn-lec 1512 counter-scaler operated under computer control. The system was run to record the counts over 100 seconds. The experiment proceeded by recording the counts in the following sequence: Typically, the number of counts recorded with the wool bale in using the 241Am source was 6 million in 200 seconds. The number recorded with the 137Cs source was 660,000 in 600 seconds. Thus the detector count rates were 30,000 and 1,100 c/s respectively. These different rates reflect the fact that the 24iAm source size was about 100 mCi and the 137Cs source was 1 mCi. The 241Am gamma flux was pre-attenuated with about 0.5 cm aluminium to reduce the count rate from this source.

The mass per unit area for the wool bales under test was estimated and then from the results found above, the mass attenuation coefficient MAC values for 241Am and 137Cs gamma rays in the non-wool and wool yield components were calculated as follows: 16 2 A 8 9 1 6 MAC for a41Am gamma rays in non-wool = 0.0236 ± 0.0004 MAC for a41Am gamma rays in wool yield wool = 0.0188 ± 0.0001 MAC for 137Cs gamma rays in non-wool = 0.00754 ± 0.00003 MAC for 137Cs gamma rays in wool yield wool = 0.00754 ± 0.00C03 Knowing the MACs as above, and the gamma ray intensities determined by experimentation, the wool yi.eld of the wool bales was calculated using the equations given earlier, and it was also found that there is a systematic relationship between reducing mineral content and increasing wool yield for raw wool.

Example 2 Meat blocks containing refrigerated meat comprising a mixture of lean and fat were analysed using the apparatus generally as shown in Fig. 1 and as described in Example 1. Each block had the dimensions 34 x 17 x 6 cm, and had a specific fat content specified by MIRINZ (the Meat Industry Research Institute of New Zealand). The meat blocks were combined in threes, so that the radiations were transmitted through 3 meat blocks 6cm thick stacked one on top of the other. By changing the blocks of various fat content in the pile, the average fat content of the pile was changed. For beef blocks used in the study of the fat content of beef, the blocks used had wt% fat values of 1-74%. For the mutton blocks the fat contents values ranged from 1-82%.

The experiment proceeded by recording the counts in the following sequence. Using a) the 241 Am source the transmitted radiation with no meat box betveen the source and detector was recorded for 100 seconds. The count rate was typically about 47000 counts/second. The counts for this period were recorded twice. b) the 241Am source the transmitted radiation count was recorded for 100 seconds with the three meat blocks between the source and detector. The count rate was typically about 3700 counts/second. The counts for this period were recorded twice. c) The 241Am source was replaced with a 137Cs source and the counts recorded over 100 seconds. The typical count rate was 400 counts per second. The counts for this period were recorded three times. d) The counts with the 137Cs source and with the meat blocks removed were recorded over 100 seconds. The typical count rate was 1100 counts per second. The counts for this period were recorded three times.

The mass attenuation coefficient (MAC) values for 241Am and 137Cs gamma rays in fat and lean meat were calculated as follows (in mks units): 2^89 1 Beef: MAC for 241Am gamma, rays in beef lean meat = 0.01350 ± 0.00003 MAC for 24lAm gamma rays in beef fat = 0.01261 ± 0.00005 MAC for 137Cs gamma rays in beef lean meat = 0,005472 ± 0.00003 MAC for 137Cs gamma rays in beef fat = 0.005472 ± 0.00003 Mutton: MAC for 241Am gamma rays in mutton lean meat = 0.01336 ± 0.00003 MAC for 241Am gamma rays in mutton fat - 0.01238 ± 0.00004 MAC for 137Cs gamma rays in mutton lean meat = 0.005472 ± 0.00003 MAC for 137Cs gamma rays in mutton fat = 0.005472 ± 0.00003 Knowing the MACs as above, and the gamma ray intensities determined by experimentation, the systematic dependence of the dual gamma ray signature on fat content was demonstrated as shown in Figs 5 and 6.

In summary, the method and apparatus of the invention provide a non-invasive means for determining wool yield or lean meat/fat content. Machines may be installed at wool stores or at wool loading facilities at shipping outlets, or in meat works or pack houses, for example. Determination of wool yield from wool packs or lean meat content without opening or sampling the contents of the packs or lean meat content provides considerable commercial advantage. 2 A 8 9 1 The foregoing describes the invention including preferred forms thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated in the scope hereof.

Claims (21)

(WHAT WE CLAIM IS: 2 /'■ 8 9 1

1. A method of determining pure wool content in raw wool or lean content in meat or vice versa, comprising irradiating the raw wool or meat with gamma ray radiation from a first source providing gamma radiation of higher energy and a second source providing gamma ray radiation of lower energy, measuring the extent to which the gamma ray radiation is transmitted through the raw wool or meat, and determining the analysis by reference to the known attenuation coefficients of the ) components of the raw wool or meat for each energy level of the source radiation.

2. A method according to claim 1 wherein the energy of the gamma radiation from the first source is sufficiently high to ensure the interaction of the radiation with the wool or meat is principally by the Compton interactions.

3. A method according to claim 2 wherein the energy level of the radiation from the first source is in the range 1000 to 100 keV.

4. A method according to claim 2, wherein the energy level of the radiation from the first source is in the range 700 to 300 keV.

5. A method according to any one of claims 1 to 5, wherein the energy level of the gamma radiation from the second source is sufficiently low to ensure the interaction of the radiation with the wool or meat is principally by the photo-electro interactions. - 18 - 2!? 8 9 1

6. A method according to claim 5, wherein the energy level of the radiation from the second source is in the range 100 to 10 keV.

7. A method according to claim 5, wherein the energy level of the radiation from the second source is in the range 80 to 20 keV.

8. A method according to any one of claims 1 to 7, wherein the > transmitted radiation intensities through the wool or meat are measured by a detector or array of detectors and the analysis is carried out by computing apparatus connected to the detector(s).

9. A method according to any one of claims 1 to 8, wherein the first radiation source is Ceasium-137 and the second radiation source is Americium-241.

10. A method according to any one of the preceding claims, wherein the wool or meat is passed by a conveyor between the irradiating means and the transmission measurement means.

11. A method of detecting pure wool content in raw wool or lean content in meat or vice versa, substantially as described herein and with reference to the examples and accompanying drawings.

12. Apparatus for detecting pure wool content in raw wool or lean content in meat which comprises means which irradiates the wool or meat with gamma - 19 - £"s / o a .3 t. -i1 o S ray radiation from a first source of higher energy and gamma ray radiation from a second source of lower energy, means which measures the extent to which the radiation is transmitted through the wool or meat, and means which analyses the measurements by reference to the known attenuation coefficients of the components of the raw wool or meat for each energy level of the source radiation.

13. Apparatus according to claim 12, wherein the energy of the gamma radiation from the first source is sufficiently high to ensure the interaction of the radiation with the wool or meat is principally by the Compton interactions.

14. Apparatus according to claim 12, wherein the energy level of the radiation from the first source is in the range 1000 to 100 keV.

15. Apparatus according to claim 13, wherein the energy level of the radiation from the first source is in the range 700 to 300 keV.

16. Apparatus according to any one of claims 12 to 15, wherein the energy level of the gamma radiation from the second source is sufficiently low to ensure the interaction of the radiation with the wool or meat is principally by the photo-electro interactions.

17. Apparatus according to claim 16, wherein the energy level of the radiation from the second source is in the range 100 to 10 keV. -20 - 2/-.8 91

18. Apparatus according to claim 16, wherein the energy level of the radiation from the second source is in the range 80 to 20 keV.

19. Apparatus according to any one of claims 12 to 18, wherein the transmitted radiation intensities through the wool or meat are measured by a detector or array of detectors and the analysis is carried out electronic measuring and computing apparatus connected to the detector(s). >

20. Apparatus according to any one of claims 12 to 19, wherein the first radiation source is Ceasium-137 and the second radiation source is Americium-241.

21. Apparatus according to any one of claims 12 to 20 comprising a conveyor which passes the wool or meat between the irradiating means and the transmission measurement means. WEST-WALKER McCABE Per: ATTORNEYS FOR THE APPLICANT -21 -