WO2006137750A1

WO2006137750A1 - Measuring fat content of meat

Info

Publication number: WO2006137750A1
Application number: PCT/NZ2006/000162
Authority: WO
Inventors: Douglas Moreland Phillips; James Langley Grogan; Terry Dean Kemp
Original assignee: Mercer Stainless Limited
Priority date: 2005-06-24
Filing date: 2006-06-26
Publication date: 2006-12-28

Abstract

A method and apparatus for measuring the chemical lean content of meat in which gas or air as a buoying fluid is used to carry out the measurement of meat density for the purposes of measuring chemical lean content of the meat. The method includes the step of direct measurement of the density of the buoying fluid. It is thus possible to overcome adiabatic issues and to speed up the cycle time of successive measurements.

Description

TITLE OF THE INVENTION MEASURING FAT CONTENT OF MEAT

BACKGROUND TO THE INVENTION

This invention relates to a method and apparatus for the measuring of chemical lean content of meat.

Buyers of meat generally have a stringent specification that needs to be met by the meat supplier or processor. One of the most important aspects of a buyer specification is the fat content of the meat or correspondingly, as it is commonly expressed, the percent chemical lean. Thus, a buyer specification might be somewhere in the range of 80-90 chemical lean.

A problem that faces the meat supplier is how, in a viable commercial operation, to calculate the chemical lean content of the meat. One method is to assess the chemical lean subjectively by visual observation during packing of cartons in a boning room. The person processing the meat will, therefore, remove or trim from the meat the amount of fat that it is believed needs to be removed in order to met the buyer specification.

More accurate means of determining the chemical lean can be used but as will be explained hereafter they are often not commercially viable either because of slowness of the method of calculating the chemical lean or because of high capital plant costs.

The practical downside of incorrectly determining the chemical lean content of meat is realised when the buyer carries out sampling of meat. By not being certain whether the supplied meat has a chemical lean which is too low or too high, the meat producer either provides the buyer with more meat than is being paid for or faces financial consequences arising out of meat being too low in chemical lean. These financial consequences can, for example, arise out of the buyer rejecting a shipment. Either way the meat supplier faces significant economic loss. Hence there is a need to provide a commercially viable and accurate means of determining the chemical lean of meat at the time of packing.

A method of determining the chemical lean content of meat that is currently being used is based on measurement of the density of boneless meat. Fat has a stable specific gravity

(density) of 0.95 while meat is also stable at 1.07. This difference is exploited in order to measure the fat content of the meat. A known method involves taking a 3kg sample from a carton of meat, vacuum packing it, and then weighing the pack in air and in water. The vacuum packing is needed to eliminate entrained air as well as make it practical to immerse the sample in water.

The results can be used to calculate sample density. This method, however, is slow, is invasive due to sampling, and requires water immersion. Even though a large sample is taken, the sample may not necessarily be representative because of the variation in each carton of meat product.

Sampling of meat product, but with consequential loss of valuable meat, arises with chemical analysis such as the Soxhlet method of chemically determining the fat content of meat. In practice, a sample is taken from a carton by boring a number of plugs from its meat content. The plugs are minced and a sub-sample is taken for analysis in the Soxhlet apparatus.

The Soxhlet apparatus cycles distilled solvent through the sample until, after a prescribed period, all of the soluble fat content is deemed to have been transferred from the sample to a re-boiling vessel. The solvent in the boiler is evaporated off and the vessel weighed for content (fat).

While this test can provide accurate results care needs to be taken in handling the sub- samples used. In view of the time taken, and the cost of each Soxhlet analysis, it is not a practical method of determining chemical lean content for a commercial meat processing operation.

It is also known to use X-ray methods to measure the chemical lean content of a packed, and often sealed, carton of meat, so that if there is an issue with the lean content the carton can be diverted back to the packing facility. However, not only is an X-ray machine a high capital cost piece of plant, it does not solve the problem facing meat processors where it is generally agreed that a chemical lean measure should take place at or before the point of packing. Also reliability issues exist with known X-ray methods and thus an accurate or consistent measurement cannot be assured.

The laboratory gas pycnometer is a commercial instrument available to determine the density of small samples of solid and porous materials between about 20 and 100 grams weight. The gas (most often helium) pycnometer has been used extensively to measure the true density of materials, especially powders, to an accuracy of up to four decimal places. The instrument depends on accurate measurement of the temperature (sometimes by atmospheric equilibration) and pressure of the gas being used in the system in order to determine the volume displaced by the sample.

While older helium pycnometer instruments can provide a reading within 30 minutes there are more modern instruments that are able to produce readings of similar accuracies but in a time of two to three minutes. While, therefore, a gas pycnometer could be used to measure the density of meat containing fat, its speed of operation is too slow for most applications in a meat processing plant.

Patent specification WO 02/25244 describes a method of determining the density of minute samples of material (super conductor) using gas (C2F6) as a compressible buoying fluid and Archimedes principle. Adiabatic issues are handled by waiting for temperature and pressure to stabilise before readings are taken. The significant delay created by the need for temperature stabilisation means that the method described in WO 02/25244 is only better than the helium pycnometer for handling the very small samples that are described in the patent specification.

SUMMARY OF THE INVENTION

There are thus limitations with the methods and apparatus known for determining chemical lean content of meat. It is thus an object of the present invention to provide a method and apparatus for use in determining the chemical lean content of meat and which provides an improvement over prior art methods and apparatus.

Broadly according to one aspect of the present invention there is provided a method for measuring the chemical lean content of meat, the method being characterised by the application of gas or air as a buoying fluid to carry out the measurement of meat density for the purposes of measuring chemical lean content of the meat.

In a preferred form of the invention, the method also includes the step of direct measurement of the density of the buoying fluid. By the direct measurement of the density of the buoying fluid it is possible to overcome adiabatic issues and to speed up the cycle time of each measurement.

According to a second broad aspect of the invention there is provided apparatus for the measurement of chemical lean content of meat, the apparatus being characterised by including a chamber incorporating weighing means and into which meat, for which the chemical lean content is to be measured, can be placed, means for increasing the air or gas pressure within the chamber and means for calculating density and as a result enabling chemical lean to be determined. In a preferred form of the apparatus there is further included an air density probe and means for monitoring changes in air density. The apparatus further includes means for relating changes in air density to changes in weight of meat as sensed by the weighing means.

It is believed that the present invention will enable whole carton quantities of meat to be used for measuring chemical lean content thereof and that, as a result, a more rapid means of measurement can be achieved in a commercially viable manner. By directly, measuring the gas density rather than using indirect means via temperature and pressure measurement, the adiabatic issues associated with some of the known methods of determining chemical lean content of meat, can be overcome.

BRIEF DESCRIPTIION OF THE DRAWINGS

Figure 1 is a schematic illustration of apparatus according to one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

The method and apparatus according to the present invention will hereinafter be described in more detail. In doing so the description will describe an apparatus, and from this description, the method according to the present invention will be apparent.

Modern load-cell technology enables the use of relatively low pressures when gas or air is used as a buoying fluid. Thus, in a preferred embodiment of the present invention, a weigh scale load-cell system incorporating one or more load-cells is enclosed by a chamber 10 capable of retaining air at a pressure of up to 2 bar (gauge). According to the preferred form of the invention the weigh apparatus uses one load-cell as a trade certifiable scale 1 1 and a second more sensitive load-cell 1 2 as the one for buoyancy measurement. The buoyancy load-cell 12 has a built in tare that makes it unsuitable for trade use. The tare enables a low range cell (3kg) able to carry a carton load (27.5kg) and to measure the 3kg of weight in the range of interest. This makes the system 10 times more sensitive than using the 30kg cell of the trade scale. The carton weight is physically transferred from the trade cell 1 1 to the buoyancy cell 1 2 as, or just after, the lid 1 3 of the chamber 10 is closed.

It will be appreciated by those skilled in the art that the different means of transferring the load from the scale 1 1 to the buoyancy cell 12 can take different forms. One form is shown in Figure 1 .

According to this form of the apparatus the trade scale 1 1 is carried by a bridge or support 14 which is in turn supported on or coupled to the piston rods 1 5 of load transfer cylinders 16. In the illustrated arrangement the load transfer cylinders are physically located externally of the pressure chamber 10 with the piston rods extending (via suitable seals) into the chamber 10 to engage with the support 14.

The meat is located in a meat tray 1 7 which sits on a support 1 8. Coupled with the trade scale 1 1 is an engagement member or assembly 19 which is engageable with the support 1 8 such that the meat tray 1 7 is supported by the trade scale 1 1 .

A second engagement member or assembly 20 is coupled to the buoyancy cell 1 2. This assembly 20 is arranged such that upon actuation of the load transfer cylinders 16 the relative position of the engagement members/assemblies 19 and 20 changes whereupon the support 18 becomes engaged on the support member/assembly 20 and the meat is thus supported by the buoyancy scale 1 2. Within chamber 10 and subjected to the same air pressure conditions will be a third load- cell 21 which carries a body 22 of material of known volume and that has a known (measured) density. This third load-cell 21 with associated body 22 of material can be likened to a probe 23 as will hereinafter be apparent.

The body of material 22 of the probe 23 can be of a material suitable for the end purpose. It is, therefore, envisaged that the body of material 22 will have a specific gravity as low as possible, typically one created by enclosing a vacuum with a lightweight rigid vessel to create a low-weight high-displacement probe. In this manner the probe will demonstrate the highest sensitivity to air density changes.

The effect of the air density (due to pressure and temperature) on the probe 23 ensures that the air density can be directly monitored and tracked as it changes. The use of the probe 23 therefore avoids the need for calculation of air (fluid) density from temperature and pressure and the attendant adiabatic issues that can cause errors. As previously outlined, temperature measurements can lead to delays because of settling times needed to reduce errors. It is, therefore, believed that by use of the probe 23, in the chamber 10, a more rapid response can be achieved, therefore, significantly reducing the time taken to determine the chemical lean of a sample of meat.

According to a preferred form of the apparatus a conveyor system (not shown) will be used to direct trays 1 7 carrying carton loads of meat product to a weigh/chemical lean measurement station. With the chamber lid or hood 13 in an open position, product can be exchanged to produce the carton target weight using the trade certified weigh scale 1 1 and associated electronics 24. The electronics 24 is coupled to all three scales 1 1 , 1 2 and 21 and is in turn coupled to computer 25. The chamber lid or hood 1 3 can then be moved into a closed position so as to create an enclosed and sealed chamber. At this point a check would normally be made to ensure that there is no interference with the weigh system and hence the measurements resulting therefrom. The air pressure in the chamber (which can be monitored via a pressure gauge 26) is then increased to a set or predetermined level while readings are taken by computer 25 via unit 24 from the product buoyancy weight scale 1 2 and also the air density measurement probe 23. As illustrated in the drawing the air supply 27 is coupled to the pressure chamber 1 0 via a regulator 28 and a pressure control valve 29. Adjustment of the regulator enables the desired pressure in the chamber to be achieved.

Continuous calculation of density for chemical lean determination is envisaged as being part of the method of the present invention, as this may help the cycle time of the measuring process, because once a stable reading is achieved, venting of air from the chamber can commence to bring the measurement cycle to an end.

According to the invention the method thus involves monitoring the density of the air in the chamber by calculation of air density from its effects on the mass of known volume (ascertained during system calibration) of the body of material of the probe 23.

This approach avoids adiabatic issues that are error prone due to their sensitivity to the measurement of air temperature and the effects of sensible and latent heat factors for gases and any moisture contained in the fluid. Continuous measurement of the air density during pressurization also has the side benefit of monitoring the product for any compressible air inclusions that will cause its volume (and hence density) to change with pressure. The observed effect is a changing product density with pressure (i.e. the buoyancy change with pressure is non-linear).

The approach requires careful consideration of the variables involved. The mass must be calculated first from the known air pressure (atmospheric) and the volume of the body of material.

Forces acting on the body of material of the probe include the actual weight of the cube (mg) hydrostatic forces and an applied force Fa to maintain the cube in static equilibrium. It will be appreciated by those skilled in the art that the applied force Fa is equivalent to the apparent weight of the cube at the particular air pressure. This can be represented by formula (1) below

Fα_x = mg -p_xVg (1 )

Note: pVg is the buoyancy component where p is the density of the buoying fluid and V is the volume of the mass involved (same for both the mass and the air displaced). It reduces the apparent weight and so it is subtracted from the force due to mass and gravity.

then Fa_x = g(m - p_xV)

Fa, and — - = m -p_xV

S

Fa therefore m = — - + P₁V g

Inserting the value for mass into (1 ) at high pressure gives the density p₂ of air at that pressure.

P₁ and p₂ are then available for substitution into equation (2) below which provides the density of the product being measured.

_^ Fa_xP₂ -Fa₂P₁

Po ^~ F ^a₁ -F ^~a₁ W

Equation (2) enables the calculation of meat product density from two known air (or gas) densities. These air densities being measured as disclosed herein. In the above it is assumed that p₂ can become p_x as a new gas pressure is attained - the case for monitoring the density of the gas and the product as the pressure increases.

Meat as a product and meat containing fat is normally incompressible and will, under the influence of increased air pressure maintain a constant volume. A constant product volume represents a linearly increasing buoying effect as buoying fluid (air) pressure increases.

However, meat product that is compressible i.e. contains air, will not present a linear density progression with increasing air density. Thus, measurements that do not show a linear increasing buoying effect can be used to flag meat product as being unacceptable for chemical lean assessment.

Product that may fall into this category is trim product (small portions). However, it might be possible to reduce or eliminate the problems associated with compressible meat product by extracting the air from between the meat portions of the meat on the tray by incorporating an initial vacuum step. Thus, for meat product that may present this problem the operating procedure of the apparatus can include a vacuum source (pump) 30 which via control valve 31 can apply a vacuum to the interior of the chamber 1 0 as to extract the air between the meat portions followed by the application of air pressure as described above.

It will be appreciated that the gas in the chamber will also buoy the weighing apparatus. This will, therefore, need to be taken into account in the measurements. Although the density of the meat product on the tray within the camber can be calculated from the absolute input provided by the load-cells of the product buoyancy weight scale it is possible to measure chemical lean by empirical means from the same information. The buoying air density value provided by the probe load-cell describes the extreme values of buoyancy possible for pure meat and pure fat (see Figure A below) and thus the range available for chemical lean assessment at a given air density. This assessment range is linear from pure meat (1 00% chemical lean) to pure fat (0% chemical lean).

Chemical Lean Measurement by Buoyancy Buoyancy effects at different air pressures (densities)

3 4

Measurement Chamber AIr Pressure (bar-gauge)

Figure A

At each measure of air density the range describing 0 to 100% chemical lean is known and the chemical lean of the product can therefore be assessed empirically since the relationship is linear.

To further describe the invention in a practical application the following outlines a calibration procedure of the system.

Before the chemical lean measurement system can be utilised it will necessary to calibrate each scale individually as if it were a weigh scale and then to follow this by calibrating the buoyancy measurement system. The buoyancy system, as described, includes the buoyancy scale 12 and the air density weigh cell system (probe 23).

Both the buoyancy scale 12 and the air density measurement system (probe 23) and their loads are affected by changing air pressure whether the change is created by the vacuum provided to eliminate entrapped air pockets in the product being measured or by the air pressure used to increase the buoying fluid density as part of the density measurement process. Whether the buoying fluid density is created by the vacuum or pressure is not material to the function of the system except that the greater the pressure differences between data points the greater the accuracy of the overall system. Capturing data at maximum vacuum and again at a pressure of 2 bar provides an air pressure or buoying fluid difference of three atmospheres, or approximately 3.8 grams/litre.

An issue to be addressed in calibration of both the buoyancy scale 12 and the probe 23 is the affect a change buoying fluid density has on the cells themselves, independently of the loads applied to them. For instance, in the case of the buoyancy cell 1 2, the bare cell with product tray 1 7 and support system (18, 20) will be buoyed by increasingly dense chamber air. The proportion of the load-cell mechanics providing any part of the buoyancy signal is difficult to calculate because of the complexity of the cell mechanics. The effects of the tray 1 7 and the support structure (1 8, 20) are less complex but best measured in-situ because of contamination and the need to keep errors low.

A similar situation exists for the air density measurement cell 21 . The volume on the cell 21 can be accurately measured so that the effect of this volume being buoyed in higher density fluid can be calculated, but, a proportion of the load-cell 21 also displaces some of the buoying air involved and will have its own influence on the system.

In both cases above the effects of portions of the load-cell mechanics on the final data produced can only be discovered via careful system calibration. It is convenient that both the buoyancy measurement load-cell 12 and the air density measurement load-cell probe 23 be calibrated together in the same operation. This approach also provides for the highest overall system accuracy. The procedure is as follows.

The trade scale 1 1 is a conventional weigh scale and can be calibrated as such.

The scale system is firstly zeroed with all trays/bins in place.

A calibration weight near full scale (27kg) is then placed in the scale 1 1 and the span of the electronics to display this weight is adjusted.

Using combinations of calibration weights, the scale 1 1 is checked at other points to ensure that the correct weight is displayed within the limits prescribed.

It is then necessary to ensure that the scale 1 1 returns to read zero when all of the calibration weights are removed from the tray/bin 1 7.

A trade scale will generally have mechanical overloading limits to prevent damage to the load-cell in the event that heavy loads are dropped on the tray/bin 17 or a full scale load is placed on one corner or edge of the tray/bin 1 7. Usually adjustable mechanical limits are provided at each corner of the frame.

The procedure is to place 1 /3^rd of the full scale capacity of the scale on the corner over the limit bolt and then to adjust the limit so that the weight indicated is just clear of interference according to the displayed weight. This is repeated for all four corner limits.

Under load or negative load limits are not required. The buoyancy measurement via buoyancy scale 1 2 has (as previously disclosed) a built in tare facility that enables a 3kg load cell to measures small changes in the weight of a large load (e.g. grams in a 27.3 kg carton of meat), a typical check-weigh cell application. The cell 1 2 is set up with tare of 25.8 kg so that at least this amount in calibration weight must be used to set the low end of the cell weighing range. Additional calibration weights will set the upper limit of the range. The accuracy requirements of this scale mean that calibration should be performed very carefully with the correct weights.

The air density cell 21 will not require any actual formal calibration. It is sufficient to place a small calibration weight (10 grams) on the cell 21 and to observe a change in the displayed output of about 300 units. This operation can be performed with the cell assembly on a test bench.

The mechanical under and overload settings on this cell 21 are important to its successful use and handling. The cell 21 is a very sensitive one that is easily damaged by rough handling, especially if the mechanical limits are not set.

The following operation will generally be performed on a test bench.

With the assembly active, the calibration nut is removed from the volume on the assembly (this simulates an increased buoying fluid density). The under-load screw setting is adjusted until it just avoids interfering with the displayed reading. It is necessary to ensure that the display stays steady while locking the screw in place.

The calibration nut is reinstated and a 50 gram calibration weight is loaded onto the top of the volume. The overload lock nut is set so that it just avoids interfering with the displayed reading.

The cell 21 will thus be ready for use. The system needs to be set up and calibrated so that the true relationship between the information captured and density is established. This calibration needs to include the air density measurement system so that compensation in calculations for air density can be accomplished. The procedure is relatively straightforward.

The procedure establishes at least two values for the buoyancy of a calibration fluid (water) so that the effects of systems hardware - both the buoyancy scale 12 and the air density monitor 23, can be factored out simultaneously.

It is assumed that the scales are properly calibrated as above. The following procedure is then carried out.

Step 1 - The bin 1 7 is placed on the trade scale 1 1 and tared.

Step 2 - The bin 17 is filled with water to register about 25.9 kg.

Step 3 - The lid 13 of the chamber 1 0 is closed and weight, buoyancy and air density measurements are captured.

Step 4 - The chamber pressure is taken up to 2 bar. After waiting for the air density cell 23 to stabilise buoyancy cell 12 and density cell data 21 is captured.

Step 5 - The chamber 1 0 is exhausted and opened. Approx 2.8 litres of water is added to the bin 17.

Step 6 - The chamber lid 1 3 is closed and the weight, buoyancy and air density data is recorded. Step 7 - The chamber pressure is taken up to 2 bar, and the pressure regulator 28 carefully adjusted to obtain a stable air density value the same as in step 4. Weight, buoyancy and the density data is captured.

Step 8 - The density cell 21 reading is checked within the bounds of the previous reading in step 4.

Step 9 - The coefficients of the equation that defines the effects of the buoyancy scale hardware against the air density measurements are calculated (Fs as illustrated in Figure B).

It is possible for the system to automatically capture and process the data from the above procedure, essentially automating the calibration of the buoyancy scale and the air density cell in a single operation.

The equations for calculating Fx and thus the coefficients for Fs are:

F₂ -F^ F₁ -F_x

(D

So that

Where: Vi is the volume of water calculated from weight and temperature at the lower end of the buoyancy scale range (25.9 kilograms ±50 grams).

Vis is the volume added and calculated from the weight and temperature of water added to the buoyancy scale (2.8 kilograms ±50 grams) Fi is the buoyancy produced by Vi at the stable high air density (p₂). F2 is the buoyancy produced by V_? at the stable high air density (p₂).

Fx is the buoyancy of the scale system (buoyancy scale only) at the stable high air density Calculation of scale buoyancy effect and calibration of density load cell can since all follow are

value

value plus

kg of water -2 8

Figure B Illustration of buoyancy scale and air density cell calibration

From the above it can be seen it is essential that the two data groups captured for the calibration are done so at the same air density as measured by the air density load cell system. The cell is calibrated in and displays arbitrary units which are only needed for calibration.

Calculation of the scale effects for any particular air density measurement then becomes:

From the straight line equation form y = mx + c and taking values form the chart above:

or

Where Fs is the buoyancy force due to the buoyancy scale hardware at the measured air density of p_x .

p_x can be a value less than p_x (or air density due to atmospheric pressure) in which case Fs will become negative. This will happen if a value for determining product density is captured during the vacuum phase of the CL measurement procedure cycle.

The system should be self-adjusting for variations in atmospheric pressure (or density) due to barometric or temperature effects.

The use of Archimedes principle to measure the density of meat containing fat in accordance with the present invention assumes that only two variables are present i.e. meat and fat. The introduction of a third variable, however, such as bone or some other foreign material can, therefore, introduce an error. Some known foreign material or bodies such as carton materials, can effectively be compensated for provided their characteristics are stable.

Bone has a relatively high density and as a result it will, up to certain level, produce an error in the chemical lean assessment. Any higher levels will produce an error so obvious that the product density would exceed 100% chemical lean and it would be apparent from the readings that the product being evaluated would need to be investigated. Accordingly the detection of bone in the product mix would be almost certain and therefore give a reading that would indicate inspection of the product was required.

The effect of other foreign bodies would depend both on their density and quantity. For example, with plastic, the effect of a plastic foreign body would depend on its density and quantity. Some plastics have a density near that of water and therefore relatively large quantities would need to be present in order to present an obvious error reading. According to the present invention the best results will be achieved when product is presented on a clean non-porous surface such as a tray that has known physical properties (density, volume, weight). For this reason it is preferred that no carton material be present. Even though it would be possible to compensate for the presence of a carton or a known amount of carton material. However, the uptake in or on carton material of another material such as water introduces an unknown that will represent an error. In any event the effects of compressed air (gas) on carton material could lead to distribution of fibre from the carton material when air is swirling as it is introduced and then released from the measurement chamber thereby causing deposits of the material onto the product.

The effects of temperature of the meat product being measured can have a bearing on the accuracy of the readings. However, it is believed that it will be possible to make adjustments for temperature of product ranging from chilled through to hot boned, initial calculations indicate that a 10° change in product temperature produces an error in the chemical lean assessment in the order of about 1 %. Chilled meat has a temperature variation of within less than 5° and hot boned less than 10°.

It is therefore believed that the present invention by measuring density with air/gas being the buoying fluid will provide a means of measuring chemical lean of meat in a manner which is sufficiently accurate and within a suitable time frame for the method to be commercially viable. However, in a more preferred form of the invention, direct measurement of air density means that temperature and pressure need not be measured as the chamber pressure will be controlled by the effects of the probe i.e. by the measured value from the probe load-cell controls air into and from the chamber to alter air pressure and thus air density.

Claims

CLAIMS:

1. A method for measuring the chemical lean content of meat, the method being characterised by the application of gas or air as a buoying fluid to carry out the measurement of meat density for the purposes of measuring chemical lean content of the meat.

2. The method of claim 1 including the step of direct measurement of the density of the buoying fluid.

3. The method of claim 2 wherein measuring takes place in a chamber and includes the step of increasing pressure within the chamber.

4. The method of claim 3 wherein the pressure is increased up to 2 bar (gauge) or greater as necessary to achieve system accuracy.

5. Apparatus for the measurement of chemical lean content of meat, the apparatus being characterised by including a chamber incorporating weighing means and into which meat, for which the chemical lean content is to be measured, can be placed, means for increasing the air or gas pressure within the chamber and means for calculating density and as a result enabling chemical lean to be determined.

6. Apparatus as claimed in claim 5 further including an air density probe and means for monitoring changes in air density.

7. Apparatus as claimed in claim 6 further including means for relating changes in air density to changes in weight of meat as sensed by the weighing means.

8. Apparatus as claimed in claim 5 or 6 wherein the air density probe is a load cell which carries a body of known volume and known density.

9. Apparatus as claimed in claim 8 wherein the body of material has a specific gravity as low as possible.

10. Apparatus as claimed in claim 9 wherein the body of material is composed of a material which substantially does not absorb water.

1 1 . Apparatus as claimed in claim 10 wherein the material is a displacement volume containing air or a vacuum or consists of some other suitable material.

12. Apparatus as claimed in any one of claims 5 to 1 1 wherein the weighing means includes a trade certifiable scale.

13. Apparatus as claimed in claim 12 wherein the weighing means includes a load cell for buoyancy measurement, the load cell having a built in tare.

14. Apparatus as claimed in claim 1 3 wherein the tare is such that the load cell is a low range load cell able to carry a predetermined load of meat.

1 5. Apparatus as claimed in claim 14 wherein the low range load cell is rated to carry substantially 3kg and tared to handle a predetermined weight of a carton of meat in the vicinity of 27.5 kg.

16. Apparatus as claimed in any one of claims 12 to 14 further including means for transferring the load from the trader certifiable scale to the buoyancy measurement load cell.

17. Apparatus for the measurement of chemical lean content of meat as claimed in any one of claims 5 to 16 substantially as herein described.

18. The method of any one of claims 1 to 4 substantially as herein described.