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In-line process control in the meat industry

25 September 2014

Laboratory analysis of meat and meat analysis is common to the food and often remains the legal means of declaring a result. However, due to the delay in obtaining results and the potential for widely differing results from the same batch, the industry has long sought rapid in-line analytical methods. Various methods exist but, Richard Batty, Meat Key Accounts Manager at FOSS discusses the different methods for the most common and important parameter; fat content.

The majority of meat used for processed foods is graded by Visual Lean (VL – literally ‘by eye’) and is produced by operators at the boning halls, dividing meat trimmings and cuts visually based on experience. This of course is carried out at speed on a processing line and is subject to large differences and variations between batches and boxes of the same VL grade.

A number of technologies for rapid fat analysis are available today. Each has its advantages and disadvantages. All methods for rapid analysis are based on ‘indirect’ analytical methods. That means the result is not from a direct measurement, as is the case for many of the traditional laboratory methods, but should be closely correlated to a direct method and this should be carefully explored with the manufacturer. As they are indirect methods, they periodically have to be verified against the reference methods. 

The choice of technology depends on the application. With X-ray transmission on a meat conveyor belt, all meat is measured and foreign objects can be detected. This technology works well with very inhomogeneous meat or mixtures and can measure both fresh and frozen meat. Parameters include fat, weight and foreign objects.  With most NIR methods, more parameters (fat, protein, moisture, collagen etc.) are available, but only a small sample of the meat is measured – consequently, the sample must be homogenous and representative of the whole batch under review. 

The use of rapid fat analysis can typically be divided into at-line analysis based on sampling and a number of in-line application.

At-line (bench/lab) solutions
This type of analytical method has been used in the meat industry for the past two decades. 
Compared to in-line analytical solutions, at-line and laboratory solutions have the serious dis-advantage that only a small fraction of the total batch is analysed, but this method can be very accurate for the sample under review. The challenge is to take a representative sample of the whole batch and experience and data review shows that this is difficult to do.

Surface scanning in-line solutions
A number of available fat analysers assess the fat content from scanning the surface of the meat (NIR reflection and NIR lateral transmission).

Using lateral transmission instead of reflection is in some cases an advantage as the light penetrates deeper into the meat. This makes the measurement less sensitive to the meat size and a larger portion (but still typically less than 20% of the batch is measured).

The solutions are normally placed after the first grinder (coarse grinder) since they do not work well with very inhomogeneous meat, i.e. VL trim. Adjustment for fat content (fat standardisation) can be made before the final grinding takes place if the scanning shows a deviating fat level. Even though these solutions are placed in-line, not all the meat is measured and that is the main disadvantage. 

In-line methods scanning through some of the meat
For ground meat based production, a couple of analytical solutions scanning through part of the meat are available. The solutions are based on microwave or X-ray technol¬ogy. The microwave solution, mounted on the tube of the coarse grinder, measures the moisture content in the meat and based on that value an indirect estimate for the fat content is calculated. The offered microwave solutions can be mounted on the tube of an existing grinder. The microwave solutions have the disadvantage that they can only measure fresh meat. It cannot be used for frozen products.

X-ray is the only technology which can measure all of the meat on a conveyor, regard¬less of the size of the meat pieces, whether it is packaged or not, or whether it is fresh or frozen. Cutting and boning plants can employ X-ray technology for optimising the fat content in their trim categories while at the same time checking for foreign objects, both for trimmings in cartons or in large 1000kg combos. The material can now be sold as Chemical Lean (CL) grade with much tighter tolerance. Similarly, processors can do the same thing and check incoming materials for conformity and mix VL grades to hit a specific and accurate CL at a batch level.

When it comes to process instrumentation, it only makes sense to measure if you can also alter it. The key is finding the critical point for monitoring and then the correct technology in order to adjust and more importantly optimise a process line. If your process needs to check meat in packaging (both fresh and frozen) and is dealing with in-homogenous samples (typically trim), this would generally lead to the monitoring point being right at the start of the process using X-ray technology. Whatever the method used, however, the use of rapid analytical methods in production is all important for meat producers, both in terms of product quality and financial gain.  

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