Finding a cure for ham
Some people like a very salty, dry-cured ham, others want their ham moist and mild. Whatever their preference, they want their ham to be more or less the same every time they buy it. "The problem is that the salt content of ham varies enormously," says Torunn Thauland Håseth.
On 13 March 2009, Torunn Thauland Håseth has her doctoral disputation, under the title "Analysis of salt in dry-cured ham and dried salted cod using computed tomography" at Nofima Mat. The scholarship is with the Dept. of Chemistry, Biotechnology and Food Science at the Norwegian University of Life Sciences (UMB), but most of the field work has been done at Nofima Mat and the UMB’s Dept. of Animal and Aquacultural Sciences. Torunn is employed at Animalia, where she will continue to work on cured meats. A CT scanner can measure the salt content of ham without destroying it. In Thauland Håseth’s view, this can solve many problems for ham producers and consumers.
Judgement has been passed by consumer tests, sensory analyses from the professional tasting panel at Nofima Mat and chemical analyses: the salt content of Norwegian cured ham varies enormously! Everybody agrees that this is a problem, but finding a solution has been difficult. Some cured meat products contain little salt, others a great deal. "That’s good, because we all have our own favourites. But there are still big variations among products of the same type, even from the same producer, and also between identical products on the same shelf in the shop. And if you take a whole ham, there are big differences depending exactly where you cut into it," says the ham expert with the new doctoral thesis on exactly this topic.
Analysed = destroyed
"Ham producers can make different types of ham for different consumers, and thereby get a better price on the market. But they then have to know how much salt is actually in their products. At the moment they must analyse the salt content chemically – but of course this ruins the ham," continues Torunn Thauland Håseth. There has never been a method of measuring a ham in several places without also destroying the ham. Until now.
Nofima Mat has been working with several other research centres to test computed tomography (CT) as a method for analysing the salt content of ham and cod, without destroying the product (a process known as non-destructive testing).
Controlling the process
The connection between CT and salt was first demonstrated in the late 1980s, but only in recent years has it come back into the spotlight. "We have measured the same ham many times during the salting and drying processes. The conclusion is that the CT scanner is a method of developing and controlling the process, so that the ham producers can get exactly the salt content they want in their products," says Torunn Thauland Håseth. It is also a method that producers can use to learn about variations in their own raw materials, so that they can achieve the most even quality in their hams.
Less precise in cod
Many are familiar with CT scanners from hospital examinations and in principle it is exactly the same machine that is used. UMB has a CT scanner that is used on animals and fish and this is the one that has been used in the trials. In her doctorate work, Thauland Håseth has mainly concentrated on ham, but has also taken similar measurements of cod. "Here the measurements were much less precise. But CT can also be used in the fisheries industry to learn about salt content and to control processes. However, there are still some hurdles to be cleared before CT can be used continuously in the production of ham, not the least of them price. At the moment, CT is only a tool for developing and optimising processes in collaboration with a research centre," stresses the new doctoral candidate.
The potential of computed tomography (CT) for non-destructive analysis of salt in pork has previously been demonstrated. However, many aspects of CT in relation to salt analysis are not fully understood. The aim of this work was to study computed tomography as a tool for non-destructive analysis of salt in ham and cod. Both authentic samples from the production of dry-cured ham and dried salted cod, and designed model samples, were studied.
The results showed how the prediction accuracy of salt varied with chemical composition of the samples, with the inclusion of fat, protein or water content, and with the voltage setting of the CT scanner. The prediction accuracy for salt was maximised by minimising the sample "background", which is the chemical composition other than salt.
Salt predictions in hams were particularly sensitive to large variations in fat content. Predictions in lean meat were more accurate. With larger variations in fat content, information on this variation was essential to allow for good calibration results. This information could be obtained by scanning at two or more voltages. Large variations in degree of drying also hampered the accuracy; however, final salt contents of dry-cured hams could be predicted by combining CT value after the salting stage with further weight loss during production.
Salt predictions in cod were less accurate compared to ham. The accuracy was the highest during the first phase of the salting process when the largest increase in salt content was observed. The accuracy was lower through the slower equilibration period and in dried samples. The use of CT to measure water and protein in cod was also investigated, and gave promising results for water.
When summarising the findings of this thesis, CT showed good results for non-destructive measurements of salt, given a calibration in the relevant compositional range. The variation in components other than salt should be limited, or additional information on this background variation should be included.