Anyone who loves Italian food is likely to have a strong opinion about the best texture of cooked pasta. But how can you gauge this?
And therefore give real, practical cooking tips? Or even know what type of pasta you prefer? Particularly as there are so many different factors affecting the texture of cooked pasta: length of cooking time, length of time left standing, size and type of pasta, as well as the brand itself. I know when I was a student the best method was always considered to be throwing a strand of spaghetti at the wall and seeing if it stuck; but looking back I think this method was more for the food fights which usually followed. Thankfully the food manufacturers have developed a more scientific method for testing the firmness of pasta, but even this is fraught with complications.
Until recently using trained panellists was considered the best tool for measuring the cooking quality of pasta products; however this is open to bias; be it localised preferences, leading to the prevention of an internationally recognised standard for testing pasta texture, or just personal, individual preferences. Using panellists is also expensive, slow and needs a large sample. Over time various different methods and instruments have been developed to evaluate pasta. However, it seems that different cooking and instrument settings in different laboratories have influenced sample rankings within the tests. These issues became apparent to Dr Mike Sissons and his colleagues, who are part of the Durum Wheat breeding program at Tamworth Agricultural Institute, in Australia. One of Mike’s jobs is to test the firmness of the Durum wheat which has come from varieties trials. To do this he has to make the spaghetti, dry it and then cook it, but the firmness is very sensitive to many of the choices made in how to test the spaghetti firmness. How many strands to test, how are they arranged, what is the speed of the cut etc. The biggest factor is over and under cooking and the continued cooking of the spaghetti after it has been removed from the water.
Mike’s experiments were to determine the effect on firmness of changing each of these factors. Differences of up to 10% were noticed between the firmness readings at Tamworth and in a collaborating laboratory in Canada. These differences far exceed differences between varieties and a standard method of testing of spaghetti firmness was desired.
Happily a paper recently published at www.redorbit.com covers this very point. The study was designed to investigate the effect of process and instrument variables on the testing of the firmness of cooked pasta and from this to devise a standard procedure that can be replicated in laboratories so that true differences can be seen between similar examples of pasta.
Three commercial spaghetti samples were used, with different strand diameters and cooked in the same way; then the texture was analysed in such a way to provide 12 different measurements per sample. Different factors such as spaghetti weight, length of strand, cooling water temperature etc were varied; this allowed for researchers to find out the best conditions for testing the pasta’s firmness. The researchers then used the linear mixed models procedures available in ASReml to analyse the firmness of the spaghetti samples.
Responses of spaghetti firmness to most of the factors was linear or could be made linear with a transformation so the fitting of a model was very simple. However the advantage with ASReml is that you can add complex variance structures to a model which often cannot be done with other packages. In this simple case ASReml allows the researchers to estimate the variance for each level of factor in each experiment and determine if any of the levels had significantly lower variance. If the model suggested differing variances the level of factor with the lower variance was recommended as the setting to use. With both the Tamworth and Canadian laboratories using a standard method the correlations between laboratories was greatly improved and average differences between the laboratories was reduced.
This study has shown that there are ways of increasing the repeatability of the results, and hence make it easier to discriminate between textural differences in different pasta samples, and shows there is an alternative to sensory analysis. The impact for laboratories, the Durum trade and pasta manufacturing industry is huge; decisions on wheat variety, ingredients, recommended cooking times etc are based on science not taste buds.
As a footnote – throwing spaghetti at the wall is still used as a valid test of stickiness, for me personally this means I can happily continue trying to redecorate my kitchen!