The Al Dente Dilemma

After a week here in Italy, I think it is safe to say that everyone has noticed the difference in the quality of real Italian pasta as opposed to what we eat in the States. I never knew the true meaning of “al dente” until I came to Italy to eat my first plate of delicious pasta. Italian kitchens are able to achieve cooked pasta that retains some firmness and texture, rather than the soft, overcooked stuff that we Americans are accustomed to. Try as we may, it is not possible to achieve true al dente perfection from a box of dried Barilla pasta. Instead, we just get underdone pasta that remains crunchy and uncooked in the middle.

Evidently, it is essential to use fresh, not boxed or packaged pasta to create a true culinary masterpiece. So why is this? A Japanese study by Horigane et. al. took this question to the lab, measuring the moisture distribution and diffusion in cooked fresh, dried, and frozen spaghetti. Using magnetic resonance imaging obtained with an NMR spectrometer they observed the moisture distribution in the different kinds of pasta, which is a more specific measurement than the bulk moisture content of the sample. MRI also enabled them to analyze the diffusion of water through the pasta over time.

The researchers found that the water diffusion at the center of the pasta varied by type of pasta. At the core of al dente pasta is ungelatinized starch, meaning that the center of the pasta is not yet cooked, at which point the bonds between starch molecules would break and absorb moisture. For dried spaghetti, it took 4 minutes longer than for fresh pasta to obtain the appropriate moisture content at the center (>40% moisture). At this level, starch gelatinization is still possible, so the center of the pasta will still cook. Also, the diffusion coefficient, or the rate at which moisture spread through the pasta after cooking, was slower for the dried pasta than for fresh pasta. This is because the drying process involved in spaghetti manufacturing deteriorates the texture of the pasta by tightening the structure of the starch molecules. Fresh pasta achieves moisture homogenization following the cooking process, while dried pasta retains more of a dry center while the outside is cooked, leading to the above-stated crunchy al dente pasta. Essentially, the researchers confirmed that the al dente state is not achievable in dried pasta because it takes longer to cook the center, at which point the outside has become overcooked.

This article concludes that the moisture transport property of spaghetti is a key to the quality of the product. However, a different study investigated the use of natural antimicrobial compounds to improve the shelf life of fresh pasta, avoiding the issue of drying or freezing altogether. A summary of their findings can be found here: http://www.foodnavigator.com/Science-Nutrition/Natural-compounds-can-boost-pasta-shelf-life-Study

Reference:

Moisture Distribution and Diffusion in Cooked Spaghetti Studied by NMR Imaging and Diffusion Model

http://elbanet.ethz.ch/wikifarm/conde/uploads/GroupC/Paper.pdf