Pesto — Mediterranean Biochemistry Part 2

When we take pesto prepared from fresh basil, fold it into steaming pasta, and allow the inimitable fragrance to rise up, we ask ourselves: with what aromatic molecules is this plant blessing us? In this second part we try to uncover the nature of this culinary-chemical marvel from an experimental point of view, and thereby come to enjoy it all the more.

Experimental Section

Compared to chemical syntheses, culinary directions tend to be rather vague, which is why for a given dish there is sometimes hundreds of different recipes. At the same time, however, recipes offer the priceless advantage that they never go fully awry, because something more or less tasty always emerges. Unfortunately, there is no peer review system associated with cookbooks, which might otherwise prevent at least some of the worst mistakes from being propagated through many cookbook generations.

With practice, a dish is typically improved, since it comes to conform more and more to the personal vision of the chef. At the end of this trial-and-error process, there may emerge, for example, “your own” recipe starting with the following instructions derived from the author’s wife. Try it out!

Pesto Annelie alla Genovese

Ingredients

• one large bunch of basil (Ocimum basilicum)
• three tablespoons of pine nuts
• one to two cloves of garlic
• high-quality olive oil
• a teaspoon of salt
• tablespoon of freshly (!) grated parmesan cheese

Preparation

Coarsely chop up the basil leaves using kitchen shears. Crush three tablespoons of pine nuts in a mortar, and then mix in a good cold-pressed olive oil. Add the chopped basil leaves and continue to grind until a smooth paste is obtained.
Add more olive oil as needed. At the end, add a tablespoon of freshly grated parmesan cheese, and mix well.

Transfer the finished pesto to a glass jar that can be tightly sealed, and cover the pesto with a layer of olive oil.

The pesto can now be kept for a prolonged period of time in the refrigerator. If the paste should become too thick, add more olive oil.

Notes

1. Basil purchased at the market should be washed and then very carefully dried with a paper towel. Basil from the garden can be used without washing.
2. The ingredients can also be minced with a blender or a hand mixer. This is of course faster and less strenuous. Take into account, however, that a mechanical process will release considerable heat, so that at least a portion of the volatile substances will be lost. The goal is not to create a smooth puree, since pesto after all is not supposed to be like ketchup, and is meant to retain a somewhat crumbly character. The reason is clear: the somewhat larger leaf remnants will become trapped on the gums and between the teeth, releasing their aroma over a longer period of time, and prolonging the pleasure of the culinary experience.
   
   A porcelain mortar like those commonly found in the laboratory is ideal, since the pressure and shear force of the pestle, together with the sharp-edged salt crystals and the hard pine nuts, will tear the fibrous leaf material, and help release the ethereal oils. Since the basil is covered with olive oil during the grinding process, volatile nonpolar aromatic substances dissolve immediately in the oil. The interplay between physical exertion, basil aroma rising up from the mortar, and the consistency of the pesto as perceived through the pestle, leads to a bodily-sensory relationship between the connoisseur and his or her pesto. What a joy!
3. Before crushing, the pine nuts can also be lightly toasted in a pan.
4. Some authors replace parmesan with pecorino, while others recommend a mixture of the two. This is entirely a matter of taste. True parmesan (Parmigiano Reggiano) is a cheese based on cow’s milk, and must be derived from the Italian provinces Parma, Emilia, Modena, Mantua, or Bologna. It never has a sharp taste, but is rather spicily nutty. Pecorino is a sheep cheese that is produced throughout Italy, although with distinctive regional notes depending on its romano, toscana, or sardo origin.
5. The parmesan or pecorino should always be freshly grated; one surely shouldn’t forego from the outset a principal source of aromatic character!
6. The mass that results prior to addition of the cheese can be frozen, with further processing as usual after thawing.
7. Soup (minestrone) and fish dishes can be refined by adding pesto, but the classic way to use it is folding it into pasta. That provides a marvelous appetizer, a light evening meal, or a delectable main course for the entire family.

Prepare spaghetti — or better yet, a more elegant type of pasta — in boiling, salted water until it is al dente. Admittedly, choosing the type of pasta is a science in its own right, but try it out anyway. Pesto tastes best with ligurian trenette (which looks like a narrow, flat kind of spaghetti, ca. 3 mm wide) or a thin tagliatelli. Trenette has just the right ratio of surface area to volume for optimum pesto uptake: not too high, as with farfalle or macaroni, and not too low, as with spaghetti. Place a portion of the pasta on a pre-warmed plate, and mix 1–2 teaspoons of pesto into it. Finally, sprinkle fresh parmesan or pecorino over the top.

When the entire room has filled with the aroma of basil, pour out a glass of dry red wine (Italian, of course!). Close your eyes, inhale deeply the monoterpenes, and give isoprene units the opportunity to dance before your mind’s eye. Surely there’s no finer way to appreciate chemistry!

Prof. Klaus Roth

Freie Universität Berlin, Germany.

The article has been published in German in:

• Chem. Unserer Zeit, 2006, 40, 200 – 206.
  DOI: 10.1002/ciuz.200600388

and was translated by W. E. Russey.

Pesto — Mediterranean Biochemistry Part 1

Klaus Roth uncovers the nature of this culinary-chemical marvel, and thereby comes to enjoy it all the more

Other articles by Klaus Roth published by ChemViews magazine:

• In Espresso — A Three-Step Preparation
  Klaus Roth proves that no culinary masterpiece can be achieved without a basic knowledge of chemistry
  DOI: 10.1002/chemv.201000003
• In Chocolate — The Noblest Polymorphism
  Klaus Roth proves only chemistry is able to produce such a celestial pleasure
  DOI: 10.1002/chemv.201000021
• In Sparkling Wine, Champagne & Co
  Klaus Roth shows that only chemistry can be this tingling
  DOI: 10.1002/chemv.201000047
• In Chemistry of a Hangover — Alcohol and its Consequences
  Klaus Roth asks how can a tiny molecule like ethanol be at the root of so much human misery?
  DOI: 10.1002/chemv.201000074
• In The Chemist's Fear of the Fugu
  Klaus Roth shows that the chemist’s fear of the fugu or pufferfish extends as far as the distinctive and intriguing poison it carries
  DOI: 10.1002/chemv.201000104
• In Chemistry of a Christmas Candle
  Klaus Roth explains that when we light a candle, the chemistry we are pursuing is not only especially beautiful, but also especially complex
  DOI: 10.1002/chemv.201000133
• Video Interview with Klaus Roth