During a lecture today we discussed the use of the pestle and mortar. One of the teams in our class was making a salsa that was ground rather than chopped. We were using tomatoes, jalapenos and Anaheim chilies, onions, lemon juice and cilantro. This process of grind gives the salsa a slightly more unique mouth feel as well as flavor imparted from the stone that composes the pestle and mortar. This particular version was made of volcanic rock from the Mexico. It was a rustic looking bowl on a three small pegs. The mortar was short and resembled an inverted snow cone with a rounded tip.
The discussion changed directions when Chef presented the class with a question. Why do we not add the onion in immediately to the mix and grind it. Onions belong to the brassica family. This is a family of vegetables that contain sulfur. These gases are released when an onion is cut. When using a sharp knife, the cells are sliced rather than crushed or popped. This prevents the mists of sulfur gases. When this gas mixes with our tears it actually creates an hydrochloric acid (HCl)
This was significant because processing the onions with all of the other ingredients causes more of the gases to get released. They overwhelm the salsa rather than enhance the flavor. The concept was, the more that an onion is processed, whether that be chopped, minced or ground, it will release more and more flavor. Some other bulbs such as shallots also share these same properties. Mincing shallots by hand will yield a more gentle flavor than if they are chopped.