Chemistry of Cooking Part Two: Sauce and Vegetables

Last week we learned all about pizza dough and how it rises. This week, we’ll take a look at another important part of pizza: the tomato sauce! Or more specifically, the tomato fruit. A lot of people may not know that tomatoes are actually fruits. Between science and cooking, the line between fruit and vegetable is often blurred.

Scientifically speaking, tomatoes are fruits because they develop in the ovary in the base of the flower and contain the plant’s seeds within it. But when using tomatoes to cook, they’re often referred to as vegetables. In fact, many fruits are used as “vegetables” because the food produced is savory instead of sweet. After all, tomato sauce isn’t sweet like applesauce! And while we’re on the subject of fruits and vegetables, it might be nice to know that some other pizza toppings aren’t what they appear to be either. Peppers and olives are fruits too, and mushrooms are neither fruit nor vegetable; they’re actually a fungus!

However, we typically don’t use chunks or slices of tomato as toppings on pizza; we make sauce with them instead! The sauce is like a smoother version of a paste, with added spices and/or herbs. Because of their rich flavor, juiciness, and soft flesh, tomatoes are easy to break down into a sauce that thickens while cooking. Pizza sauce is made with tomatoes, as well as tomato paste. In the activity that follows, we’ll go over how to make pizza sauce with fresh tomatoes, but we’ll just use store-bought paste.


Let’s Make Pizza Sauce!

What you need:

• 5 pounds of fresh cored whole tomatoes
  
• 3 tablespoons extra-virgin olive oil
  
• 2 medium onions, chopped
  
• 4 cloves garlic, minced
  
• ¾ teaspoon dried basil
  
• ¾ teaspoon dried thyme
  
• ¾ teaspoon dried oregano
  

• 1¾ teaspoons salt
  
• ½ teaspoon freshly ground pepper
  
• 2 tablespoons tomato paste
  

Step One - Prepare the Tomatoes:

• Bring a large pot of water to a boil.
  
• Using a knife, make a small X at the very bottom of each tomato. Plunge the tomatoes into the boiling water and hold there until the skins are loosened (use tongs to protect your own skin!).
  
• Transfer the boiled tomatoes to a bowl of ice water for one minute.
  
• With a paring knife, peel the the tomato’s skin, starting with the X at the bottom.
  
• Chop each tomato, keeping all the juice.
  

Step Two - Simmer:

• Heat the oil in a dutch oven over medium heat.
  
• Add the chopped onions and stir while cooking to a golden brown (about 4-6 minutes). Then add the garlic and cook for an additional minute.
  
• Add the tomatoes (and any juice), basil, thyme, oregano, salt, and pepper. Bring to a boil.
  
• Reduce the heat and simmer until the sauce thickens into the desired consistency (about two hours).
  
• Taste your sauce and season it with more salt and pepper to your liking.
  

Step Three - Blend:

• After simmering, transfer the sauce into a blender. Add the tomato paste and blend until smooth. Be careful when you blend this hot liquid!
  

Your pizza sauce is now ready! You can cover its container and put it in the refrigerator for up to three days, or freeze the sauce for later use for up to six months!


References:
https://en.oxforddictionaries.com/explore/is-a-tomato-a-fruit-or-a-vegetable
https://www.ncbi.nlm.nih.gov/pubmed/11192026
http://www.compoundchem.com/2014/10/02/tomatoes/
http://www.eatingwell.com/recipe/250096/homemade-pizza-sauce/

Image Credits:

Buissinne, Steve. “Bush Tomatoes”. Released into the public domain. Uploaded on 3/3/2017 from publicdomainpictures.net
Chaffin, Holly. “Pizza Slice”. Released into the public domain. Uploaded on 3/3/2017 from publicdomainpictures.net
Denyer, Circe. “Pizza Sauce”. Released into the public domain. Uploaded on 3/4/2017 from publicdomainpictures.net