Cell walls. Enzymes and amino acids. Knife skills. And how to cut our food to get the flavors just right.
Food is held together by relatively weak intermolecular forces such as van dar Waals forces and hydrogen bonding. They can be broken fairly easily. Thus when we use a knife to apply pressure on them, we are able to cut up our food (see the details in the 1-Minute NomNom “Slice slice baby!“).
What happens when we cut vegetables and fruits is that the cells walls are broken. The enzymes in the cell walls that were originally separated from the amino acids in the cells themselves now mingle and react with each other. New chemical compounds result.We have all encountered this before. When we cut onions, the escaped enzymes called lachrymatory-factor synthase react with the amino acid sulfoxides (sulfur compounds) stored in the cells. Eventually, a volatile sulfur gas is formed. It wafts up to the eyes, stinging them. We start to tear as our tear glands produce reflex tears to wash away the irritant (you can read all about onions, crying and how to prevent them in the 1-Minute NomNom “Knife me and you’ll sulfur the consequences“).
When we cook the onions, heat converts the pungent chemical compounds into milder compounds, but it still retains a fairly strong flavor. Hence how strong this flavor we desire to see in our dishes determines how much we want to cut up our onions.
Cutting our onions up into larger slices will damage less cell walls, less enzymes and amino acids mix, and we get a milder flavor. Chopping them up finely, or even using a food processor or blender, thoroughly mashes up the cells walls. Most of the enzymes and amino acids will react, and this will give us a very onion-y dish (and make us cry buckets).
What is true of onions is also true of most other foods (except they less likely to such tear jerkers). That is why cooking sites and books often emphasize knife skills (also see above video), so that we get our food flavors just right from the point we start slicing and chopping. Understanding the science behind it all raises those knife skills even further. This understanding will also guide us in choosing the right knives and appliances to turn our recipes into great dishes.
Like this? Cut to the chase and like me to discover more. All you need is a minute a day to explore the world’s marvels through the phenomenon of food!
photos: in order – depositphotos/pressmaster; blueringmedia; robynmac;asimojet