Sucrose. Proteins. Heat. And what no one tells you about caramelized vegetables and fruits.
Ah, yummy caramelized onions! You can use them as a topping in burgers and sandwiches, mix them into salads, and even put them in a soup such as French onion soup.
Caramelized onions are the result of caramelization where sucrose is broken down by heat into its simple sugars fructose and glucose. Volatile chemicals are released and sugar molecules combine to form new compounds and polymers. These give new flavors, colors, and aromas (read all about it in the 1 Minute NomNom “Burn (sugar) baby burn”).
Try identifying all the flavors and aromas in caramelized onions though, and you begin to suspect that the science of caramelization can’t be the only one giving us that complex range of tastes and smells.
And you are right. Maillard reactions are also taking place. Even though an onion has natural sucrose, which can be broken down by caramelization, it also has protein. According to the USDA, there are 1.1 grams of protein for every 100 grams of onion.
This seemingly small amount of protein has a big impact. Maillard reactions only take place when amino acids in the proteins react with the sugars under heat. They form new flavor compounds that react with more amino acids to form larger molecules, giving us the golden brown caramel and also the brown crusts we see on meats, breads, pastries, and donuts (read all about it in the “How now, brown cow?” 1-Minute NomNom).
Hence, just as caramel, despite sounding like the root word of caramelization, involves Maillard reactions as well as caramelization, so it is with the word “caramelized”. “Caramelized” anything, be it onions bananas, carrots, lemons etc could very well be misnomers. As long there is some protein content in the vegetables or fruits (bananas for example also have 1.1 grams of protein for every 100 grams), when we heat them up to sufficiently high temperatures, we will get both caramelization and Maillard reactions.
Which is not to say that is a bad thing. It’s good in fact, because we get food that is more flavorful, more aromatic, and more complex. Which simply means the food is yummier. No misnomers about that!
Don’t tell us you onion like this 1-Minute NomNom? 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/lenyvavsha; MSPhotographic; beyondasnapshot; jabiru; sarymsakov