I wrote an article on the science behind broth making a couple of months ago (750 words). I am sure that with the combine experience of the membership here, this article may be debatable but I have given this recipe to a few already and they have converted.
Chicken broth’s secret revealed
By Luc H.
You think homemade chicken broth is not worth making? With a simple culinary technique and a little food chemistry, you can make an exceptional chicken broth at home.
A good chicken broth is neither salty, herbal nor spicy for its main purpose is to enhance the flavour of a recipe, to make it savoury. To obtain this characteristic, a chicken broth requires to be made using a mirepoix which is an ancient yet trusted French cooking technique. Basically, it consists of slowly cooking a selection of diced vegetables with oil.
Before starting this recipe note that the technique matters more then the precision in measurements. Trim the thighs, wings and breasts off an average size uncooked chicken and reserve the parts for another recipe. Keep the skin, trimmings, carcass and neck (if available) for the broth. Dice one carrot, onion and celery stalk per chicken carcass. Heat a skillet to medium high. Cover the whole bottom with a thin coat of oil. Add the diced vegetables. Reduce the heat to medium low. Do not cover. To succeed a mirepoix, you must avoid browning the vegetables yet cook out most of the water they contain. Hint: listen to the sizzle. The sizzle is the noise water makes when it escapes the heated vegetables in the form of steam. During this process, oil enters into the voids the escaping steam leaves behind Keep listening closely, add some oil as needed for the vegetables will soak it up. Stir occasionally and reduce the heat gradually to avoid browning. When the sizzle becomes very weak and the vegetables are soft, take the pan off the heat. The mirepoix process can take up to 30 minutes. Transfer the cooked vegetables into a pot with the chicken carcass and trimmings then fill with fresh water to barely cover the bones. Bring to a boil. Reduce heat to maintain a simmer. Do not cover. Simmer until the chicken carcass easily falls apart (about 2 hours). Strain the hot broth. It will taste surprisingly bland. Cool, refrigerate overnight then remove the solidified fat. Leave a little fat behind for added richness. Use the defatted broth for recipes.
This precious liquid will enrich any recipe that calls for broth because of its composition of natural flavour enhancers. One of them is monosodium glutamate (yes! MSG). Why? A little food chemistry will help explain. The vegetables used in this recipe contain mostly water and sugars. Unlike white sugar, yet chemically similar, these sugars are bound to each other like scaffolding which, give vegetables their rigidity. When these structures are heated correctly they breakdown in their individual sugar units. Since they can resist in boiling water yet overreact when exposed to slightly higher heat by caramelizing, the window between those temperature limits is where these sugar structures breakdown controllably. Since boiling water never exceeds 100 C (212F) but oil can, the way to reach this tight temperature range is by replacing the water in the vegetables with oil while maintaining a low enough temperature to avoid browning. The liberated sugar units prevented from caramelizing are maintained in a reactive state. Here lies the chemistry secret of the mirepoix technique.
Although these reactive sugars have flavour enhancing abilities, the story does not end here. These sugars can react with proteins. Any protein is like a pearl necklace of linked amino acids. Amino acids, the pearls, come in various chemical shapes. These reactive sugars, called reducing sugars, can attack the links between amino acids of proteins. Some proteins are found in the vegetables but more come from the carcass in the hot simmering broth. This reaction, called hydrolysis, liberates amino acid units. One particularly important amino acid is Glutamic acid. In the hot broth, free Glutamic acid readily converts to its salt form, monosodium glutamate or MSG, a potent flavour enhancer in cooking.
To make an exceptional broth you need to follow a scientifically sound and a culinary proven technique: the mirepoix. The controlled decomposition of vegetables to synthesize reducing sugars, free amino acids and MSG makes this broth an exceptional flavour enhancer. A key ingredient in my kitchen. Not all MSGs are nutritionally equal though but the type in this broth is wholesome.
I eat science everyday, do you?