Vegetable stock is a liquid mixture, typically water-based, that is heated with vegetables to infuse it with flavor. There are a number of companies that offer pre-made stock that can be purchased from a grocery store and used in making soups and other dishes. It is also fairly easy to make vegetable stock, which often begins with a number of chopped vegetables including carrots, onion, and celery that are heated in a large pot. A large amount of water is then added to these and allowed to simmer for some time, before being strained away to leave only the liquid behind.
The basic purpose of vegetable stock is to act as a liquid base for the creation of soups, stews, and other dishes that require liquid and flavor. Many recipes that require water be used and heated in their preparation, such as rice or soup, can have the water replaced with stock to introduce more flavor. Commercial brands of vegetable stock are available from a number of manufacturers and can be found at many stores. Both home and commercial cooks often prefer to make their own stock, however, as it allows them to control the flavors used and it is quite easy to make.
Vegetable stock usually begins with a wide range of vegetables that are chopped or diced. They should typically be chopped fairly fine, as the more surface area available for each piece increases the amount of flavor that can be easily extracted from it. Aromatic vegetables like onions and carrots are typically added to a hot pot with some oil, allowing them to cook and soften before any other ingredients are added to the pot.
Additional vegetables often used in making stock include celery and shallots, though mushrooms can also be used and introduce a great deal of flavor. Herbs and spices are quite popular, such as parsley, thyme, and bay leaves that are usually added along with other vegetables into the pot. Depending on the preferences of the person making the vegetable stock, other ingredients like some peppercorns, salt, and vegetables such as leaks, tomatoes, and bell peppers can also be added.
Once these vegetables are heated, then a great deal of water is added to the pot; the amount depends on the number of vegetables used. Cold water should typically be used for vegetable stock, since different types of vegetables release water-soluble flavors at varying temperatures. This ensures that as the temperature rises in the cold water, it goes through as wide a range of temperatures as possible to extract these flavors. Once the water is heated, it is allowed to simmer for a half hour or an hour, and then strained of the solid matter leaving only the vegetable stock behind.