By Barbara Zatto, Contributing Editor
Fall and winter is the perfect time to enjoy the warm, earthy flavors of roasted spices and vegetables. The air turns cooler, and our bodies begin to crave hearty food. While some typically limit their thinking of roasted vegetables to a roasted carrot or cauliflower, you can roast almost every vegetable or whole spice and intensify its flavors. Roasting brings out a natural sweetness and deepens flavors. Just consider garlic. In its raw form, garlic is bitter and pungent. Yet roasted garlic is sweet and mild, and you can spread six cloves of roasted garlic over a slice of bread just like butter.
Roasting equals chemistry
Oven heat allows sugars in the vegetables to caramelize and their carbohydrates or starches to break down, boosting flavor and providing strong visual appeal. The browning, caramelizing, and crisping of vegetables that happens with roasting tantalizes the senses of sight, taste, smell and even touch. This caramelization occurs when vegetables containing a high concentration of carbohydrates are cooked at high temperatures, i.e., roasting, and sets off a chain of chemical reactions:
• As food is heated, its sucrose melts and starts to boil. This process generally happens between 250 and 350oF. This is known as caramelization.
• Once the caramelization temperature is reached, the sucrose begins to decompose into its component monomer molecules, glucose and fructose.
• A series of complex chemical reactions take place between the molecules and results in creating caramel flavor compounds.
Caramelizing by roasting creates many flavors compounds. One of the most-important flavor compounds produced is diacetyl. Diacetyl is generated during the initial stages of caramelization and has a butterscotch flavor. Other important flavor compounds produced include the furans hydroxymethylfurfural and hydroxyacetylfuran, and maltol, from disaccharides, and hydroxymaltol from monosaccharides, which together contribute to give the sweet, slightly burnt flavor of caramel. The flavors created by roasting can vary depending on the type of vegetable roasted.
Another chemical reaction roasting creates is the breakdown of carbohydrates, or the polysaccharide starch, present in all root vegetables. Starch is a common form of carbohydrate, composed of several thousand glucose units, linked together by glycosidic bonds. When foods containing starch are cooked, the heat can break the glycosidic bonds linking the glucose units together and effectively break up the polysaccharides to release the glucose monosaccharides. This imparts a natural sweetness to the cooked food and makes roasted vegetables sweeter than raw or steamed veggies.
To get great roasted vegetables, the two main factors to keep in mind are heat and surface area. Working at around 400°F is a good start. Surface area is important because you want to roast vegetables in one even layer. Small cuts of vegetables will have more roasted surface area in relation to their insides than larger cuts; longer shapes will have more surface area than blocky cuts. Adjust the heat and surface area to fine-tune flavors. Prefer more browning? Turn up the oven temperature. Prefer vegetables that are more cooked than roasted? Cut the vegetables smaller and turn the temperatures down.
Both broiling and oven roasting can be used. Fire-roasted vegetables have a nice char and a smoky flavor, and the vegetables tend to be firmer because the roasting happens fast. Oven-roasted vegetables tend to brown (versus char) and will be slightly sweeter and softer, because the roasting happens slower and flavors develop more.
Roasting spices it up
Roasting or toasting dry spices releases the aromatic and flavorful oils in the spice. When these oils are released, flavors in spices get fuller, earthier and richer. In some spices, including cinnamon and ginger, roasting brings out sweet notes.
Spices have two main flavoring components that are released during the roasting process. The first is the volatile, or essential, oil which gives the spice its aroma. The second are oleoresins responsible for the spice’s flavor.
For spices, dry-roasting them is best by using a heavy pan on low or medium-low heat so the spices don’t burn. Shake the pan gently while roasting to ensure even roasting—it only takes a few minutes to roast them. Just rely on the aroma to tell you they’re done. When using a combination of spices, it is best to roast each spice individually to preserve the flavor and to avoid scorching one spice before another is suitably roasted; each spice will have a slightly different ideal roasting time. Industrial versions of roasted spices are available.
Roasted spices already add a depth of flavor to Southwestern American, Thai, Indian, Mexican (particularly in mole sauces) and Moroccan food, and the flavor-boosting technique is gaining broader acceptance in the United States. Roasted spices are an excellent addition to marinades, chutneys, seasoning pastes, sauces, rubs and entrées. For example, roasted cumin, fennel seeds, ginger and cinnamon form a base for almost any of these cuisines. Because ginger and cinnamon get sweeter as they roast, they can balance the heat in some spice blends and barbecue sauces.
Roasting around the world
Roasted vegetables are enjoyed around the world with different ethnic flavors and spices, with spices and seasonings often added to the vegetables before roasting. Italians prefer all types of seasonal vegetables roasted with the savory herbs thyme and rosemary. Moroccan cuisine calls for cumin, paprika, saffron, coriander, chiles (roasted and ground) and ginger on roasted potatoes, pumpkin, zucchini and onions. In the Caribbean, chefs choose a slightly sweeter approach, coating roasted vegetables with cinnamon, cloves, ginger, red wine vinegar and soy sauce. In Mediterranean cuisine, roasted root vegetables such as eggplant, peppers, artichoke and squash are often seasoned with balsamic vinegar after roasting.
