In many backyard barbecues, "Let's grill tonight" translates as "Let's eat meat tonight." That's not really surprising since grilled meat products create hundreds of complex aroma and flavor compounds. While grilled vegetables create less of these crave-inducing compounds, they do develop delicious flavor profiles that can make them popular with "veg-avoiders."
Whether wood, coal or gas is used as the heat source, the flavor of grilling is determined by browning reactions that depend on carbohydrates and protein.
Non-Enzymatic Browning Reactions: Maillard Reaction and Caramelization
When meat, poultry and fish are exposed to a high and dry heat, they experience a Maillard reaction. This is a process which yields hundreds of complex aroma and flavor compounds ranging from savory and meaty to floral and earthy.
Caramelization is a browning process from heating sucrose or sugars such as fructose or glucose, also known as reducing sugars. Caramelization requires higher temperatures than Maillard reactions.
Because meat products also include the simple sugar ribose, some caramelization flavors also may be detectable. While vegetables meet two of the requirements for a Maillard reaction, their low protein content (compared to meat products) limits flavor development.
Annette Hottenstein, MS, RD, the "Sensory Scientist" and host of the Food Sommelier podcast, explains that grilling typically exposes vegetables to higher heat than other cooking methods. At these high temperatures, new complex volatile flavor components become available as natural sugars caramelize.
Caramelization flavor compounds are less complex than those from Maillard reactions, but don't disappoint. They produce a flavor range that includes butterscotch, sherry, rum or toasty notes.
Vegetables with high levels of reducing sugars and protein, such as corn, sweet potato, onion and eggplant create tasty flavors from both types of browning reactions. Some vegetables even can develop a "meaty" taste element, thanks to sulfur. Vegetables with an amino acid linked to sulfur, such as cysteine, create more savory elements or a meatiness. Cysteine is plentiful in cruciferous vegetables and alliums such as onions. Onions contain both cysteine and naturally high sugar content. This combination explains why grilled onions and caramelized onions are such coveted additions in many meals.
Grilled vegetables also offer pleasant contrasting textures. Hottenstein shared that she particularly enjoys the crispy tips of grilled asparagus and how the heat of the grill intensifies the green flavor components while adding a smoky dimension.
4 Vegetable Grilling Tips
Fresher Is Better
Some vegetables such as sweet corn rapidly convert natural sugars to starch after harvest. Less natural sugars means less flavor and could lead to a mealy texture.
For dense or slow-cooking vegetables such as carrots or potatoes, you have two options: Either partially pre-cook before placing on the grill; or, grill the surface first on direct heat, then finish cooking on the warming rack.
Coated or Naked
Dry the surface of vegetables before coating lightly with oil or marinade. Or, instead grill whole eggplants or peppers with no oil or marinade for smoky, charred skin aroma compounds.
Consider Veggie Density
Vegetables such as zucchini, eggplant, tomatoes that are less dense due to high water content grill quickly in general and even faster if sliced or quartered. It’s best to not mix them with dense vegetables, such as root vegetables, to ensure even grilling results