Today, you’d have to be born at the end of the Great Depression to remember a time when not all homes and apartments had ovens, and those that did often had ovens that were less than stellar. Even modern ovens can be wildly out of calibration, require long time periods to preheat, have inconsistent temperatures throughout their volume, or have wide swings in temperature during the cooking cycle. Recipes have attempted to mitigate these deficiencies by instructing the reader where in the oven to place a baking sheet or to turn the baking sheet part of the way through the cooking.
The switch to electric ovens, which began in the 1920s and became almost complete after the end of the Second World War, meant that restaurant ovens didn’t need to be left on all day. It also meant that temperature regulation for both home and commercial ovens became less an art and more a matter of setting a dial.
All these factoids aside, it is still amazing that it might be less than fifty years since roasted vegetables became ubiquitous on restaurant menus. Some researchers credit the first roasted vegetables to a restaurant called Al Forno, which opened in Providence, Rhode Island, in 1980. As the name implies, al forno means ‘baked’ in Italian, everything was cooked in the oven. Apparently, their first successful roast vegetable was asparagus. It is now common to roast almost any vegetable.
Why say ‘roast vegetables’ instead of ‘baked vegetables’? I have concluded that the preferred term is one of convention, and that no other consistent definition exists. I’ve heard cooking teachers say that baking refers to sweet products and roasting refers to savoury products, and yet we say ‘baked potatoes’ when we cook potatoes whole with their skins intact in the oven (at least we do when they are not being referred to as ‘jacket potatoes’) and ‘roast potatoes’ when we cook them peeled and cut-up. We bake a meatloaf, but roast a leg of lamb.
Whereas ovens during the twentieth century only had a ‘bake’ setting, modern ovens may have a ‘roast’ setting in addition to the ‘bake’ setting. The advent of these settings corresponded to when the electric elements were moved from being inside the oven box to its outside. With the ‘bake’ setting, the oven is heated only from the bottom. With the ‘roast’ setting, the oven is heated from both the top and bottom. Now, instead of using the ‘bake’ setting when roasting our leg of lamb, we use the ‘roast’ setting. The effect on the finished dish is that the meat develops a crust faster, even though the temperature is still set the same.
Now that we have modern ovens that truly reach high temperatures, why aren’t vegetables roasted more often at home? Over my years of teaching I’ve heard many reasons, from ‘I don’t know how to’ to ‘I don’t know how to turn my oven on’, and from ‘It makes too much of a mess’ to ‘It takes too long.’ All these reasons are unfortunate because roasting produces very tasty vegetables. When properly cooked, roast vegetables have an agreeable brown crust and property cooked interiors.
The brown crust is really two types of non-enzymatic browning and is relative to the components of the vegetables and the application of heat. Caramelisation is a poorly understood reaction that produces hundreds of nutty flavours by subjecting the sugars in the vegetable to pyrolysis. Carrots contain the sugars glucose, fructose, and sucrose. Three-quarters of the sugar is glucose and the remainder is almost equally divided between the other two sugars. At a neutral pH, the fructose begins to caramelise at 110°C (230°F) and the other two sugars begin to caramelise at 160°C (320°F). Since the last two sugars make up almost 90% of the sugar in a carrot, they dominate the non-enzymatic browning due to caramelisation.
The second type of non-enzymatic browning that occurs with roasted vegetables is the Maillard reaction, which is named after the French chemist who first described it in 1912. This browning happens mostly at a lower temperature, 140 to 165°C (284 to 329°F), and thus precedes some browning due to caramelisation. The Maillard reaction is a chemical reaction between amino acids and reducing sugars. In carrots, the reducing sugars are the monosaccharides fructose and glucose, which make up almost 90% of the sugar in carrots. The amino acid in carrots that the reducing sugars most like to react with is lysine, which constitutes about 5% of the amino acids present.
From the above we can see that there is a wide range of temperatures that we can roast carrots at to achieve a browning effect on the surface. Why not all the way through the carrot? Remember that the carrot consists mostly of water. Water boils at a temperature of 100°C (212°F) or lower, depending on your elevation. It takes about thirty-five times more energy to turn the liquid water in a cell into steam – this is referred to as change of state – then to raise the temperature of the cell one degree. As the carrot heats up and the water in the cells approaches its boiling point, the cell walls begin to fracture. This is the process of the carrot becoming tender instead of crunchy. If water is still present, because of the energy required to cause the change of state, the interior of the carrots cannot reach a browning temperature. See 21. Steamed Carrots, for further discussion about steaming carrots.
To roast carrots you’ll need a wide, heatproof container so you can spread the carrots into a single layer. My preferred container is a rimmed baking sheet, but you can also use a shallow baking pan or dish. Both conventional and convection ovens cook primarily by radiant heat. Radiant heat is what you feel from the sun when you are outside. To lower the heat hitting your body, you stand in the shade. In an oven, the sides of a pan act like a beach umbrella. The food in the pan takes longer to cook depending on how high the sides of the pan are. Since there is no liquid to be concerned with while roasting carrots, it is only necessary to have sides high enough to keep the carrots from rolling off the baking sheet when it is moved from your countertop to your oven and on the return trip.
The carrots to be roasted can either be pared or not. Carrots that are not pared develop almost a peel-able skin when roasted. This makes for an interesting combination of textures in the finished dish. The carrots pieces need to be close to the same size and shape so each piece takes about the same time to cook. When roasting whole carrots, I prefer their diameter to be about
The carrots don’t have to be in long pieces when they are roasted. Typical supermarket carrots can be pared and then sliced diagonally into
Beside the carrots, the other two ingredients required for the roasting are a little oil and some salt. The oil can be ordinary vegetable oil or something more exotic. The function of the oil is mostly to prevent sticking and to help the surface of the carrots develop a nice patina. Choose an oil that can handle high heat, which most refined oils can. Using an expensive extra-virgin olive oil or a fancy nut oil works, but they impart little or no flavour to the final dish. I’m conservative – and cheap – so I use a plain olive oil for roasting carrots.
Ordinary table salt is fine for roasting. The function of the salt is to bring out the flavour and sweetness of the carrots. It is not in the dish to impart a salty taste or crunchy texture. Science says that people prefer their food to be salted at a rate of about 0.5%. That would mean about a teaspoon for every 450 g (1 lb) of carrots. Some of the salt sticks to the carrots. Some of the salt stays in the mixing bowl with the excess oil. I’d start with a single three-finger pinch for that amount of carrots, and then in the future add more based on how the first try works out. With practice you develop a feel for the salt needed for any quantity.
When the curtain raises on the finished dish, I think that exotic, coarse salt gets in the way of the carrots being the stars of the show. If you must add some salt to the finished dish, I’d suggest you sprinkle a small amount of either fleur de sel or some pure, flaked finishing salt over the carrots after they have been plated.
If you want, fresh or dried herbs can be added. The leaves of the herbs can either be finely cut and added with the oil, or whole sprigs can be placed over the carrots on the baking sheet. Either way the leaves blacken by the time the carrots are cooked. If whole sprigs are used, many of the leaves fall off the stems and remain on the roast carrots when the stems are discarded at the end of the cooking. With small leaves, such as those found on thyme, this is not a problem. The contrary is the case if whole sprigs of a herb like rosemary are used.
Spices can be mixed with carrots before the oil is added. I’d stick to one or two, and in small amounts. The spices should be ground into their powder form rather than using whole seeds or pieces. Spices that readily come to mind to use with carrots are cumin and coriander. A deeply smoked, Spanish paprika could also be very interesting to use. Even when the spices are mixed with the carrots before the oil they still may form clumps once the oil is added. It’s just something you must watch out for and correct if it happens.
With the loose herbs and ground spices, you can judge how much to add in a similar manner to the salt. If after your first pinch and mix, it is hard to see the herb or spice, more may be needed.
The actual process required to roast the carrots is much simpler than it sounds after reading all of the above. After cutting them to shape, place the carrots in a large, wide bowl. Sprinkle some salt and, if you are using them, whatever herbs or spices. How much to use is a matter of experience and personal taste.
Give the combination a thorough mixing with either one hand or by tossing the contents in the bowl. To toss the contents without soiling your hands or another implement, move the bowl upwards so the contents slide up the far side of the bowl and into the air by pulling the bowl sharply towards your body. Then catch everything while moving the bowl outward and under the carrots. That’s how the pros do it.
Sprinkle enough oil over the carrot mixture so that they glisten. Start with a little and then toss the carrots as suggested above to mix everything evenly. If the carrots appear a little dry, add some more oil and mix again. If you add too much oil, let the carrots drain in the bowl for a few moments.
Transfer the oiled and seasoned carrots to a plain, rimmed, metal baking sheet. Arrange the carrots in a single layer. If the carrots have flat spots, first line the baking sheet with a silicone-rubber baking mat. I don’t like to use greaseproof paper for this application because it moves and tears when the carrots are flipped during cooking. The baking mat has some insulative qualities so the roasting may take longer when it is used.
If you have a convection oven, set it to about 205°C (400°F) with the convection fan on. If you have a conventional oven, set it to 220°C (425°F). Place the baking sheet with the carrots on a rack near the centre of the oven. If you are using a countertop-style convection oven, place the baking sheet on the bottom rack. It is not necessary to preheat the oven since the carrots are not being cooked ‘to the clock’.
The carrots take between fifteen minutes and an hour to cook. You’ll know that they are done when the tip of a small knife can easily be inserted into a few of the carrots. Until you become familiar with how the progress of cooking feels, I suggest that you try this first when the carrots are raw and then every ten minutes or so while the carrots cook. As the carrots start to cook, you’ll feel the knife tip begin to easily go through the outer area of the carrots, but then come to an uncooked region in the centre. As the carrots cook, the uncooked region shrinks until it is no longer there. Remember that your goal throughout all of this is to test for doneness, not to drive the knife through the carrot like you’re plunging a stake into a vampire’s heart. Press as lightly as you can with your knife while still trying to advance it.
The carrots need to be turned at least once during the roasting. Until you develop a feel for how long the carrots take to cook in your oven, test and flip them every fifteen to twenty minutes or so. The carrots tend to brown more on their bottoms then their tops, at least they do in my oven. Turning them more frequently evens out the colour but slows down the cooking. I use a fish spatula and a shake of the baking sheet for turning the carrots. Use what you have that works.
When you turn and test the carrots, remove the baking sheet all the way from the oven and close the oven door. Ovens can cool down rapidly when the door is open. This is partially why the carrots take longer to cook if you turn and test too often. All of this gets easier with a bit of practice.
When the carrots are cooked, sprinkle them with a little finishing salt, if that is your intention. I think the carrots are better if served plated. Use your imagination and arrange the carrots on the plate in an attractive manner.
If you are not serving the carrots right away, transfer them to a bowl and cover the bowl with foil. Set the bowl in a place with no drafts and cover it further with a heavy towel. The carrots should stay warm for up to an hour.
If you want to roast the carrots ahead, the cold, cooked carrots can be reheated in a bowl tightly covered with plastic wrap. Set the bowl in a 90°C (200°F) oven until the carrots are warm. Alternately, the bowl can be placed over a pot of simmering water. If the plastic wrap is applied so it doesn’t leak, it balloons up when the carrots are warm. It looks cool!
The carrots don’t have to be served warm. Roast carrots make a very nice salad, especially if the original carrots are small, not pared, and consisting of a variety of colours. Even if the carrots were large and sliced, they still can make a satisfying salad. If necessary, cut the carrots into bite-sized pieces. They may have enough oil on them already, but if you’d like a bit more, add just enough oil to make the carrots glisten lightly. This is a place where nut oils, like walnut or hazelnut oil, work beautifully. A few drops of a mild vinegar heightens the flavour. A little more salt may also be helpful. Trust your ability to taste, but remember to look for subtlety in the flavours.
Roasting works well with all root vegetables, but it also works with vegetables like Brussels sprouts, asparagus, and onions. It works less well with vegetables that easily expel lots of water such as tomatoes, peppers, and small squashes where the seeds are not removed prior to cooking. Large, hard squashes are great roasted, but they need to have their seeds removed first and be cut into manageable pieces.