Recently I've started to roast vegetables without adding oil in a bid to eat healthier. However, they end up coming out of the oven looking more dry instead of crisp and browned, with not as much of that roasted flavour. Casual googling has lead me to the Maillard reaction, but is this reaction affected by the amount oil covering the food?

  • 1
    If your goal is just eating healthier, changing the type of oil may help without impacting the appearance, although it will probably affect the flavor (though that may be a good thing depending on your personal taste). Commented May 22, 2020 at 14:05
  • It doesn't take much oil to promote browning. I use a pump oil sprayer, and it just takes a little misting to get good browning on most foods (at least, all of the ones I've tried).
    – Joe
    Commented May 22, 2020 at 16:53
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    A little off-topic but the idea of eliminating oil (in general) to be healthier is dubious at best. As long as we are not talking about trans-fats, removing oil from your vegetables will mainly make you feel less satiated and inhibit the absorption of fat-soluble vitamins.
    – JimmyJames
    Commented May 22, 2020 at 17:59

3 Answers 3


The Malliard reaction is quite complex. The article I linked defines it as

many small, simultaneous chemical reactions that occur when proteins and sugars in and on your food are transformed by heat, producing new flavors, aromas, and colors.

Oil does not necessarily need to be present, though, especially with regard to meats, fat is often there. If you scroll down to the comments, someone does ask the author about oil and marinades. He replies that "fats, under high heat, produce their own separate browning reaction."

Maillard is not a reaction of fats, but the browning of fats works in tandem with the Maillard reaction to produce flavors and aromas.

Oil does promote caramelization of vegetables in a roasting situation, which is what it appears you are missing. It doesn't take much for the desired effect.

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    One way to get the effect from oil without using much is to spray it on, you use tiny amounts but still get a coating.
    – GdD
    Commented May 22, 2020 at 7:06

Butter, specifically the milk components (sugars and proteins), turns brown and flavorful when cooked. Clarified butter doesn't have nearly the same effect.

Fat on vegetables also slows evaporation while roasting, leaving more moisture in them.

Oils will also get hotter, than evaporating water, which allows the vegetables brown more.

A little bit of pure olive oil can go a long way to all of the above points.

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    In other words, oil is not part of the Maillard reaction, but can affect the temperature and moisture content when and where it occurs. Commented May 22, 2020 at 15:44

I'm pretty sure that I'll is not part of the Maillard reaction, which by definition happens between proteins and carbohydrates. But remember, browning is much more than only a Maillard reaction.

I can confirm your observation that oil creates a better texture on roasted vegetables, and if I had to guess, I would say that it turns the roasting process slightly in the direction of frying, which accounts for the nice surface through the typical processes there (different rates of heat transfer, different starch gelation, different amounts of steam escaping, etc.).

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