The three browning reactions in food

0:00 It is common among cooks to refer

0:02 to any food browning under heat as caramelization.

0:08 People will say that meat is caramelized when

0:11 it gets a good crust on it, or bread.

0:13 Is this wrong?

0:15 Well, I think it depends on what you mean by wrong.

0:20 There are multiple browning reactions that happen in food,

0:24 and caramelization is but one of them.

0:28 All the food browning reactions can be sorted into two categories:

0:33 enzymatic and non-enzymatic browning.

0:37 Enzymatic is the kind of browning that happens when

0:40 you cut fruit and leave it open to the air.

0:43 It's a kind of oxidation.

0:45 Plants naturally biosynthesize a broad class of chemicals known as phenols.

0:51 Phenols are involved in lots of the beautiful

0:54 colors and delicious smells that attract pollinators to plants,

0:58 or that attract fruit-eating animals like us who might help the plant reproduce

1:04 by taking the fruit somewhere else to eat

1:06 it and thereby dropping the seeds somewhere.

1:09 When you cut the fruit, you bust through cell walls and release an enzyme,

1:15 which is a kind of protein, called polyphenol oxidase.

1:20 You also expose the cut surface to air, and in the presence of oxygen,

1:25 polyphenol oxidase oxidizes the phenols,

1:29 or chemically changes them with oxygen into new things.

1:33 Specifically in this case, quinones,

1:37 which are another class of organic compounds

1:39 that are toxic to microorganisms and yucky to insects.

1:44 Basically, when the plant is wounded,

1:47 it produces this layer of polymerized quinones to protect itself.

1:52 It's a kind of Band-Aid.

1:54 The quinones then react with proteins and free amino acids

1:59 in the fruit to produce a class of brown-colored compounds known as melanin.

2:06 Yes, melanin.

2:07 The stuff that makes fruit brown is the same stuff that makes people brown.

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3:40 Anyway, we were just talking about enzymatic browning,

3:43 like when you cut fruit and leave it out.

3:45 And none of that is caramelization.

3:48 Caramelization is one of the two non-enzymatic browning reactions in food,

3:54 both of which can be observed via this little s'mores maker

3:58 toy that my kids won at one of those kitty casino arcades.

4:03 We kind of love it.

4:05 Caramelization is something that happens when sugar meets heat.

4:10 Only heat and sugar are involved.

4:13 How much heat is required depends on the pH

4:17 of the environment and on which sugar you are caramelizing.

4:21 In low pH acidic conditions,

4:24 fructose can caramelize at just over the boiling point,

4:28 which is not very hot at all.

4:31 That's why high fructose foods are more

4:34 likely to have those caramel flavor notes.

4:37 Glucose caramelizes at like low baking temperatures.

4:43 Sucrose caramelizes at normal baking temperatures.

4:47 One hypothesis as to why 350° F,

4:50 180° C is a common default oven temperature is that it's

4:55 sort of the lowest heat that is likely to caramelize most sugars.

5:00 Though maltose needs it a little bit hotter than that.

5:03 And what is this caramelization?

5:07 Basically, it's just the sugars breaking apart

5:10 and reforming into a million new organic compounds.

5:14 Some of the sugars polymerize or link

5:17 together into giant structures known as caramelans, caramelens, and caramelins.

5:27 Solid naming convention there, science.

5:31 No opportunity for confusion at all.

5:34 Anyway, these big sugar polymers absorb light and so they look brown.

5:40 You also get a lot of much smaller

5:42 volatile molecules that easily vaporize and we smell them.

5:46 The big one in caramel is called diacetyl,

5:50 which smells intensely like butter because it's also in butter.

5:55 And with massive exposure,

5:58 diacetyl is responsible for the disease known as popcorn lung,

6:01 but that's not a real hazard of eating caramel.

6:06 If you over caramelize sugar with too much heat,

6:09 you start breaking these compounds down into chemicals

6:13 that get gradually closer and closer to pure carbon.

6:15 So, the sugar turns bitter and black.

6:18 That's burning.

6:20 The other kind of non-enzymatic browning

6:23 in food is the famous Maillard reaction,

6:27 named after the French chemist who first described it in 1912.

6:32 He was trying to replicate the natural process of protein

6:35 synthesis in a lab and then he stumbled on this thing.

6:38 The Maillard reaction happens when sugar and amino

6:42 acids react with each other in hot, dry conditions.

6:48 Marshmallow is a great example because it is a sugar

6:51 syrup foam stabilized with protein like egg white or gelatin,

6:55 which provides the amino acids.

6:58 Between low to middle baking temperatures,

7:02 the sugars and proteins break down and parts of them

7:06 recombine to make new compounds that are super unstable and lead

7:10 to more compounds that are also unstable in a whole crazy

7:14 chain reaction unfolds resulting in lots

7:17 of complex chemicals with complex flavors.

7:20 It really is too complicated to explain in much greater detail in this context.

7:25 The particular compounds that create the brown

7:28 color in Maillard reaction are known as melanoids,

7:33 which is to say they're not melanin, but they're like melanin.

7:38 Some of the compounds created by the Maillard reaction smell toasty.

7:43 Some of them smell nutty.

7:45 Others taste umami-y,

7:48 and it all depends on the specific amino acids and the specific

7:51 reducing sugars involved and the exact heat and the exact conditions.

7:57 One useful thing to know is that the Maillard

8:00 reaction is enhanced in high pH or alkaline conditions.

8:06 That's why you soak pretzels in a lye to make them Maillard faster.

8:12 You get a super brown thin piece of bread that is

8:15 still soft on the inside because it browns so fast.

8:18 Acidic low pH conditions actually inhibit the Maillard reaction.

8:24 The more yogurt you put in your naan dough,

8:27 the less it's going to brown because of the acid.

8:31 It's a big difference compared to caramelization.

8:35 Caramelization is enhanced by extreme pH in either direction, basic or acidic.

8:42 That alone may be a good enough

8:44 reason to keep these two things linguistically separate.

8:49 And yet, cooks often refer to either

8:52 kind of non-enzymatic browning as caramelization.

8:56 And generally speaking, I think that's fine, if you care what I think.

9:03 Fact is, both kinds of browning are usually

9:07 happening at the same time when you brown almost

9:10 anything because virtually all foods contain at least

9:13 a little sugar and at least a little protein.

9:17 Meat is mostly protein,

9:19 but it naturally contains some sugar because animals run on glucose.

9:24 Onions contain a ton of sugar,

9:26 but also some protein because all known life forms contain protein.

9:33 The more protein and sugar your food has, the more browning you're going to get.

9:38 Both Maillard and caramelization are generally happening

9:42 in most cooking at the same time.

9:45 It's just a matter of which is the dominant reaction.

9:50 But if you want to keep yourself out of most trouble,

9:53 if you want to immunize yourself against attacks by pedants, just say browning.

10:00 Whether it's caramelization, Maillard,

10:04 enzymatic browning, just call it browning.

10:07 It's all browning.

10:09 That is all.