The three browning reactions in food

0:00 It is common among cooks to refer to any food  browning under heat as "caramelization." People  

0:08 will say that meat is caramelized when  it gets a good crust on it, or bread.

0:13 Is this wrong? Well, I think it depends  on what you mean by "wrong." There are  

0:21 multiple browning reactions that happen in  food and caramelization is but one of them.

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

0:33 enzymatic and non-enzymatic. Enzymatic  is the kind of browning that happens  

0:40 when you cut fruit and leave it open  to the air. It's a kind of oxidation.

0:46 Plants naturally biosynthesize a broad  class of chemicals known as phenols.

0:51 Phenols are involved in lots of the colors  and smells that attract pollinators to plants,  

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

1:04 by taking the fruit somewhere to  eat it and dropping the seeds.

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. You also expose the cut surface to air,  

1:23 and in the presence of oxygen, polyphenol  oxidase oxidizes the phenols, or chemically  

1:30 changes them with oxygen into new things  — specifically, in this case, quinones,  

1:37 which are another class of organic compounds that  are toxic to microorganisms and yucky to insects.

1:44 Basically, when the plant  is wounded, it produces this  

1:48 layer of polymerized quinones to  protect itself. It's a band aid.

1:54 The quinones then react with proteins  and free amino acids in the fruit to  

2:00 produce a class of brown-colored  compounds known as melanin. Yes,  

2:06 melanin. 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, like when you  

3:43 cut fruit and leave it out, and none of that  is caramelization. Caramelization is one of  

3:50 the two non-enzymatic browning reactions in  food, both of which can be observed via this  

3:57 little 'smores maker toy my kids won at one of  those kiddie casino arcades. We kinda love it.

4:06 Camelization is something that happens when sugar  meets heat. Only heat and sugar are involved.

4:14 How much heat is required depends  on the ph of the environment,  

4:18 and on which sugar you're caramelizing.  In low ph, acidic conditions, fructose  

4:25 can caramelize at just over the boiling  point, which is not very hot at all. That's  

4:32 why high-fructose foods are more likely to have  those caramel flavor notes. Glucose caramelizes  

4:39 at like low-baking temperatures, sucrose  caramelizes at normal baking temperatures.

4:47 One hypothesis as to why 350ºF/180ºC  is a common default oven temperature  

4:54 is that's the lowest heat that is  likely to caramelize most sugars,  

5:00 though maltose needs it a little hotter  than that. And what is this caramelization?

5:07 Basically it's just the sugars breaking apart and  reforming into a million new organic compounds.  

5:14 Some of the sugars polymerize, or link together  into giant structures known as caramelans,  

5:22 caramelens, and caramelins —  solid naming convention there,  

5:29 science. 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, volatile  molecules that easily vaporize and we smell  

5:46 them. The big one in caramel is called  diacetyl, which smells intensely like butter,  

5:52 because it's also in butter, and with  massive exposure it's responsible for  

5:59 the disease known as popcorn lung, but  that's not a real hazard of eating caramel.

6:06 If you over caramelize sugar with too much  heat you start breaking these compounds down  

6:11 into chemicals that get gradually  closer and closer to pure carbon,  

6:16 so the sugar turns bitter  and black. That's burning.

6:20 The other kind of non-enzymatic browning  in food is the famous Maillard Reaction,  

6:28 named after the French chemist who first  described it in 1912. He was trying to  

6:33 replicate the natural process of protein synthesis  in a lab and then he stumbled on this thing.

6:38 The Maillard Reaction happens when sugar and  

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

6:48 Mashmallow is a great example because it is  a sugar syrup foam stabilized with protein,  

6:54 like egg white or gelatine,  which provides the amino acids.

6:58 Between low to middle baking temperatures, the  sugars and proteins break down and parts of them  

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

7:12 unstable and a whole crazy chain reaction unfolds  resulting in lots of complex chemicals with  

7:19 complex flavors. It's really too complicated  to explain in much greater detail here.

7:25 The particular compounds that create the  brown color are known as melanoidins,  

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 smell nutty, others taste umami-y,  and it all depends on the specific amino  

7:50 acids and reducing sugars involved and  the exact heat and the exact conditions.

7:57 One useful thing to know is that the Maillard  Reaction is enhanced in high ph, or alkaline  

8:05 conditions. That's why you soak pretzels in  lye, to make them Maillard faster. You get  

8:12 a super brown thin piece of bread that's still  soft on the inside, because it browned so fast.

8:18 Acidic, low ph conditions inhibit the  maillard reaction. The more yogurt  

8:25 you put in your naan dough, the less  it's gonna brown, because of the acid.

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

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

8:43 alone, may be a good enough reason to keep  these two things linguistically separate.

8:49 And yet, cooks often refer to  either kind of non-enzymatic  

8:54 browning as "caramelization," and generally  speaking, I think that's fine, if you care.  

9:03 Fact is, both kinds of browning are usually  happening when you brown almost anything,  

9:11 because virtually all foods contain at least  a little sugar and a little protein. Meat is  

9:18 mostly protein but it naturally contains some  sugar, because animals run on glucose. Onions  

9:25 contain a ton of sugar, but also some protein,  because all known lifeforms contain protein.

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

9:38 Both Maillard and caramelization are generally  happening in most cooking, it's just a matter of  

9:46 which is the dominant reaction. But, if you want  to keep yourself out of most trouble, if you want  

9:54 to immunize yourself against attacks by pedants,  just say "browning." Whether it's caramelization,  

10:02 maillard, enzymatic browning, just call it  browning. It's all browning. That is all.