Don't cry over your onions!

     After I posted a picture of myself cutting 50 lb of onions on Facebook a couple weeks ago, I got many people asking me the same question: did you have to wear goggles to prevent the tears from pouring down. The answer is, if you cut the onions the right way, you don't get teary. Allium species including onions, garlic, chives, and leeks are able to synthesize a unique set of secondary sulfur metabolites derived from the amino acid cysteine. When the tissue in the onions are crushed during chopping, an enzyme called alliinase is activated to break down the amino acid-based compound S-alkyl-L-cysteine S-oxide (alliin) to an alkylated sulfenic acid and 2-aminoacrylate. When two sulfenic acid molecules condense, they produce a  new compound called allicin. Sulfenic acid will bind to another enzyme, lachrymatory factor synthase (LFS), producing a volatile compound, propanthial S-oxide, a.k.a., the tear-inducing factor that makes you cry like a baby. 

                    

     I have heard of some absurd ways to reduce the unpleasant eye irritation caused by onions. Like, cutting onions in water, or chill the onions before cutting (to slow down the activities of the enzymes in onion), or just wear a pair of ski goggles. I have tried some of the methods above. Some worked, some didn't. And then one day in my cooking class, I finally learned the most legit and reliable way of cutting onions without getting teary. The key is, to cut along the grains of the onion, so that you crush the min. amount of cells which in turn will release the min. amount of lachrymatory factors. Since then, I have passed the trick to many people around me who suffered the eye irritations by onions. But judged from the confused looks on my friends' faces after they got my verbal description, I decided to make a quick sketch to illustrate what I mean by cutting onions "the right way". This by no means the only way to cut onions. But at least to me, I now seldom shed a tear while cutting these troublemakers.

After Step 4 in the illustration, you will get diced onions. If you want to get really small dices, you need a Step 5 to slice the onion horizontally. Imagine the cuts in Step 3 are on the x axis, cuts in Step 4 are on the y axis, then Step 5 would be on the z axis, perpendicular to Step 3 and 4.  If you want to julienne the onions to get slices, stop at Step 3. If you want onion rings on your burgers or something else, you need to halve the onion along its waist to get a cross section in Step 1. 

Boost the taste of your dishes by Maillard Reaction!

     As I mentioned in my last post, the French stew was cooked by the same technique that I learned in 2 other stews from my classes. Basically, you brown the meat first, then you continue baking the meat in the oven in some kind of sauce/stock. Prior to my cooking classes, I have only watched my mom making beef stews and never really made one myself.  The Chinese way of making stews is quite different: you first blanch the meat in boiling water, after you skim out the floating impurities, you add soy sauce, cooking alcohol and other spices and slowly finish cooking the meat on the stove (an easier alternative is to use a pressure cooker). "Browning the meat" was a foreign concept to me. So I did some reading, and found out that this "browning reaction" actually has a name. It's called the Maillard reaction. 

bis(2-methyl-3-furyl) disulfide

     The Maillard reaction was discovered by Louis-Camille Maillard in the early 20th century, when he was trying to heat up amino acids and sugars and the mixture turned brown.The molecules produced by amino acids and the reducing sugars absorb light and create a nice brown pigment in cooked meat. However, the colouring of the food is not the only outcome from the reaction. What is more important is that the reaction enhances the flavours and aromas. Like in roast beef, cysteine, an amino acid in protein, reacts with ribose, a sugar in the meat. Together, they produce a sulfurous molecule, bis(2-methyl-3-furyl) disulfide, which is responsible for the distinct smell of beef! Other amino acids and sugars are involved in similar Maillard reactions in baked goods.
     As for many chemical processes, temperature needs to be carefully monitored. The Maillard reaction proceeds at a fairly high temperature of 130 ºC/265 ºF. If the meat surface is covered in water, the temperature will stop climbing when it reaches 100 ºC, at which temperature water evaporates and you can't really go any higher than that. This is why when you brown the meat, the surface needs to stay dry so that the heat will exceed 100 ºC. However, if you over heat the meat, at 180 ºC or higher, pyrolysis (a.k.a., burning) kicks in and it will burn the meat instead. I guess the Maillard reaction is one of those high-maintenance reactions that require your undivided attention. Luckily for people like me, who have short attention spans, browning happens fast and it usually takes 2-4min per side of the meat. 
     Happy browning, my carnivorous friends!