[Explanation: Change of protein by heat]

The protein of meat congeals when heated. The protein is a large molecule in which such elements as carbon, hydrogen and nitrogen combine. If it is further heated after it has congealed, its combination is broken and it becomes a compound called melanoidin with a chemical amino-carbonyl reaction to oxygen in air and others.
Melanoidin is light brown and has a good smell. The good smell when meat is grilled is that of melanoidin.


Since sugars and protein or amino acids are contained in various food, melanoidin is produced by grilling many food thereby making the food more delicious. However, since melanoidin is easy to volatize, its smell disappears if it is heated for a long period of time with low heat. So, it is a secret of cooking to grill food for a short period of time over a high flame. Moreover, the reaction causes carbonization over 200 degrees. Since the main element is protein, it smells bad if it is burned and so care must be taken.