"balut sa puti" ("wrapped in white") when it is white; the embryo inside is insufficiently developed to show a beak, feathers or claws, and the bones are undeveloped. These are made from very specific egg types, less than five days old and with no visible surface cracks. The duration of egg incubation is a matter of local preference. In the Philippines, balut is generally incubated for 14 to 18 days before being boiled for consumption. At about 14 to 16 days of incubation, the embryo floats on top of the egg white and yolk, and the balut is called "mamatong". For most balut makers, the ideal incubation is said to be 17 days old. There are other versions of balut. In the Cambodian version, pong tea khon, the egg is incubated for 18 to 20 days. In the Vietnamese version, trứng vịt lộn, the egg is incubated for 19 to 21 days, when the embryo is old enough to be recognizable as a baby duck and has bones that will be firm but tender when cooked. Some men prefer to eat an embryo that is much more developed, "...so that it looks gross, because that is a way to prove your manhood." Chemistry of cooking During the cooking process, changes occur in the food chemistry of balut, such as the sol dispersion of water molecules within the embryonic fluid. This liquid becomes the broth for the solid which are parts of the duck within the egg. Although balut mainly consists of protein, fat is present and is emulsified within the fertilized embryo. After cooking, it can be considered a protein gel (depending on the length of time it was cooked). Heating high-protein food such as balut can cause the chemical changes to take place and fully or partially denature proteins, causing the surface to become thick and causing an irreversible gel protein to form. Temperature has a significant impact on the final taste and texture of the cooked balut. Warm temperatures of change the taste and texture of the yolk by making it more grainy. This can be attributed to the changes in proteins, and their partial denaturation, during the heating and incubation process. When boiling or cooking eggs, the white of the egg tends to solidify because the proteins are denatured in an irreversible reaction and turn from transparent to an opaque white. Physical and chemical changes in the