I would say death, or decay, begins after the last breath. I think if we look at what exactly decomposition is in the human body and what scripture/history tells us, I think we can deduce that his body did not decay. Jesus died but did not experience decomposition. Because He was brutally murdered and died yet did not decay but rose again, He "destroyed death" and successfully fulfilled the punishment and propitiation for our sin. I would say the very central message of the gospel.
2 Timothy 1:10
"but it has now been revealed through the appearing of our Savior, Christ Jesus, who has destroyed death and has brought life and immortality to light through the gospel."<
First some unpleasant reality of what normally happens upon death:
"Decomposition begins several minutes after death, with a process called autolysis, or self-digestion. Soon after the heart stops beating, cells become deprived of oxygen, and their acidity increases as the toxic by-products of chemical reactions begin to accumulate inside them. Enzymes start to digest cell membranes and then leak out as the cells break down. This usually begins in the liver, which is enriched in enzymes, and in the brain, which has high water content; eventually, though, all other tissues and organs begin to break down in this way. Damaged blood cells spill out of broken vessels and, aided by gravity, settle in the capillaries and small veins, discolouring the skin."
"Body temperature also begins to drop, until it has acclimatised to its surroundings. Then, rigor mortis – the stiffness of death – sets in, starting in the eyelids, jaw and neck muscles, before working its way into the trunk and then the limbs."
"Most internal organs are devoid of microbes when we are alive. Soon after death, however, the immune system stops working, leaving them to spread throughout the body freely. "
"Once self-digestion is under way and bacteria have started to escape from the gastrointestinal tract, putrefaction begins. This is molecular death – the breakdown of soft tissues even further, into gases, liquids and salts. It is already under way at the earlier stages of decomposition but really gets going when anaerobic bacteria get in on the act.
Putrefaction is associated with a marked shift from aerobic bacterial species, which require oxygen to grow, to anaerobic ones, which do not. These then feed on the body’s tissues, fermenting the sugars in them to produce gaseous by-products such as methane, hydrogen sulphide and ammonia, which accumulate within the body, inflating (or ‘bloating’) the abdomen and sometimes other body parts.
This causes further discolouration of the body. As damaged blood cells continue to leak from disintegrating vessels, anaerobic bacteria convert haemoglobin molecules, which once carried oxygen around the body, into sulfhaemoglobin. The presence of this molecule in settled blood gives skin the marbled, greenish-black appearance characteristic of a body undergoing active decomposition.
As the gas pressure continues to build up inside the body, it causes blisters to appear all over the skin surface. This is followed by loosening, and then ‘slippage’, of large sheets of skin, which remain barely attached to the deteriorating frame underneath. Eventually, the gases and liquefied tissues purge from the body, usually leaking from the anus and other orifices and frequently also leaking from ripped skin in other parts of the body. Sometimes, the pressure is so great that the abdomen bursts open."
"Each fly deposits around 250 eggs that hatch within 24 hours, giving rise to small first-stage maggots. These feed on the rotting flesh and then moult into larger maggots, which feed for several hours before moulting again. After feeding some more, these yet larger, and now fattened, maggots wriggle away from the body"
"Life after death: the science of human decomposition" - Moheb Costandi, neuroscientist
"Within 3– 6 hours after death, the body’s muscular tissues become rigid and are unable to relax, and this is known as rigor mortis
24-72 hours after death - Internal organs begin to decompose.
3-5 days after death - Body starts bloating. Blood-containng foam begins leaking from mouth and nose.
8-10 days after death - Massive decompostion of organs in abdomin accumulate massive gas; body turns from green to red becuase of blood decomposition.
Several weeks after death - Nails and teeth begin to fall.
1 month after death - Body starts to liquefy "
I think we can look at the example of Lazarus after Jesus brought him back from death.
Jesus, once more deeply moved, came to the tomb. It was a cave with a stone laid across the entrance. “Take away the stone,” he said. “But, Lord,” said Martha, the sister of the dead man, “by this time there is a bad odor, for he has been there four days.” Then Jesus said, “Did I not tell you that if you believed, you would see the glory of God?”<
The dead man came out, his hands and feet wrapped with strips of linen, and a cloth around his face. Jesus said to them, “Take off the grave clothes and let him go.”<
Six days before the Passover, Jesus arrived at Bethany, where Lazarus lived, whom Jesus had raised from the dead. Here a dinner was given in Jesus’ honor. Martha served, while Lazarus was among those reclining at the table with him.<
Lazarus was sufficiently dead, and should have been sufficiently rotting as well, yet people would come from all over to see him and he would even dine and recline among him. Any decomposition, besides being horrendous, would have made him unclean and would not have been able to be around so close to so many.
A week later his disciples were in the house again, and Thomas was with them. Though the doors were locked, Jesus came and stood among them and said, “Peace be with you!” Then he said to Thomas, “Put your finger here; see my hands. Reach out your hand and put it into my side. Stop doubting and believe.”<
Jesus had the physical 'wounds' from His life yet if He was experiencing decomposition fluids, maggots, and stench would have already been coming from the hole in His side leaving Thomas' experience to be less than exuberant.
After his suffering, he showed himself to these men and gave many convincing proofs that he was alive. He appeared to them over a period of forty days and spoke about the kingdom of God.<
1 Peter 3:18
For Christ died for sins once for all, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive by the Spirit,<