In collecting gases off of six humans and 26 different animals, researchers identified 452 distinct chemical compounds. Specifically, human corpses emit a unique five-chemical cocktail — comprised of 3-methylbutyl pentanoate, 3-methylbutyl 3-methylbutyrate, 3-methylbutyl 2-methylbutyrate, butyl pentanoate and propyl hexanoate — that separates them from the rest of the animal kingdom. “The next step in our research is to see whether the same compounds are found in buried, full decomposing bodies in the field and to see whether dogs trained on the mixture respond more specific[ally] to human decomposing bodies.” If this cocktail passes muster, the find could pave the way for developing an electronic nose that can do what dogs do, she adds. PHOTOS: Patenting Death 
 
 “The mixture of (these) compounds might be used in the future to more specifically train cadaver dogs,” analytical chemist Eva Cuypers told Science. Since then, the list of carbon-based, or organic, compounds given off during decay has grown quite long, but there have been conflicting reports about which ones are emitted only by humans. Pig remains are often used as human analogues ( Table 1 ) because of their similarity in hair coverage, weight, fat to muscle ratio, gut fauna and biochemistry [ 5 , 16 , 20 ]. The new research is the first to look at how the two similar animals decompose in the same conditions. Rosier identified the compounds in the collected gases and compared them among species. “But there are still many steps before creating a synthetic substance to train cadaver dogs.” 
 
 “I don’t think there’s one specific thing that says it’s human,” adds John Sagebiel, an analytical chemist at the University of Nevada, Reno, who was also uninvolved in the study. The jars’ screw caps, which let in some air, had stoppered holes that allowed her to periodically take samples of the gases building up inside. At first, sulfur-containing compounds seemed to distinguish the different species, but they were not unique to humans or even present in all humans. But it was not clear whether the decomposition process was the same because the two species had never been studied under identical conditions. After one month, the sulphur-containing compounds are the most important compounds that devide the species in the y-direction in the plot. During 6 months, 452 VOCs were found in the headspace of the decomposing remains. Pig remains in particular have often been used in past decomposition studies because of their similarities to human bodies (which are often hard to come by): They have the same microbes in their guts, the same percentage of body fat, and similar hair as people. This might be due to the fact that these compounds were only found in very small trace amounts. For that reason, pigs have been used in most previous decomposition studies.  In the aftermath of California’s recent forest fires, cadaver dogs sniffed beyond burning homes, charred forest, and even other dead animals to pick up the unique scent of human victims. Esters are described to be degradation products of muscles, fat tissue and carbohydrates [4, 16]. She set up other jars with pig, mouce, mole, rabbit, turtle, frog, sturgeon, or bird remains. Ultimately, eight compounds distinguished pig and human remains from those of other animals, and five esters separated pigs from humans, the researchers report this month in PLOS ONE. Cuypers’s graduate student Elien Rosier started by putting tissue samples and organs from six autopsied corpses in jars in a lab closet. And Arpad Vass, who is associated with the University of Tennessee, Knoxville, Body Farm and has compiled a list of compounds released by decomposing humans, points out that the use of specific tissues—versus a whole body—and the isolation of those tissues in jars means the researchers are looking at just a subset of the bacteria and other environmental factors that influence decomposition.
– Thanks to a team of researchers from Belgium, we may be close to synthesizing and, yes, possibly even bottling and selling the smell of human death, Discovery reports. Eva Cuypers and her team at the University of Leuven separated the tissues and organs of six humans and 26 different animals, placing them in jars to decompose over the next six months. By collecting the gases building up in the jars, researchers identified 452 organic compounds, according to Science. Eight of those compounds were found only in decomposing humans and surprisingly human-like pigs, and five of them were unique to humans. These five compounds—called esters—were created by decomposing muscles, carbohydrates, and fat, Discovery reports. The esters create a "singular chemical cocktail" in decomposing humans and could explain why so-called cadaver dogs are able to sniff out dead people amid any number of competing smells, including other dead animals, Science reports. Cuypers and her team published their findings last week. They believe the results could be used to better train cadaver dogs or even create a machine that could do the same job. And Discovery points out the synthetic smell of decomposing human bodies could prove popular at Halloween parties. Experts have questioned components of the research—including the separation of tissue and organs—and Cuypers plans a follow-up study using full bodies buried in a field, Science reports. (The smell of corpses can also reveal when a person died.)