Cadaverine (1,5-diaminopentane) is a reactive amine vapor that begins to emerge from a human body shortly after death. Along with putrescine (1,4-diaminobutane), another amine vapor, cadaverine will react with a carbohydrate material such as that found on the Shroud as a nanoscale coating on some of the fibers. The chemical reaction is called a Maillard reaction.
A Maillard reaction is a chemical reaction between an amino acid and a reducing saccharide, often requiring the addition of moderate heat. Like caramelization, it is a form of non-enzymatic browning. The reactive carbonyl group of the saccharide interacts with the nucleophilic amino group of the amino acid. The process produces numerous flavor and odor molecules. Dozens of flavoring compounds can be produced. The Maillard reaction is essential in the artificial flavoring industry.
The Maillard reaction is also significant in that it produces a yellowing or browning color. An example is artificial sun tanning lotion. In the production of dark beer, the color comes from a Maillard reaction that takes place during brewing.
The reaction is named after the chemist Louis-Camille Maillard who investigated it in the 20th century.
A Maillard reaction is significant in Shroud of Turin research because it is one of the leading hypotheses for image formation. It has been proposed that a chemical reaction occurred that selectively changed a carbohydrate layer of starch fractions and sugars that coated some of the Shroud's fibers. The amine gases produced by a dead body are extremely reactive chemically. Within a few hours, in an environment such as a tomb, a body starts to produce heavier amines in its tissues such as putrescine (1,4-diaminobutane), and cadaverine (1,5-diaminopentane). This will produce the color we see in the carbohydrate layer.
These layers, visible with phase-contrast microscopy, are extremely thin. On the Shroud they have been observed to be approximately 180 to 600 nanometers thick. This is in the range of the wavelengths of visible lights. Where they are imaged, that is where they are chemically changed, they are thinner. This is chemically expected. The cellular fibers, which host the carbohydrate layers, are not colored.
