>> Return to List of FAQ Questions
What is a Maillard reaction (Chemistry)?
According to Wikipedia:
The Maillard reaction is a chemical reaction between an amino acid and a reducing sugar, usually requiring the addition of heat. Like caramelization, it is a form of non-enzymatic browning. The reactive carbonyl group of the sugar interacts with the nucleophilic amino group of the amino acid, and interesting but poorly characterized odor and flavor molecules result. This reaction is the basis of the flavoring industry, since the type of amino acid determines the resulting flavor.
In the process, hundreds of different flavor compounds are created. These compounds in turn break down to form yet more new flavor compounds, and so on. Each type of food has a very distinctive set of flavor compounds that are formed during the Maillard reaction. It is these same compounds that flavor scientists have used over the years to create artificial flavors.
Although used since ancient times, 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 hypothesis 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.
It is important to note that the carbohydrate layer can be dissolved with diimide or stripped away with an adhesive leaving clear, colorless fiber. This is true whether it has undergone a color-producing color change or not. Chemist Ray Rogers describes the layers, composed of a complex mixture of conjugated systems:
There is absolutely no doubt that the image color exists in a thin layer on the surface of image fibers. The layer is amorphous, and it seems to have an index of refraction relatively close to that of the linen fiber. The layer is quite brittle, and many flakes of the color have flaked off of the fibers. Colorless cellulose can be seen where image color has flaked off. The flakes can be seen and identified on the adhesive of sampling tapes. The flakes have the chemical properties of the intact image color on the fibers.
See: What is the nature of the Shroud of Turin cloth?
>> Return to List of FAQ Questions
© 2004 Daniel R. Porter, Bronxville, New York
