Why does organic material turn dark brown when it decomposes?

Context

Organic matter, regardless of its original color or form, tends to turn dark brown as it decomposes. This color change is observed in both plant and animal matter, and it occurs whether the matter is solid or liquid. The question arises as to the chemical reason behind this color transformation and whether there is a specific "organic ground state" that all organic substances eventually degrade to.

Simple Answer

• Organic matter contains pigments called melanins, which are dark brown or black.
• As organic matter decomposes, enzymes break down the pigments, releasing melanins.
• Melanins absorb light, giving the decomposing matter a dark color.
• The darker the color, the more advanced the decomposition process.
• Eventually, all organic matter will turn dark brown as it fully decomposes.

Detailed Answer

The browning of decomposing organic matter is primarily due to the presence of pigments called melanins. Melanins are dark brown or black pigments found in various organisms, including plants, animals, and even microorganisms.

As organic matter undergoes decomposition, enzymes released by microorganisms break down the complex organic compounds into simpler substances. This breakdown process includes the release of melanins, which contribute to the dark coloration.

Melanins have the ability to absorb light, particularly in the visible spectrum. This absorption of light gives the decomposing matter its characteristic dark color, ranging from light brown to deep brown or even black.

The darkness of the color is often an indicator of the extent of decomposition. The more advanced the decomposition process, the more melanins are released, resulting in a darker color.

Ultimately, as organic matter fully decomposes, the accumulation of melanins leads to the dark brown coloration that is commonly observed in decaying plant and animal matter.