I just posted last night about a problem I had with a head of lettuce that was covered in brown spots. Littledevils said the spots were most likely russet spotting, so I did a bit of research on it. Russet spotting is caused by ethylene gas.
Ethylene gas "will permeate through produce cardboard shipping boxes, wood and even concrete walls.
While ethylene is invaluable due to its ability to initiate the ripening process in several fruits, it can also be very harmful to many fruits, vegetables, flowers, and plants by accelerating the aging process and decreasing the product quality and shelf life. The degree of damage depends upon the concentration of ethylene, length of exposure time, and product temperature. One of the following methods should be used to ensure that ethylene-sensitive produce is not exposed: a) Ethylene producing items (such as apples, avocados, bananas, melons, peaches, pears, and tomatoes) should be stored separately from ethylene-sensitive ones (broccoli, cabbage, cauliflower, leafy greens, lettuce, etc.). Also, ethylene is emitted by engines. Propane, diesel, and gasoline powered engines all produce ethylene in amounts large enough to cause damage to the ethylene-sensitive produce items mentioned;" ... (source:
http://www.ethylenegas.com/ethylene.htm)
So, in addition to improper storage and handling of produce, exposure to ethylene gas from a combustion engine, like those found on a tractor or transport truck, can speed up the ripening and spoilage of produce well before it reaches the store.
