This antioxidant chemical (C6H7NaO5) is used in the food industry to keep processed meat, such as hot dogs and beef sticks, from turning strange colors. It works as a meat preservative by aiding the action of nitrites during the curing process. It is also used in some sprinkle-on preparations that are used to prevent cut fresh fruit from turning brown. On fruit, it works by inhibiting enzymes that cause browning by scavenging oxygen and by reducing quinones.
This chemical appears as a white, odorless powder. In solutions, it has a pH of 5 or 6. It is the sodium salt of erythorbic acid and is chemically similar to ascorbic acid (vitamin C), which was used for the same purposes before this compound was developed. However, sodium erythorbate only gives the body 1/20th of the vitamin C one would get from taking regular vitamin C. It is made from sugar, commonly beet and cane sugar.
Industrially, this chemical is sometimes used as a reducing agent. For instance, it has been used as a developing agent in fluids used for photographic processing.
There was a totally-unfounded rumor going around a few years back that sodium erythorbate is made from ground-up earthworms. Repeat after me: no worms were harmed in the making of this chemical. Possibly the rumor got started after someone realized that the Middle English word for "earth" is "erthe" and mistakenly made the connection with "eryth". Or, perhaps the texture, taste and general mysterymeatishness of many cheap hot dogs lends credence to the notion that they contain earthworms.
Some of the information in this writeup was gleaned from http://www.pmpinc.com/product/eribate/fruit.html. Much of the rest was taken from the science dictionary at http://biotech.icmb.utexas.edu/; I oversaw the development of the dictionary (the website was mothballed in 1998) and I believe I wrote the entry this is based on.