Yes, there are preservatives added to prevent the meat from turning brown.
CO + Hemoglobin (Hb) = Carboxyhemoglobin (COHb) will prevent the meat from COLOR oxidizing for UP TO 30 DAYS! Your meat may be rotten, but the color will still look fresh.
http://www.nytimes.com/2006/02/21/na...1890d3&ei=5070
And preservatives are not just in meat either. For instance, petroleum based waxes are commonly added in citrus fruits to prevent the fruits from drying. Dried mushroom, especially the imported varieties, are commonly laced in formaldehyde.
There are approximately 5000 types of food preservatives the US currently use. Most are not labeled.