From:
McDonald's USA Ingredients Listing for Popular Menu Items
McRib Bun:
Enriched flour (bleached wheat flour, malted barley flour, niacin, reduced iron, thiamin mononitrate, riboflavin, folic acid), water, yeast, high fructose corn syrup.
Contains 2% or less of the following: salt, corn meal, wheat gluten, soybean oil, partially hydrogenated soybean and/or cottonseed oils, dextrose, sugar, malted barley flour, cultured wheat flour, calcium sulfate, ammonium sulfate, soy flour, dough conditioners (sodium stearoyl lactylate, datem, ascorbic acid, azodicarbonamide, mono- and diglycerides, ethoxylated mono- and diglycerides, monocalcium phosphate, enzymes, guar gum, calcium peroxide), calcium propionate (preservative), soy lecithin.
CONTAINS: WHEAT AND SOY.
McRib Pork Patty:
Pork, water, salt, dextrose, preservatives (citric acid, BHA, TBHQ).
McRib Sauce:
Water, high fructose corn syrup, tomato paste, distilled vinegar, molasses, natural smoke flavor (plant source), food starch-modified, salt, sugar, spices, soybean oil, xanthan gum, onion powder, garlic powder, chili pepper, sodium benzoate (preservative), caramel color, beet powder.
Nutrition Breakdown:
Calories: 500
Calories from fat: 240 (almost half)
Protein: 22g
Fat: 26g
Saturated Fat: 10g
Cholesterol: 70g
Carbohydrates: 44g
Sodium: 980mg
A little more about the "McRib Pork Patty" from the Chicago Tribune:
"Restructured meat products are commonly manufactured by using lower-valued meat trimmings reduced in size by comminution (flaking, chunking, grinding, chopping or slicing). The comminuted meat mixture is mixed with salt and water to extract salt-soluble proteins. These extracted proteins are critical to produce a “glue” which binds muscle pieces together. These muscle pieces may then be reformed to produce a “meat log” of specific form or shape. The log is then cut into steaks or chops which, when cooked, are similar in appearance and texture to their intact muscle counterparts."Not only does the McRib start with one of the most sorry animals, the factory-farmed pig, but it uses otherwise unmarketable parts from that animal. Likewise the McNugget, except with a chicken.
...
"Most people would be extremely unhappy if they were served heart or tongue on a plate," he observed. "But flaked into a restructured product it loses its identity. Such products as tripe, heart, and scalded stomachs are high in protein, completely edible, wholesome, and nutritious, and most are already used in sausage without objection." Pork patties could be shaped into any form and marketed in restaurants or for airlines, solving a secondary problem of irregular portion size of cuts such as pork chops."
...
"In 1981 McDonald's introduced a boneless pork sandwich of chunked and formed meat called the McRib, developed in part through check-off funds [micro-donations from pork producers] from the NPPC [National Pork Producers Council]. It was not as popular as the McNugget, introduced in 1983, would be, even though both products were composed of unmarketable parts of the animal (skin and dark meat in the McNugget). The McNugget, however, benefited from positive consumer associations with chicken, even though it had none of the "healthy" attributes people associated with poultry."