Pork quality is a combination of several factors including, nutrient makeup and density, aroma, color, flavor, tenderness and marbling. The best quality pork displaying each of these elements is a result of genetics (breeding) and diet and environmental factors (feeding).
The best quality pork is from swine that have quality-oriented genetics, are healthy and have been fed a diverse, nutrient dense diet and have been allowed to a degree of maturation where they have deposited inter-muscular fat.
High quality pork
Genetics play a big role in the production of quality pork. Key genetic traits related to pork quality are the ability to deposit inter-muscular fat (where many nutrients, such as vitamin D, are stored), a propensity to tenderness and color (which is thought to be a proxy for nutrient density.)
Pigs raised outdoors, on a variety of natural foods are more nutrient dense than hogs raised on bland, grain-based formulated feeds.
Jacob Springs pork quality
Industrial pork quality
The pork industry has a name for their own, low quality product, PSE pork; Pale, Soft and Exudative. This is a recognized fault in the pork industry's product and although the industry spent millions on an advertising campaign to convince the public that pork should indeed be considered "the other white meat" (chasing the "success" of the poultry industry) the industry recognizes paleness, softness and the excessive shrinkage caused by the meat exuding water upon cooking as flaws in it's product.
Reasons for the low quality pork
Industrial breeding, excessive grain feeding, general nutrient deficiency lack of access to sunlight, focus on "lean" meat, focus on feed conversion ratios.
Adaptations to the low quality pork
increased use of nitrates, flavorings, sugar and salt in industrial pork products.
How the industry overcame consumer objections to their low quality products
Gradual change in accepted standards over generations, marketing campaigns such as "the other white meat", focus on "value added", highly "doctored" pork products based on nitrates, flavorings, sugar and salt.