Ash and calcium as measures of bone in meat and bone mixtures

Bone content of mechanically recovered meat is usually controlled by setting calcium limits, but these limits may allow more bone in some products because calcium content of fresh bone is variable. Studies involving deposition of energy, nutrients, and minerals are also dependent on ash or calcium to determine bone content of carcasses. However, ash and calcium, which is 37% of bone ash, varies by age of animal, presence or absence of tissues such as marrow or cartilage that are associated with bone, and state of bone hydration. Literature that reports ash content of bone and factors associated with its variability is the focus of this review. Based on the literature reviewed, a conversion factor of 4.5 for calcium percentage to fresh cortical bone percentage from round bones of cows, fed beef, lambs, pigs and hens is recommended. A conversion factor of calcium percentage to fresh bone percentage of 5.0 is recommended for all veal and broiler bones and for flat bones.