ARS | Publication request: Physical distribution and characteristics of meat & bone meal protein

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2008
Publication Date: February 1, 2009
Citation: Garcia, R.A., Phillips, J.G. 2009. Physical distribution and characteristics of meat & bone meal protein. Journal of the Science of Food and Agriculture. 89(2):329-336.

Interpretive Summary: The use of meat & bone meal (MBM) in animal feed has been progressively restricted over the past two decades, and new outlets for MBM are required in order to avoid negative environmental and economic consequences. Development of new applications for other high-protein agricultural products has been facilitated by transforming the agricultural products into intermediate forms that are easier to utilize. In this research, we used several experimental techniques to gather the information necessary before designing a process to make such an intermediate product from MBM. The upper limits of MBM protein were established and characteristics of soluble MBM protein were measured. Results from investigations into the physical distribution of protein in MBM reveal that it may be more economical to remove the bone particles from MBM before extracting MBM protein. It was determined that a large portion of MBM protein is collagen, a finding which helps in choosing the most promising end-user applications to develop. Several obstacles were noted, including the poor solubility and non-uniformity of MBM. The results indicate which methods of producing an intermediate will be the most appropriate.

Technical Abstract: Meat & bone meal (MBM) is a high-protein commodity produced by the rendering of fat from unmarketable animal tissue. Concerns related to bovine spongiform encephalopathy have progressively restricted MBM’s conventional use as a feed ingredient. Consequently, significant attention has focused on the development of new applications for MBM. New applications will more readily be developed from an MBM protein isolate that is relatively concentrated, homogenous and soluble. Rational design of a process to produce such an isolate requires knowledge of the host biological matrix, the physical distribution of the protein in the matrix, and the properties of the protein itself; the present study examines these aspects of MBM. MBM consists of particles derived from bone and particles derived from soft tissue. The proportions of bone and soft tissue vary, but on average greater than 80% of protein in MBM is in the soft tissue particles. MBM protein is a complex and severely degraded mixture of many protein types. Under mild conditions only 4.6% of bone protein and 15% of soft tissue protein can be solubilized; aggressive but impractical conditions can solubilize much more of the protein, but invariably greater than 45% of the protein remains insoluble. This low solubility and other factors preclude the quantitative determination of MBM's protein type profile, but amino acid analysis reveals that collagen accounts for approximately 17% of the protein in soft tissue particles and 26% of that in bone particles. Molecular mass analysis of the extractable fraction of MBM protein reveals weight-average molecular masses of 71.1-86.7 kDa and high polydispersity, depending on particle type, extraction conditions and raw material species. Overall results suggest that practical production of an MBM protein isolate will have to incorporate limited hydrolysis, possibly downstream from an extraction of the easily-soluble fraction.