The optical properties of bovine bone as an indicator of possible uses

Context

Bone is the most abundant animal by-product. Every year, around 63 mt/ year of bones from beef and dairy cattle are produced worldwide, with 7.2 mt/year of that from Europe. Currently, this by-product is either recovered for use in low value-added products such as pet food, or it is exported or incinerated. But bone has various mechanical, thermal, electrical and biological properties that could be used for innovative biobased products. Leveraging this potential requires understanding the variability of bone: while its chemical composition remains virtually immutable, its structure, divided into five levels, can change with certain biological factors such as animal age and bone anatomy. Researchers used terahertz time-domain spectroscopy (THz-TDS) to determine some of the optical properties of bone, namely the refractive index (n) and absorption coefficient (k). Bones of different ages and anatomies (femur/tibia) were analysed. The optical properties were linked to the extractability of organic matter and minerals from bone.

Results

The femur and tibia represent two different clusters; the tibial cluster is more homogeneous than the femoral cluster. Age accounts for around 27% of total variability and anatomy around 68%. The refractive index rises with age, while the absorption coefficient decreases with age. The femur showed more obvious variations. The refractive index was positively correlated with bone mineral extractability, meaning that when using the same process, an older femur produces a better yield of minerals than a younger one, and even more so when compared to a tibia of the same age. Meanwhile, the absorption coefficient was positively correlated with organic matter extractability (and especially collagen, mainly from the tibias). This parameter was lower in the tibias than in the femurs.

Future outlook

Biomass variability, which is considered an obstacle to high value-added recovery, has not been widely studied. This study was the first time research has sought to identify markers in bovine bone to use the material in more targeted applications. This was also the first time THz-TDS was used to study the optical properties of bone. The advantage of THz-TDS, which is the most recent spectroscopy technique (discovered in 1990), is that it provides information that is not accessible with infrared radiation and allows several optical properties to be directly measured.

Partnerships

Institute of Physics, Pontificia Universidad Católicade Chile, Chile - ANID – Millennium Science Initiative Program, Millennium Institute for Research in Optics (MIRO), Chile - FTMC – Terahertz Photonics Laboratory, Centre for Physical Sciences and Technology, Lithuania

Contact

Vincenza Ferraro UR QuaPA vincenza.ferraro@inrae.fr