Preparation of instant yak bone powder by using instant catapult steam explosion and its physicochemical properties

Abstract: In order to solve the problem of insolubility of bone powder and improve preparation process, the instant yak bone powder was prepared by liquefying yak bone with instant catapult steam explosion (ICSE), and the elemental nutrients and physicochemical properties of which were also analyzed comparing with the bone powder prepared by traditional ball-milling method.Firstly, according to the liquefaction rates of yak bone and the yields of bone powder under different pressures and maintaining times, the best ICSE condition was selected. The yields were calculated based on dry material after sieving and spray drying. Then, the physicochemical properties including the chemical structure, particle size distribution, micro-morphology, instant solubility, sedimentation, protein solubility and calcium release of yak bone powder were analyzed and compared.The results showed that the highest yield of yak bone powder was 46.16% prepared by ICSE technology under 1.5 MPa for 30 min. Therefore, the instant powder was prepared by this condition, and its nutritional components and physicochemical characteristics were analyzed. By analyzing the molecular weight distribution of peptides in liquefaction under 1.5 MPa for 30 min, it was found that bone collagen was broken into peptides with different molecular weights, and the peptides with molecular weight less than 0.5 kDa accounted for 26.14%.Also, we found that the bone microstructure treated by ICSE was looser and more porous observed by scanning electron microscope. Compared with the ball-milling yak one powder, the chemical structure of ICSE yak bone powder had no obvious change since the peak positions of Fourier infrared spectroscopy were similar. The median particle size of ICSE yak bone powder was 5.61 μm, which was significantly smaller (P <0.05) than that of ball-milling yak bone powder, and the particle size distribution was more uniform because of the regular normal distribution while the median particle size of ball-milling yak bone powder was 19.68 μm with a skewed distribution.Through the determination of basic ingredients of yak bone powder, it was found that both protein and fat contents of yak bone powder prepared by ICSE were significantly (P <0.05) higher than that of ball-milling yak bone powder while ash was less. Meanwhile, the contents of main minerals such as P, Ca, Mg, K, Zn decreased significantly (P <0.05) in ICSE yak bone powder while that of Na increased significantly. Additionally, the ICSE yak bone powder had better solubility and stability than ball-milling yak bone powder. It is soluble in water at room temperature, and no obvious precipitation occurs within 10 minutes. Comparatively, it gradually became clear and transparent with the extension of time for ball-milling yak bone powder. Besides, the protein solubility of ICSE yak bone powder increased significantly (P <0.01), which were 97.17%, 95.29%, 82.07% at 37 ℃, 60 ℃, 100 ℃ while the ball-milling yak bone powder were 4.07%, 6.47%, 10.17%, respectively. In addition, the calcium release of ICSE yak bone powder could reach 67.42 mg/g while that of ball-milling yak bone powder was only 14.25 mg/g. The ICSE method for preparing instant yak bone powder can shorten the preparation time and improve the product quality. Therefore, ICSE technology can be used as a new and efficient method to improve the value of bone byproducts.