Study On The Preparation Of Yak Bone Powder And Its Anti-Osteoporosis Activity

With the development of aging society,the incidence of osteoporosis is rising.At present,the research on prevention and cure of osteoporosis mainly focuses on drug treatment,ignoring the adjustment of the overall metabolic state of the body,which generally has some side effects.Therefore,it is of great significance to find some bioactive substances with little by-effects which can well prevent osteoporosis.The research purpose is to study the effect of yak bone powder with different particle sizes on physicochemical and digestive characteristics alone with anti-osteoporosis.Finally,the optimal particle size and mechanism of yak bone powder for anti-osteoporosis will be verified,which can also provide theoretical and technical support for the future development of functional food with high-activity from yak bone.In order to reduce the degreasing rate and improve the quality of yak bone powder,the ultrasonic assisted organic solvent degreasing method was investigated based on the thighbone of Qinghai yak in this paper,and the nutrient contents and physicochemical properties were analyzed comparing with the traditional boiling degreasing method.Results suggested that ethyl acetate was the optimal degreasing solvent with optimum degreasing conditions as follows:ultrasonic power is 500 W;ultrasonic time is30min;the ratio of liquid to material?v:m?is 6,under which condition the degreasing rate could reach92.00%,while that of boiling method is just 71.25%.Meanwhile,the loss rate of protein and collagen were 8.11%,11.05%,respectively,which were dramatically lower?P<0.05?.And there was a serious loss of Na,K,Fe and Mn in cooked yak bone while the loss about Fe,Zn,Mn in ultrasonic skimmed yak bone was slightly.Moreover,no significant difference had been observed about the chemical structure and calcium release of bone powder?P>0.05?.In conclusion,the ultrasonic assisted organic solvent degreasing method could remain more nutrients with the higher degreasing rate.Secondly,the effect of different median particle sizes?19.92?m,49.94?m,76.65?m,96.73?m and 128.37?m?on both physicochemical and digestive characteristics of yak bone powder were investigated.The results showed that there were no significant differences in the contents of basic nutrients?protein,fat,water,ash and carbohydrate?,total amino acids,hydroxyproline and minerals in bone meal with different particle sizes?P>0.05?.Besides,different particle sizes made no contribution to the chemical structure change based on the fourier transform infrared spectroscopy.However,the brightness,protein solubility and water holding capacity were enhanced as the particle size decreased.The digestibility of bone meal with different particle sizes was studied by digestion system in vitro.The protein digestibility of bone meal with D₅₀0 of 19.92 um was 28.53%after intestinal digestion,while that of bone meal with D₅₀ of 128.37um is 16.10%which was significantly lower than the former?P<0.05?.The free amino acid contents of each digesta were different,among which that of tyrosine?Tyr?,phenylalanine?Phe?,lysine?Lys?and arginine?Arg?were much higher,while all increased with the decrease of particle size.However,the relative contents of peptides with molecular weight less than 0.5kDa declined with smaller particle size as well as the calcium and phosphorus release which were 3.27³.84 mg/g and 1.34¹.65 mg/g,respectively.Above all,the particle size affected the physicochemical and digestive properties of yak bone meal to a great extent.In order to investigate the effect of yak bone powder with different particle sizes on the anti-osteoporosis,three median particle sizes?19.92?m,76.65?m,128.37?m?were used to feed ovariectomized rats.The results showed that the apparent absorption rates of calcium and phosphorus reached 53.37⁵5.12%and 55.26⁵8.51%,respectively.Compared with the model group,the content of osteocalcin,alkaline phosphatase and tartrate-resistant acid phosphatase in serum of yak bone meal increased significantly?P<0.05?.However,there was no significant difference in both bone density and trabeculae between experiment groups?P>0.05?.In conclusion,yak bone meal showed anti-osteoporosis activity in ovariectomized rats,but the bone meal with different median particle sizes from 19.92?m to 128.37?m did not lead to significant difference in anti-osteoporosis.