Optimization of the Purification Process of Yak Casein Phosphopeptide and Its Calcium Absorption-promoting Effect.

To investigate the properties and calcium-holding capacity of yak casein phosphopeptide (CPP), this experiment was carried out using yak casein as the raw material, with trypsin being used for enzymatic hydrolysis. Static adsorption test was performed to determine the eluent, and the effects of sample amount, sample flow rate and eluent concentration on the purification process of CPP. The basic composition, functional properties, and in vitro inhibitory capacity against calcium phosphate and ferrous ion precipitation of purified CPP were examined. A low-calcium mouse model was established, and the ability of CPP to promote calcium absorption in mice was investigated using body weight, organ index, serum biochemical parameters, femur index, bone density and bone calcium as the indicators. The experimental results showed that the best purification effect on the CPP was obtained under the following conditions: 0.2 mol/L dilute hydrochloric acid as the eluent, 3 mL/min as the loading flow rate, and 100 mL as the loading volume, leading to a nitrogen to phosphorus molar ratio of 6.8, a phosphorus recovery of 95.5%, a glutamic acid content of 18.55% and a serine content of 6.01%. In vitro calcium promotion experiments showed that the purified CPP could effectively prevent the precipitation of calcium phosphate and ferrous ions. The results of animal experiments showed that after 28 d of feeding, the organ indices of all mice were within a reasonable range. After purification, CPP showed no chronic toxicity. The medium- and high-dose groups had significantly higher blood calcium and phosphorus levels than those of the model group (P<0.05), and had extremely significantly lower alkaline phosphatase (ALP) values than those in the model group (P<0.01). The femoral bone index in the high-dose group was significantly higher than that in the calcium carbonate group (P<0.05). The bone calcium and bone density of the medium- and high-dose CPP groups were significantly higher than those of the model group (P<0.05). In conclusion, this experiment can provide a theoretical basis for the development of functional yak milk foods and a reference for the subsequent research on yak milk's bioactive peptides. [ABSTRACT FROM AUTHOR]