Studies On Effecting Of Different Fermentation Processes On The Yield Of CPPs And Its Functional Properties

In this study, firstly, skim milk powder was used to prepare yogurt by mixing fermentation of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The single factor, orthogonal and Box-Behnken design tests had been carried out to study the effect fermentation conditions (time, temperature, strain ratio) on the yield of CPPs in yogurt. Secondly, the degree hydrolysis experiments were found to discuss the optimum conditions of hydrolysis for pure milk and yogurt by trypsin as well as it had effect on the production of CPPs under optimum conditions. CPPs were prepared by the methods of calcium-ethanol precipitation and the contents were determined by spectrophotometry. Finally, function properties of CPPs were studied by the way of pH-Stat.The single factor, orthogonal and Box-Behnken design tests showed that L18:St was2:1; the fermentation temperature was40℃; the fermentation time was4hours in12%skim milk by inoculating3%. The yield of CPPs in yogurt was379.4mg/100g under these conditions.The hydrolysis experiments demonstrated the best conditions for hydrolysis of pure milk and yogurt by trypsin. The conditions inculded the ratio of enzyme to substrate which was1:100, the reaction time which was3hours, and the hydrolysis reaction which occurred at37℃and pH8.0. Under this conditions the degree of hydrolysis respectively in pure milk and yogurt were20.40%,27.55%, and the yield of CPPs were146mg/g,207mg/g.The function test demonstrated that compared with the commercial CPPs, CPPs from yogurt could better prevent the formation of calcium phosphate and ferrous phosphate. As the CPPs concentration increased, they could better promote calcium and ferrum absorption. Temperature variation had no great effect on the formation of calcium phosphate when the temperature was below90℃. The pH between8and9was best for CPPs to prevent the formation of calcium phosphate. CPPs which worked along with citric acid or xylitol, exhibited synergistic effect on the preventing of formation of calcium phosphate.