The Preparation Of Calcium Propionate And Calcium Lactate From Waste Duck Eggshell

Our country is a superpower of eggs production and consumption in the world,while the eggshell is usually discarded as waste. The main component of duckeggshell is CaCO3, which accounts for over95%of the dry weight of the shell ishigher than the egg shell. The eggshell will make serious environmental pollutionwithout be treated. In this paper, the Ca source of duck eggshell was used as materialsto develop and utilize. The preparation of calcium propionate which was used as foodpreservative was under the condition of ultrasound-assisted, and the preparation ofcalcium lactate was under the condition of anaerobic fermentation. Both methodswere optimized to get the best process conditions. The main conclusions are asfollows:(1) In the experiments of preparation of calcium propionate byultrasound-assisted with duck eggshell: According to single factor and responsesurface experiments, the influences of each single factors for experiment wereanalyzed. The results showed that the optimal experimental conversion rate and puritywere under the condition of the acid diluted ratio was1:9.4, the particle size of theshell was50mesh, the reaction time was2h, the reaction temperature was61.5℃, theultrasonic power was351.6W, the impurity agent was1g/5g, and the impuritytemperature was70℃, respectively. The conversion rate of eggshells reached to94.05%, the purity of calcium propionate reached to95.42%which was analysed byHPLC.(2) In the experiments of preparation calcium lactate under the condition ofanaerobic fermentation: According to single factors and orthogonal experiments, theinfluences of each single factor for the conversion rate and purity of duck eggshellcalcium lactate were analyzed. The results showed that under the condition of initialglucose concentration was70g/L, the inoculum concentration was5%, the particlesize was40mesh, the eggshell dosage was8g/200mL, the shaker shaking speed was80r/min, fermentation temperature was37℃, fermentation time was72h and impuritydosage was0.75g/5g respectively, the best experiment results were obtained. Under the optimum conditions, the duck eggshell conversion rate reached to93.03%, andthe calcium lactate purity reached to96.72%(higher than the national standard whichwas defined≥95%) at the same time.(3) The economic analysis result showed that preparation of1kg calciumpropionate by the ultrasound-assisted method would be cost12.089Yuan, profitswere increased170%and the cost of production were decreased6.85%; preparationof1kg calcium lactate would be cost9.507Yuan, profits were increased44.6%andthe cost of production were decreased10.1%.The preparation conditions of calcium propionate by ultrasound-assisted methodand preparation of calcium lactate by anaerobic fermentation were simple, the purityof the productions was relatively high, and meanwhile economic benefits wereremarkable. The research provided a good environmental benefits, social benefits andpromotion prospects.