Eggshell waste transformation to calcium chloride anhydride as food-grade additive and eggshell membranes as enzyme immobilization carrier

In continuation of our efforts to fully utilize eggshell waste (ESW), here we report the possibility of ESW transformation to calcium chloride (CaCl ) anhydride of food-grade additive purity and eggshell membranes (ESMs) as potential enzyme immobilization carriers. ESW chemical transformation by 5% (w/v) hydrochloric acid to CaCl solution and ESM completely devoid of the remnants of ESW calcium carbonate was performed in the constructed 15 L batch reactor during 4 h at room temperature, followed by separation of ESM from CaCl solution by filtration. ESW-derived CaCl solution containing the excess hydrochloric acid was neutralized by adding calcium hydroxide, concentrated to approximately 1/8th of volume, and spray dried. Separated ESM was washed with water and acetone, dried, and ground to a size of less than 0.5 mm. The ESW transformation process produced 102.42 ± 3.31 g of CaCl anhydrous and 2.48 ± 0.28 g of ESM per 100 g of ESW dry matter. ESW-derived CaCl fulfilled all criteria for food-grade additive, while obtained ESM showed their suitability for lipase immobilization by adsorption.