• Ultrasound/low-acid processing repurposed eggshells into food-grade Ca salts. • CaCO 3 was converted into Ca-CIT and Ca-ACE as functional ingredients. • Recovered CaCO 3 showed higher porosity and lower bulk density vs commercial. • Pb, Cd, As, Hg were <LOQ; E. coli and Salmonella spp. were not detected. • At 10 g/kg, salts raised muffin Ca 6–10 × and altered pH, porosity and texture. Eggshell (ES) waste is generated in large quantities but remains underutilized, despite being a naturally calcium (Ca)-rich by-product. In this study, a non-thermal, ultrasound-assisted, low-acid process was developed to convert ES into food-relevant Ca ingredients, namely Ca carbonate (CaCO 3 ), Ca citrate (Ca-CIT), and Ca acetate (Ca-ACE). The safety and functionality were evaluated in a muffin system. The recovered CaCO 3 consisted of calcite and exhibited a bulk density of 0.77 g/cm 3 , lower than that of commercial CaCO 3 at 1.18 g/cm 3 . The ES-derived powders exhibited high Ca content, 38.9% in CaCO 3 , 21.0% in Ca-CIT, and 23.2% in Ca-ACE. Heavy metals including Pb, Cd, As, and Hg were below the limits of quantification. Escherichia coli and Salmonella spp. were not detected, while yeast and mold counts remained low (31 to 33 CFU/g). Fortification at 10 g/kg increased muffin Ca content from 43.0 mg/100 g FW in the control to 292.2–430.7 mg/100 g, corresponding to a 6–10-fold increase. The form of Ca influenced muffin structure, primarily associated with differences in pH and solubility behavior. Crumb pH decreased from 7.2 (control) to 7.1 with CaCO 3 and to 6.0–6.6 with Ca-CIT, mixed Ca salts, and Ca-ACE, respectively. Muffin porosity increased from 47.3% to 52.9–53.8% in samples containing CaCO 3 and Ca-CIT, whereas Ca-ACE was associated with a decrease in porosity to 40.0% and increase in hardness up to 35.4 N. Sensory properties were generally comparable to the control, with no gritty or calcareous mouthfeel. Overall, Ca salt type was associated with differences in physicochemical properties and corresponding variations in muffin structure and texture. These findings contribute to a better understanding of structure-property-function relationships in Ca-fortified foods.
Kočetkovs et al. (Fri,) studied this question.