Effect of calcium enrichment on the composition, conformation, and functional properties of soy protein

Plant-based diets with sufficient calcium (Ca) supplements are needed to protect the body from Ca deficiencies. The Ca enrichment of protein ingredients during fractionation can provide a new route to increase the Ca content in plant-based products. We, therefore, investigated if the partial replacement of NaOH by Ca(OH)₂ during the neutralization step of the fractionation process affects the functional properties of the protein-rich fractions. The protein and oil content of the obtained soy protein-rich fractions (SPFs) were not affected by the use of Ca(OH)₂. Moreover, when the Ca content in the SPF was lower than a certain threshold value (6.5 mg Ca/g protein), the functional properties and conformation of SPF did not change significantly. Higher Ca content in the SPF, however, led to protein-rich fractions with larger particle size, higher thermal stability, lower NSI and WHC_P values, and weaker gel networks. Thus, any addition of Ca higher than a certain threshold changes the properties of the proteins significantly, which can alter the applicability of the fractions in plant-based food products. Nonetheless, this study showed that with partial replacement of NaOH by Ca(OH)₂, the enrichment of SPF with Ca is possible without strongly influencing the SPF properties.