Plant-based diets have gained significant traction due to their potential benefits for human health and environmental sustainability. However, achieving nutritional adequacy in these diets presents challenges, particularly regarding calcium (Ca) and sodium (Na) balance. While animal-derived dairy products are naturally rich in highly bioavailable Ca, most plant sources are deficient in this essential mineral or contain absorption inhibitors like phytate. This makes it difficult to meet the recommended dietary intake of 1000 mg Ca/day without fortified foods or supplements. Concurrently, a pressing issue in the plant-based product sector is their excessively high Na content, with market analyses consistently showing that plant-based meats exceed the Na levels of their animal-based counterparts, contravening WHO recommendations. This creates a paradox where plant-based foods, often perceived as inherently healthier, may contribute to negative health outcomes associated with high Na intake. Therefore, a critical need exists for innovative processing strategies that can simultaneously reduce Na and enhance the Ca content in plant-protein ingredients, thereby aligning the nutritional profile of plant-based foods with consumer health expectations.

Soy protein isolate (SPI), a key ingredient in plant-based foods, exemplifies this issue; raw soybeans contain only 2 mg Na/100 g (dry basis), but conventional SPI production via wet fractionation process intensively uses NaOH for protein solubilisation and neutralization, resulting in a final product with a Na content to approximately 1000 mg/100 g. This study addressed these dual nutritional challenges by innovating the traditional SPI production process through the partial replacement of NaOH with Ca(OH)₂ during soy protein fractionation. We systematically investigated the effects of substituting NaOH with Ca(OH)₂ during both the protein solubilisation and neutralization steps on the yield, mineral composition, and functional properties of the resulting soy protein fractions (SPF), to determine optimal conditions for producing nutritionally enhanced yet functionally viable ingredients.

Our research demonstrated that strategic incorporation of Ca(OH)₂ significantly modified the nutritional and functional profile of SPFs. Using Ca(OH)₂ during the solubilisation step enhanced protein recovery yields, while substitution during neutralization step successfully produced high-Ca, low-Na SPF with up to 90% reduction in Na content compared to conventional SPI. Crucially, we identified a critical threshold of 6.5 mg Ca/g protein below which Ca enrichment did not substantially alter protein conformation or functional properties. SPF maintained excellent solubility, water holding capacity, and formed strong gel networks when Ca content remained below this threshold. However, exceeding this level induced significant structural and functional changes: increased particle size and thermal stability, reduced solubility and water binding capacity, and weaker gel formation due to Ca-induced protein aggregation. These findings provided a practical framework for developing nutritionally optimized soy proteins that simultaneously address the critical needs for Na reduction and Ca fortification in plant-based foods. The resulting SPF represented a promising functional ingredient for creating healthier soy-based meat alternatives and dairy substitutes that align with both nutritional guidelines and consumer expectations for clean-label, sustainable protein sources, thereby advancing innovation in alternative protein applications within the hydrocolloid-based food matrix.