Plant-based dairy alternatives often require calcium fortification and texture modifiers or stabilisers to meet both the nutritional and functional standards of their dairy counterparts. Dietary calcium intake is determined not only by the amount consumed but also by the efficiency of its delivery, which depends on its release from the food matrix during digestion. Structural changes arising from texture modifiers, as well as interactions between calcium and these modifiers, may influence calcium release and bioaccessibility during digestion; however, research on this topic remains limited.

In this study, a plant-based yoghurt alternative model was developed using 5% pea protein and 1% GDL to induce acid gelation. The acid-induced gels were fortified with insoluble CaCO₃ (30 mM; 1200 ppm Ca) and modified using different doses (0, 0.2, and 1.0% w/w) of a gelling agent, low-methoxyl (LM) pectin. Gel textural and structural properties were characterised using a texture analyser and confocal laser scanning microscopy. The calcium-fortified gels were subjected to dynamic in vitro gastric digestion using a Human Gastric Simulator, combined with static oral and intestinal phases. Digesta were collected at 30-minute intervals to determine pH, total solids, and calcium profiles. Total, soluble, and ionic calcium were quantified using microwave plasma atomic emission spectrometry (MP-AES) and a calcium-selective electrode.

Results showed that gels with higher hardness and more compact microstructure slowed gastric emptying, which in turn delayed total calcium release in both gastric and intestinal phases. However, ionic and soluble calcium release appeared to be unaffected by gel structure or its breakdown during digestion in this acidic gel system. In addition to enhancing gelation, LM pectin stabilised ionic/soluble calcium in the intestinal phase and prevented precipitation with phosphate or carbonate, resulting in a more sustained and higher ionic calcium release in the 1.0% pectin sample.

Overall, these findings indicate that while gel texture does not govern calcium release in acid-induced gels, the incorporation of LM pectin can alter the fate of calcium during digestion. This work provides insights for designing plant-based dairy alternatives that achieve efficient micronutrient fortification alongside desirable techno-functional properties.