DAIRY MATRIX STRUCTURE SHAPES MINERALS BIOACESSIBILITY DURING IN VITRO DIGESTION UNDER OLDER ADULT’S CONDITIONS

Aging is associated with reduced bone and muscle mass, making adequate calcium (Ca) and magnesium (Mg) intake essential. However, the nutritional benefits of these minerals depend not only on their concentration in dairy products but also on their bioaccessibility, which is influenced by processing-induced structural changes and age-related digestive alterations. Therefore, this study evaluated the effect of different dairy matrix structures on the bioaccessibility of Ca and Mg under older adult’s digestive conditions. A fluid matrix (FM) was prepared by diluting milk protein concentrate in water to obtain 13% protein. An enzymatic gel (EG) was produced by in-package coagulation of FM, whereas an acid gel (AG) was obtained through lactic fermentation. Samples were subjected to the INFOGEST protocol adapted for older adult’s, and Ca and Mg bioaccessibility was determined by flame atomic absorption spectrometry (FAAS). Data were analyzed by ANOVA. EG exhibited the highest total Ca content (461.93 mg/100 g), followed by AG (406.02 mg/100 g) and FM (373.09 mg/100 g), likely due to syneresis during enzymatic coagulation. No significant differences were observed in total Mg content among the products. Regarding bioaccessibility, EG exhibited the lowest Ca bioaccessibility (65.68%), whereas FM (86.07%) and AG (83.03%) showed significantly higher values (p < 0.05). In contrast, coagulation enhanced Mg bioaccessibility, with AG (99.94%) and EG (100.46%) exhibiting significantly higher values than FM (95.58%). These findings indicate that dairy matrix structure modulates mineral release during digestion according to each mineral distribution within the matrix. Calcium, predominantly associated with casein micelles at the natural pH of milk, may become less available following enzymatic coagulation because of greater retention within the protein network. Furthermore, interactions during digestion, including peptide release, fatty acid distribution, and mineral complexation, may further affect Ca solubilization. In contrast, coagulation enhanced Mg bioaccessibility by promoting retention of the serum phase within the protein network. During digestion, progressive degradation of this structure may promote gradual Mg release, which is predominantly present in the soluble phase and therefore remains readily available in the digestive medium. Thus, modifying dairy matrix structure may represent an effective strategy to optimize essential mineral delivery in older adults.