Abstract

Addressing age-related health issues through better nutrition is vital as the population ages. Sustainable food systems focus on low-impact ingredients like brown seaweed, which needs minimal resources and has health benefits. However, concerns about heavy metals in brown seaweed pose safety challenges. After confirming the safety of a Durvillaea incurvata extract containing phlorotannins and mannitol, which showed an 80% reduction in heavy metals and no impact on cell viability, this study assessed the bioaccessibility of polyphenols, including phlorotannins, and the stability of antioxidant capacity during in vitro digestion in both standard and older adult models. It also compared these results with two commercially available seaweed products: micronized capsules and rehydrated salad. Crude extract exhibited the highest level of antioxidant compounds before digestion in the Folin-Ciocalteu (22.5 mg PhE/g dw) and DMBA (0.8 mg PhE/g dw) assays. Bioaccessibility indices reached 1005% and 332% in the standard and older adult models, respectively, when total soluble polyphenols were used as the measurement standard. The DMBA assay confirmed an increase in phlorotannins after digestion, likely due to the release of polyphenols previously bound to the food matrix. However, the differences observed between the two digestion models did not exhibit the same magnitude of change. The digested crude extract remained stable in older adults (DPPH and ORAC), while the micronized seaweed showed the highest DPPH value but decreased after digestion. Correlation analysis revealed matrix-dependent relationships between phenolic content and antioxidant capacity, highlighting the role of compound bioaccessibility in Durvillaea incurvata products. These results support the use of crude extracts as safe and effective ingredients in foods for older adults.