Effects of microalgae incorporation on nutrient digestibility and antioxidant activity of gluten-free muffins after simulated chewing and digestion in adults and older adults

Abstract

This study aimed to evaluate the effects of microalgae incorporation, chewing conditions, and digestive models on carbohydrate and protein digestibility, total phenolic content, and antioxidant activity of gluten-free muffins, using in vitro boluses produced by a compression–shear–decompression process in a rheometer. To this end, gluten-free muffins, with and without microalgae (spirulina and chlorella), were formulated, and their chemical and mechanical properties were characterised. In vitro boluses were prepared with normal and deficient chewing, and the granulometric and mechanical properties were determined. Oro-gastrointestinal digestion was simulated in vitro by reproducing the conditions of adults and older adults. The results demonstrated that the rheometer was a reliable instrument for simulating in vitro bolus formation, closely mimicking in vivo conditions. The addition of microalgae increased protein, ash, and fibre content, reduced carbohydrate content, increased hardness, and decreased cohesiveness. It also improved protein digestibility, reduced starch digestibility, and increased total phenolic content and antioxidant activity. Furthermore, poor chewing reduced starch digestibility but favoured the release of phenolic compounds, whereas older adult digestion reduced both protein and starch digestibility while increasing the release of total phenolic compounds and antioxidant activity. This study highlights that both mastication and age-related digestive alterations exert a decisive impact on starch and protein digestibility, as well as phenolic compounds and antioxidant activity.