Bioactive compound-loaded food-grade bigels: (II) Delivery systems focusing on the bioaccessibility of chlorophylls and the effects of microstructure and 3D printing

Bigels, as emerging biphasic systems, show great potential for bioactive compound delivery and as materials for 3D printing. In this study, food-grade bigels were developed as carriers of natural chlorophylls, designed also to support 3D printing applications. The bigels were formulated using agar-based hydrogels and carnauba wax-based oleogels at varying H:O ratios (80:20, 60:40, 40:60, 20:80). Natural chlorophyll extracts from Arthrospira platensis and Scenedesmus obliquus were selected due to their distinct chlorophyll profiles. The study focused on the effects of hydrogel:oleogel ratios (H:O) and 3D printing on the stability, micellarization, and bioaccessibility of chlorophylls during in vitro digestion. Microstructural analysis revealed that variations in the H:O ratio induced structural transitions in the bigels, shifting from an oleogel-in-hydrogel to a hydrogel-in-oleogel configuration. The in vitro digestion study demonstrated that both the H:O ratio and the 3D printing process substantially influenced chlorophyll bioaccessibility, with higher oleogel concentrations promoting greater micellization and bioaccessibility. For A. platensis extracts, the post-digestion chlorophyll profile was dominated by pheophytins, whereas S. obliquus extracts were predominantly composed of oxidized chlorophyll derivatives, such as 13²-OH-pheophytin. In SO-bigels, b series are more bioaccessible than a series. Notably, 3D printing altered the bigels' microstructure while enhancing total chlorophyll bioaccessibility. This study highlights the potential of bigels as effective delivery systems for natural chlorophylls, offering valuable insights into the modulation of bioaccessibility through H:O ratio adjustments and the integration of 3D printing technology.