Preservation of β-carotene in liquid or solid lipid nanoparticles and their behavior during in vitro digestion: a mechanistic kinetic study

Lipid-based solid nanoparticles (SNPs) are a potential strategy to protect and deliver lipophilic bioactive compounds, such as carotenoids. The fat crystalline state renders tightly packed triglyceride structures, thus potentially protecting them against oxidative degradation. However, this might also hinder the lipolysis during digestion, thus the release and absorption of bioactive compounds may be compromised. The use of solid fats with a low melting point to formulate SNPs might be interesting for targeted lipolysis. Thus, SNPs with β-carotene-enriched cocoa butter (COA) or coconut oil (CNUT) and liquid nanoparticles (LNPs) with corn oil (CO) (5% w/w) stabilized with Tween80 (0.5% w/w) were fabricated by hot or cold homogenization, respectively. The β-carotene stability during storage (48 days at 25 ºC) and their lipolysis and subsequent carotenoid bioaccessibility kinetics during in vitro digestion was studied. The particle diameter of the NPs was around 500 nm, and remained stable during the storage period. COA-NPs presented a higher β-carotene stability in comparison with CNUT-NPs, yet was similar to the one of CO-NPs, with a 70 % β-carotene retention after 48 days in the COA or CO-NPs as opposed to 15 % in the CNUT-NPs. During digestion, the triacylglycerides hydrolysis kinetics and subsequent formation of lipid digestion products was faster and to a higher extent in the COA and CO-NPs compared to the CNUT-NPs. This might be due to (i) a higher melted/crystallized triacylgycerides ratio in the COA-NPs or (ii) a preferential digestibility of C18 fatty acids present in COA and CO by intestinal lipase as opposed to C12 present in CNUT. Despite the lower concentration of lipid digestion products in mixed micelles for the CNUT-NPs, the carotenoid bioaccessibility was similar for the three studied systems, with final values above 60%. This results show the potential to modulate lipid digestion by designing lipid nanoparticles with specific characteristics.status: publishe