Impact of emulsifier nature and concentration on the stability of β-carotene enriched nanoemulsions during in vitro digestion
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The presence of emulsifiers facilitates the formation of nanoemulsions and helps on their stabilisation. At the same time, behaviour of nanoemulsions along the gastrointestinal tract mainly depend on their composition, affecting the bioaccessibility of the encapsulated compound. The goal of this work
was to study how β-caroteneenriched nanoemulsions prepared with different emulsifiers (Tween 20, lecithin, sodium caseinate, sucrose palmitate) and concentrations (2-8%) would affect their stability (particle size and zeta potential) during an in vitro gastrointestinal tract (GIT). The lipid digestibility, as well as the β-carotene bioaccessibility of nanoemulsions, was also determined. Nanoemulsions stabilised with Tween 20, lecithin and sodium caseinate did not present any variation in particle size under stomach conditions. After intestinal GIT phase, all nanoemulsions experienced physical changes, either increasing or reducing their particle size depending on the nature and concentration of emulsifier used. The zeta potential of all nanoemulsions was maintained negative throughout the GIT, being less negative after the stomach GIT phase (between -24.2 and -1.4 mV). Lecithinstabilised nanoemulsions presented the highest number of free fatty acids when emulsifier concentration increased from 2 to 8%.In this sense, nanoemulsions containing 8% of lecithin exhibited the highest β-carotene bioaccessibility (23.5%), suggesting that lecithin can enhance lipid digestion and bioaccessibility of β-carotene encapsulated within nanoemulsions. This work elucidates the importance of not only the emulsifier nature but also the concentration used when designing nanoemulsions as delivery systems of lipophilic compounds.