Preparation, Characterization And In Vitro Digestion Of Fucoxanthin Emulsion

Emulsion-based systems are particularly suitable for delivering lipophilic components to solve the problem of low water-solubility, poor instability and low bioaccessibility. Using the structured lipid as the carrier oil, and high-pressure homogenization, this paper prepared the fucoxanthin emulsions, and examined the conditions and in vitro digestion. The concrete content as follows:(1) Structured lipid was synthesized from pine nut oil and linseed oil with lipase-catalysed interesterification.. The structured lipid contained 90% of unsaturated fatty acids, with 13.87% of △5 unsaturated fatty acids. Interestingly, the amount of△5unsaturated fatty acids at sn-2 position of structured lipid was increased to 9.61%, from 2.55%. At the same time, the content of pinolenic acid at sn-2 position was significantly increased form 1.85% to 7.84% in structured lipid.(2) The effect of different homogenization conditions, emulsifier type and concentration, temperature and co-emulsifier on the physicochemical properties of fucoxanthin nanoemulsion was investigated. The results showed that the droplet diameter decreased with increasing homogenization pressure and passes. The minimum droplet diameter(154 nm, PDI = 0.19) could be obtained after 4 passes at 120 MPa by high-pressure homegenization. The droplet diameter also strongly affected by emulsifier type, which showed the diameter was in the order of SDS < Tween 80 < sodium caseinate. What is more, the diameter decreased with emulsifier concentration and holding temperature(P < 0.05). After adding different levels of glycerol, appreciably decreased droplet size was founded in Tween 80 and SDS stabilized fucoxanthin nanoemulsion rather than in sodium caseinate stabilized one, indicating Tween 80 and SDS stabilized fucoxanthin nanoemulsion were more sensitive to viscosity than sodium caseinate stabilized one. The electrical charge and droplet diameter were constant at different pH conditions for Tween 80 stabilized fucoxanthin nanoemulsion, while SDS and sodium caseinate stabilized emulsions undergo great changes both in charge and diameter at acid conditions(P < 0.05). After storage at 37 °C for 30 days, the fucoxanthin amount of residue was higher in nanoemulsion than in organic phase, suggesting fucoxanthin nanoemulsion enhanced the stability of fucoxanthin.(3) We have shown that the fucoxanthin can successfully be incorporated into food-grade namoemulsions with the structured lipid, focusing on the particle diameter on the physicochemical stability and in vitro bioaccessibility of fucoxanthin-enriched emulsion or nanoemulsions. The unstable emulsion separated easily, while the nanoemulsions with small diameter were extremely stable to coalescence during a month storage study at the different temperature. The degradation rate of fucoxanthin increased with the dereasing diameter. The emulsion containing large droplets was unstable to flocculate in the stomach stage, following a decrease in particle after in intestine. Conversely, the nanoemulsions with small particle diameters behaved fairly similar trend at simulated digestion model: the gatric fluid had no remarkable effect on the diameter and charge of emulsions. There was an appreciable increase in average size and negative charge of droplets after intestine incubation. The sizes of emulsions were increased to 2201, 1592, 1870 nm; While the charge were decreased to-41 mV,-44 mV,-45 mV, respectively. The rate and extent of structured lipid digestion strongly depend on the initial droplet size, increasing with decreasing particle diameter. The amount of fatty acids was 53.4%, 72.7%, 82.1%, 85.9%, respectively. We also observed that the fucoxanthin bioaccessibility was proved to be positively correlated with the extent of pipolysis, and the increase of the released FFAs could improve the bioaccessibility. The bioceedssibility of the four fucoxanthin emulsions were 16.7%, 33.9%, 44.3%, 46.7%, respectively.