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Mulrooney, Steven
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Mulrooney, Steven
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Mulrooney, Steven
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- PublicationFood Emulsions: their role in enhancing the stability and bioavailability of Vitamin DThis research investigated the formulation, stability and digestion of vitamin D loaded mixed micelles to develop a novel food delivery system for vitamin D. Mixed micelles were prepared with different fatty acids and phospholipid concentrations and their stability to salts was investigated. Mixed micelles formed at NaCl and KCl concentrations from 20–100mM with octanoic acid (C8) or stearic acid (C18). Mixed micelle size increased with increasing phospholipid concentration for C8 and C18, but micelles were inconsistently or not formed outside these concentrations. The hydrodynamic size of mixed micelles increased from 3.8nm for C10 to 4.4nm for C18. Vitamin D incorporation in micelles was not influenced by the fatty acid used. Understanding the stability and formation of mixed micelles and vitamin D loading is a crucial first step to improve vitamin D delivery in foods. Chapter 3 explored the stability of vitamin D loaded mixed micelles subjected to food processing and storage regimes. Shearing (speeds 8,000–20,500rpm) and high-pressure processing (600MPa, 120sec) resulted in no change in mixed micelle size (4.1–4.5nm), reflecting micelle stability to these processes. Mixed micelles improved the retention of vitamin D following exposure to UV-C light, near UV/visible light and heat treatments. Mixed micelles protected vitamin D from degradation over four weeks at 4 or -20°C. Overall, mixed micelles protected vitamin D from degradation in food processing and storage, and may be beneficial to fortify foods with vitamin D. Chapter 4 investigated the ability of mixed micelles to improve vitamin bioaccessibility in vitro compared to oil-in-water emulsions. Vitamin D loaded emulsions were formed with olive or coconut oil alone or with added phospholipid, and two mixed micelle systems. Throughout in vitro digestion, particle size, fatty acid release and vitamin D bioaccessibility were measured. After digestion, particles in the size range 6-10nm were present for the emulsions, but not for the mixed micelle systems. Vitamin bioaccessibility in olive or coconut emulsions was 75% and 78%, respectively, ~90% with added phospholipid and ~90% for the micelles. All systems tested had similar vitamin D concentration in the mixed micelle phase obtained after digestion. Differences in bioaccessibility were attributed to a higher concentration of vitamin D present in the total digesta for the olive and coconut oil emulsions. The in vitro study showed the potential of mixed micelles to deliver vitamin D and may be as effective as an oil-in-water emulsion at delivering vitamin D. Chapter 5 involved two human studies; Study A) a cross-over post prandial study examined changes in 25(OH)D following consumption of four vitamin D fortified drinks (non-lipid, olive oil, fish oil or mixed micelle based); Study B) a randomised, placebo-controlled trial investigated changes in 25(OH)D concentrations over four weeks following daily consumption of an olive or coconut oil based emulsion fortified with 20µg of vitamin D, a 20µg vitamin D supplement, or a placebo control dairy drink. In Study A, a vitamin D fortified olive oil emulsion increased serum 25(OH)D concentration in insufficient participants (baseline serum 25(OH)D <50nmol/L) but the micelle formulation did not improve vitamin D absorption in this group. There were no significant changes in serum 25(OH)D concentration in vitamin D sufficient participants (baseline serum 25(OH)D =50nmol/L) for any of the vitamin D fortified drinks tested. Study B found that an olive or coconut oil based vitamin D fortified emulsion was as effective at increasing 25(OH)D as a vitamin D supplement in vitamin D insufficient older adults. However, only a coconut oil vitamin D emulsion was as effective as a vitamin D supplement in vitamin D sufficient older adults. In both studies baseline 25(OH)D predicted responses to vitamin D and these responses differed in vitamin D sufficient and insufficient groups.
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