Characterization of fish oil-in-water emulsions using light-scattering,nuclear magnetic resonance,and gas chromatography-headspace analyses |
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Authors: | Email author" target="_blank">Zhiping?ShenEmail author Punsandani?Udabage Iko?Burgar Mary?Ann?Augustin |
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Affiliation: | (1) Commonwealth Scientific and Industrial Research Organisation (CSIRO) Manufacturing and Infrastructure Technology, 3168 Clayton, Victoria, Australia;(2) Food Science Australia, 671 Sneydes Rd., 3030 Werribee, VIC, Australia |
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Abstract: | The effect of the molecular environment on the physical and oxidative properties of homogenized or microfluidized fish oil-in-water
emulsions (5% w/w tuna oil in pH 7 phosphate buffer) stabilized by whey protein isolate (WPI, 1 or 5% w/w) or lecithin (2.5%
w/w) was examined. Laser light-scattering measurements showed that WPI-stabilized emulsions had smaller particle sizes than
lecithin-stabilized emulsions, and that higher pressures reduced the particle size. WPI afforded more protection against oil
oxidation than did lecithin, as evidenced by the lower headspace propanal of emulsions as measured by GC-headspace analysis,
despite the larger interface in WPI-stabilized emulsions. Reducing the concentration of WPI in emulsions from 5 to 1% decreased
the oxidative stability of WPI-stabilized emulsions. The 1H NMR transverse relaxation times (T
2) of FA chains in emulsion droplets stabilized by the same surfactants made by homogenization or microfluidization were different
and not always related to particle size. The higher mobility (i.e., longer T
2) of the unsaturated parts of the FA chains within an oil droplet, compared with the saturated parts, suggests that the unsaturated
components tended to stay in the core of the oil droplets. This experimental result supports the hypothesis reported in other
literature that the more unsaturated FA are buried in the oil core of oil-in-water emulsions. The lack of a universal correlation
between particle size and oxidation suggests that the mobility of particles in an emulsion has an influence on the rate of
oxidation. |
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Keywords: | Fish oil-in-water emulsion headspace (HS) analysis lecithin n− 3 fatty acids NMR particle size propanal relaxation time (T 2) whey protein isolate |
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