| Budget Amount *help |
¥16,160,000 (Direct Cost: ¥15,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2007: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2006: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 2005: ¥6,500,000 (Direct Cost: ¥6,500,000)
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| Research Abstract |
The effects of droplet size and emulsifiers on oxidative stability of polyunsaturated triacylglycerol (TAG) in oil-in-water (o/w) emulsion were investigated. Hydroperoxide (HPO) formation, oxygen uptake (02 uptake) and secondary oxidation product contents were measured as oxidation indices. The o/w emulsion consisting of 10% (w/w) cod liver oil TAG, 1% (w/w) emulsifier, 100μM ethylenediamine-N,N,N',N'-tetraacetic acid tripotassium salt dehydrate (EDTA-3K) and 26 mM citrate buffer (pH 6.6) was prepared by a membrane filtration technique using `Shirasu' porous glass (SPG) ceramic membranes with single pore size of 0.8, 1, 3, or 10 μm. Sucrose lauryl ester or polyglycerol lauryl ester was used as an emulsifier. The SPG membranes with single pore sizes of 0.8, 3.1 or 10 pm successfully prepared the single dispersion emulsions with droplet sizes of 0.806±0.0690, 3.28±0.0660 or 10.7+0.106 μm (mean±S.D.), respectively. The oxidative stability of the o/w emulsions were evaluated at 40 °C in th
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e dark for 120 hrs. The HPO contents and 02 uptake decreased with decreasing the droplet sizes of the o/w emulsions; the HPO contents in the emulsion with a mean droplet size of 0.831 gm were significantly lower than those of the emulsion with a mean droplet size of 12.8 gm for up to 120 hrs of oxidation time. The residual oxygen contents in the headspace air of the vials containing o/w emulsion with a mean droplet size of 0.831 pm were lower compared with those of the emulsion with a mean droplet size of 12.8 gm. Hexanal developed from soybean oil TAG o/w emulsions with smaller droplet size showed significantly lower contents than those of the larger droplet size emulsions. Consequently, the oxidative stability of TAG in o/w emulsion could be controlled by the size of oil droplet even though the origins of TAG were different.
Spin-spin relaxation time of protons of the acyl residues on TAG in the o/w emulsions measured by ^1H-NMR suggested that the motional frequency of some acyl residues was shorter in the o/w emulsions with a smaller droplet size. The effect of 'wedge' due to hydrophobic acyl residues of the emulsifiers was proposed as a possible mechanism to explain the difference in oxidative stability between the o/w emulsions with different droplet sizes.
By conducing organoleptic analysis, we investigated the effect of oil droplet size on human preference to the taste of oil-in-water (o/w) emulsions to which several tastants were added. Two singly-dispersed o/w emulsions different in oil droplet sizes consisting of 10% triacilglycerol (TAG) purified from tuna, sardine or soybean oil, 0.5% emulsifier and water were prepared by ceramic membrane filtration. Organoleptic analysis showed that the impressions of sweetness, bitterness and umami, which were developed by addition of certain taste substances, were different between o/w emulsions with different oil droplet sizes. The results of two-bottle choice tests, which were carried out using olfactory-blocked mice, showed that o/w emulsions with 1.00〓m droplets with added sweet or bitter substances were preferred to emulsions with 5.50-〓m droplets. These results suggest that the droplets size of o/w emulsions remarkably influences certain taste impressions created by added taste substances. Less
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