ジアシルグリセロールの乳化性に及ぼす卵黄成分および食塩の影響

DAGの乳化性に及ぼす卵黄成分および食塩の影響について明らかにするためにTAGと比較検討し,以下の結果を得た。1)HDFで調製したエマルションはTAG,DAG共に粘性係数および降伏値が小さかった。一方,LDFで調製したTAGエマルションは,高い粘性係数と降伏値を有し安定性が高かった。DAGでは両特性値共にTAGのそれより低く,やや不安定であった。2)食塩1.0%添加はHDFで調製したTAG,DAGエマルションの粘性係数および降伏値を高めたが,DAGではやや不安定な流動曲線となった。食塩の添加はLDFエマルションの粘性係数および降伏値を低下させた。3)HDFで調製したエマルションの粒度分布は2つのピークを有し,DAGのメジアン径はTAGのそれよりやや大きかった。食塩添加により,TAGの大粒子は減少し,ピークは1つになった。DAGにおいても大粒子のピークは小さくなった。LDFで調製したDAGエマルションのメジアン径はNaCl添加,無添加共にTAGのそれより大きく,標準偏差も大きかった。4)遠心分離による乳化層の評価をした結果,LDFで調製したDAGエマルションでは,TAGより乳化安定性が高かったが,DAGではNaCl添加で乳化層に一部亀裂が生じた。

The fractions mainly containing high-density lipoproteins (HDF) and low-density lipoproteins (LDF) were separated from hen egg yolk. Oil-in-water emulsions to simulate mayonnaise were prepared with egg yolk, HDF or LDF, 3.5% acetic acid and triacylglycerol (TAG) or diacylglycerol (DAG). The same amounts of HDF and LDF as those present in the egg yolk were used for the preparation, and the volume of the aqueous phase of the emulsion prepared with HDF or LDF was adjusted to the same volume as that of the egg yolk by adding water. The flow behavior and oil-particle-size distribution of each emulsion were respectively determined by a cone-and-plate viscometer and a fine-particle-counting analyzer. Each emulsion was centrifuged. The stability of the emulsion was evaluated by the volume of the remaining emulsified layer after centrifugation. The viscosity of the emulsions prepared with HDF was lower than that of the emulsions prepared with egg yolk for both TAG and DAG. The emulsion prepared with LDF showed markedly higher viscosity than that prepared with egg yolk when TAG was used, this effect being similar, although much less pronounced, when DAG was used. Emulsions containing sodium chloride in the concentration range of 1-5% in the aqueous phase were prepared, and the same determinations were conducted. The addition of 1% salt increased the viscosity of the emulsions prepared with HDF whether TAG or DAG was used. Above 2% of added salt, the HDF emulsions would not form when TAG was used, although slightly unstable HDF emulsions formed when DAG was used. The viscosity of the TAG emulsions prepared with LDF decreased gradually with increasing concentration of salt, although those prepared with egg yolk increased with increasing salt concentration. The DAG emulsions prepared with LDF became unstable by adding salt, although the addition of salt below 2% increased the viscosity of the DAG emulsions prepared with egg yolk, before becoming unstable with salt addition above 3%. It is concluded that LDF does not act favourably as an emulsifying agent for DAG, while HDF is probably more favourable for DAG than for TAG. Further experiments are needed to clarify the action of these fractions on DAG.

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KJ00004435123

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