Research on the Emulsifying Properties of Diacylglycerol

本研究旨在阐明二酰基甘油(DAG)的乳化特性，它在分子结构上与常见的脂类三酰甘油(TAG)不同。基本实验体系：对油相体积分数(φ)为0.5的1：1油：蛋黄水溶液，考察了蛋黄水溶液浓度、pH值和氯化钠加入量的影响。PH对DAG的界面张力的影响小于TAG。虽然pH值对乳液的平均粒径没有影响，但在pH值为6时制得的DAG乳液具有较高的粘度。结果表明：1.在DAG乳液中加入氯化钠降低了界面张力，显著增加了乳液体积。模拟蛋黄酱乳状液：在1：1蛋黄：3.5%醋酸水相，φ为0.7：1的乳状液中测试了盐的浓度和类型(氯化钠、氯化钾、氯化钙、氯化镁、硫酸镁)，每种盐的加入都减小了乳状液的平均粒径，增加了乳状液的粘度。特别是在DAG中加入少量的氯化钠，大大提高了乳液的粘度。2)在蛋黄高密度组分和低密度组分中，高密度组分的乳化性略有利于DAG。低密度组分对DAG的乳化效果不明显，而以蛋黄为乳化剂制备的蛋黄酱状浓缩乳状液有效地显示了蛋黄的乳化能力，所制得的DAG乳状液比TAG乳状液具有更小的粒径和更高的粘度。3)DAG乳液在制备过程中粘度的变化，在φ为0.55时，粘度大于TAG，尤其是在φ为0.6时，粘度迅速增加。此外，在φ为0.6时，DAG中吸附到油滴界面的蛋白质比TAG乳液中的更多。

The present study was conducted to elucidate the emulsion characteristics of diacylglycerol (DAG), which differs in molecular structure from triacylglycerol (TAG), a common lipid.1. Basic experimental system : The effects of aqueous egg yolk concentration, pH, and NaCl addition on 1:1 oil : aqueous egg yolk solutions with an oil phase volume fraction (φ) of 0.5 were tested. The effect of pH on interfacial tension was smaller for DAG than TAG. Although pH had no effect on the mean particle diameter of the emulsions, the DAG emulsion prepared at pH 6 had high viscosity. The addition of NaCl to the DAG emulsion decreased interfacial tension and significantly increased emulsion volume.2. Simulated-Mayonnaise emulsion systems: The following were tested in emulsions with 1 : 1 egg yolk : 3.5% acetic acid solution in aqueous phase with φ of 0.7: 1) For concentration and type of salt (NaCl, KCl, CaCl_2, MgCl_2, MgSO_4), the addition of each salt decreased mean particle diameter and increased viscosity for all emulsions. In particular, addition of small amounts of NaCl to DAG greatly increased the viscosity of the emulsions. 2) Of high-density and low-density fractions of egg yolk, emulsifiability of the high-density fraction was slightly favorable for DAG. While the low-density fraction was found to be ineffective for DAG, a mayonnaise-like concentrated emulsion prepared using egg yolk as the emulsifier effectively demonstrated the emulsifying ability of egg yolk and produced DAG emulsions with smaller particle diameter and higher viscosity than for TAG emulsions. 3) Regarding changes in the viscosity of DAG emulsions during the preparation process, viscosity became greater than that of TAG above φ of 0.55, and in particular, rapidly increased above φ of 0.6. In addition, more protein was adsorbed to the oil droplet interface in DAG than in TAG emulsions at φ of 0.6.