Research on the Emulsifying Properties of Diacylglycerol

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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.