Effects of Heating Temperature, pH and Ionic Strength on the Stability of Flammulina velutipes Emulsions

The aim of this study was to evaluate the stability of the Flammulina velutipes emulsion when the environmental factors (such as temperature, pH and ionic strength ) changes. The 1.0% and 2.0% oil-in-water emulsions were prepared using Flammulina velutipes as raw material. The effects of heating temperature (30~90 ℃), pH (3~11) and the ionic strength (0~0.7 mol/L NaCl) on emulsions stability were analyzed by measuring the appearance, creaming index (CI), particle size distribution, average particle size, Zeta potential, the thermal stability, and observing the microstructure. The results showed that the 1.0% Flammulina velutipes emulsion delaminated with the increase of temperature from 4 ℃ to 90 ℃. The 2.0% Flammulina velutipes emulsion remained stable and the absolute value of Zeta potential was maintained at 29.10~29.40 mV at 4~90 ℃. The stability of 1.0% Flammulina velutipes emulsion was significantly (P<0.05) affected by pH, with obvious delamination at pH3 and 5. The 2.0% Flammulina velutipes emulsion had higher tolerance for pH, and showed no delamination at pH≥7, this was attributed that the average particle size of the 2.0% emulsion significantly (P<0.05) decreased, and the droplet particles were more uniform and fine. With the increasing of the ionic strength, the CI and average particle size of 1.0% Flammulina velutipes emulsion increased, the absolute value of Zeta potential decreased, and the thermal stability deteriorated. In contrast, the 2.0% Flammulina velutipes emulsion did not delaminate with the increase of the ionic strength, and the average particle size remained at 385.20~414.60 nm, and the thermal ability was stable. Hence, the higher concentration (2.0%) of Flammulina velutipes emulsion had good emulsion stability and could resist changes in heating temperature, pH, and ionic strength. As a result, the 2.0% Flammulina velutipes emulsion is expected to be used as a natural emulsifier from edible fungi in the food industry.