Suppressive Effects of Salts on Droplet Coalescence in a Commercially Available Fat Emulsion During Freezing for Storage

Abstract

To assess possible improvements in the practical use of long-term freezing storage for commercially available fat emulsions, the effects of salts on coalescence (fusion) of emulsions during freeze-thawing cycles were studied. For this purpose, apparent size changes were measured by dynamic light scattering, and the dispersed droplets were directly observed by freeze-fracture electron microscopy before and after the freeze-thawing processes. Intravenous high-calorie nutrient fluid, based on soybean oil in water (2.2 wt% glycerin) and emulsified by egg phosphatides, was selected as a representative commercially available fat emulsion. Possible mechanisms of the suppressive effects of various salts (Li, Na, K, Rb, and Cs chlorides) on coalescence during repeated freezing with liquid nitrogen and subsequent thawing were examined in terms of the zeta-potential of the emulsion droplets and differential scanning calorimetry heating curves of the water-salt-glycerin ternary solution. The suppressive effects of salts on the coalescence of the emulsion droplets during freeze-thaw cycles could be ascribed to the suppression of ice crystal formation and the condensation of the droplets in unfrozen aqueous channels between the ice crystals during the freezing cycle.

Factors Influencing the Freeze‐Thaw Stability of Emulsion‐Based Foods

“…There are a number of additional physicochemical processes that can also promote emulsion instability after freezing of an emulsion (Thanasukarn and others ). If all of the water phase is frozen, then there may be insufficient free water present to fully hydrate the protein molecules adsorbed to the fat droplet surfaces (Strauss and Hauser ; Ausborn and others ; Komatsu and others ), which can promote increased droplet–droplet interactions. Ice crystallization also leads to an increase in the ionic strength and a change in pH of the nonfrozen aqueous phase surrounding the fat droplets, which will change the strength of the electrostatic interactions between charged fat droplets (Komatsu and others ; Cornacchia and Roos ), thereby promoting flocculation.…”

Coalescence of Lipid Emulsions in Floating and Freeze–Thawing Processes: Examination of the Coalescence Transition State Theory

“…It has been known that the condensation of the lipid bilayer vesicles in the narrow channels leads to aggregation and coalescence in the F-T procedure (4,5,17). Table 1 (the fourth row) shows droplet coalescence in the TO/egg PC/Chol and TC/egg PC emulsions.…”

“…When emulsions freeze, the lipid droplets become progressively concentrated and come into contact with one another in unfrozen aqueous channels between the ice crystals. The condensation of the lipid droplets in the narrow channels could lead to aggregation as well as to coalescence in the F-T process (4,5).…”

Preparation of n-octadecane nanocapsules by using interfacial redox initiation in miniemulsion polymerization

“…Consequently, the FTP makes the particles unstable and leads to aggregation or flocculation, and eventual phase separation over time. 17 As shown in Figure 2 (a and b), PMMA and PSt nanoparticles prepared without noctadecane were settled down in the bottom layer of the tubes due to the density difference between polymers and water. On the contrary, n-octadecane/PMMA and n-octadecane/PSt nanocapsules were floated in the upper layer due to the lower density of n-octadecane.…”