Effects of addition of diacylglycerols on fat crystallization in oil-in-water emulsion

Abstract

The effects of addition of diacylglycerols (DAGs) on the crystallization behavior of n‐hexadecane dispersed in oil‐in‐water emulsion (oil 20% and water 80%, v/v) were studied by differential scanning calorimetry (DSC) and ultrasonic velocity measurement. In an attempt to modify the crystallization rate of n‐hexadecane, five DAGs having the fatty acid moieties of behenic (DAB), stearic (DAS), palmitic (DAP), lauric (DAL) and oleic acid (DAO) were added to n‐hexadecane, which was mixed with water and Tween 20 for emulsification. The DSC study showed that the addition of DAB, DAS or DAP (1.0 wt‐% with respect to n‐hexadecane) increased the crystallization temperature (Tc) of a n‐hexadecane/water emulsion from 3 °C (without DAG) to 8 °C, whereas the addition of DAL and DAO showed no effect. The ultrasonic velocity measurement also revealed that the addition of DAGs resulted in increasing the Tc of n‐hexadecane in O/W emulsion. These effects were discussed by taking into account the formation of molecular aggregates at the interface due to the addition of DAGs, which act as a template for crystallization of n‐hexadecane. The template‐assisted crystallization depends on the structure of the fatty acid chains present in the DAG: the longer the fatty acid moiety of DAG , the more is the crystallization of n‐hexadecane in O/W emulsion accelerated.

Phase Transitions and Microstructure of Emulsion Systems Prepared with Acylglycerols/Zinc Stearate Emulsifier

“…As mentioned earlier in the previous section, ZnSt crystals are able to effectively adsorb at the water−oil interface. Additionally, as reported by Awad and co-workers, glycerol distearate can form interfacial templates in O/W emulsions and accelerate the crystal nucleation rate in an emulsified oil phase. Thus, it is highly possible that the combination of these two compounds in the water-rich O/W dispersion could determine the formation of the interfacial layer that covered the droplets of crystallized oil phase.…”

Phase Transitions and Microstructure of Emulsion Systems Prepared with Acylglycerols/Zinc Stearate Emulsifier

“…As mentioned earlier in the previous section, ZnSt crystals are able to effectively adsorb at the water−oil interface. Additionally, as reported by Awad and co-workers, glycerol distearate can form interfacial templates in O/W emulsions and accelerate the crystal nucleation rate in an emulsified oil phase. Thus, it is highly possible that the combination of these two compounds in the water-rich O/W dispersion could determine the formation of the interfacial layer that covered the droplets of crystallized oil phase.…”

Structural Characterization of Lecithin-Stabilized Tetracosane Lipid Nanoparticles. Part II: Suspensions

“…They exhibited characteristic precrystallization events in their cooling scans that were attributed to a freezing of the emulsifier at the interface prior to the crystallization of the droplets. 3,5,8,10 However, in the present study, the crystallization is most probably not mediated by a freezing of the DMPC molecules at the surface because no precrystallization events prior to the main crystallization peak were observed in the μDSC cooling scans. This can be explained by the fluid acyl chains of DMPC because the main phase transition temperature, T m , of DMPC of ∼24 °C is below the crystallization temperature, T c , of the nanodroplets (at ∼30 °C for TCS-d50 and 35 °C for TCS emulsions).…”

“…Another surface-mediated crystallization mechanism was discussed for alkane and triglyceride emulsions stabilized with emulsifiers possessing sufficiently long saturated acyl chains (and thus a sufficiently higher crystallization temperature than the supercooled oil droplets). They exhibited characteristic precrystallization events in their cooling scans that were attributed to a freezing of the emulsifier at the interface prior to the crystallization of the droplets. ,,, …”

Impact of Surfactant Properties on Oxidative Stability of β-Carotene Encapsulated within Solid Lipid Nanoparticles

“…The observed increase in crystallization temperature of the lipid matrix for the high-melting surfactants suggests that tripalmitin crystallization may have been promoted by surface-heterogeneous nucleation initiated by the surfactant . This type of nucleation has been suggested to be promoted by solidification of surfactant molecules absorbed at droplet surfaces ,− . The emulsion droplets coated by high-melting surfactants crystallized at significantly higher temperatures than those stabilized by low-melting surfactants: 30.3 ± 0.1 °C for HM-lecithin, 24.4 ± 0.1 °C for Tween 60, 21.2 ± 0.1 °C for LM-lecithin, and 21.0 ± 0.1 °C for Tween 80.…”

“…The observed increase in crystallization temperature of the lipid matrix for the high-melting surfactants suggests that tripalmitin crystallization may have been promoted by surface-heterogeneous nucleation initiated by the surfactant (35). This type of nucleation has been suggested to be promoted by solidification of surfactant molecules absorbed at droplet surfaces (28,(35)(36)(37)(38)(39)(40)(41). The emulsion droplets coated by high-melting surfactants crystallized at significantly higher A small exothermic peak was observed in the DSC thermograms around 50 °C for the HM-lecithin-coated droplets (Figure 1), which suggested that the surfactant layer at the droplet surface may have crystallized before the carrier lipid within the droplet interior.…”

Phase Transitions and Microstructure of Emulsion Systems Prepared with Acylglycerols/Zinc Stearate Emulsifier

“…As mentioned earlier in the previous section, ZnSt crystals are able to effectively adsorb at the water−oil interface. Additionally, as reported by Awad and co-workers, glycerol distearate can form interfacial templates in O/W emulsions and accelerate the crystal nucleation rate in an emulsified oil phase. Thus, it is highly possible that the combination of these two compounds in the water-rich O/W dispersion could determine the formation of the interfacial layer that covered the droplets of crystallized oil phase.…”

Structural Characterization of Lecithin-Stabilized Tetracosane Lipid Nanoparticles. Part II: Suspensions

“…They exhibited characteristic precrystallization events in their cooling scans that were attributed to a freezing of the emulsifier at the interface prior to the crystallization of the droplets. 3,5,8,10 However, in the present study, the crystallization is most probably not mediated by a freezing of the DMPC molecules at the surface because no precrystallization events prior to the main crystallization peak were observed in the μDSC cooling scans. This can be explained by the fluid acyl chains of DMPC because the main phase transition temperature, T m , of DMPC of ∼24 °C is below the crystallization temperature, T c , of the nanodroplets (at ∼30 °C for TCS-d50 and 35 °C for TCS emulsions).…”

“…Another surface-mediated crystallization mechanism was discussed for alkane and triglyceride emulsions stabilized with emulsifiers possessing sufficiently long saturated acyl chains (and thus a sufficiently higher crystallization temperature than the supercooled oil droplets). They exhibited characteristic precrystallization events in their cooling scans that were attributed to a freezing of the emulsifier at the interface prior to the crystallization of the droplets. ,,, …”

Impact of Surfactant Properties on Oxidative Stability of β-Carotene Encapsulated within Solid Lipid Nanoparticles

“…The observed increase in crystallization temperature of the lipid matrix for the high-melting surfactants suggests that tripalmitin crystallization may have been promoted by surface-heterogeneous nucleation initiated by the surfactant . This type of nucleation has been suggested to be promoted by solidification of surfactant molecules absorbed at droplet surfaces ,− . The emulsion droplets coated by high-melting surfactants crystallized at significantly higher temperatures than those stabilized by low-melting surfactants: 30.3 ± 0.1 °C for HM-lecithin, 24.4 ± 0.1 °C for Tween 60, 21.2 ± 0.1 °C for LM-lecithin, and 21.0 ± 0.1 °C for Tween 80.…”

“…The observed increase in crystallization temperature of the lipid matrix for the high-melting surfactants suggests that tripalmitin crystallization may have been promoted by surface-heterogeneous nucleation initiated by the surfactant (35). This type of nucleation has been suggested to be promoted by solidification of surfactant molecules absorbed at droplet surfaces (28,(35)(36)(37)(38)(39)(40)(41). The emulsion droplets coated by high-melting surfactants crystallized at significantly higher A small exothermic peak was observed in the DSC thermograms around 50 °C for the HM-lecithin-coated droplets (Figure 1), which suggested that the surfactant layer at the droplet surface may have crystallized before the carrier lipid within the droplet interior.…”

Phase Transitions and Microstructure of Emulsion Systems Prepared with Acylglycerols/Zinc Stearate Emulsifier

“…As mentioned earlier in the previous section, ZnSt crystals are able to effectively adsorb at the water−oil interface. Additionally, as reported by Awad and co-workers, glycerol distearate can form interfacial templates in O/W emulsions and accelerate the crystal nucleation rate in an emulsified oil phase. Thus, it is highly possible that the combination of these two compounds in the water-rich O/W dispersion could determine the formation of the interfacial layer that covered the droplets of crystallized oil phase.…”

Structural Characterization of Lecithin-Stabilized Tetracosane Lipid Nanoparticles. Part II: Suspensions

“…They exhibited characteristic precrystallization events in their cooling scans that were attributed to a freezing of the emulsifier at the interface prior to the crystallization of the droplets. 3,5,8,10 However, in the present study, the crystallization is most probably not mediated by a freezing of the DMPC molecules at the surface because no precrystallization events prior to the main crystallization peak were observed in the μDSC cooling scans. This can be explained by the fluid acyl chains of DMPC because the main phase transition temperature, T m , of DMPC of ∼24 °C is below the crystallization temperature, T c , of the nanodroplets (at ∼30 °C for TCS-d50 and 35 °C for TCS emulsions).…”

“…Another surface-mediated crystallization mechanism was discussed for alkane and triglyceride emulsions stabilized with emulsifiers possessing sufficiently long saturated acyl chains (and thus a sufficiently higher crystallization temperature than the supercooled oil droplets). They exhibited characteristic precrystallization events in their cooling scans that were attributed to a freezing of the emulsifier at the interface prior to the crystallization of the droplets. ,,, …”

Impact of Surfactant Properties on Oxidative Stability of β-Carotene Encapsulated within Solid Lipid Nanoparticles

“…The observed increase in crystallization temperature of the lipid matrix for the high-melting surfactants suggests that tripalmitin crystallization may have been promoted by surface-heterogeneous nucleation initiated by the surfactant . This type of nucleation has been suggested to be promoted by solidification of surfactant molecules absorbed at droplet surfaces ,− . The emulsion droplets coated by high-melting surfactants crystallized at significantly higher temperatures than those stabilized by low-melting surfactants: 30.3 ± 0.1 °C for HM-lecithin, 24.4 ± 0.1 °C for Tween 60, 21.2 ± 0.1 °C for LM-lecithin, and 21.0 ± 0.1 °C for Tween 80.…”

“…The observed increase in crystallization temperature of the lipid matrix for the high-melting surfactants suggests that tripalmitin crystallization may have been promoted by surface-heterogeneous nucleation initiated by the surfactant (35). This type of nucleation has been suggested to be promoted by solidification of surfactant molecules absorbed at droplet surfaces (28,(35)(36)(37)(38)(39)(40)(41). The emulsion droplets coated by high-melting surfactants crystallized at significantly higher A small exothermic peak was observed in the DSC thermograms around 50 °C for the HM-lecithin-coated droplets (Figure 1), which suggested that the surfactant layer at the droplet surface may have crystallized before the carrier lipid within the droplet interior.…”