TY - JOUR
T1 - Formulation and characterization of food-grade microemulsions as carriers of natural phenolic antioxidants
AU - Chatzidaki , Maria D.
AU - Mitsou, Evgenia
AU - Yaghmur, Anan
AU - Zenakis, Aristotelis
AU - Papadimitriou, Vassiliki
PY - 2015/10/20
Y1 - 2015/10/20
N2 - Food-grade W/O microemulsions based on lecithin, caprylic/capric triglycerides, isopropyl myristate, alcohols and water were formulated and structurally characterized to be used as potential carriers of natural food antioxidants. Different well-known food antioxidants including gallic acid, p-hydroxybenzoic acid, protocatechuic acid and tyrosol were successfully encapsulated in the aqueous cores of the microemulsions. A pseudo-ternary phase diagram was constructed to determine the extent of the monophasic area that corresponds to an inverted type microemulsion. Apparent hydrodynamic diameter measurements of empty and loaded microemulsions were performed using dynamic light scattering (DLS) and swollen micelles with diameters smaller than 10. nm were detected. Interfacial properties of the microemulsions were studied by electron paramagnetic resonance (EPR) spectroscopy employing the nitroxide spin probe 5-doxylstearic acid (5-DSA). A small increase in spin probe mobility upon addition of the antioxidants was observed; whereas the rigidity of the surfactants was not affected. Cryogenic transmission electron microscopy (Cryo-TEM) indicated the existence of entangled thread-like reversed micelles. Finally, the investigated phenolics were assessed and compared for their radical scavenging activity using an EPR approach based on free radicals. The encapsulated gallic acid showed the highest antioxidant activity (0.93. mM trolox equivalents) as compared to other antioxidants assessed within the frame of this study.
AB - Food-grade W/O microemulsions based on lecithin, caprylic/capric triglycerides, isopropyl myristate, alcohols and water were formulated and structurally characterized to be used as potential carriers of natural food antioxidants. Different well-known food antioxidants including gallic acid, p-hydroxybenzoic acid, protocatechuic acid and tyrosol were successfully encapsulated in the aqueous cores of the microemulsions. A pseudo-ternary phase diagram was constructed to determine the extent of the monophasic area that corresponds to an inverted type microemulsion. Apparent hydrodynamic diameter measurements of empty and loaded microemulsions were performed using dynamic light scattering (DLS) and swollen micelles with diameters smaller than 10. nm were detected. Interfacial properties of the microemulsions were studied by electron paramagnetic resonance (EPR) spectroscopy employing the nitroxide spin probe 5-doxylstearic acid (5-DSA). A small increase in spin probe mobility upon addition of the antioxidants was observed; whereas the rigidity of the surfactants was not affected. Cryogenic transmission electron microscopy (Cryo-TEM) indicated the existence of entangled thread-like reversed micelles. Finally, the investigated phenolics were assessed and compared for their radical scavenging activity using an EPR approach based on free radicals. The encapsulated gallic acid showed the highest antioxidant activity (0.93. mM trolox equivalents) as compared to other antioxidants assessed within the frame of this study.
U2 - 10.1016/j.colsurfa.2015.03.060
DO - 10.1016/j.colsurfa.2015.03.060
M3 - Journal article
SN - 0927-7757
VL - 483
SP - 130
EP - 136
JO - Colloids and Surfaces A: Physicochemical and Engineering Aspects
JF - Colloids and Surfaces A: Physicochemical and Engineering Aspects
M1 - 483
ER -