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Formulation and characterization of food-grade microemulsions as carriers of natural phenolic antioxidants
Örebro University, School of Science and Technology. Natl Hellen Res Fdn, Inst Biol Med Chem & Biotechnol, Athens 11635, Greece.
Natl Hellen Res Fdn, Inst Biol Med Chem & Biotechnol, Athens 11635, Greece..
Univ Copenhagen, Fac Hlth & Med Sci, Dept Pharm, DK-1168 Copenhagen, Denmark..
Natl Hellen Res Fdn, Inst Biol Med Chem & Biotechnol, Athens 11635, Greece.;Univ Orebro, Sch Sci & Technol, MTM Res Ctr, Orebro, 31705, Sweden..
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2015 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 483, 130-136 p.Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2015. Vol. 483, 130-136 p.
Keyword [en]
W/O microemulsion, Gallic acid, Antioxidant, EPR, DLS, Cryo-TEM
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-50111DOI: 10.1016/j.colsurfa.2015.03.060ISI: 000362146200017Scopus ID: 2-s2.0-84941745179OAI: oai:DiVA.org:oru-50111DiVA: diva2:925741
Available from: 2016-05-03 Created: 2016-05-03 Last updated: 2017-10-18Bibliographically approved
In thesis
1. Formulation and characterization of W/O nano-dispersions for bioactive delivery applications
Open this publication in new window or tab >>Formulation and characterization of W/O nano-dispersions for bioactive delivery applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main objective of this study was the formulation of food-grade water-in-oil (W/O) nano-dispersions based mainly on medium or long-chain triglycerides. Two types of dispersions were formulated and structurally compared, namely emulsions and microemulsions. The systems were used as matrices for encapsulating targeted bioactive molecules with specific characteristics such as antioxidants or peptides.

The structural characterization of the formulated systems was investigated using techniques such as Electron Paramagnetic Resonance (EPR) spectroscopy, Dynamic Light Scattering (DLS), Cryogenic Transmission Electron Microscopy (Cryo-TEM) and Small Angle Xray Scattering (SAXS). The existence of swollen inverse micelles was revealed for the case of microemulsions whereas larger droplets still at the nano-scale were observed for the case of emulsions. Structural differences in the presence of the bioactive molecules or induced by the alteration of components were also observed.

In order to study the efficacy of the formulations, the proposed loaded systems were assessed either using EPR spectroscopy or Well Diffusion Assay (WDA) depending on the bioactive molecule. It was found that the encapsulated molecules retained their claimed characteristics when encapsulated to the proposed matrices.

Finally, some of the formulated dispersions were investigated for their behavior under gastrointestinal (GI) conditions. A two-step digestion model using recombinant Dog Gastric Lipase (rDGL) and Porcine Pancreatic Lipase (PPL) was proposed to simulate lipid hydrolysis in humans. The studies revealed significant decrease of the rDGL specific activity in the presence of the microemulsion while in the presence of lower percent of surfactants (case of emulsion) no alterations were observed.

Place, publisher, year, edition, pages
Örebro: Örebro university, 2016. 77 p.
Series
Örebro Studies in Chemistry, ISSN 1651-4270 ; 16
Keyword
nano-dispersions, encapsulation, food, DLS, EPR, Cryo-TEM, SAXS, pH-stat, digestion, antioxidants, gastric lipase, pancreatic lipase
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-49454 (URN)978-91-7529-141-3 (ISBN)
Public defence
2016-05-26, Billbergska huset, hörsal B, Örebro universitet, Fakultetsgatan 1, Örebro, 10:15 (English)
Opponent
Supervisors
Available from: 2016-03-22 Created: 2016-03-22 Last updated: 2017-10-17Bibliographically approved

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