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Formulation and characterization of W/O nano-dispersions for bioactive delivery applications
Örebro University, School of Science and Technology.
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 [en]
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: urn:nbn:se:oru:diva-49454ISBN: 978-91-7529-141-3 (print)OAI: oai:DiVA.org:oru-49454DiVA: diva2:913725
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
List of papers
1. Low shear-rate process to obtain transparent W/O fine emulsions as functional foods
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2014 (English)In: Food Research International, ISSN 0963-9969, E-ISSN 1873-7145, Vol. 62, 533-540 p.Article in journal (Refereed) Published
Abstract [en]

Edible transparent emulsions of the water-in-oil (W/O) type are highly sought after and currently not available. In such materials, the water droplets can be advantageously used as reservoirs to encapsulate biologically active hydrophilic substances (minerals, antioxidants, etc.). The emulsions must remain transparent, fluid and kinetically stable to meet consumers' requirements. In this paper, we describe a simple yet versatile process to fabricate food grade transparent W/O emulsions. Our method involves the preparation of coarse emulsions which are submitted to shear under laminar flow conditions to reduce their average droplet size. The process generates negligible heat and consequently, it preserves the integrity of thermally sensitive compounds. The obtained emulsions contain between 5 and 10 wt.% of aqueous droplets whose average droplet size is lower than 200 nm. They are kinetically stable for at least 2 months. Transparency results from the relatively low droplet size and the incorporation in the aqueous phase of hydrophilic solutes that decrease the refractive index mismatch between the two immiscible phases.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
W/O nanoemulsion, emulsification, coalescence, Ostwald ripening
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-50112 (URN)10.1016/j.foodres.2014.03.069 (DOI)000340015100063 ()2-s2.0-84899521137 (Scopus ID)
Available from: 2016-05-03 Created: 2016-05-03 Last updated: 2017-11-30Bibliographically approved
2. Formulation and characterization of food-grade microemulsions as carriers of natural phenolic antioxidants
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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
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
Keyword
W/O microemulsion, Gallic acid, Antioxidant, EPR, DLS, Cryo-TEM
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-50111 (URN)10.1016/j.colsurfa.2015.03.060 (DOI)000362146200017 ()2-s2.0-84941745179 (Scopus ID)
Available from: 2016-05-03 Created: 2016-05-03 Last updated: 2017-11-30Bibliographically approved
3. Microemulsion versus emulsion as effective carrier of hydroxytyrosol
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2016 (English)In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 137, no 1, 146-151 p.Article in journal (Refereed) Published
Abstract [en]

Two edible Water-in-Oil (W/O) dispersions, an emulsion that remains kinetically stable and a microemulsion which is spontaneously formed, transparent and thermodynamically stable, were developed for potential use as functional foods, due to their ability to be considered as matrices to encapsulate biologically active hydrophilic molecules. Both systems contained Medium Chain Triglycerides (MCT) as the continuous phase and were used as carriers of Hydroxytyrosol (HT), a hydrophilic antioxidant of olive oil. A low energy input fabrication process of the emulsion was implemented. The obtained emulsion contained 1.3% (w/w) of surfactants and 5% (w/w) aqueous phase. The spontaneously formed microemulsion contained 4.9% (w/w) of surfactants and 2% (w/w) aqueous phase. A comparative study in terms of structural characterization of the systems in the absence and presence of HT was carried out. Particle size distribution obtained by Dynamic Light Scattering (DLS) technique and interfacial properties of the surfactants' layer, examined by Electron Paramagnetic Resonance (EPR) spectroscopy indicated the involvement of HT in the surfactant membrane. Finally, the proposed systems were studied for the scavenging activity of the encapsulated antioxidant toward galvinoxyl stable free radical showing a high scavenging activity of HT in both systems.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Emulsion, Microemulsion, Hydroxytyrosol, DLS, EPR, Antioxidant activity
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-50110 (URN)10.1016/j.colsurfb.2015.04.053 (DOI)000367491200017 ()25999235 (PubMedID)2-s2.0-84951573458 (Scopus ID)
Available from: 2016-05-03 Created: 2016-05-03 Last updated: 2017-11-30Bibliographically approved
4. Microemulsions as potential carriers of nisin: effect of composition on the structure and efficacy
Open this publication in new window or tab >>Microemulsions as potential carriers of nisin: effect of composition on the structure and efficacy
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(English)Manuscript (preprint) (Other academic)
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-50113 (URN)
Available from: 2016-05-04 Created: 2016-05-03 Last updated: 2017-10-17Bibliographically approved
5. Water-in-Oil microemulsions versus emulsions as carriers of hydroxytyrosol: an in vitro gastrointestinal lipolysis study using the pHstat technique
Open this publication in new window or tab >>Water-in-Oil microemulsions versus emulsions as carriers of hydroxytyrosol: an in vitro gastrointestinal lipolysis study using the pHstat technique
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(English)Manuscript (preprint) (Other academic)
National Category
Other Chemistry Topics
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-50119 (URN)
Available from: 2016-05-04 Created: 2016-05-03 Last updated: 2017-10-17Bibliographically approved

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