Flaxseed Oil Emulsions Research Articles

Ultrasonic assisted oil-in-water emulsions stabilized by flaxseed protein isolate: influence of different oils

In this study, the physicochemical properties and stability of ultrasonic assisted flaxseed protein isolates (FPI) emulsions containing medium chain triglycerides (MCT), soybean oil, flaxseed oil, or docosahexaenoic acid (DHA) algae oil were investigated. The particle size distribution, zeta-potential, turbiscan stability index (TSI), and backscattering profiles were determined. The results showed that the emulsions containing flaxseed oil had the smallest droplet size and the lowest TSI value after 30 min ultrasonic treatment. Flaxseed oil emulsions showed the best storage stability with minimum clarified layer and cream layer after 10 days storage. MCT emulsions were more sensitive to salt, and less stable than other oil emulsions. Soybean oil, flaxseed oil, and DHA oil emulsions had good stability under low ionic strengths (0–50 mM NaCl), and became unstable under high ionic strengths (150 and 300 mM). Thermal treatment had great influence on the particle size distribution of emulsions. The particle size of the four oils emulsions increased after heating at 90 °C for 30 min. However, the particle size of DHA oil and flaxseed oil emulsions decreased after heating at 50 °C for 30 min. In conclusion, ultrasonic treatment is one of the effective ways to improve stability of FPI-stabilized emulsions, which are based on the oil type and ultrasound intensity. The effects of oil type and chain length on particle size and stability of FPI-stabilized emulsions could be further studied.

Formulation and Evaluation of Spray-Dried Reconstituted Flaxseed Oil-in-Water Emulsions Based on Flaxseed Oil Cake Extract as Emulsifying and Stabilizing Agent.

Spray drying of emulsions is a promising way of increasing their durability, offering the possibility of reconstitution, with the addition of water. The present study aimed to examine the properties of flaxseed oil cake extract (FOCE) as an emulsifying and stabilizing agent for spray-dried reconstituted oil-in-water emulsions. Maltodextrin: starch: flaxseed oil emulsions with FOCE or distilled water as liquid phases, and 10% and 20% of oil were spray-dried at 180 °C. The solubility, flowability, cohesiveness, bulk, and tapped densities of the spray-dried powders were analyzed. Additionally, the characteristics of initial and reconstituted emulsions, such as stability, creaming index, color, particle size, and rheological properties were evaluated. Results showed that FOCE could be an adequate emulsifier for spray-dried emulsions with a high oil content providing high stability after reconstitution, when compared to emulsions based only on maltodextrin–starch wall material with water as the liquid phase. This study showed an encouraging way for producing natural and plant-based spray-dried oil-loaded emulsions for food applications.

Towards the systematic design of multilayer O/W emulsions with tannic acid as an interfacial antioxidant.

This work discusses the possibility of designing multilayer oil-in-water emulsions to introduce the maximum possible amount of an antioxidant at the droplet interfaces for the optimal protection of a linseed oil core against oxidation, using a systematic three-step colloidal procedure. An antioxidant (here Tannic Acid – TA) is chosen and its interactions with a primary emulsifier (here Bovine Serum Albumin – BSA) and several polysaccharides are first examined in solution using turbidity measurements. As a second step, LbL deposition on solid surfaces is used to determine which of the polysaccharides to combine with BSA and tannic acid in a multilayer system to ensure maximum presence of tannic acid in the films. From UV-vis and polarization modulation infrared reflection–absorption (PM-IRRAS) spectroscopic measurements it is suggested that the best components to use in a multilayer emulsion droplet, together with BSA and TA, are chitosan and pectin. BSA, chitosan and pectin are subsequently used for the formation of three-layer linseed oil emulsions, and tannic acid is introduced into any of the three layers as an antioxidant. The effect of the exact placement of tannic acid on the oxidative stabilization of linseed oil is assessed by monitoring the fluorescence of Nile red, dissolved in the oil droplets, under the attack of radicals generated in the aqueous phase of the emulsion. From the results it appears that the three-stage procedure presented here can serve to identify successful combinations of interfacial components of multilayer emulsions. It is also concluded that the exact interfacial placement of the antioxidant plays an important role in the oxidative stabilization of the valuable oil core.

Fabrication and characterization of whey protein isolates- lotus seedpod proanthocyanin conjugate: Its potential application in oxidizable emulsions

Emulsified ω-3 polyunsaturated fatty acid have expanding application in different food matrix with improved water solubility while still prone to oxidation. Lotus seedpod proanthocyanidin (LSPC) was grafted to whey protein isolate (WPI) to create nature-derived antioxidant emulsifiers. 1HNMR, SDS-PAGE and multiple spectrometry showed that the structure of protein was changed after grafting. DPPH and FRAP measurements showed that WPI-LSPC conjugate (90.53 ± 1.48% of DPPH scavenging, 691.85 ± 4.54 μg/mL for FRAP assay) possessed a much better antioxidant ability than WPI (17.06 ± 3.34% of DPPH scavenging, 10.43 ± 0.26 μg/mL for FRAP assay). Ultrasonic emulsification and DSC experiments showed that WPI-LSPC conjugate were more effective at forming and stabilizing the flaxseed oil emulsions than pure WPI, with higher thermostability. Likewise, low levels of primary and secondary oxidation products were formed for the conjugate than the pure protein in O/W systems after storage, again suggesting WPI-LSPC could be used as fine antioxidant emulsifiers in oxidizing delivery systems.

Characterization of Flaxseed Oil Bimodal Emulsions Prepared with Flaxseed Oil Cake Extract Applied as a Natural Emulsifying Agent.

Currently, a majority of oilseeds plants are converted into byproducts and waste materials during processing. Press cakes are rich in valuable biopolymers, such as proteins and polysaccharides (fiber, lignans, etc.). In this study flaxseed oil cake extract (FOCE) was used to stabilize flaxseed oil-in-water emulsions. The effect of FOCE with various flaxseed oil concentrations (10–50% v/v) on several physicochemical properties of emulsions, such as stability, rheology, color and particle size was investigated. The rheological parameters suggested that all samples were non-Newtonian fluids, whereas particle size measurements and calculation SPAN index provided information about the broadness of emulsions particle size distribution. FOCE was able to efficiently stabilize oil/water interfaces with a high oil content. Results obtained for FOCE were compared with effects for synthetic emulsifier (Tween 80) and separated FOCE compounds (flaxseed gum and flaxseed protein). FOCE emulsifying activity is a result of different water-holding and oil-binding capacities of flaxseed gum and protein. This result is an intriguing conclusion regarding the necessity for using pure emulsifiers, showing the possibility of using a bio-based extract containing biopolymers, which is part of the principles of circular economy and the idea of zero-waste. The results give the opportunity to use FOCE as an ingredient in efficient flaxseed oil emulsions stabilizer for food applications.

Nutrient release and oxidative stability during in vitro digestion of linseed oil emulsions produced from cow milk, soy drink, and green tea extract

The fortification with ω-3 fatty acids is of great interest, but their vulnerability to oxidation can adversely affect the nutritional quality of food. The objective of this study was to emulsify linseed oil in cow milk or soy drink, with or without adding green tea extract, and compare the nutrient release and lipid oxidation during in vitro gastrointestinal digestion. A protein-free emulsion, prepared with Tween 20, was also studied. The soy-based emulsions showed the highest fatty acid release, but exhibited lower proteolysis in comparison with the cow milk emulsions. Emulsions produced with Tween 20 were the most sensitive to oxidation during digestion, while the emulsions prepared in soy drink were more stable than the emulsions prepared in cow milk. The aggregation pattern of oil droplets under gastric conditions was shown to contribute to the emulsion oxidative stability. Green tea extract reduced the oxidative degradation and acted synergistically with cow milk and soy drink to reduce the formation of lipid oxidation products during digestion. This study shows the potential of cow milk and soy drink constituents, combined to green tea, to enhance the oxidative stability during digestion of emulsions rich in ω-3 fatty acids.

Emulsifying and Anti-Oxidative Properties of Proteins Extracted from Industrially Cold-Pressed Rapeseed Press-Cake.

One of the functional proteins in rapeseed—the amphiphilic protein oleosin—could be used to stabilize emulsions. The objectives of this study were to extract oleosins from cold-pressed rapeseed press-cake, optimize the extraction process, and investigate their emulsifying and anti-oxidative capacity. The proteins were recovered from industrially cold-pressed rapeseed press-cake at different alkali pHs. Emulsifying properties and oxidation rates were assessed. Oleosin extracted at pH 9 stabilized smaller emulsion droplets than oleosin extracted at pH 12, although the protein yield was higher at pH 12. Emulsions were formulated from flaxseed oil and corn oil and were stabilized by oleosin, bovine serum albumin, de-oiled lecithin and Tween 20 h and the emulsions were stored in accelerated conditions (30 °C) for 12 days. Oleosin stabilized emulsions to the same extent as commercial food-grade emulsifiers. Flaxseed oil emulsions stabilized by oleosin had a significantly lower concentration of malondialdehyde (MDA) which indicates a lower oxidation rate compared to BSA, de-oiled lecithin and Tween 20. For corn oil emulsions, oleosin and BSA had a similar capacity to delay oxidation and were significantly more efficient compared to de-oiled lecithin and Tween 20. Rapeseed oleosin recovered from cold-pressed rapeseed press-cake could be a suitable natural emulsifier with anti-oxidation properties.

Physicochemical Composition and Nutritional Properties of Deer Burger Enhanced with Healthier Oils.

Deer meat is characterized by low fat and cholesterol contents and high amounts of protein and polyunsaturated fatty acids. In this regard, the aim of this work was to assess the influence of pork backfat substitution by healthier oils on chemical composition, fatty acid profile, texture profile and sensory analysis of deer burger. In addition, pH, color parameters and lipid oxidation were evaluated at 0, 6, 12 and 18 days of storage. For this study, four different treatments of deer burgers—100% pork backfat, 100% tiger nut oil, 100% chia oil, and 100% linseed oil—were elaborated. The fat replacement reduced fat and protein contents and increased moisture amounts, whereas ashes and texture parameters of deer burgers were not affected. Fatty acid profile was significantly improved with the animal fat replacement. In this regard, a significant decrease in saturated fatty acids was found in all reformulated batches, whereas in chia and linseed burger samples a dramatic increase in polyunsaturated fatty acids, omega-3 content and a reduction of n-3/n-6 ratio was observed. In the deer burger prepared with tiger nut oil a significant increase in monounsaturated fatty acids was found. Another important aspect is that the replacement of animal fat by tiger nut or linseed oil emulsion did not affect the global acceptance of deer burgers. Regarding color parameters, redness was the most affected during the whole display presenting a reduction around 50% after 18 days of storage. On the other hand, thiobarbituric acid reactive substances (TBARS) values were also affected by fat replacement and storage time, observing the highest values (2.43 mg MDA/kg) in deer burgers prepared with chia at the end of refrigerated period. Finally, from a commercial point of view, the possibility of making claims such as “low fat burgers”, “reduced saturated fat” or “high content of omega-3” makes the reformulated burgers more attractive to the consumer.

Improved Water Repellency and Dimensional Stability of Wood via Impregnation with an Epoxidized Linseed Oil and Carnauba Wax Complex Emulsion

Natural wood is susceptible to moisture during its practical use, limiting not only service life but also the range of uses. In this study, plant extracts, specifically linseed oil and carnauba wax (both environmentally friendly and water-repellent substances), were examined as a means to mitigate limitations of natural wood. Stable and homogenous epoxidized linseed oil/carnauba wax emulsions with an average particle size less than 230 nm were used as a modifier to enhance the performance of wood. Weight percentage gain, bulking coefficient, micromorphology, chemical structure, moisture adsorption, contact angle, water repellency, and dimensional stability of treated wood were measured. Using a scanning electron microscope (SEM), it was observed that carnauba wax and epoxidized linseed oil acted as a mechanical barrier and could partially cover or block vessels, pits, and wood rays. Furthermore, the hydrophobicity of wood increased significantly after emulsion impregnation. However, there was no obvious chemical reaction between epoxidized linseed oil and the main components of wood in the Fourier transform infrared spectroscopy (FTIR) results. The combined effect of epoxidized linseed oil and carnauba wax was apparent in both decreased water absorption and dimensional deformation. Poplar wood impregnated with an epoxidized linseed oil/carnauba wax complex emulsion shows potential for improving water-related properties. Thus, the complex emulsion modification can improve the inherent shortcoming of poplar wood effectively.

Effect of emulsifiers on linseed oil emulsion structure, lipolysis and oxidation during in vitro digestion.

Health benefits have been associated with the consumption of omega-3 polyunsaturated fatty acids (PUFA). Linseed oil is rich in long chain omega-3 PUFA, but can generate toxic compounds due to its high susceptibility to oxidation. The nature of the emulsifier can affect both lipolysis and oxidation during digestion since these phenomena occur at the oil-water interface. The objective of this study was to compare the effect of low-molecular weight surfactants (cetyltrimethylammonium bromide (CTAB), Citrem), protein (sodium caseinate, fish gelatin) and polysaccharides (gum arabic, modified starch) on the structure of linseed oil emulsions, lipolysis and formation of reactive oxidation species during in vitro digestion. The emulsion stabilized with Citrem underwent extensive coalescence in the gastric phase, which strongly decreased the extent of lipid digestion and reduced the formation of oxidation markers relative to other emulsions. Emulsions stabilized by proteins and modified starch showed aggregation with partial coalescence in the gastric phase, but protein-stabilized emulsions showed better resistance to oxidation. This study shows that emulsifier properties affect the susceptibility of the emulsion to aggregation and coalescence in the gastrointestinal environment, and strongly influence the extent of lipid digestion and the formation of reactive oxidation products. These findings point out the importance of the choice of the emulsifier to control the lipid digestibility and the protection of sensible lipids thus promoting optimal nutritional properties in omega-3-enriched foods.

Effect of thymol and Pickering stabilization on in-vitro digestion fate and oxidation stability of plant-derived flaxseed oil emulsions

The aim of this study was to evaluate the effect of Pickering stabilization by biopolymer-based particles (bioparticles), consisting of flaxseed protein and polysaccharides, and of the addition of thymol to the oil phase on the oxidation stability, and digestion fate of flaxseed oil (FO) emulsions, compared to bulk FO and conventional emulsions stabilized by polysorbate 80 (PS80). Applying Pickering stabilization and thymol simultaneously was a successful approach to retard FO oxidation. Moreover, lipid digestion was slower in bioparticle-stabilized emulsions compared to PS80 stabilized emulsions. The thymol bioaccessibility increased after incorporation into FO Pickering emulsions in comparison to the bulk oil. The results suggested that the combination of Pickering stabilization and thymol addition to the oil phase can be used as a promising way of protecting highly unsaturated oils such as FO against oxidation. These emulsions are also applicable for designing functional foods with controlled lipid digestion.

Fabrication of pea protein-tannic acid complexes: Impact on formation, stability, and digestion of flaxseed oil emulsions

There is growing interest in the identification of plant-based functional ingredients for utilization within the food industry. Complexes were fabricated from pea protein (PP) and tannic acid (TA) and then their ability to act as antioxidant emulsifiers in flaxseed oil-in-water emulsions was studied. PP-TA complex formation was investigated using isothermal titration calorimetry and turbidity analysis, which suggested hydrogen bonding and hydrophobic interactions were important in their assembly. PP-TA-stabilized emulsions containing small droplets could be formed at relatively high TA levels. Moreover, PP-TA complexes had strong antioxidant activity, which extended the shelf life of flaxseed oil emulsions. The composition of the PP-TA complexes impacted the aggregation state of the lipid droplets under simulated gastric conditions, which affected the rate and extent of lipid digestion. This study shows PP-TA complexes can be used for fabricating flaxseed oil delivery systems with enhanced oxidative stability and good digestibility.

Bioparticles of flaxseed protein and mucilage enhance the physical and oxidative stability of flaxseed oil emulsions as a potential natural alternative for synthetic surfactants

Flaxseed protein (FP) and mucilage (FM) complex bioparticles as sustainable ingredients were assembled by electrostatic interaction for plant-based Pickering stabilization of flaxseed oil (FO)-in-water emulsions. The effect of FO content (1–5 wt%) on droplet size and accelerated creaming stability of the emulsions was evaluated, from which it was found that 2.5 wt% FO emulsion had the smallest initial droplet size (i.e. D[4,3] = 8 μm) and creaming velocity (2.9 μm/s). The microstructure of the emulsions was observed using Cryo-SEM, confocal and optical microscopy, showing a thick layer of the particles on the oil surface responsible for the stabilization. The physical stability of FO emulsions stabilized by complex bioparticles against various environmental stress conditions (pH, salt and temperature) was higher compared to plain FP- and polysorbate 80-stabilized emulsions. Thus, the droplet size of FP-stabilized emulsions (pH 3) increased from 21 to 38 μm after thermal treatment (80 °C), whereas the size distribution of particle-stabilized emulsions hardly changed. The latter emulsions also remained stable during 28 days of storage and displayed good stability against a wide range of pH conditions (2–9) and salt concentrations (0–500 mM) with no sign of oiling-off. The complex particles as Pickering emulsifiers were successful to depress the FO oxidation at 4 °C and 50 °C. This study could open a promising pathway for producing natural and surfactant-free emulsions through Pickering stabilization using plant-based biopolymer particles for protecting lipophilic bioactive components.

Effect of milk proteins and food-grade surfactants on oxidation of linseed oil-in-water emulsions during in vitro digestion

Health benefits are associated with polyunsaturated fatty acids, but their sensitivity to oxidation may generate toxic oxidation species. The objective of this study was to compare the effect of milk proteins (casein, whey protein) and surfactants (Citrem, Tween 20) on the in vitro digestion and oxidation of linseed oil emulsions. The emulsion produced with Tween 20 resisted coalescence in the gastric phase and showed the highest concentrations of free fatty acids and reactive carbonyl compounds in the intestinal digestion phase. The Citrem-stabilized emulsion showed extensive coalescence in the gastric environment, which reduced lipolysis and the formation of advanced oxidation species. The protein-stabilized emulsions showed aggregation with some coalescence in the gastric phase, and casein provided better protection than whey protein against oxidation. This study suggests that the mechanism of emulsion destabilization in the gastric environment and the type of protein can modulate lipolysis and oxidation during in vitro digestion.

Antioxidant activity of milk and polyphenol-rich beverages during simulated gastrointestinal digestion of linseed oil emulsions.

Polyunsaturated fatty acids (PUFA) are associated with health benefits. However, high PUFA intake increases the risk of lipid oxidation and formation of potentially toxic lipid oxidation species. The objective of this study was to determine the antioxidant activity of milk fractions (whole milk, skim milk, acid whey, ultrafiltration (UF) permeate) and polyphenol-rich beverages (green tea, grape juice) during simulated gastrointestinal digestion. We also determined the effect of milk and polyphenol-rich beverages on the formation of advanced oxidation species during in vitro digestion of PUFA-rich emulsion. Antioxidant activity during digestion of milk fractions emphasized the important role of proteins (more specifically caseins) and the contribution of fat to the antioxidant capacity of milk. In comparison to milk, the antioxidant activity of polyphenol-rich beverages was at least four times higher. During digestion of a PUFA-rich emulsion, the formation of 4-hydroxyhexanal (4-HHE) and 4-hydroxynonenal (4-HNE) in the intestinal phase were respectively reduced by 60% and 75%, in the presence of milk or polyphenol-rich beverages. Further reduction was observed when the emulsion was co-digested with both, milk and polyphenol-rich beverages (89% for 4-HHE and 93% for 4-HNE). These results suggest that the combination of milk and polyphenol-rich beverages increases the antioxidant activity and synergistically reduces the formation of toxic lipid oxidation species during simulated digestion of PUFA-rich foods.

Protection of emulsified polyunsaturated fatty acids against in vitro ruminal biohydrogenation by polyphenol oxidase: Characterization of the cross-linked emulsion

In the current study, linseed oil emulsions were cross-linked by polyphenol oxidase to study the effect of emulsion characteristics on the protection of polyunsaturated fatty acids against biohydrogenation by rumen bacteria in vitro. Polyphenol oxidase (PPO) catalyzes the oxidation of diphenolic substrate to o-quinones which are reactive towards amino- and thiol- groups on proteins, forming a complex of covalently bound protein cross-linked by protein-bound phenols (PBP). Such cross-linking of protein-stabilized emulsions was shown to yield high in vitro ruminal protection of polyunsaturated fatty acids before, by addition of PPO extract and diphenolic substrate to protein-stabilized emulsions. The current study examined the relationship between characteristics of cross-linked emulsions and in vitro ruminal protection by evaluation of two hypotheses: protection efficiency would be impaired when 1) the amount of PPO in the emulsion decreased or 2) the amount of non-adsorbed protein in the emulsion increased. Hence, in a first experiment, emulsions containing the same protein concentration and varying amounts of PPO extract (0,2-0,8 g/g) were analyzed, while in experiment 2, emulsions containing varying amounts of non-adsorbed protein and a similar amount of PPO extract (0,8 g/g) were investigated. In the latter experiment, variation in non-adsorbed protein was obtained by altering the emulsifier concentration (10 or 0 mg/g whey protein isolate) and/or removal of the majority (>90%) of the non-adsorbed protein after emulsion preparation, i.e. washing of the emulsion, before addition of PPO extract. In vitro ruminal biohydrogenation was evaluated after 24 h in a rumen-simulated environment containing rumen inoculum. Results of experiment 1 showed protection efficiency decreased for decreasing amounts of PPO extract. Additionally, in vitro ruminal protection was found to be positively correlated to mean droplet size, protein load and proportion of PBP in the free protein fraction of the emulsions after cross-linking, while proportion of PBP in the adsorbed protein layer did not differ between treatments. In experiment 2, an increase in emulsifier concentration from 10 to 50 g/g WPI lowered the amount of PBP in both protein fractions. Washing of 50 mg/g WPI emulsions, enhanced in vitro ruminal protection of 18:3n-3 and 18:2n-6 and increased the proportion of PBP in both free and adsorbed protein. Moreover, protein load and the amount of total adsorbed PBP were positively affected by washing. Comparison of emulsions with similar protein load between experiments showed in vitro ruminal protection efficiency increased for higher proportions of PBP in the adsorbed protein layer. Moreover, an excess of PBP on the possible binding positions on the adsorbed protein seemed to promote in vitro ruminal protection efficiency.

Oxidative and physical stability, rheological properties and sensory characteristics of ‘salad dressing’ samples formulated with flaxseed oil and n-OSA starch

Flaxseed oil is one of the richest sources of Omega-3. This work was aimed at evaluating the physical qualities, sensory properties and the stability of a formulation for salad dressing characterized by a partial enrichment with flaxseed oil upon refrigerated storage. Samples were stabilized by n-OSA starch and sodium caseinate, and they were comparable with samples which had egg yolk only. All formulated dressings appeared as a weak gel-like structure with strong shear thinning behavior. The experimental data was fitted with the power-law model for all samples. The samples showed various degrees of oxidative stability after 90 days of storage. Salad dressings containing n-OSA starch and sodium caseinate (samples 1–4) exhibited a small phase separation at the bottom of the tubes in the third month of storage, while no oiling-off was observed. In the presence of egg yolk (sample 5), a higher stability was observed with no phase separation or oiling-off. When there was 5% (w/w) flaxseed oil, a higher sensory quality was obtained in general. Increasing the percentage of flaxseed oil replacement in salad dressings and prolonging the storage time led to a decrease in the L factor. Salad dressings could be enriched aptly with flaxseed oil emulsions (while being stabilized by n-OSA starch and caseinate).

Techno-functional properties of yoghurts fortified with walnut and flaxseed oil emulsions in guar gum

The present study aimed at fortification of yoghurt with walnut and flaxseed oils using guar gum. Both the oils were added separately at a concentration of 2% along with two different concentrations of guar gum (0.025% and 0.05%). Fortified yoghurt samples were studied for functional, rheological, microbial and antioxidant properties. Fatty acid profile and oxidative shelf-life of the product was also determined. The addition of oil increased syneresis, antioxidant activity and malondialdehyde formation in yoghurts while the microbial count decreased. Gum addition, significantly (P < 0.05) decreased pH, syneresis, and increased the oxidative stability, antioxidant activity of yoghurt samples while no significant (P > 0.05) effect on microbial content was seen. All yoghurt samples showed pseudo plastic flow behavior with yield stress that increased with increase in gum and oil concentration. Gum and oil addition increased G′, G″, and composite viscosity of yoghurt samples. Walnut fortified yoghurt samples showed significantly (P < 0.05) higher MUFA and PUFA levels among all the samples. Walnut oil fortification showed higher sensory parameters and superior overall quality characteristics than flaxseed oil fortification. Hence, walnut oil is a better option for fortification of yoghurts with essential fatty acids than flaxseed oil.

Kinetic approach to study the relation between in vitro lipid digestion and carotenoid bioaccessibility in emulsions with different oil unsaturation degree

Emulsions were prepared with oils (5%w/v) differing in unsaturation degree (olive, soybean or linseed oil) and sucrose ester (0.5%w/v) used as emulsifier. The oils studied were enriched with carotenoids from carrot or tomato purees. All emulsions were in vitro digested and characterised at the level of lipolysis and carotenoid micellarisation kinetics in the small intestinal phase. Olive oil emulsions led to a faster and more extensive lipolysis and carotenoid bioaccessibility compared to soybean and linseed oil emulsions. Monounsaturated fatty acids present in olive oil might be more hydrophobic in comparison to polyunsaturated fatty acids from soybean or linseed oil, leading to micelles with greater capacity of solubilising hydrophobic carotenoids. The obtained results evidence the potential of the oil unsaturation degree for modulating lipolysis and carotenoid bioaccessibility in the gastrointestinal tract and moreover, exemplify the relevance of a kinetic approach including modelling of different lipolysis species to quantitatively prove their interrelation.

Nanostructured lipid carrier (NLC) as a strategy for encapsulation of quercetin and linseed oil: Preparation and in vitro characterization studies

Due to their poor solubility in hydrophilic matrices and chemical instability, the applications of quercetin and linseed oil in functional foods are limited. In this work we have encapsulated quercetin and linseed oil into NLC by high pressure homogenization technique. Quercetin and linseed oil co-loaded nanoparticles were less than 100 nm in diameter and spherical in shape. Nano-encapsulated quercetin was found to be presented in NLC with less ordered lipid cores as an encapsulated amorphous form. And the solubility of quercetin in hydrophilic matrices consisted of linseed oil and surfactants was improved by at least 1300 folds. The addition of linseed oil improved the in vitro antioxidant activities of quercetin loaded NLCs. Besides, the in vitro release of quercetin from NLC exhibited a sustained pattern. Lower lipid oxidation was found in quercetin and linseed oil co-loaded NLC compared with conventional linseed oil emulsion. Finally, storage study indicated that the fabricated NLCs were stable for more than 3 months at 25 °C. In conclusion, NLC could be a promising vehicle for delivery of hydrophobic bioactive compounds and ω-3 unsaturated fatty acids in food industry.