Review on the Antioxidant Activity of Phenolics in o/w Emulsions along with the Impact of a Few Important Factors on Their Interfacial Behaviour

This review paper focuses on the antioxidant properties of phenolic compounds in oil in water (o/w) emulsion systems. The authors first provide an overview of the most recent studies on the activity of common, naturally occurring phenolic compounds against the oxidative deterioration of o/w emulsions. A screening of the latest literature was subsequently performed with the aim to elucidate how specific parameters (polarity, pH, emulsifiers, and synergistic action) affect the phenolic interfacial distribution, which in turn determines their antioxidant potential in food emulsion systems. An understanding of the interfacial activity of phenolic antioxidants could be of interest to food scientists working on the development of novel food products enriched with functional ingredients. It would also provide further insight to health scientists exploring the potentially beneficial properties of phenolic antioxidants against the oxidative damage of amphiphilic biological membranes (which link to serious pathologic conditions).

Encapsulation of Carotenoids as Food Colorants via Formation of Cyclodextrin Inclusion Complexes: A Review

The use of natural carotenoids as food colorants is an important trend of innovation in the industry due to their low toxicity, their potential as bio-functional ingredients, and the increasing demand for natural and organic foods. Despite these benefits, their inclusion in food matrices presents multiple challenges related to their low stability and low water solubility. The present review covers the main concepts and background of carotenoid inclusion complex formation in cyclodextrins as a strategy for their stabilization, and subsequent inclusion in food products as color additives. The review includes the key aspects of the molecular and physicochemical properties of cyclodextrins as complexing agents, and a detailed review of the published evidence on complex formation with natural carotenoids from different sources in cyclodextrins, comparing complex formation methodologies, recovery, inclusion efficiency, and instrumental characterization techniques. Moreover, process flow diagrams (PFD), based on the most promising carotenoid-cyclodextrin complex formation methodologies reported in literature, are proposed, and discussed as a potential tool for their future scale-up. This review shows that the inclusion of carotenoids in complexes with cyclodextrins constitutes a promising technology for the stabilization of these pigments, with possible advantages in terms of their stability in food matrices.

pH-Dependent complexation between β-lactoglobulin and lycopene: Multi-spectroscopy, molecular docking and dynamic simulation study

This study aims to investigate the effect of pH levels (pH 7.0 and pH 8.1) on binding ability of β-lactoglobulin (β-LG) with lycopene (LYC) and elucidate interaction mechanisms using multi-spectroscopy and molecular docking study. β-LG at pH 8.1 showed a stronger binding affinity to lycopene than that at pH 7.0 according to binding constant, binding number, energy transfer efficiency, and surface hydrophobicity. Lycopene bound to protein mainly by van der Waals force in the form of static quenching mode and preferred to interact with β-LG at the top of barrel for both pH levels. Molecular dynamic simulation revealed that β-LG/LYC complex at pH 8.1 was more stable than at pH 7.0. β-LG/LYC complexes formed at pH 8.1 showed significantly higher ABTS radical scavenging activity than samples at pH 7.0 (p < 0.05). Data obtained may contribute valuable information for preparing a whey protein-based delivery system for lycopene.

Supercritical CO2 extraction of lycopene from pink grapefruit (Citrus paradise Macfad) and its degradation studies during storage

Lycopene was extracted from pink grapefruit using SC-CO₂ and rice bran oil as co-solvent. Response surface methodology was employed to evaluate the individual and interactive effects of three process parameters varied at five levels i.e. pressure (250, 300, 375, 450 & 500 bar), temperature (55, 60, 70, 80 & 85 °C), and extraction time (60, 90, 135, 180 & 210 min). Single optimum point for multiple response variables was achieved at 325 bar, 64 °C, and 143 min with overall desirability of 0.92 at which 70.52 ± 3.65% (lycopene extraction efficiency) and 11154 ± 148 ppm (γ-oryzanol) were predicted. Extraction temperatures of more than 80 °C and time beyond 180 min led to the isomerization of lycopene. Lycopene storage at 3 °C, 10 °C, & 25 °C showed average k and half-life values as 0.018, 0.030, & 0.075 and 40, 23, & 9 days, respectively for first-order degradation kinetics; depicting faster degradation at higher storage temperatures.

Synergistic enhancement of loading contents and chemical stability of lycopene distributing both inside and on the oil/water interface

Loading contents and chemical stability of lycopene were synergistically enhanced after dispersion in genipin-crosslinked-chitosan (CS) stabilized high internal phase emulsions (HIPEs). HIPEs could be prepared with the parameters for the emulsifiers of CS concentration from 0.5 to 5 mg/mL, pH value from 5.5 to 7.5, and CS/genipin mass ratio from 2:1 to 20:1. High loading content of lycopene, up to 0.25 wt% was achieved, with emulsifier in the final system only 1 mg/mL. As the loading contents were elevated, increasing amount of lycopene distributed in HIPEs in the form of insoluble crystals. Meanwhile, density of oil droplets decreased and the shape changed from polygon to sphere, which is supposed to be related to the interaction between the crystal and the oil-water interface. Stability of lycopene against ultraviolet, temperature, hydrogen peroxide, and iron ions was improved significantly, which could be ascribed to the layer of genipin-crosslinked-CS on oil droplet surface and the crystal status of lycopene. The storage stability of lycopene was improved tremendously after encapsulation by HIPEs. PRACTICAL APPLICATION: Low loading content of lycopene in emulsion systems is not conducive to the evaluation of its biological function in subsequent experiments, as well as their real application in food industry. It is also crucial to improve the stability of lycopene for the practical application in food industry. In this work, the loading content in delivery system and the chemical stability of lycopene are improved through encapsulation with high internal phase emulsions (HIPEs). The significance of these results may have implications in fields spanning from colloidal science to functional foods applications.

Improving the Stability of Lycopene from Chemical Degradation in Model Beverage Emulsions: Impact of Hydrophilic Group Size of Emulsifier and Antioxidant Polarity

The chemical stability of the lipophilic bioactives encapsulated in emulsions can be influenced by emulsion droplet interfacial characteristics as well as by the ability of antioxidants incorporated in emulsion to prevent the degradation of the encapsulated compounds. Therefore, this study evaluated the effects of the interfacial characteristics of emulsions and the polarity of antioxidants on the storage stability of lycopene in emulsions. Emulsions with 5% (w/w) oil containing lycopene (30 µmol/kg emulsion) were prepared using a series of polyethylene glycol acyl ether-type emulsifiers through microfluidization. Change in lycopene content in emulsions was monitored by high performance liquid chromatography. Our findings show that the hydrophilic group size (or length) of emulsifiers and the emulsifier concentration at the interfacial film play a role, albeit minor, in controlling the storage stability of lycopene encapsulated in emulsions. Lipophilic (tert-butylhydroquinone (TBHQ)) and amphiphilic (lauryl gallate) antioxidants similarly improved the storage stability of lycopene in emulsions from acid- and radical-mediated degradation, independent of the characteristics of interfacial films of emulsions. However, TBHQ inhibited the degradation of lycopene in emulsions more effectively than lauryl gallate under conditions intended to accelerate the acid-mediated degradation of lycopene. Therefore, our findings can provide helpful information about what type of emulsifiers and antioxidants can be chosen for preparing food emulsions capable of maximizing the stability of lycopene encapsulated therein.

Phenolic Acids of Plant Origin-A Review on Their Antioxidant Activity In Vitro (O/W Emulsion Systems) Along with Their in Vivo Health Biochemical Properties

Nature has generously offered a wide range of herbs (e.g., thyme, oregano, rosemary, sage, mint, basil) rich in many polyphenols and other phenolic compounds with strong antioxidant and biochemical properties. This paper focuses on several natural occurring phenolic acids (caffeic, carnosic, ferulic, gallic, p-coumaric, rosmarinic, vanillic) and first gives an overview of their most common natural plant sources. A summary of the recently reported antioxidant activities of the phenolic acids in o/w emulsions is also provided as an in vitro lipid-based model system. Exploring the interfacial activity of phenolic acids could help to further elucidate their potential health properties against oxidative stress conditions of biological membranes (such as lipoproteins). Finally, this review reports on the latest literature evidence concerning specific biochemical properties of the examined phenolic acids.

Chemical Stability of Lycopene in Processed Products: A Review of the Effects of Processing Methods and Modern Preservation Strategies

Lycopene, one of the most dominant carotenoids in a person's diet, is a well-known natural compound that has protective effects against chronic diseases. Industrial and domestic processing and storage conditions significantly influence retention and isomerization of lycopene; thus, in recent years, great attention has been given for their preservative effects of lycopene. This review highlights recent strategies that have been developed to preserve lycopene in processed products, especially in tomato pulp, puree, paste, and juice. The key factors influencing lycopene degradation and isomerization, such as ingredients and intensity of thermal treatments, are also discussed. Special attention was paid to the crystalline structures of lycopene which facilitate its resistance to degradation and isomerization. Emerging non-thermal processing methods, such as ultrasound and high-pressure processing (HPP), are critically evaluated for their preservation of thermo-labile compounds. Novel trends to improve lycopene stability by micro- and nanoencapsulation and addition of antioxidants are also included to examine their efficacy to protect against light, heat, oxygen, and other oxidative processes. Finally, recommended processing and storage conditions are discussed to provide strategies to retain the highest possible amount of bioactive lycopene until consumption.

Inclusion Complexes of Lycopene and β-Cyclodextrin: Preparation, Characterization, Stability and Antioxidant Activity

In this study, the inclusion complexes of lycopene with β-cyclodextrin (β-CD) were prepared by the precipitation method. Then the inclusion complexes were characterized by the scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV), microscopic observation, liquid chromatography, differential scanning calorimetry (DSC) and phase-solubility study. Moreover, the stability and antioxidant activity were tested. The results showed that lycopene was embedded into the cavity of β-CD with a 1:1 stoichiometry. Moreover, the thermal and irradiant stabilities of lycopene were all significantly increased by the formation of lycopene/β-CD inclusion complexes. Antioxidant properties of lycopene and its inclusion complexes were evaluated on the basis of measuring the scavenging activity for 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and superoxide anion radicals. The results showed that the scavenging activity of DPPH radicals was obviously increased by the formation of the inclusion complex with β-cyclodextrin at concentrations of 5–30 μg/mL, however, some significant positive effects on the scavenging activity of hydroxyl and superoxide anion radicals were not observed and the reasons are worth further study.

Impact of antioxidant on the stability of β-carotene in model beverage emulsions: Role of emulsion interfacial membrane

The effect of the thickness and density of droplet interfacial membrane on the chemical stability of β-carotene in emulsions was investigated, and its impact on the effectiveness of oil-soluble antioxidants to retard β-carotene degradation was examined. β-Carotene was incorporated into the emulsions stabilized by PEGylated emulsifiers having various-sized hydrophilic groups. In the presence of oxidative stresses (pH, iron ions, and radicals in this study), it was observed that the interfacial thickness was relevant to the stability of β-carotene encapsulated into emulsion droplets. Particularly, iron-mediated carotene degradation was effectively retarded in the emulsions having a thin interfacial membrane than ones with a thick interfacial membrane. The interfacial denseness also affected β-carotene stability but its ability to retard β-carotene degradation was influenced by the interfacial thickness. Although β-carotene degradation rate decreased upon the addition of oil-soluble antioxidants, its antioxidant activity depended on what prooxidant promoted the degradation of β-carotene in the emulsions.

Interfacial Antioxidants: A Review of Natural and Synthetic Emulsifiers and Coemulsifiers That Can Inhibit Lipid Oxidation

There has been strong interest in developing effective strategies to inhibit lipid oxidation in emulsified food products due to the need to incorporate oxidatively labile bioactive lipids, such as ω-3 fatty acids, conjugated linoleic acids, or carotenoids. Emulsifiers or coemulsifiers can be utilized to inhibit lipid oxidation in emulsions. Both of these molecular types can adsorb to droplet surfaces and inhibit lipid oxidation, but emulsifiers can also stabilize droplets against aggregation whereas coemulsifiers cannot. There are a host of existing emulsifiers, covalent conjugates, or physical complexes that have the potential to inhibit lipid oxidation by a variety of mechanisms. Existing emulsifiers with antioxidant potential consist of surfactants, phospholipids, proteins, polysaccharides, and colloidal particles. Conjugates and complexes are typically formed by covalently or physically linking together a surface-active molecule with an antioxidant molecule. This article reviews the molecular and physicochemical basis for the surface and antioxidant activities of emulsifiers and coemulsifiers, highlights the important properties of interfacial layers that can be engineered to control lipid oxidation, and outlines different kinds of existing emulsifiers, conjugates, and complexes that can be used to inhibit oxidation.

Are lutein, lycopene, and β-carotene lost through the digestive process?

The bioavailability of many carotenoids has been assessed, but little attention has been given to the metabolism of these antioxidant compounds during digestion.

Retaining Oxidative Stability of Emulsified Foods by Novel Nonmigratory Polyphenol Coated Active Packaging

Oxidation causes lipid rancidity, discoloration, and nutrient degradation that decrease shelf life of packaged foods. Synthetic additives are effective oxidation inhibitors, but are undesirable to consumers who prefer "clean" label products. The aim of this study was to improve oxidative stability of emulsified foods by a novel nonmigratory polyphenol coated active packaging. Polyphenol coatings were applied to chitosan functionalized polypropylene (PP) by laccase assisted polymerization of catechol and catechin. Polyphenol coated PP exhibited both metal chelating (39.3 ± 2.5 nmol Fe(3+) cm(-2), pH 4.0) and radical scavenging (up to 52.9 ± 1.8 nmol Trolox eq cm(-2)) capacity, resulting in dual antioxidant functionality to inhibit lipid oxidation and lycopene degradation in emulsions. Nonmigratory polyphenol coated PP inhibited ferric iron promoted degradation better than soluble chelators, potentially by partitioning iron from the emulsion droplet interface. This work demonstrates that polyphenol coatings can be designed for advanced material chemistry solutions in active food packaging.

Designing food delivery systems: challenges related to the in vitro methods employed to determine the fate of bioactives in the gut

This review discussesin vitroavailable approaches to study delivery and uptake of bioactive compounds and the associated challenges.

Effects of antioxidants on the stability of β-Carotene in O/W emulsions stabilized by Gum Arabic

The potential of oil-in-water emulsions as a β-carotene delivery system was examined in this study. Oil-in-water (O/W) emulsions containing β-carotene were formed by gum arabic with α-tocopherol, tertiary butyl hydroquinone (TBHQ) and ascorbyl palmitate, respectively. The influence of antioxidants on the chemical degradation of β-carotene in gum arabic stabilized emulsions was investigated at 4, 25, 45 and 65 °C in the dark, respectively. An accelerated photo-oxidation test was carried out at 45 °C (450 W/m(2)). Moreover, β-carotene degradation rate constants (k 1-value), activation energy (E a ) and decimal reduction time (D-value) were estimated to interpret the degradation kinetics. The impact of antioxidants on the thermal stability of β-carotene in diluted emulsions was generally in the following order: α-tocopherol > TBHQ > ascorbyl palmitate. α-Tocopherol was found to be the most effective to the antioxidation of β-carotene at the concentration of 0.10 wt% under light exposure. It was concluded that the stability of β-carotene in oil-in-water emulsions could be improved by the presence of different antioxidants.

Maxima in antioxidant distributions and efficiencies with increasing hydrophobicity of gallic acid and its alkyl esters. The pseudophase model interpretation of the "cutoff effect"

Antioxidant (AO) efficiencies are reported to go through maxima with increasing chain length (hydrophobicity) in emulsions. The so-called "cutoff" after the maxima, indicating a decrease in efficiency, remains unexplained. This paper shows, for gallic acid (GA) and propyl, octyl, and lauryl gallates (PG, OG, and LG, respectively), that at any given volume fraction of emulsifier, the concentrations of antioxidants in the interfacial region of stripped corn oil emulsions and their efficiency order follow PG > GA > OG > LG. These results provide clear evidence that an AO's efficiency correlates with its fraction in the interfacial region. AO distributions were obtained in intact emulsions by using the pseudophase kinetic model to interpret changes in observed rate constants of the AOs with a chemical probe, and their efficiencies were measured by employing the Schaal oven test. The model provides a natural explanation for the maxima with increasing AO hydrophobicity.

Crystals and crystallization in oil-in-water emulsions: implications for emulsion-based delivery systems

Many bioactive components intended for oral ingestion (pharmaceuticals and nutraceuticals) are hydrophobic molecules with low water-solubilities and high melting points, which poses considerable challenges to the formulation of oral delivery systems. Oil-in-water emulsions are often suitable vehicles for the encapsulation and delivery of this type of bioactive component. The bioactive component is usually dissolved in a carrier lipid phase by either dilution and/or heating prior to homogenization, and then the carrier lipid and water phases are homogenized to form an emulsion consisting of small oil droplets dispersed in water. The successful development of this kind of emulsion-based delivery system depends on a good understanding of the influence of crystals on the formation, stability, and properties of emulsions. This review article addresses the physicochemical phenomena associated with the encapsulation, retention, crystallization, release, and absorption of hydrophobic bioactive components within emulsions. This knowledge will be useful for the rational formulation of effective emulsion-based delivery systems for oral delivery of crystalline hydrophobic bioactive components in the food, health care, and pharmaceutical industries.