Lipid Oxidation In Emulsions Research Articles

Lipid Oxidation in Emulsions Fortified with Iron-Loaded Alginate Beads.

The potential use of iron-loaded alginate beads to fortify oil-in-water (O/W) emulsions was studied. Iron-loaded alginate beads with different sizes (0.65, 0.84, 1.5 and 2 mm) were produced by ionic gelation with calcium chloride, leading to 81% encapsulation efficiency (EE) of ferrous sulfate. These beads were added to O/W emulsions to investigate their effect on lipid oxidation. The use of iron-loaded alginate beads inhibited lipid oxidation in emulsions, compared to a control emulsion with the same concentration of free ferrous sulfate in the continuous phase, but did not totally prevent it. Results obtained with scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX) analysis showed that some reactive iron was present at the surface of the beads. Oxidation of the lipid droplets was slightly higher for smaller alginate beads, suggesting that the reaction could be linked to the total bead surface. When covering iron-loaded beads with an extra layer of alginate, lipid oxidation was inhibited, which confirmed the role of reactive surface-bound iron. This study shows that the location of iron within the encapsulates plays a crucial role in the chemical stability of fortified foods and should be taken as a starting point in the design of iron-fortified food products.

Antioxidant Activities of Sorghum Kafirin Alcalase Hydrolysates and Membrane/Gel Filtrated Fractions.

Sorghum has a significant amount of proteins, especially kafirin; however, limited information is available on evaluating its potential for peptide antioxidants. The objectives of this study were to: (1) investigate the effects of two key variables, enzyme-to-substrate ratio and reaction time on kafirin hydrolysis using Alcalase; (2) evaluate the antioxidant performances of the hydrolysates and fractions from membrane ultrafiltration and gel filtration; and (3) identify peptide sequences in the antioxidant fraction using MALDI-TOF/TOF MS. Kafirin hydrolysates prepared at enzyme-to-substrate ratio of 0.4 Au/g and 4 h had a good balance of antioxidant activity, yield, and economic efficiency. Medium-sized fraction of hydrolysates (5–10 kDa) from membrane filtration possessed the highest antioxidant activities among various fractions. The fraction also unveiled a good inhibition effect against lipid oxidation in emulsion and ground meat systems. Smaller-sized fraction (F3) collected through gel-filtration chromatography had significantly stronger antioxidant activities than other fractions, and 26 representative peptide sequences were identified in the fraction.

Interaction effect of tocopherol homologs with peppermint extract on the iron-catalyzed oxidation of soybean oil-in-water emulsion.

Interaction between tocopherol homologs and peppermint extract added to oil-in-water emulsions was studied during iron-catalyzed oxidation. Emulsions consisted of tocopherol-stripped soybean oil and citrate buffer (4:6, w/w) with/without addition of peppermint extract (400mg/kg) and α-, γ-, or δ-tocopherol (600mg/kg), and were oxidized in the iron presence at 25°C. Lipid oxidation of emulsions was evaluated based on hydroperoxide contents and p-anisidine values. Lipid oxidative stability of emulsions was improved by added peppermint extract, and co-added γ- and δ-tocopherols further reduced lipid oxidation, however, α-tocopherol increased it. Tocopherol contents did not change during oxidation. Polyphenol degradation in the emulsion with added peppermint extract was lower and slower by γ- and δ-tocopherols, however, α-tocopherol showed opposite results. The results suggest that co-addition of tocopherols to the emulsion containing peppermint extract shift a major role of polyphenols as antioxidants from scavenging lipid (peroxy) radicals to tocopherol radical scavenging.

Can we prevent lipid oxidation in emulsions by using fat-based Pickering particles?

Interest has recently been rising in the development of food-compatible Pickering emulsions, i.e., particle-stabilized emulsions, and various biobased particles have been demonstrated as useful for such a purpose. Most of the related work has focused on the physical stability of the emulsions, but whether such particles can be advantageous in terms of chemical stability, and in particular, with regard to lipid oxidation, is largely unexplored. Recently, we found that colloidal lipid particles (CLPs) are efficient Pickering stabilizers, and the objective of the present study was to investigate the oxidative stability of emulsions stabilized with those particles. Three types of sunflower oil-in-water (O/W) emulsions were considered: Pickering emulsions stabilized with colloidal lipid particles (CLPs) made of high melting point (HMP) fat (tripalmitin or palm stearin), adsorbed onto the liquid oil droplets; and, as references, two conventional sodium caseinate-stabilized emulsions, of which one contained only liquid oil, and the other liquid oil mixed with HMP fat as the core of the emulsion droplets. In the presence of iron, the latter oxidized faster than conventional liquid oil and Pickering emulsions, resulting in 2- to 3-fold higher amounts of primary and secondary lipid oxidation products. This may be due to intra-droplet HMP fat pushing oxidizable lipids towards the oil-water interface, which would promote lipid oxidation. This shows that the localization of solid fat in O/W emulsions affects lipid oxidation. We also found that CLP-stabilized Pickering emulsions had similar oxidation rates as conventional sodium caseinate-stabilized emulsions containing only liquid oil. This suggests that the potential of such Pickering particles to prevent lipid oxidation is limited. This could be because diffusion of small pro-oxidant molecules is not hindered by Pickering particles, as they cannot form an interfacial barrier that is structurally homogeneous at such a small scale.

Control of antioxidant efficiency of chlorogenates in emulsions: modulation of antioxidant interfacial concentrations.

Controlling the interfacial concentrations of antioxidants (AOs) in oil-in-water emulsions can be regarded as a unique approach for increasing the efficiency of AOs in inhibiting the oxidation of lipids. Classical methods to determine the AO distribution in binary systems cannot be employed and their distribution needs to be assessed in the intact emulsion. We have employed a well-established kinetic method to determine the distribution of a homologous series of AOs derived of chlorogenic acid in olive oil-in-water emulsions and analyse the effects of AO hydrophobicity on their distributions and their efficiencies. Results indicate that variations in the efficiency of chlorogenates in emulsions are due to differences in their interfacial concentrations. Their interfacial concentrations AOI were much higher (20- to 150-fold) than their stoichiometric concentrations. On the other hand, their concentrations in the oil region were 1.5- to 0.1-fold. Results also show the complex effect of the oil-to-water ratio employed in the preparation of the emulsions on the (AOI ) values. Results highlight the key role of the interfacial region and of its composition (interfacial AO molarity, emulsifier concentration, oil-to-water ratio) in interpreting the efficiency of AOs in inhibiting lipid oxidation in emulsions. Thus, a careful modulation of these parameters is necessary to ensure optimum AO efficiency. © 2019 Society of Chemical Industry.

Effects of microbial transglutaminase treatment on physiochemical properties and emulsifying functionality of faba bean protein isolate

The potential use of microbial transglutaminase (MTG)-treated faba bean protein isolate (FBPI) as emulsifiers to maintain physical and oxidative stability of oil-in-water (O/W) emulsion was investigated. MTG-treated FBPIs (MTG-FBPIs) were prepared by incubating with MTG for 60, 120 or 240 min. O/W emulsions were stabilized by 3% (w/v) of MTG-FBPIs or control-FBPI (treated with inactive MTG) and stored at 37 °C for 7 days. MTG treatments induced cross-linking in FBPI, raised the protein net surface charges by 5%–8%, and increased the emulsion particle size by 19%–135%. MTG treatment for 120 and 240 min but not 60 min induced excessive surface hydrophobicity, resulting in decreased emulsifying activity and physical stability of emulsion. By day 7, all MTG-treated FBPIs showed similar inhibiting effects against lipid oxidation in emulsion, indicated by less conjugated dienes and hexanal production. MTG-FBPIs moderately promoted protein oxidation (120 min > 240 min ≈60 min). Thus, prolonged MTG treatment should be avoided to prevent accelerated protein oxidation and droplets coalescence. MTG treatment for 60 min makes FBPI a potential emulsifier to maintain physical stability while improving lipid oxidative stability in emulsion, potentially attributed to thicker interfacial layer, larger droplet size, and protective effect of protein.

The ability of oxygen scavenging packaging to inhibit vitamin degradation and lipid oxidation in fish oil-in-water emulsions

Abstract The impact of commercial oxygen scavenging packaging on lipid oxidation in fish oil-in-water (O/W) emulsions and vitamin degradation was determined. Oxygen scavenging packaging effectively reduced dissolved oxygen concentration in buffer (pH 3, 5, and 7) by >95% as measured by an oxygen fluorometer over 3 days at 32 °C. Lipid oxidation in emulsions, as measured by lipid hydroperoxides and thiobarbituric acid reactive substances (TBARS), was effectively inhibited by oxygen scavenging packaging regardless of pH (3 and 7), fat concentration (1 and 20%), or in the presence of sodium chloride (0 and 250 mM). Analysis of ascorbic acid and α-tocopherol degradation demonstrated that the oxygen scavenging packaging was able to protect both water and fat-soluble vitamins. This work suggests that active packaging can sufficiently reduce oxygen levels in O/W emulsions to greatly extend the oxidative stability without the addition of exogenous antioxidants. Industrial significance Increased pressure by consumers to remove food additives requires innovative solutions to maintain the shelf life of foods and minimize food waste. Active packaging that reduces oxygen to levels low enough to inhibit oxidative spoilage could provide a potential ‘clean label’ solution to food additives since the antioxidant technology is provided by the packaging system. Oxygen scavenging packaging described in this work reduced packaged oxygen by >98% under a variety of conditions expected in foods and inhibited lipid oxidation of fish oil-in-water emulsions. The impact of this work could improve food quality and extend shelf life for oxidatively susceptible O/W emulsions. In addition, oxygen scavenging active packaging greatly decreased the degradation of essential vitamins suggesting that it could improve the nutritional quality of foods.

The prooxidant activity of salts on the lipid oxidation of lecithin-stabilized oil-in-water emulsions

Salts reduction/substitution have gained a lot interest from food industry since the US Food and Drug Administration (FDA) has issued a draft guidance for salt reduction. However how changes of salts in food formulation could influence lipid oxidation is still not fully understood. Using oil-in-water emulsions stabilized by a natural emulsifier – lecithin at pH 7.0 as a model system, this study evaluated how salts affect the physical parameters of the emulsion, the chelating activity of lecithin and thus the lipid oxidation of these emulsions. Results showed that salts increased the particle size, the negative charge of the oil droplets, and the amount of iron chelated by lecithin. Lipid oxidation lag phases were shortened by addition of salts, by 1 day and 2 days for lipid hydroperoxides and thiobarbituric acid reactive substances measurements respectively. These results provide some new insights on the mechanisms of how salts could affect the lipid oxidation of food 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.

Phenolic residues in spruce galactoglucomannans improve stabilization of oil-in-water emulsions

HypothesisAmphiphilic character of surfactants drives them at the interface of dispersed systems, such as emulsions. Hemicellulose-rich wood extracts contain assemblies (lignin-carbohydrate complexes, LCC) with natural amphiphilicity, which is expected to depend on their chemical composition resulting from the isolation method. Lignin-derived phenolic residues associated with hemicelluloses are hypothesized to contribute to emulsions’ interfacial properties and stability. ExperimentsWe investigated the role of phenolic residues in spruce hemicellulose extracts in the stabilization of oil-in-water emulsions by physical and chemical approach. Distribution and changes occurring in the phenolic residues at the droplet interface and in the continuous phase were studied during an accelerated storage test. Meanwhile, the physical stability and lipid oxidation in emulsions were monitored. FindingsNaturally associated lignin residues in GGM act as vehicles for anchoring these hemicelluloses into the oil droplet interface and further enable superior stabilization of emulsions. By adjusting the isolation method of GGM regarding their phenolic profile, their functionalities, especially interfacial behavior, can be altered. Retaining the native interactions of GGM and phenolic residues is suggested for efficient physical stabilization and extended protection against lipid oxidation. The results can be widely applied as guidelines in tailoring natural or synthetic amphiphilic compounds for interfacial stabilization.

Soy peptide nanoparticles by ultrasound-induced self-assembly of large peptide aggregates and their role on emulsion stability

In this study, soy peptide nanoparticles (SPN), originated from large peptide aggregates formed during hydrolysis of soy protein isolate, were fabricated using ultrasound, and were further investigated for their potential role as effective stabilizers to prepare oil-in-water (O/W) emulsions. The self-assembled SPN showed spherical appearance with small particle size (104.10 nm) and homogenous size distribution (PDI∼0.20). The physical properties and oxidative stability of O/W emulsions stabilized by SPN were then evaluated. Interestingly, although the prepared emulsion showed a rapid creaming shortly after homogenization, the droplet size and size distribution did not change significantly throughout the storage, which could be explained by the complete coverage of SPN onto the droplet surface, thus preventing droplets coalescence. In addition, lipid oxidation in emulsions, as evaluated by the formation of lipid hydroperoxides and volatile hexanal, was also well suppressed, which should be mainly due to the excellent antioxidant capacity of bioactive SPN at the oil-water interface as well as in the continuous phase. For better utilization of SPN, HPMC/Tween 80 were then incorporated, lowering the interfacial tension and forming mixed interface together with SPN, which further facilitate the formation of a finely distributed emulsion with smaller droplet size and improved oxidative stability. These results indicated that the novel peptide-based nanoparticles could be used as bifunctional and effective emulsifiers for preparing stable O/W emulsion systems.

Alkyl caffeates as antioxidants in O/W emulsions: Impact of emulsifier type and endogenous tocopherols

Antioxidant addition can be one strategy to limit lipid oxidation in emulsions. Research has proven that an important factor regarding the efficacy of antioxidants is their localization in the emulsion; however, other factors such as interactions with other components can also have an impact. Thus, the aim was to evaluate the impact of emulsifiers (Citrem and Tween80) and presence of endogenous tocopherols on the efficacies of caffeic acid and caffeates (C1–C20) as antioxidants in emulsions. Lipid oxidation was evaluated during storage and partitioning of caffeic acid and caffeates was estimated by measuring their concentrations in the aqueous phase. Partitioning of caffeic acid and caffeates was influenced by emulsifier type and the presence of endogenous tocopherols. Caffeic acid was the most efficient antioxidant in Citrem and Tween stabilized emulsions in the presence of endogenous tocopherol. In contrast, for Tween stabilized emulsions, caffeic acid acted as a prooxidant and the evaluated caffeates acted as strong antioxidants in the absence of endogenous tocopherol. Thus, when endogenous tocopherol was present lipophilization of caffeic acid did not increase its efficacy as an antioxidant. It is suggested that the differences observed in antioxidant efficiency with different emulsifiers and with and without endogenous tocopherols is due to emulsifier–antioxidant interactions and antioxidant–antioxidant interactions in the emulsions.Practical applications: Food emulsions contain endogenous tocopherols, thus, the impact of endogenous tocopherols on the efficacy of applied antioxidants is of interest to the industry. So far the hypotheses about antioxidant in emulsions are based on simple emulsions systems without the presence of tocopherols. The finding in this study revealed that both emulsifier type and the presence of endogenous tocopherol had an impact on the efficacy of caffeic acid and caffeates due to emulsifier–antioxidant and antioxidant–antioxidant interactions. This highlights the importance of evaluating the antioxidant in each emulsion system before selecting antioxidants for optimal protection against lipid oxidation.CAT value determined in oil‐in‐water micro emulsions with caffeic acid and caffeates (100 μM) and with and without endogenous tocopherol and lipid oxidation is initiated with the water soluble radical AAPH.

The effect of antioxidants on quantitative changes of lysine and methionine in linoleic acid emulsions at different pH conditions.

Plants are an important source of phenolic compounds. The antioxidant capacities of green tea, thyme and rosemary extracts that contain these compounds have been reported earlier. However, there is a lack of accessible information about their activity against lipid oxidation in emulsions and inhibit the interaction of lipid oxidation products with amino acids. Therefore, the influence of green tea, thyme and rosemary extracts and BHT (butylated hydroxytoluene) on quantitative changes in lysine and methionine in linoleic acid emulsions at a pH of isoelectric point and a pH lower than the isoelectric point of amino acids was investigated. Total phenolic contents in plant extracts were determined spectrophotometrically by using Folin-Ciocalteu's reagent, and individual phenols by using HPLC. The level of oxidation of emulsion was determined using the measurement of peroxides and TBARS (thiobarbituric acid reactive substances). Methionine and lysine in the system were reacted with sodium nitroprusside and trinitrobenzenesulphonic acid respectively, and the absorbance of the complexes was measured. Extract of green tea had the highest total polyphenol content. The system containing antioxidants and amino acid protected linoleic acid more efficiently than by the addition of antioxidants only. Lysine and methionine losses in samples without the addition of antioxidants were lower in their isoelectric points than below these points. Antioxidants decrease the loss of amino acids. The protective properties of antioxidants towards methionine were higher in a pH of isoelectric point whereas towards lysine in pH below this point. Green tea, thyme and rosemary extracts exhibit antioxidant activity in linoleic acid emulsions. Moreover, they can be utilized to inhibit quantitative changes in amino acids in lipid emulsions. However, the antioxidant efficiency of these extracts seems to depend on pH conditions. Further investigations should be carried out to clarify this issue.

Differences in antioxidant activity between two rice protein concentrates in an oil‐in‐water emulsion

Two formulations of rice protein concentrates (RPC) derived from brown rice were evaluated for their antioxidant activity in bulk oil and in oil‐in‐water emulsions. Bulk oils were mixed with RPC and heated to 180°C, and total polar compounds and triacylglycerol polymerization were measured. Minimal antioxidant activity was observed in the bulk oil phase. Rice protein concentrates were incorporated into soybean oil‐in‐water emulsions, which were oxidized at 50°C for 8 days. Lipid oxidation in emulsions was assessed via peroxide values (PV), headspace oxygen levels, headspace volatile oxidation products, and fatty acid analysis. One of the RPC treatments showed some antioxidant activity in emulsions, suggesting that RPC could potentially be used to extend shelf life and preserve product quality.Practical applications: Naturally derived antioxidants that can inhibit oxidation in edible oils are in high demand. As consumers become more label‐conscious, synthetic antioxidants are falling out of favor. Rice proteins offer a means of antioxidant capability in emulsions, which may have applications in improving shelf life and/or product quality in a variety of foods, including sauces, salad dressings, and dairy products. Rice protein concentrations show more promise in emulsions than in bulk oil.Protein concentrates derived from brown rice (left) were incorporated into oil‐in‐water emulsions (center) and showed differing abilities to suppress lipid oxidation (linolenic acid, shown right).

Industrial Applications of Selected JFS Articles

Industrial Applications of Selected <i>JFS</i> Articles

Effects of composition and processing variables on the oxidative stability of protein-based and oil-in-water food emulsions

ABSTRACTBecause many common foods are emulsions (mayonnaise, coffee creamers, salad dressing, etc.), a better understanding of lipid oxidation mechanisms in these systems is crucial for the formulation, production, and storage of the relevant consumer products. A research body has focused on the microstructural and oxidative stability of protein-stabilized oil-in-water emulsions that are structurally similar to innovative products that have been recently developed by the food industry (e.g., non-dairy creams, vegetable fat spreads, etc.) This review presents recent findings about the factors that determine the development of lipid oxidation in emulsions where proteins constitute the stabilizing interface. Emphasis is given to “endogenous” factors, such as those of compositional (e.g., protein/lipid phases, pH, presence of transition metals) or processing (e.g., temperature, droplet size) nature. Improved knowledge of the conditions that favor the oxidative protection of protein in emulsions can lead to their optimized use as food ingredients and thereby improve the organoleptic and nutritional value of the related products.

Effects of salts on oxidative stability of lipids in Tween-20 stabilized oil-in-water emulsions

Lipid oxidation in oil-in-water (O/W) emulsions is an important factor determining the shelf life of food products. Salts are often present in many types of emulsion based food products. However, there is limited information on influence of salts on lipid oxidation in O/W emulsions. Thus, the purpose of this study was to examine the effects of sodium and potassium chloride on lipid oxidation in O/W emulsions. Tween 20 stabilized corn O/W emulsions at pH 7.0 were prepared with different concentrations of sodium chloride with or without the metal chelators. NaCl did not cause any changes in emulsion droplet size. NaCl dose-dependently promoted lipid oxidation as measured by the lipid oxidation product, hexanal. Both deferoxamine (DFO) and ethylenediaminetetraacetic acid (EDTA) reduced lipid oxidation in emulsions with NaCl, with EDTA being more effective. Potassium chloride showed similar impact on lipid oxidation as sodium chloride. These results suggest that salts are able to promote lipid oxidation in emulsions and this effect can be controlled by metal chelators.

Lipid Oxidation In Oil-In-Water Emulsions: A Mini Review

Emulsion technology has been emerged into food industries widely. Researches in emulsion and its application have been done intensively particularly to understand emulsion behavior in relation to its stability. Stability of emulsion indicates stability of food products therefore attempt to identify the causes of instability increases. This mini review underlines lipid oxidation in oil in water emulsion including emulsion definition, factors involved in determining the rate of lipid oxidation, common cause of oxidative instability and some case examples of lipid oxidation in emulsion.

Characterization of Ultrasonically Prepared Flaxseed oil Enriched Beverage/Carrot Juice Emulsions and Process-Induced Changes to the Functional Properties of Carrot Juice

This study reports on the formation of stable emulsion of flaxseed oil (1 % v/v) in carrot juice (CJFO) using 20-kHz ultrasound (US) at 176 W and 4 min of processing time. The shear forces generated by acoustic cavitation are responsible for the production of emulsion droplets of size 0.6 μm. Pectin acted as an emulsifier providing stability by creating electrostatic repulsion (ζ potential −30 mV) between emulsion droplets and the emulsions were stable up to 8 days at 4 ± 2 °C. The viscosity of the emulsion remained unchanged with sonication time (up to 8 min) and upon storage. The unaffected flow behavior of emulsions was an advantage to adapt it to existing pipelines in food industries. Sonication led to an increase in carotenoid content to about 1.5 mg/100 ml of juice. In addition, an increase in lipid oxidation of emulsion was observed due to prooxidant characteristics of carotenoid. However, industrially, it can be prevented by adding antioxidants or by providing inert gas blanket to the process cell. In total, the formation of stable emulsions without addition of external emulsifiers and stabilizers, by using US process, is perceived a positive step towards new product/process development.

Antioxidant capacity of hydrolyzed animal by-products and relation to amino acid composition and peptide size distribution.

The antioxidative capacity of six different tissue hydrolysates (porcine colon, heart and neck and bovine lung, kidney and pancreas) were tested by three different assays monitoring iron chelation, ABTS radical scavenging and inhibition of lipid oxidation in emulsions, respectively. The hydrolysates were also investigated with respect to amino acid composition and peptide size distribution. The hydrolysates contained peptides ranging from 20kDa to below 100Da with a predominance of peptides with low molecular weight (53.8 to 89.0% below 3kDa). All hydrolysates exhibited antioxidant activity as assessed with all three methods; inhibition of lipid oxidation ranging from 72 to 88% (at a final protein concentration of 7mg/mL), iron chelation capacity from 23 to 63% (at 1.1mg/mL), and ABTS radical scavenging from 38 to 50% (at 10μg /mL). The antioxidant activity did not correlate with the proportion of low molecular weight peptides in the hydrolysed tissues, but with the content of specific amino acid residues. The ABTS radical scavenging capacity of the tissues was found to correlate with the content of Trp, Tyr, Met and Arg, whereas the ability to inhibit the oxidation of lineoleic acid correlated with the content of Glu and His. The chosen animal by-products thus represent a natural source of antioxidants with potential for food application.