Influence of oil droplet size on the oxidative stability of the free and encapsulated fractions of freeze-dried microencapsulated sunflower oil

The effect of oil droplet size (ODS) on the oxidative stability (OS) of dried microencapsulated oils has been scarcely studied, and results are contradictory. A few studies have shown increased OS when the ODS was reduced and this was attributed to a decrease in the surface oil content (SOC). Yet, in such studies, only the total oil fraction was evaluated. In the present work, the free (FO) and encapsulated oil (EO) fractions of freeze-dried microencapsulated sunflower oil were analysed to study the effect of changes in the ODS by using different homogenisation pressure (15 or 70 MPa) in the emulsification step. The OS of both the free and encapsulated fractions increased when the ODS was significantly reduced in two samples with different encapsulation matrix, namely caseinate/lactose and maltodextrin/sucrose/gelatine. A reduction in the SOC would explain the increased stability of the FO, but not that of the EO. An additional protective role of the interfacial film could have been involved. In conclusion, if the encapsulation matrix and the interfacial region are effective as oxygen barriers, a reduction in the ODS of the parent emulsion by an increase in the homogenisation pressure will result in capsules more stable against lipid oxidation.     

Limonene encapsulation in freeze-drying of gum Arabic-sucrose-gelatin systems

Encapsulation of limonene in freeze-drying of various matrices consisting of gum Arabic, sucrose and gelatin was studied. Retention of limonene in freeze-drying was observed by measuring absorbance at 252 nm using a spectrophotometer. Two different levels of limonene, in the weight ratios (w/w) of 9:1 and 8.5:1.5 (total solids (TS):limonene) were studied. Highest amount of limonene (75.3±0.3% of initially added amount) in the emulsions homogenised at 25 MPa (4 MPa in second stage) followed by freeze-drying, was retained in a matrix consisting of gum Arabic, in the ratio of 9:1 (w/w). A mixture consisting of gelatin-sucrose-gum Arabic in the w/w ratio of 0.66:0.17:0.17 retained highest amount (71.8±0.1% of initially added amount) of limonene in the ratio (w/w) of 8.5:1.5 (TS:limonene). A matrix consisting of gum Arabic-sucrose-gelatin (1:1:1 w/w/w) with added limonene at a ratio (w/w) of 9:1 (TS:limonene), was used to study the effects of ultra high-pressure homogenisation (50-250 MPa) on limonene encapsulation in freeze-drying. Highest amount (84% of initially added amount) of limonene was retained in the emulsions homogenised at a pressure of 100 MPa. Electron micrograph of freeze-dried matrix of gum Arabic-sucrose-gelatin in the weight ratio of 1:1:1 suggested that it possessed a flake like structure, which was free of dents and shrinkage. A mixture consisting of gum Arabic-sucrose-gelatin is an efficient encapsulant for limonene encapsulation by freeze-drying.     

Particle size distribution and homogenisation efficiency in high-pressure homogenisation of wheat germ oil-water system

Wheat germ oil (WGO) is well-known as a good source of vegetable oil due to its nutrients and health benefits. Emulsification is a process that improves the incorporation of oil into food. High-pressure homogenisation (HPH) is a nonthermal and soft technique with enormous potential in oil-in-water emulsification. This paper focussed on the application of HPH for emulsification of WGO-in-water system. Influences of homogenisation pressure (100–300 bar), oil fraction (10–20% v/v) and lecithin adding (0–0.2% w/v of content) on the homogenisation were evaluated based on distribution of particles diameter and homogenisation efficiency. The increase in operating pressure and lecithin ratio decreased the particle size and increased the emulsion stability, and vice versa for oil fraction. The findings imply that the investigated factors significantly influenced particle size and emulsion system stability. The regression model between mean particle diameter and technical conditions of emulsion was established. With HPH treatment conditions of 300 bar operating pressure, 10% (v/v) oil fraction and 0.2% (w/v) lecithin created an emulsion system with a mean particle size of 3.32 µm, more than 50% of the volume of particles smaller than 1.5 µm of diameter and the homogenisation efficiency of 98.61%. HPH exhibits high efficiency and potential in WGO-in-water emulsification application.     

Effect of Ultra-high-pressure Homogenization on Structure and on Rheological Properties of Soy Protein-stabilized Emulsions

ABSTRACT: An ultra high-pressure homogenizer (20 to 350 MPa) was used to realize fine food emulsions stabilized by soy proteins. The first aim of the work was to understand how dynamic high-pressure processing affects soybean globulin conformation. Then, the effect of homogenizing pressure on the emulsions structure and rheology was investigated. High-pressure homogenization caused denaturation of proteins due to strong mechanical forces and high temperatures encountered in the valve. Droplet sizes of emulsions were greatly reduced with high-pressure homogenization and Newtonian liquid emulsions were converted into shear-thinning emulsion gels by homogenization at pressures above 250 MPa. Hydrophobic interactions between proteins were supposed to cause the gel-like network structure of emulsions.     

Rheology and microstructure of myofibrillar protein-plant lipid composite gels: Effect of emulsion droplet size and membrane type

Composite gels were prepared from 2% myofibrillar protein (MP) with 10% imbedded pre-emulsified plant oils (olive and peanut) of various particle sizes at 0.6 M NaCl, pH 6.2. Dynamic rheological testing upon temperature sweeping (20-70 °C at 2 °C/min) showed substantial increases in G′ (elastic modulus) of MP sols/gels with the addition of emulsions, and the G′ increases were inversely related to the emulsion droplet size. Furthermore, gels containing emulsified olive oil had a greater (P < 0.05) hardness than those containing emulsified peanut oil. Regardless of oil types, MP-coated oil droplets exhibited stronger reinforcement of MP gels than Tween 80-stablized oil droplets; the latter composite gels had considerable syneresis. Light microscopy with paraffin sectioning revealed a stable gel structure when filled with protein-coated oil droplets, compared to gels with Tween 80-treated emulsions that showed coalesced oil droplets. These results suggest that rheological characteristics, hardness, texture, and water-holding capacity of MP gels were influenced by type of oils, the nature of the interfacial membrane, and the size of emulsion droplets.     

Characteristics of submicron emulsions prepared by ultra-high pressure homogenisation: Effect of chilled or frozen storage

Model O/W pre-emulsions at an initial temperature of 24 °C and pH 6.3, and containing (w/w) 4.3% whey proteins plus 15, 30 or 45% peanut oil were processed using a ∼15 L/h homogeniser with a high pressure (HP) valve immediately followed by cooling heat exchangers. The effect of ultra-high pressure homogenisation (UHPH) between 100 and 300 MPa (P₁) or of recycling (1–3 homogenisation passes) at 200 MPa was investigated on the droplet size distribution, size indices and viscosity. Fluid temperatures were measured at the inlet (T₁) and outlet (T₂) of the HP-valve, and after immediate cooling downstream of the HP-valve (T₃) as they varied throughout UHPH. Short-life heating phenomena and mechanical energy involved in droplet processing were clearly influenced by emulsion composition. Oil droplet diameters decreased when (P₁) increased from 100 to 300 MPa leading to submicron droplets at ≥200 MPa. Monomodal distributions with droplets well below 0.3 μm were obtained after recycling at 200 MPa for the three oil contents, with a peak at 138 nm (distribution in volume) or 60–70 nm (in number frequency). The emulsion behaviour varied from fluid (and quite Newtonian) to thick (and shear thinning) depending on the droplet size reduction and the oil volume fraction. Emulsions displayed an excellent stability vs. creaming and coalescence after 9 d storage at 5 °C. Freezing followed by 13 d storage at −24 °C then thawing, induced an increase in particle sizes depending both on the oil volume fraction and (P₁). After UHPH at 200–225 MPa (±recycling), the freezing/thawing process maintained most of oil droplet size below 1 μm at 15% (w/w) oil, and induced mainly oil droplet aggregation through SDS-labile interactions at higher oil contents.     

Encapsulation of emulsified tuna oil in two-layered interfacial membranes prepared using electrostatic layer-by-layer deposition

Tuna oil-in-water emulsions (5 wt% tuna oil, 100 mM acetate buffer, pH 3.0) containing droplets stabilized either by lecithin membranes (primary emulsions) or by lecithin–chitosan membranes (secondary emulsions) were produced. The secondary emulsions were prepared using a layer-by-layer electrostatic deposition method that involved adsorbing cationic chitosan onto the surface of anionic lecithin-stabilized droplets. Primary and secondary emulsions were prepared in the absence and presence of corn syrup solids (a carbohydrate widely used in the micro-encapsulation of oils) and then their stability to environmental stresses was monitored. The secondary emulsions had better stability to droplet aggregation than primary emulsions exposed to thermal processing (30–90 °C for 30 min), freeze-thaw cycling (−18 °C for 22 h/30 °C for 2 h), high sodium chloride contents (200 mM NaCl) and freeze-drying. The addition of corn syrup solids decreased the stability of primary emulsions, but increased the stability of secondary emulsions. The interfacial engineering technology used in this study could lead to the creation of food emulsions with novel properties or improved stability to environmental stresses.     

Thermal Stability of Invertase in Reduced-Moisture Amorphous Matrices in Relation to Glassy State and Trehalose Crystallization

The thermal stability of enzyme invertase in reduced-moisture model systems of maltodextrin (MD), polyvynilpyrrolidone (PVP; MW 40,000) and trehalose heated at 90°C was studied. Significant invertase inactivation was observed in heated glassy PVP and MD systems kept well below their glass transition temperature (T_g), but the enzyme was fairly stable in rubbery trehalose systems. However, at moisture contents which allowed trehalose crystallization rapid thermal inactivation of invertase was observed. Invertase inactivation in heated PVP, MD and trehalose systems of reduced-moisture could not be predicted on the basis of glass transition and this was particularly true for trehalose. Conditions which would allow collapse of the systems and crystallization of trehalose were fairly well predicted based on the estimated T_g of model systems.     

Encapsulation of vitamin E in edible emulsions fabricated using a natural surfactant

Vitamin E is a fat-soluble vitamin widely used in pharmaceutical, supplement, food, and cosmetic preparations that must be encapsulated before it can be dispersed into aqueous-based products. The purpose of this study was to develop “all-natural” oil-in-water emulsions that could be used to incorporate vitamin E into functional food and beverage products. These emulsions were stabilized by a natural food-grade surfactant (Q-Naturale^®) isolated from the bark of the Quillaja saponaria Molina tree. The influence of oil phase composition (vitamin E to medium chain triglyceride (MCT) ratio), aqueous phase composition (glycerol to water ratio), and surfactant type (Q-Naturale^®versus Tween 80) on the size of the droplets produced by high pressure homogenization was examined. Small droplets could not be formed using only vitamin E acetate as the oil phase because of its very high viscosity, but they could be formed when ≥20% MCT was incorporated into the oil phase prior to homogenization. In the absence of glycerol, Q-Naturale^® was capable of forming emulsions containing relatively small droplets (d < 400 nm) from oil phases containing relatively high vitamin levels (60–80%). This droplet size could be decreased (d < 250 nm) by incorporating 50% glycerol in the aqueous phase prior to homogenization to increase its viscosity and decrease its interfacial tension. Tween 80 was more effective than Q-Naturale^® at producing small droplets when the oil phase contained low levels of vitamin E acetate (≤40%), but the opposite was true at higher vitamin levels. These results indicate that a natural surfactant (Q-Naturale^®) is effective at forming edible Vitamin E delivery systems that could be used in functional food and beverage applications.     

均质条件与大米饮料乳化稳定性关系研究

探讨了不同的均质条件对油滴粒径分布的影响及与乳化液稳定性之间的关系。结果证明,在均质压力为两次40MPa,均质温度为60℃下,乳化体系最为稳定,利于大米饮料保持良好的外观稳定性。     

Impact of free fatty acid concentration and structure on lipid oxidation in oil-in-water emulsions

Free fatty acids are strong prooxidants in both bulk and emulsified oils. Addition of oleic acid to an oil-in-water emulsions increased lipid hydroperoxide and hexanal formation at free fatty acid concentrations as low as 0.1% of the lipid. The prooxidant effect of free fatty acids was dependent on fatty acid type with lipid oxidation rates being in the order of linolenic < linoleic < oleic. There were no significant differences in lipid oxidation rates when free fatty acid isomers with cis or trans double bonds were compared. The prooxidant activity of the free fatty acids was postulated to be due to their ability to attract prooxidant metals as well as co-oxidise the triacylglycerol in the oil. Overall, these results show that the oxidative stability of oil-in-water emulsions is strongly linked to both the concentration and type of free fatty acids present.     

Health Benefits of Anthocyanins and Their Encapsulation for Potential Use in Food Systems: A Review

Anthocyanins are one of the six subgroups of large and widespread group of plant constituents known as flavonoids. These are responsible for the bright and attractive orange, red, purple, and blue colors of most fruits, vegetables, flowers and some cereal grains. More than 600 structurally distinct anthocyanins have been identified in nature. Earlier, anthocyanins were only known for their coloring properties but now interest in anthocyanin pigments has intensified because of their possible health benefits as dietary antioxidants, which help to prevent neuronal diseases, cardiovascular illnesses, cancer, diabetes, inflammation, and many such others diseases. Ability of anthocyanins to counter oxidants makes them atherosclerosis fighters. Therefore, anthocyanin-rich foods may help to boost overall health by offering an array of nutrients. However, the incorporation of anthocyanins into food and medical products is a challenging task due to their low stability toward environmental conditions during processing and storage. Encapsulation seems to be an efficient way to introduce such compounds into these products. Encapsulating agents act as a protector coat against ambient adverse conditions such as light, humidity, and oxygen. Encapsulated bioactive compounds are easier to handle and offer improved stability. The main objective of this review is to explore health benefits of anthocyanins and their extraction, characterization, encapsulation, and delivery.     

Electrospraying of water in oil emulsions for thin film coating

Electrospraying of water-in-oil emulsions was investigated to produce thin edible barriers. A reproducible model surface was used, namely cellulose membranes of which permeability is well-established. PGPR-based emulsions were stable during electrospraying and produced a fine stable jet spray; emulsions prepared with lecithin and span80 produced unstable jets and only sporadic sprays. The droplet size decreased to 50 ± 10 μm by the addition of water droplets till 3% but remained constant at higher water volume fractions. On the other hand, the addition of protein and salt influenced the droplet size and radius values up to 200 μm were found. The addition of whey protein isolate (10% w/w) resulted in films with water vapour barrier properties that were at least 70% better than lipid only, therewith showing that addition of protein enhances the integrity of the films.     

Lipid Oxidation in Oil-in-Water Emulsions: Impact of Molecular Environment on Chemical Reactions in Heterogeneous Food Systems

The susceptibility of lipids to oxidation is a major cause of quality deterioration in food emulsions. The reaction mechanism and factors that influence oxidation are appreciably different for emulsified lipids than for bulk lipids. This article reviews the current understanding of the lipid oxidation mechanism in oil‐in‐water emulsions. It also discusses the major factors that influence the rate of lipid oxidation in emulsions, such as antioxidants, chelating agents, ingredient purity, ingredient partitioning, interfacial characteristics, droplet characteristics, and ingredient interactions. This knowledge is then used to define effective strategies for controlling lipid oxidation in food emulsions.     

Determination of Heterocyclic Amines in Meat Matrices Using Enhanced Matrix Removal‐Lipid Extraction and Liquid Chromatography–Tandem Mass Spectrometry

A simple, fast, and efficient method, “enhanced matrix removal of lipids” (EMR‐lipid), was proposed, optimized, and validated for identifying five polar heterocyclic amines (HCAs) in meat samples that ranged from high‐protein (beef and chicken) to high‐fat (pork bacon) matrices. The protocol involves an initial solid–liquid phase extraction followed by a rapid dispersive solid‐phase extraction using EMR‐lipid sorbents and salting‐out partitioning. Acetonitrile containing formic acid at two levels (1% and 2%) efficiently extracted HCAs from different meat matrices. Liquid chromatography–tandem mass spectrometry (MS/MS) with selective reaction monitoring mode was developed for qualitative and quantitative analysis. The highest MS/MS responses and better peak separation of analytes were achieved by adjusting mobile phases to pH 3.0 with instrumental detection limits between 0.01 and 0.05 ng/mL. Good linearity of standard curves was obtained in both pure solvents and postspiked meat extracts between 0.5 and 50.0 ng/mL. The validation results showed good precision, accuracy, and sensitivity for detecting HCAs in spiked meat samples. Satisfactory recoveries of four HCAs were achieved: 65% to 111% in beef, 71% to 106% in bacon, and 42% to 77% in chicken. Matrix effects were also assessed and showed less than –20% of ion suppression in bacon extract, while a medium to high signal suppression was observed in beef (–37% to –55%) and chicken (–28% to –52%). This optimized EMR‐lipid method provides acceptable results and advantages for determining trace level HCAs in complex meat matrices.     

Analysis of Starch in Food Systems by High‐Performance Size Exclusion Chromatography

Starch has unique physicochemical characteristics among food carbohydrates. Starch contributes to the physicochemical attributes of food products made from roots, legumes, cereals, and fruits. It occurs naturally as distinct particles, called granules. Most starch granules are a mixture of 2 sugar polymers: a highly branched polysaccharide named amylopectin and a basically linear polysaccharide named amylose. The starch contained in food products undergoes changes during processing, which causes changes in the starch molecular weight and amylose to amylopectin ratio. The objective of this study was to develop a new, simple, 1‐step, and accurate method for simultaneous determination of amylose and amylopectin ratio as well as weight‐averaged molecular weights of starch in food products. Starch from bread flour, canned peas, corn flake cereal, snack crackers, canned kidney beans, pasta, potato chips, and white bread was extracted by dissolving in KOH, urea, and precipitation with ethanol. Starch samples were solubilized and analyzed on a high‐performance size exclusion chromatography (HPSEC) system. To verify the identity of the peaks, fractions were collected and soluble starch and beta‐glucan assays were performed additional to gas chromatography analysis. We found that all the fractions contain only glucose and soluble starch assay is correlated to the HPSEC fractionation. This new method can be used to determine amylose amylopectin ratio and weight‐averaged molecular weight of starch from various food products using as low as 25 mg dry samples.     

Encapsulation of Beta‐carotene in Lipid Microparticles Stabilized with Hydrolyzed Soy Protein Isolate: Production Parameters,Alpha‐tocopherol Coencapsulation and Stability Under Stress Conditions

The objectives of this research were to study the encapsulation of beta‐carotene (BC) in solid lipid microparticles (SLM) of palm stearin (PS) and stabilized with hydrolyzed soy protein isolate (HSPI), and also to investigate the effect of alpha‐tocopherol (TOC) addition to the systems. Through the characterizations of SLM produced with different formulations, it was verified that systems with 5% (w/v) PS, 1.0% (w/v) HSPI, and 0.3% (w/v) xanthan gum (XG) presented the highest stability, with average diameters of approximately 1.2 μm. This formulation was applied for the production of BC‐loaded SLM, with different concentrations of TOC. In SLM containing TOC, nearly 75% of encapsulated BC was preserved after 45 d of storage. The kinetic profiles for degradation of encapsulated BC were fitted to a pseudo‐1st‐order model, and the results showed that the main difference among the systems with different BC:TOC ratios was the residual concentration of BC. The stability of the BC‐loaded SLMs was also studied after stress conditions, and the results showed that the SLMs were able to support thermal treatments over 60 °C but presented low stability after different ionic strength stresses.     

Towards a better understanding of the pectin structure-function relationship in broccoli during processing: Part I—macroscopic and molecular analyses

To investigate the structure-function relationship of pectin during (pre)processing, broccoli samples (Brassica oleracea L. cultivar italica) were subjected to one of the following pretreatments: (i) low-temperature blanching (LTB), (ii) LTB in combination with Ca²⁺ infusion, (iii) high-pressure pretreatment (HP), (iv) HP in combination with Ca²⁺ infusion, or (v) no pretreatment (control sample), whether or not in combination with a thermal treatment of 15 min at 90 °C. The macroscopic attributes of broccoli were linked to the chemical structure of broccoli pectin. By enhancing the cross-linking of pectic polymers, both LTB and HP reduced the texture loss that occurred during thermal processing of broccoli. During these pretreatments, homogalacturonan was de-esterified by pectin methylesterase, which led to changes in pectin solubility. When LTB or HP was combined with Ca²⁺ infusion, changes in the structure of pectin occurred, however not always reflected at the macroscopic level. The degree of esterification of pectin in Ca²⁺-soaked broccoli samples was lower compared to non-Ca²⁺-soaked samples and, in addition, a higher amount of ionically cross-linked pectin was retrieved.