High-pressure Valve Homogenizer Research Articles

Impact of Operating Parameters on the Production of Nanoemulsions Using a High-Pressure Homogenizer with Flow Pattern and Back Pressure Control

The main objective of this study was to establish the relative importance of the main operating parameters impacting the formation of food-grade oil-in-water nanoemulsions by high-pressure homogenization. The goal of this unit operation was to create uniform and stable emulsified products with small mean particle diameters and narrow polydispersity indices. In this study, we examined the performance of a new commercial high-pressure valve homogenizer, which has several features that provide good control over the particle size distribution of nanoemulsions, including variable homogenization pressures (up to 45,000 psi), nozzle dimensions (0.13/0.22 mm), flow patterns (parallel/reverse), and back pressures. The impact of homogenization pressure, number of passes, flow pattern, nozzle dimensions, back pressure, oil concentration, emulsifier concentration, and emulsifier type on the particle size distribution of corn oil-in-water emulsions was systematically examined. The droplet size decreased with increasing homogenization pressure, number of passes, back pressure, and emulsifier-to-oil ratio. Moreover, it was slightly smaller when a reverse rather than parallel flow profile was used. The emulsifying performance of plant, animal, and synthetic emulsifiers was compared because there is increasing interest in replacing animal and synthetic emulsifiers with plant-based ones in the food industry. Under fixed homogenization conditions, the mean particle diameter decreased in the following order: gum arabic (0.66 µm) > soy protein (0.18 µm) > whey protein (0.14 µm) ≈ Tween 20 (0.14 µm). The information reported in this study is useful for the optimization of the production of food-grade nanoemulsions using high-pressure homogenization.

Comparison of homogenization processes for the development of green O/W emulsions formulated with N,N-dimethyldecanamide

The target of this work was to compare the yield of three homogenization processes (two different rotor–stator devices and a high-pressure valve homogenizer) for the development of O(green solvent)/W emulsions containing an eco-friendly emulsifier. Rheology, laser diffraction, optical microscopy and multiple light scattering were the main techniques used to assess the efficiency of homogenization methods. First the best values of the processing variables were obtained for each homogenizer and secondly a comparison of properties of emulsions prepared with these optimum processing conditions was carried out. The results obtained revealed that the more stable emulsions were prepared with an Ultraturrax T25.

A Further Step in the Development of Oil-in-Water Emulsions Formulated with a Mixture of Green Solvents

Finding alternatives to traditional organic solvents is one area in green chemistry that has generated great interest in recent years. This work provides new possibilities for the preparation of ecological oil-in-water (O/W) emulsions. Model emulsions that may be used as matrices for agrochemical formulations have been investigated. Specifically, this paper deals with O/W emulsions formulated with a mixture of green solvents and a polyoxyethylene glycerol ester as emulsifier. First, an optimum ratio of solvents was found, after which the droplet size distribution, physical stability, and flow properties of emulsions obtained using two rotor-stator devices (toothed geometry vs emulsor screen) and two high-pressure homogenizers (high pressure valve homogenizer, HPVH, vs microfluidizer) were compared using several processing variables. Considering its low Turbiscan stability index and the absence of coalescence, 75/25 (N,N-dimethyldecanamide/α-pinene) was the optimum ratio of biosolvents. All samples showed ...

Physicochemical characterization and stability of chia oil microencapsulated with sodium caseinate and lactose by spray-drying

Microencapsulation is an alternative to protect chia oil from the adverse influence of the environment, since this oil is susceptible to oxidation due to their high content of polyunsaturated fatty acids (PUFAs). The aim of this study was to investigate the influence of the operating conditions (homogenization pressure for emulsifying and spray-drying inlet/outlet temperatures) on the physicochemical properties of chia oil microencapsulated with sodium caseinate and lactose by spray-drying. Oil-in-water emulsions were prepared with 10%wt/wt sodium caseinate, 10%wt/wt lactose and 10%wt/wt chia oil using a high pressure homogenizer at 400 and 600bar. These emulsions were spray-dried at inlet/outlet temperatures of 135/70°C and 170/90°C. The microcapsules were approximately spherical in shape with some small pores and a polydisperse particle size distribution, recording moisture contents of 1.48–3.52g/100g (d.b.). The encapsulation efficiency was >90% in all cases. The particle size distributions of parent and reconstituted emulsions displayed a unimodal distribution. The emulsion reconstituted of microcapsules obtained from emulsions at 400bar presented a higher initial particle size (D [4,3]=0.48–0.54μm; D [3,2]=0.31–0.33μm) than those prepared at 600bar (D [4,3]=0.33–0.35μm; D [3,2]=0.24–0.25μm). The dispersibility of microcapsules was assessed by measuring the change in droplet obscuration as a function of time. Physical stability of the different reconstituted emulsions was studied by recording the backscattering profiles (BS) as a function of the cell length and time. Regarding oxidative stability during storage, chia bulk oil showed higher peroxide values (PV) than microencapsulated oil during storage. The microcapsules obtained from emulsions at 600bar showed higher PV than those at 400bar. The results indicate that the microencapsulation process consisting of emulsification using high-pressure valve homogenizer and subsequent spray-drying is suitable for preparing sodium caseinate-lactose-based microcapsules containing chia oil.

Effects of Homogenization Models and Emulsifiers on the Physicochemical Properties of β-Carotene Nanoemulsions

Microfluidization and high pressure valve homogenization were applied to prepare β-carotene nanoemulsions, and the mathematical relationship between homogenization pressures and emulsion temperatures, homogenization pressures/cycles, and droplet sizes, were established. Emulsions through Microfluidizer had lower temperature and much smaller droplet sizes, compared with those through high pressure valve homogenizer. Four emulsifiers were compared for their capacities to stabilize nanoemulsions. The two large molecule emulsifiers, octenyl succinate starch (OSA) and whey protein isolate (WPI), were less effective for the formation of nanoemulsions with smaller droplets than the two small molecule emulsifiers, polyoxyethylene sorbitan monolaurate (Tween 20, TW) and decaglycerol monolaurate (DML). The nanoemulsion containing WPI was the most stable, while the one containing DML was the least stable. During storage, significant degradation of β-carotene occurred in all nanoemulsions, especially in the DML stabilized one, while WPI showed the greatest capacity to protect β-carotene from degradation.

Preparation and Characterization of Water/Oil and Water/Oil/Water Emulsions Containing Biopolymer-Gelled Water Droplets

The purpose of this study was to create water-in-oil (W/O) and water-in-oil-in-water (W/O/W) emulsions containing gelled internal water droplets. Twenty weight percent W/O emulsions stabilized by a nonionic surfactant (6.4 wt % polyglycerol polyricinoleate, PGPR) were prepared that contained either 0 or 15 wt % whey protein isolate (WPI) in the aqueous phase, with the WPI-containing emulsions being either unheated or heated (80 degrees C for 20 min) to gel the protein. Optical microscopy and sedimentation tests did not indicate any significant changes in droplet characteristics of the W/O emulsions depending on WPI content (0 or 15%), shearing (0-7 min at constant shear), thermal processing (30-90 degrees C for 30 min), or storage at room temperature (up to 3 weeks). W/O/W emulsions were produced by homogenizing the W/O emulsions with an aqueous Tween 20 solution using either a membrane homogenizer (MH) or a high-pressure valve homogenizer (HPVH). For the MH the mean oil droplet size decreased with increasing number of passes, whereas for the HPVH it decreased with increasing number of passes and increasing homogenization pressure. The HPVH produced smaller droplets than the MH, but the MH produced a narrower particle size distribution. All W/O/W emulsions had a high retention of water droplets (>95%) within the larger oil droplets after homogenization. This study shows that W/O/W emulsions containing oil droplets with gelled water droplets inside can be produced by using MH or HPVH.

Effect of molecular weight and degree of deacetylation of chitosan on the formation of oil-in-water emulsions stabilized by surfactant–chitosan membranes

The objective of this study was to establish the influence of polyelectrolyte characteristics (molecular weight and charge density) on the properties of oil-in-water emulsions containing oil droplets surrounded by surfactant–polyelectrolyte layers. A surfactant-stabilized emulsion containing small droplets ( d 32 ≈ 0.3 μm ) was prepared by homogenizing 20 wt% corn oil with 80 wt% emulsifier solution (20 mM SDS or 2.5 wt% Tween 20, 100 mM acetate buffer, pH 3) using a high-pressure valve homogenizer. This primary emulsion was then diluted with various chitosan solutions to produce secondary emulsions with a range of chitosan concentrations (3 wt% corn oil, 0–1 wt% chitosan). The influence of the molecular characteristics of chitosan on the properties of these emulsions was examined by using chitosan ingredients with different molecular weights (MW ∼ 15, 145, and 200 kDa) and degree of deacetylation (DDA ∼ 40, 77, and 92%). The electrical charge and particle size of the secondary emulsions were then measured. Extensive droplet aggregation occurred when the chitosan concentration was below the amount required to saturate the droplet surfaces, but stable emulsions could be formed at higher chitosan concentrations. The ζ-potential and mean diameter ( d 32 ) of the particles in the secondary emulsions was not strongly influenced by chitosan MW, however the chitosan with the lowest DDA (40%) produced droplets with smaller mean diameters and ζ-potentials than the other two DDA samples examined. Interestingly, we found that stable multilayer emulsions could be formed by mixing medium or high MW chitosan with an emulsion stabilized by a non-ionic surfactant (Tween 20) due to the fact the initial droplets had some negative charge. The information obtained from this study is useful for preparing emulsions stabilized by multilayer interfacial layers.

Influence of Droplet Characteristics on the Formation of Oil-in-Water Emulsions Stabilized by Surfactant−Chitosan Layers

The objective of this study was to establish the optimum conditions for preparing stable oil-in-water emulsions containing droplets surrounded by surfactant-chitosan layers. A primary emulsion containing small droplets (d32 approximately = 0.3 microm) was prepared by homogenizing 20 wt% corn oil with 80 wt% emulsifier solution (20 mM SDS, 100 mM acetate buffer, pH 3) using a high-pressure valve homogenizer. The primary emulsion was diluted with chitosan solutions to produce secondary emulsions with a range of oil and chitosan concentrations (0.5-10 wt% corn oil, 0-1 wt% chitosan, pH 3). The secondary emulsions were sonicated to help disrupt any droplet aggregates formed during the mixing process. The electrical charge, particle size, and amount of free chitosan in the emulsions were then measured. The droplet charge changed from negative to positive as the amount of chitosan in the emulsions was increased, reaching a relatively constant value (approximately +50 mV) above a critical chitosan concentration (C(Sat)), which indicated that saturation of the droplet surfaces with chitosan occurred. Extremely large droplet aggregates were formed at chitosan concentrations below C(Sat), but stable emulsions could be formed above C(Sat) provided the droplet concentration was not high enough for depletion flocculation to occur. Interestingly, we found that stable multilayer emulsions could also be formed by mixing chitosan with an emulsion stabilized by a nonionic surfactant (Tween 20) due to the fact the initial droplets had some negative charge. The information obtained from this study is useful for preparing emulsions stabilized by multilayer interfacial layers.

Influence of Environmental Stresses on Stability of O/W Emulsions Containing Cationic Droplets Stabilized by SDS−Fish Gelatin Membranes

Oil-in-water (O/W) emulsions containing small oil droplets (d32 approximately 0.22 microm) stabilized by sodium dodecyl sulfate (SDS)-fish gelatin (FG) membranes were produced by an electrostatic deposition technique. A primary emulsion containing anionic SDS-coated droplets (zeta approximately -40 mV) was prepared by homogenizing oil and emulsifier solution using a high-pressure valve homogenizer (20 wt % corn oil, 0.46 wt % SDS, 100 mM acetic acid, pH 3.0). A secondary emulsion containing cationic SDS-FG-coated droplets (zeta approximately +30 mV) was formed by diluting the primary emulsion with an aqueous fish gelatin solution (10 wt % corn oil, 0.23 wt % SDS, 100 mM acetic acid, 2.00 wt % fish gelatin, pH 3.0). The stabilities of primary and secondary emulsions with the same oil concentration to thermal processing, ionic strength, and pH were assessed by measuring particle size distribution, zeta potential, microstructure, destabilized oil, and creaming stability. The droplets in secondary emulsions had good stability to droplet aggregation at holding temperatures from 30 to 90 degrees C for 30 min, [NaCl] < or = 100 mM, and pH values from 3 to 8. This study shows that the ability to generate emulsions containing droplets stabilized by multilayer interfacial membranes comprised of two or more types of emulsifiers, rather than a single interfacial layer comprised of one type of emulsifier, may lead to the development of food products with improved stability to environmental stresses.

Influence of environmental stresses on stability of oil-in-water emulsions containing droplets stabilized by β-lactoglobulin– ι-carrageenan membranes

An oil-in-water emulsion (5 wt% corn oil, 0.5 wt% β-lactoglobulin ( β-Lg), 0.1 wt% ι-carrageenan, 5 mM phosphate buffer, pH 6.0) containing anionic droplets stabilized by interfacial membranes comprising of β-lactoglobulin and ι-carrageenan was produced using a two-stage process. A primary emulsion containing anionic β-Lg coated droplets was prepared by homogenizing oil and emulsifier solution together using a high-pressure valve homogenizer. A secondary emulsion containing β-Lg– ι-carrageenan coated droplets was formed by mixing the primary emulsion with an aqueous ι-carrageenan solution. The stability of primary and secondary emulsions to sodium chloride (0–500 mM), calcium chloride (0–12 mM), and thermal processing (30–90 °C) were analyzed using ζ-potential, particle size and creaming stability measurements. The secondary emulsion had better stability to droplet aggregation than the primary emulsion at NaCl ⩽ 500 mM, CaCl 2 ⩽ 2 mM, and holding temperatures ⩽60 °C for 20 min. The interfacial engineering technology used in the study could therefore lead to the creation of food emulsions with improved stability to environmental stresses.

Factors influencing the production of o/w emulsions stabilized by β-lactoglobulin–pectin membranes

A primary emulsion was prepared by homogenizing 10 wt% corn oil with 90 wt% aqueous β-lactoglobulin solution (0.5 wt% β-lg, pH 3 or 7) using a two-stage high-pressure valve homogenizer. This emulsion was mixed with aqueous pectin (citrus, 59% DE) stock solution (2 wt%, pH 3 or 7) and NaCl solution to yield secondary emulsions with 5 wt% corn oil, 0.225 wt% β-lactoglobulin, 0.2 wt% pectin and 0 or 100 mM NaCl. The final pH of the emulsions was then adjusted (3–8). Primary and secondary emulsions were ultrasonically treated (30 s, 20 kHz, 40% amplitude) to disrupt any flocculated droplets. Secondary emulsions were more stable than primary emulsions at intermediate pHs. Secondary emulsions prepared at pH 7 had smaller particle diameters (0.35 to ∼6 μm) than those prepared at pH 3 (0.42 to ∼18 μm) across the whole pH range studied, and also had smaller diameters than the primary emulsions (0.35 to ∼14 μm). Ultrasound treatment reduced the particle diameter of both primary and secondary emulsions and lowered the rate of creaming. The presence of NaCl screened the charges and thus the electrostatic interaction between biopolymer molecules and primary emulsion droplets. Secondary emulsions were more stable to the presence of 100 mM NaCl at low pHs (3–4) than primary emulsions. This study shows that stable emulsions can be prepared by engineering their interfacial membranes using the electrostatic interaction of natural biopolymers, especially at intermediate pHs where proteins normally fail to function.

Production and characterization of oil-in-water emulsions containing droplets stabilized by beta-lactoglobulin-pectin membranes.

Oil-in-water emulsions containing droplets stabilized by beta-lactoglobulin (beta-Lg)-pectin membranes were produced using a two-stage process. A primary emulsion containing small droplets (d(32) approximately 0.3 microm) was prepared by homogenizing 10 wt % corn oil with 90 wt % aqueous solution (1 wt % beta-Lg, 5 mM imidazole/acetate buffer, pH 3.0) using a high-pressure valve homogenizer. The primary emulsion was then diluted with pectin solutions to produce secondary emulsions with a range of pectin concentrations (5 wt % corn oil, 0.45 wt % beta-Lg, 5 mM imidazole/acetate buffer, 0-0.22 wt % pectin, pH 3.0). The electrical charge on the droplets in the secondary emulsions decreased from +33 +/- 3 to -19 +/- 1 mV as the pectin concentration was increased from 0 to 0.22 wt %, which indicated that pectin adsorbed to the droplet surfaces. The mean particle diameter of the secondary emulsions was small (d(32) < 1 microm) at relatively low pectin concentrations (<0.04 wt %), but increased dramatically at higher pectin concentrations (e.g., d(32) approximately 13 microm at 0.1 wt % pectin), which was attributed to charge neutralization and bridging flocculation effects. Emulsions with relatively small mean particle diameters (d(32) approximately 1.2 microm at 0.1 wt % pectin) could be produced by disrupting flocs formed in secondary emulsions containing highly negatively charged droplets, for example, by sonication, blending, or homogenization. The particles in these emulsions probably consisted of small flocs containing a number of protein-coated droplets bound together by pectin molecules. These emulsions had good stability to further particle aggregation up to relatively high ionic strengths (< or =500 mM NaCl) and low pH (pH 3). The interfacial engineering technology used in this study could lead to the creation of food emulsions with improved physicochemical properties or stability.

Evidence that homogenization of BSA-stabilized hexadecane-in-water emulsions induces structure modification of the nonadsorbed protein.

The structural modification of globular proteins (bovine serum albumin, BSA) in the aqueous phase of emulsions produced by homogenization was studied using front-face fluorescence spectroscopy (FFFS). A series of hydrocarbon oil-in-water emulsions (30 wt % n-hexadecane, 0.35 wt % BSA, pH 7.0) were homogenized to differing degrees with a high-speed blender and a high-pressure valve homogenizer. The wavelength of the maximum in the tryptophan emission spectrum (lambda(max)) of serum phases collected from the emulsions by centrifugation was measured and compared to lambda(max) values of BSA solutions subjected to the same homogenization conditions. There was no significant (p < 0.05) change in lambda(max) with homogenization conditions for BSA solutions. In contrast, lambda(max) of serum phases from emulsions blended for 2 min in a high-speed blender was significantly smaller (p < 0.05) than nontreated BSA solutions (Deltalambda(max) = 2 nm). In addition, there was a further significant decrease in lambda(max) of the serum phases with an increasing number of passes of the emulsion through the high-pressure valve homogenizer (e.g., Deltalambda(max) = 4 nm for 12 passes). This study shows that globular proteins present in the aqueous phase of a hexadecane-in-water emulsion after homogenization could be altered, which is probably caused by surface modification of the protein structure during temporary adsorption to emulsion droplet surfaces during homogenization.

Influence of environmental conditions on the stability of oil in water emulsions containing droplets stabilized by lecithin-chitosan membranes.

Oil-in-water emulsions containing cationic droplets stabilized by lecithin-chitosan membranes were produced using a two-stage process. A primary emulsion containing anionic lecithin-coated droplets was prepared by homogenizing oil and emulsifier solution using a high-pressure valve homogenizer (5 wt % corn oil, 1 wt % lecithin, 100 mM acetic acid, pH 3.0). A secondary emulsion containing cationic lecithin-chitosan-coated droplets was formed by diluting the primary emulsion with an aqueous chitosan solution (1 wt % corn oil, 0.2 wt % lecithin, 100 mM acetic acid, and 0.036 wt % chitosan). The stabilities of the primary and secondary emulsions with the same oil concentration to thermal processing, freeze-thaw cycling, high calcium chloride concentrations, and lipid oxidation were determined. The results showed that the secondary emulsions had better stability to droplet aggregation during thermal processing (30-90 degrees C for 30 min), freeze-thaw cycling (-10 degrees C for 22 h/30 degrees C for 2 h), and high calcium chloride contents (</=500 mM CaCl(2)) and exhibited less lipid oxidation (peroxide formation) than primary emulsions. The interfacial engineering technology used in this study could lead to the creation of food emulsions with improved stability to environmental stresses.

Production and characterization of O/W emulsions containing cationic droplets stabilized by lecithin-chitosan membranes.

Oil-in-water emulsions containing cationic droplets stabilized by lecithin-chitosan membranes were produced using a two-stage process. A primary emulsion was prepared by homogenizing 5 wt % corn oil with 95 wt % aqueous solution (1 wt % lecithin, 100 mM acetic acid, pH 3.0) using a high-pressure valve homogenizer. This emulsion was diluted with aqueous chitosan solutions to form secondary emulsions with varying compositions: 1 wt % corn oil, 0.2 wt % lecithin, 100 mM acetic acid, and 0-0.04 wt % chitosan (pH 3.0). The particle size distribution, particle charge, and creaming stability of the primary and secondary emulsions were measured. The electrical charge on the droplets increased from -49 to +54 mV as the chitosan concentration was increased from 0 to 0.04 wt %, which indicated that chitosan adsorbed to the droplet surfaces. The mean particle diameter of the emulsions increased dramatically and the emulsions became unstable to creaming when the chitosan concentration exceeded 0.008 wt %, which was attributed to charge neutralization and bridging flocculation effects. Sonication, blending, or homogenization could be used to disrupt flocs formed in secondary emulsions containing droplets with high positive charges, leading to the production of emulsions with relatively small particle diameters (approximately 1 microm). These emulsions had good stability to droplet aggregation at low pH (< or =5) and ionic strengths (<500 mM). The interfacial engineering technology utilized in this study could lead to the creation of food emulsions with improved stability to environmental stresses.

Slurry preparation by high-pressure homogenization for cadmium, copper and lead determination in cervine liver and kidney by electrothermal atomic absorption spectrometry.

Homogenization with a flat valve homogenizer in combination with high-speed blending was evaluated for the preparation of slurries suitable for the ETAAS determination of cadmium, copper and lead concentrations in six SRMs and in frozen cervine liver and kidney. Fresh tissue (approximately 2 g) or powdered SRM (approximately 0.1 g) was dispersed, at high speed, in 20 ml of ethanol-water (1 + 9 v/v) containing 0.25% m/m tetramethylammonium hydroxide. The resulting suspension was passed through a high-pressure flat valve homogenizer. Determinations performed on the resulting homogenate, provided estimates for Cd, Pb and Cu concentrations that were within 27, 23 and 18% of the certified values, respectively, for the six SRMs. In all instances, the experimental results did not differ significantly from the certified values. For frozen tissues there was good agreement between the concentrations as determined by slurry homogenization-ETAAS and conventional digestion-ICP-MS. In addition, no significant differences were detected between the slopes of the calibration curves for external standards and standard additions to homogenized sample (SRMs or fresh tissue). Moreover, replicate determinations of analyte concentrations in slurries at various times post-preparation did not detect any segregation of the homogenates during 6 d. For these matrices at least, short-term sample storage had no discernible effect on the analyte apparent concentrations. The applicability of the process was limited only by the levels of contaminating Pb and Cu introduced into the sample by the homogenizer.

Homogenization of milk emulsions:use of microfluidizer

The operating efficiency of a laboratory scale microfluidizer had been compared to that of a high pressure valve homogenizer using either pasteurized whole milk or recombined milk. Microfluidization was found to be a very effective method for reducing fat globule size and was only slightly affected by changes in operating pressure. The back pressure module on the microfluidizer had a marginal effect on particle size increase. As a result, the homogenization effect was always greater than that of conventional homogenization. Only very small amounts of serum protein but high levels of casein were found on fat surfaces after microfluidization. The protein load was higher than predicted on the basis of decreases in globule size. Microfluidization had little effect on the formation of fat clusters in milk. The higher protein load probably inhibited fat clustering.

Determination of protein and fat in meat by transmission Fourier transform infrared spectrometry

Stabilized dry calibration powders and sample preparation protocols were developed for the rapid determination of protein and fat in raw meat by Fourier transform infrared (FTIR) spectrometry. Ground meat samples were suspended in 0.1 mol l–1 NaOH at 67 °C, emulsified at 1360 atm (138 MPa) in a custom-designed high-pressure valve homogenizer and injected into a 37 µm FTIR transmission cell. Otherwise insoluble elastin particles were also reduced to colloidal proportions by shear forces during their forced passage through the valve gap of the homogenizer. Characteristic IR absorption bands of protein (1548.6 cm–1) and fat 1744.6 (CO) cm–1 were used for calibration. Under optimum sampling and emulsification conditions, the multiple correlation coefficients for calibration (seven standards) were in the range 0.9999–1.0000 and the reproducibility was superior to results obtained by conventional chemical methods. The simple correlation coefficients of FTIR predictions versus protein and fat concentrations obtained by primary chemical methods ranged between 0.9941 and 0.9996 depending on the sampling and sample preparation strategy. The accuracy of the spectrometric results was limited by two extrinsic factors: the analytical performance of the reference chemical methods used to standardize the calibration powders and the degree of homogeneity of the raw samples.