Effect of processing conditions on physicochemical properties of astaxanthin nanodispersions

A top-down approach based on an emulsification–evaporation technique was used to prepare nanodispersions of astaxanthin. Response-surface methodology was employed to investigate the effect of the main processing conditions, namely, the applied pressure (20–90 MPa), number of cycles (0–4) and evaporation temperature (16–66 °C), on the average particle size, polydispersity index and astaxanthin concentration of the nanodispersions. Second-order polynomial regression models expressing the astaxanthin nanodispersion properties as functions of the main processing variables were significantly (p < 0.05) fitted, with high coefficient-of-determination values (R² > 0.90). A multiple-optimisation procedure showed that the optimum conditions of pressure, number of cycles of homogenization and evaporation temperature, were 50 MPa, two cycles and 47 °C, respectively. A statistical assessment showed insignificant (p > 0.05) differences between experimental and predicted values, thus verifying the adequacy of the final reduced models fitted for explaining the variation of emulsion properties, as a function of homogenization and evaporation conditions.     

Developing a three component stabilizer system for producing astaxanthin nanodispersions

Astaxanthin nanodispersions were prepared using Polysorbate 20 (PS20), sodium caseinate (SC) and gum Arabic (GA), solely or in combinations, as stabilizer system, through a solvent-diffusion process. The interactions among these three surface active compounds, in the formation, physicochemical and stability characterization of produced nanodispersions were studied by applying a simplex centroid mixture design. Quadratic or special cubic regression models were fitted for variations of all studied responses as function of significant (p < 0.05) interaction effects between stabilizer components’ proportions, with acceptable determination coefficients (>0.70). Multiple-response optimization predicted that by using 29% (w/w) PS20, 6% (w/w) GA and 65% (w/w) SC as a three component stabilizer system, an astaxanthin nanodispersion could be produced with the most desirable physicochemical characteristics and highest physicochemical stability. At this optimum stabilizer components proportions, the corresponding predicted response values for mean particle size, polydispersity index (PDI) and total astaxanthin loss were predicted to be 114.6 nm, 0.261 and 680 mg/L, respectively. The optimum astaxanthin nanodispersions also showed 2.06% and 1.05% particle size growth at 25 °C and 5 °C, 4.56% and 1.29% PDI growth at 25 °C and 5 °C, and 20% (w/w) astaxanthin loss at 25 °C after 8 weeks of storage. The absence of significant (p > 0.05) differences between the experimental and predicted values of the response variables confirmed the adequacy of the fitted models.     

β-Carotene nanodispersions: preparation,characterization and stability evaluation

The aim of the present study was to investigate the preparation of β-carotene nanodispersions as potential active ingredients for food formulations. Nanodispersions containing β-carotene were obtained by a process based on an emulsification–evaporation technique. The preparation method consisted of emulsifying an organic solution of β-carotene in an aqueous solution containing emulsifier using two different homogenizers (a conventional homogenizer and a microfluidizer), followed by direct solvent evaporation under reduced pressure. The influence of different homogenizing conditions (pressure and cycle) and two organic/aqueous phase ratios on particle size parameters and content of β-carotene was investigated. In addition, the stability of β-carotene nanodispersions was carried out at a storage temperature of 4 °C. The particle size distribution of β-carotene in nanodispersions was demonstrated with a laser diffraction particle size analyzer and the retention of β-carotene in the prepared nanodispersions was studied by high-pressure liquid chromatography. In general, homogenization pressure and cycle had significant (P < 0.05) effects on various particle size parameters. A volume-weighted mean diameter (D_4,3) of β-carotene nanoparticles, ranging from 60 to 140 nm, was observed in this study.     

High-pressure homogenization of orange juice to inactivate pectinmethylesterase

A homogenizer was used to treat orange juice at five pressures (0–250 MPa) and three initial temperatures (22, 35 and 45 °C). A maximum of five passes for the selected conditions were used to process orange juice. Pectinmethylesterase (PME) activity, microbial load, cloudy appearance, and vitamin C were evaluated in just squeezed and homogenized orange juices. A reduction of 50.4, 49.4 and 37.8% of PME activity was observed in juice homogenized by one pass at 250 MPa at the initial temperatures of 22, 35, and 45 °C, respectively. Pectinmethylesterase activity in orange juice was reduced as passes number was increased. The final temperature of the five times homogenized orange juice was not beyond 28 and 37 °C after being treated at 100 and 250 MPa, respectively. More than 30 and 80% of enzyme activity was reduced after five passes at 100 and 250 MPa, respectively. Less that 8.7 × 10² and 1.85 × 10³ CFU/mL of mesophiles and yeasts plus molds, respectively, were counted in orange juice treated five times at 100 MPa. The cloudy appearance of the homogenized orange juice was maintained for 12 days under low temperature conditions.

Industrial relevance

“Cold pasteurization” of orange juice, using a homogenizer as a high-pressure procedure, could be an alternative to thermal processing to avoid sensory, nutritional and physiochemical changes in juice. This process may deliver a pasteurized orange juice with characteristics similar to just squeezed orange juice. In addition to reduce the microbial load, homogenization may reduce pectinmethylesterase enzyme, which may cause phase-separation in juice and consequently give an unwanted appearance that consumers dislike. Additionally, homogenized orange juice appearance could be stable during several days before being brought to the consumers' daily eating table.     

Effect of sucrose fatty acid esters on the particle characteristics and flow properties of phytosterol nanodispersions

The effect of four different types of sucrose fatty acid esters as nonionic emulsifiers on the physicochemical properties of water-soluble phytosterol nanodispersions was investigated. In general, the mean particle sizes of the prepared phytosterol nanodispersions ranged from 2.8 to 259.9 nm. The phytosterol content in the final prepared nanodispersions ranged from 230.4 to 504.6 mg/l. All of the prepared phytosterol nanodispersions exhibited pseudoplastic flow behavior, with low yield stress ranging from 0.630 to 9.183 mPa and a low consistency coefficient of 0.608-88.710 mPas. Less than 1.5 μl of hexane residues per liter of prepared nanodispersions was found in the prepared phytosterol nanodispersions. Transmission electron microscopy (TEM) demonstrated that the prepared phytosterol nanoparticles were spherical in shape. In general, the sucrose fatty acid esters P-1570, L-1695 and S-1570 are appropriate for use in the preparation of phytosterol nanoparticles with small mean particle size at monomodal distribution with high clarity in appearance.     

Effect of polyglycerol esters of fatty acids on physicochemical properties and stability of β‐carotene nanodispersions prepared by emulsification/evaporation method

The effects of six different polyglycerol esters of fatty acids (PGEs) as nonionic emulsifiers on the physicochemical properties and stability of β‐carotene nanoparticles in oil‐in‐water dispersions produced by an emulsification/evaporation technique were examined. The β‐carotene particle size was measured by a laser diffraction technique, and the stability and retention of β‐carotene during various preparation steps and storage were determined by HPLC. In the prepared nanodispersions the β‐carotene particle size decreased with increasing degree of glycerol polymerisation and decreasing carbon number of the fatty acid group in the PGE. The particle size of β‐carotene in nanodispersions containing polyglycerol monooleate was generally larger than that in the presence of polyglycerol monolaurate. During storage at 4 °C, although the β‐carotene content in the nanodispersions showed a significant ( P < 0.05) decrease with increasing storage period, the size distribution of β‐carotene was almost unchanged in all prepared nanodispersions. In general, the mean diameter of β‐carotene nanoparticles ranged from 85 to 132 nm. In the light of their ability to physically stabilise β‐carotene particle formation, it is suggested that PGEs with a high degree of glycerol polymerisation may be useful in the preparation of β‐carotene nanodispersions. The best stabilisation was obtained using 10 g kg^?1 decaglycerol monolaurate. Copyright © 2004 Society of Chemical Industry     

Effects of ultra-high pressure homogenization on microbial and physicochemical shelf life of milk

The effect of ultra-high pressure homogenization (UHPH) on microbial and physicochemical shelf life of milk during storage at 4°C was studied and compared with a conventional heat preservation technology used in industry. Milk was standardized at 3.5% fat and was processed using a Stansted high-pressure homogenizer. High-pressure treatments applied were 100, 200, and 300 MPa (single stage) with a milk inlet temperature of 40°C, and 200 and 300 MPa (single stage) with a milk inlet temperature of 30°C. The UHPH-treated milks were compared with high-pasteurized milk (PA; 90°C for 15 s). The microbiological quality was studied by enumerating total counts, psychrotropic bacteria, lactococci, lactobacilli, enterococci, coliforms, spores, and Pseudomonas. Physicochemical parameters assessed in milks were viscosity, color, pH, acidity, rate of creaming, particle size, and residual peroxidase and phosphatase activities. Immediately after treatment, UHPH was as efficient (99.99%) in reducing psychrotrophic, lactococci, and total bacteria as was the PA treatment, reaching reductions of 3.5 log cfu/mL. Coliforms, lactobacilli, and enterococci were eliminated. Microbial results of treated milks during storage at 4°C showed that UHPH treatment produced milk with a microbial shelf life between 14 and 18 d, similar to that achieved for PA milk. The UHPH treatments reduced the L* value of treated milks and induced a reduction in viscosity values of milks treated at 200 MPa compared with PA milks; however, these differences would not be appreciated by consumers. In spite of the fat aggregates detected in milks treated at 300 MPa, no creaming was observed in any UHPH-treated milk. Hence, alternative methods such as UHPH may give new opportunities to develop fluid milk with an equivalent shelf life to that of PA milk in terms of microbial and physicochemical characteristics.     

Adiabatic compression heating coefficients for high-pressure processing – A study of some insulating polymer materials

In high-pressure processing (HPP), equipment design has largely been based on trial-and-error experimentation. For the design of the insulating carrier in high-pressure thermal (HPT) processing, it is imperative to know the extent of compression heating of the materials used, to achieve the best combination of insulation, compression heating and other design features to give the most uniform temperature treatment to the product. In this study, the compression heating properties of high-density polyethylene (HDPE), polypropylene (PP) and polytetrafluoroethylene (PTFE) during high-pressure processing were investigated under near-adiabatic conditions. The plastic polymers were pressurised at varying initial temperatures (5–90 °C) up to 750 MPa. Pressure/temperature profiles were recorded and numerically analysed with a purpose-developed software algorithm to obtain pressure- and temperature-dependent compression heating properties.     

Preparation and characterisation of water-soluble phytosterol nanodispersions

The purpose of this study was to prepare and characterise water-soluble phytosterol nanodispersions for food formulation. The effects of several factors were examined: four different types of organic phases (hexane, isopropyl alcohol, ethanol and acetone), the organic to aqueous phase ratio and conventional homogenisation vs. high-pressure homogenisation. We demonstrated the feasibility of phytosterol nanodispersions production using an emulsification–evaporation technique. The results showed that hexane was able to produce the smallest particle size at a mean diameter of approximately 50 nm at monomodal distribution. Phytosterol nanodispersions prepared with a higher homogenisation pressure and a higher organic to aqueous phase ratio resulted in significantly larger phytosterol nanoparticles (P < 0.05). Phytosterol loss after high-pressure homogenisation ranged from 3% to 28%, and losses increased with increasing homogenisation pressure. Elimination of the organic phase by evaporation resulted in a phytosterol loss of 0.5–9%.     

Effects of pH,Ions, and Thermal Treatments on Physical Stability of Astaxanthin Nanodispersions

In this work, astaxanthin nanodispersions were prepared using selected three component stabilizer system through a solvent-diffusion technique, with the particle size of 98.3 nm. The stability of produced nanodispersions against pH, salts, and heating were then evaluated. The produced nanodispersions exhibited good physical stability under wide ranges of pH (except around isoelectric point), sodium ion concentrations, and relatively high-temperature treatments (up to 60°C). However, formation of large particles was observed in either presence of calcium ions or higher thermal treatments (more than 60°C).     

Emulsifying properties of collagen fibers: Effect of pH,protein concentration and homogenization pressure

The emulsifying properties of collagen fibers were evaluated in oil-in-water (O/W) emulsions produced under different conditions of pH, protein content and type of emulsification device (rotor–stator and high-pressure homogenizer). The stability, microstructure and rheology of the O/W emulsions were measured. The phase separation and droplet size of the emulsions prepared using the rotor–stator device (primary emulsion) decreased with protein concentration and reduction in pH, allowing the production of electrostatically stable emulsions at pH 3.5. In contrast, emulsions at higher pH values (4.5, 5.5 and 7.5) showed a microscopic three-dimensional network responsible for their stability at protein contents higher than 1.0% (w/w). The emulsions at pH 3.5 homogenized by high pressure (up to 100 MPa) showed a decrease in surface mean diameter (d₃₂) with increasing pressure and the number of passes through the homogenizer. These emulsions showed droplets with lower dispersion and d₃₂ between 1.00 and 4.05 μm, six times lower than values observed for primary emulsions. The emulsions presented shear-thinning behavior and lower consistency index and viscosity at higher homogenization pressures. In addition, the emulsions showed a less structured gel-like behavior with increase in homogenization pressure and number of passes, since the pressure disrupted the collagen fiber structure and the oil droplets. The results of this work showed that the collagen fiber has a good potential for use as an emulsifier in the food industry, mainly in acid products.     

The effect of high-pressure treatment on functional components of shrimp (Litopenaeus vannamei) cephalothorax

High-pressure (HP) technology has been applied to extend the shelf life of shrimps by inhibiting enzymes with PPO activity or microorganisms. However, there is very little information on its effect on relevant compounds from a nutritional or functional point of view, such as fatty acids, α-tocopherol, astaxanthin, and hemocyanin, which constitutes the main objective of the present work. Shrimp cephalothoraxes were HP processed at 200, 400, or 600 MPa/18 °C/15 min or three consecutive 5 min cycles. It was found that hemocyanin was partially denatured at pressures up to 400 MPa, resulting in lower PPO activity, and it was totally denatured at 600 MPa, although 20% residual PPO activity remained. Astaxanthin, α-tocopherol, and total antioxidant activity were stable whichever HP treatment was applied, whereas 600 MPa caused a slight reduction of eicosapentaenoic acid (C20:5n3, EPA) and docosahexaenoic acid (C22:6n3, DHA). Despite this reduction, the ω-6/ω-3 fatty acids ratio was very low (1).Industrial relevanceShrimps are high-value fishery products with a very short shelf life under refrigeration, mainly because of microbial growth and development of melanosis. Thermal treatment is effective for extending shelf life, but it affects the nutritional quality of shrimps through degradation of bioactives such as polyunsaturated fatty acids, tocopherols, or astaxanthin, which are mainly located in the cephalothorax. High pressure is a non-thermal processing technology that has been proved to extend shrimp shelf life, but very little information can be found on its effect on the above-mentioned compounds as well as on the melanosis-inducing hemocyanin. Such basic knowledge is very important for industrial application of high-pressure technology to extend the shelf life of shrimps.     

Emulsions stabilized by heat-treated collagen fibers

The emulsifying properties of collagen fiber were modified by heat treatment at temperatures ranging from 50 to 85 °C for 20 or 60 min. In addition to heat treatment, the influence of pH (3.5 and 9.2) and the emulsifying process (rotor-stator device and high-pressure homogenizer) were evaluated on oil-in-water emulsions stabilized by collagen fiber through visual analysis (stability), microstructure and rheological measurements. Emulsions homogenized using solely the rotor-stator device showed phase separation and a larger mean droplet size (d₃₂), except for the emulsion composed by non-heated collagen fiber. The alkaline emulsions showed lower kinetic stability, since collagen fibers have a lower net charge (zeta potential) at higher pH values, decreasing the electrostatic stability process. Heat treatment slightly decreased the protein charge and significantly reduced the insoluble protein content, suggesting a decrease in the emulsifying properties of the collagen fiber. The use of high-pressure homogenization (20-100 MPa) made it possible to produce acid emulsions with a reduced droplet size and distribution. At 20 MPa, the emulsions showed a higher d₃₂ value (between 3.17 and 1.18 μm), while at 60 and 100 MPa the emulsions presented lower d₃₂ values (between 0.74 and 0.94 μm) without any significant variation between the different heat-treated collagen fibers, but showing a noticeable decrease in emulsion viscosity and elasticity with increases in the homogenization pressure and heat treatment.     

Application of ultrasonic wave celerity measurement for evaluation of physicochemical properties of olive oil at high pressure and various temperatures

High-pressure processing is a powerful technology for food preservation. The knowledge of foods properties in the high-pressure range is important to develop and optimize such processes by means of mathematical modeling and simulation. Ultrasonic methods are rapid, non-invasive and can be used to characterize foods like edible oils (e.g., composition, purity, and quality assessment). In this paper, they were applied for the investigation of physicochemical properties of olive oil at high pressure at different temperatures. The sound wave velocity was measured by the pulse-transmission method and the corresponding oil density was additionally determined from the monitoring of sample volume change. Measurements were conducted in the pressure range up to 600 MPa, for temperatures from 20 to 50 °C. Intermolecular free length, isothermal and adiabatic compressibility versus pressure were calculated using measured sound speed and density isotherms. Discontinuities in the measured isotherms of sound speed and density versus pressure indicate the presence of liquid-to-solid phase transitions. The kinetics of the liquid-to-solid phase transition was also investigated. The transformation times of olive oil augment with increasing temperature. This study can be broadened to other liquid foodstuffs to investigate the influence of temperature on their physicochemical properties at high pressure.     

Maintenance of breast milk immunoglobulin A after high-pressure processing

Human milk is considered the optimal nutritional source for infants. Banked human milk is processed using low-temperature, long-time pasteurization, which assures microbial safety but involves heat denaturation of some desirable milk components such as IgA. High-pressure processing technology, the subject of the current research, has shown minimal destruction of food macromolecules. The objective of this study was to investigate the influence of pressure treatments on IgA content. Moreover, bacterial load was evaluated after pressure treatments. The effects of high-pressure processing on milk IgA content were compared with those of low-temperature, long-time pasteurization. Mature human milk samples were heat treated at 62.5°C for 30 min or pressure processed at 400, 500, or 600 MPa for 5 min at 12°C. An indirect ELISA was used to measure IgA in human milk whey obtained after centrifugation at 800 × g for 10 min at 4°C. All 3 high-pressure treatments were as effective as low-temperature, long-time pasteurization in reducing the bacterial population of the human milk samples studied. After human milk pressure processing at 400 MPa, 100% of IgA content was preserved in milk whey, whereas only 72% was retained in pasteurized milk whey. The higher pressure conditions of 500 and 600 MPa produced IgA retention of 87.9 and 69.3%, respectively. These results indicate that high-pressure processing at 400 MPa for 5 min at 12°C maintains the immunological protective capacity associated with IgA antibodies. This preliminary study suggests that high-pressure processing may be a promising alternative to pasteurization in human milk banking.     

Flaxseed oil – Whey protein isolate emulsions: Effect of high pressure homogenization

The effect of high-pressure homogenization (20–100 MPa) and the number of homogenization cycles (1–7) on the stability of flaxseed oil - whey protein isolate emulsions was evaluated. All the emulsions were stable to creaming for at least 9 d of storage. An increase in homogenization pressure from 20 to 80 MPa and number of passes through the homogenizer up to 3, decreased the mean droplet size of the O/W emulsions despite the higher polydispersity. Emulsions homogenized at lower pressures (20 MPa) showed a monomodal distribution of the particles, whereas, an increase in pressure to 80 MPa led to a bimodal distribution, indicating droplets coalescence. High-pressure homogenization (80 MPa) and an increase in the number of homogenization cycles, led to the formation of high molecular weight aggregates (>200 kDa), which favored an increase in viscosity of the emulsions. The increase in homogenization pressure also increased the formation of primary oxidation products, which could be explained by the increase in temperature and in the surface area of the droplets.     

Supercritical CO2 extraction of oil from Arctic charr side streams from filleting processing

Although Arctic charr side streams contain limited amounts of fish flesh, they are a rich fish oil source (46.3 ± 0.6%). The aim of the study was to investigate the potential for valorization of Arctic charr filleting side streams through the extraction of oil by supercritical CO₂ technology. The effect of temperature (40 °C and 80 °C) and pressure (20, 35 and 45 MPa) on the final extract after supercritical fluid extraction (SFE) was evaluated. Temperature increase enhanced the yield but decreased the antioxidant activity at 45 MPa, did not affect the yield and the antioxidant activity at 35 MPa, whereas yield was limited at 20 MPa and 80 °C. Extracts were rich in monounsaturated fatty acids (56.7–58.3%, especially oleic acid 37.2–38.0%), and polyunsaturated fatty acids (20.2–26.1%, especially DHA 7.3–11.4%). The presence of astaxanthin significantly preserved the extracts from oxidation.Industrial relevanceSupercritical carbon dioxide extraction is a green technology appropriate for the recovery of non-polar and heat sensitive compounds. The extracted Arctic charr oils were rich in polyunsaturated fatty acids and astaxanthin which inhibited oxidation in combination with the absence of oxygen and light during the process. This technology could be an excellent alternative for more sustainable valorization of fish processing side streams.     

Effect of high-pressure homogenization on droplet size distributions and rheological properties of model oil-in-water emulsions

A new ultra high-pressure homogenizer (STANSTED, UK) going up to 350 MPa, was used to realize very fine oil-in-water emulsions. The effect of homogenizing pressure (from 20 to 300 MPa) was studied on model emulsions stabilized by whey proteins. Oil droplet size distributions were measured by laser-light scattering. Rheological properties were characterized with a coaxial cylinder rheometer. The results showed significant modifications in the structure and the texture of emulsions with increasing pressure. Ultra high-pressure homogenizing conditions brought about the high oil content emulsions (>40% w.w.b) from shear-thinning behaviors (at 20 MPa) to Newtonian behaviors (at 300 MPa). Droplet size was reduced with increasing pressure. However, the flow curves could not be fully explained by the droplet size distributions.     

Initial study on high pressure jet processing using a modified waterjet on physicochemical and rennet coagulation properties of pasteurized skim milk

Developments in material science and engineering have enabled high pressure jet (HPJ) processing at >500 MPa. The objective of this study was to characterize the physicochemical properties of pasteurized skim milk processed at pressures from 0 to 500 MPa using waterjet technology, to explore novel uses of this technology for milk. The apparent particle size of casein micelles increased from approximately 180–220 nm in milk processed from 0 to 200 MPa to approximately 280 nm in milk treated at 500 MPa. All milk samples were shelf-stable up to 14 days at 4 °C. The viscosity of skim milk processed at 400 and 500 MPa almost doubled (4.2 mPa s) when compared with control unprocessed milk (2.2 mPa s). Increasing HPJ processing pressure changed the structure–function properties of the casein micelles and no rennet-induced coagulation was observed for milk processed at 500 MPa.     

Potentialities of High-Pressure Homogenization to Inactivate Zygosaccharomyces bailii in Fruit Juices

ABSTRACT: This experimental work was aimed to evaluate the effects of repeated high-pressure homogenization (HPH) treatments at 100 MPa on the inactivation and regrowth of Zygosaccharomyces bailii inoculated in apricot and carrot juices. Thus, the spoilage yeast was inoculated in both the juices at level of about 5 log CFU/g and the 2 systems were treated with a lab-scale Panda homogenizer for 8 passes at 100 MPa. Microbiological and chemico-physical analyses were performed immediately after the treatment and during the juice storage at room temperature. Microbial data highlighted that yeast inactivation increased with the number of passes applied. Eight passes at 100 MPa allowed yeast inactivation higher than 2.5 log CFU/mL regardless of the juice considered. On the contrary, the juice type affected the yeast fate (growth or death) over the storage at 25 °C. In fact, Z. bailii was able to attain the spoilage threshold (6 log CFU/mL) in apricot juice, although with growth kinetics dependent of the survivor levels after HPH treatment. In carrot juice this microorganism was unable to recover over the storage in the most severely treated samples. The HPH treatment had a significant effect on apricot juice pH and viscosity, while no significant effect was observed in carrot juice. The viscosity measurements showed that the application of one pass at 100 MPa resulted in the triplication of apricot viscosity index. No further significant viscosity increase (P > 0.05) was observed increasing the number of passes at 100 MPa. Practical Application: The results obtained in the present study and the proposed technology could be exploited by the industries of the beverage sector to increase the shelf life of these kinds of products. Moreover, from a technological point of view, the increase of viscosity, following the high-pressure homogenization treatment, represents a tool to expand the product gamma without the use of gelling additives or thermal treatments, which are detrimental for the sensorial and nutritional properties of this kind of products.