Ultra-high Pressure Homogenization Research Articles

An ultrahigh pressure homogenization technique for easily exfoliating few-layer phosphorene from bulk black phosphorus

We have developed an easy and efficient method for exfoliating few-layer sheets of black phosphorus (BP) in N-methyl-2-pyrrolidone, using ultra-high pressure homogenization (UPH). The BP was first exfoliated into sheets that were a few atomic layers thick, using a homogenizer for only 30 min. Next, a double centrifugation procedure was used to separate the material into few-layer nanosheets that were examined by X-ray diffraction, atomic force microscopy (AFM), transmission electron microscopy (TEM), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), and energy-dispersive X-ray (EDX) spectroscopy. The results show that the products are specimens of phosphorene that are only a few-layer thick.

Ultra-high pressure homogenisation process for production of reduced fat mayonnaise with similar rheological characteristics as its full fat counterpart

Abstract The potential of (ultra) high pressure homogenisation (UHPH) for production of emulsion (example of mayonnaise) with 28% of sunflower oil without thickeners and artificial emulsifiers was investigated. For purposes of comparison, a commercially available full fat (CFFM) and low fat mayonnaise (CLFM) were analysed. The emulsions were characterized by measuring the fat droplet size distribution, structure by confocal laser scanning microscopy (CLSM) and rheological properties applying flow and oscillatory tests one day after the processing. The droplet size and microscopic images of UHPH produced emulsion revealed smaller fat droplets and a more even distribution of components, compared to the CFFM and CLFM. Similar consistency index of UHPH low fat emulsion compared to the CFFM was obtained in pressure range from 250 to 300 MPa. In the same pressure range the UHPH emulsion showed higher firmness parameter compared to CFFM. The results of the study showed clear potential of UHPH technology for production of emulsion reduced in fat, free of additional thickeners and artificial emulsifiers. Industrial relevance text Mayonnaise is considered as one of the most popular sauces worldwide with high fat content. High pressure homogenisation (HPH) is a new continuous technique for preparation and stabilisation of emulsions, by means of significantly reducing the size of oil droplets and improving interactions between emulsifier and fat phase. This allows for production of oil-in-water (o/w) emulsions with reduced fat content. Further, emulsion with reduced amount of emulsifiers or completely free of thickeners can be produced. The results of this study could be of great importance for consideration of scale-up possibilities and future implementation of UHPH in food industry for production of low fat emulsions, having a clean label. Moreover, the process could stimulate interest in product development and optimisation of existing processes. A consumer friendly product reduced in fat and with clean label could be produced.

Microbiological stabilization of tiger nuts’ milk beverage using ultra-high pressure homogenization. A preliminary study on microbial shelf-life extension

Tiger nuts’ milk beverages are highly perishable products. For this reason, the interest of food industry for their commercialization makes necessary the application of preservation treatments to prolong their shelf-life. In the current study, the effect of ultra-high pressure homogenization (UHPH) on the microbiological and sensory qualities of tiger nuts’ milk beverage was evaluated. Characteristics of UHPH-treated products (at 200 and 300 MPa, with inlet temperature of 40 °C) were compared with those of raw (RP) and conventionally homogenized-pasteurized (H-P) beverages, after treatment and during cold storage at 4 °C. Microbiological quality of beverages was studied by enumerating total counts, psychrotrophic bacteria, lactobacilli, enterobacteria, molds and yeasts, and mesophilic spores. Evolution of color and sensory characteristics of beverages were also determined. Microbiological shelf-life of the tiger nuts’ milk beverages was extended from 3 to 25, 30 and 57 days by applying H-P and UHPH treatments at 200 and 300 MPa, respectively. Color of beverages was the only attribute that differentiated UHPH samples from the others, with greater luminosity and whiteness. Hence, UHPH treatments showed to be an alternative to the conventional H-P for obtaining tiger nuts’ milk beverages with an improved microbiological shelf-life and good sensorial characteristics.

Physicochemical properties and storage stability of soybean protein nanoemulsions prepared by ultra-high pressure homogenization

This study investigated the effects of the ultrahigh pressure homogenization (pressure, protein concentration, oil phase fraction, pH, temperature, and ionic strength) and storage on the properties of nanoemulsions (100–500nm range), which were stabilized by laboratory-prepared soybean protein isolate (SPI), β-conglycinin (7S) and glycinin (11S). The nanoemulsions made with SPI, 7S and 11S proteins exhibited considerable stability over various ionic strengths (0–500mM NaCl), pH (<4 or >7), thermal treatments (30–60°C) and storage (0–45days). The far-UV spectra of SPI, 7S, 11S dispersions, and SPI-, 7S-, 11S protein-stabilized nanoemulsions were analyzed for the protein structural changes following lipid removal. The ultra-high pressure homogenization changed the secondary structure of SPI, 7S, 11S proteins in the nanoemulsions, and enhanced their stability. This study demonstrated that SPI, 7S, and 11S proteins can be used as effective emulsifiers in nanoemulsions prepared by ultra-high pressure homogenization.

Effect of ultra‐high‐pressure homogenization at moderate inlet temperatures on volatile profile of milk

AbstractThe aim of this work was to evaluate the volatile profile of whole milk treated by ultra‐high‐pressure homogenization (UHPH) at 300 MPa with inlet temperature (Ti) = 65, 75, and 85 °C, comparing the results to Ultra High Temperature (UHT) milk. From the results, in UHT milk, ketones and dimethyl thrisulfide concentration was higher than in any other sample. On the contrary, the concentration of aldehydes in UHPH‐treated milk samples was higher than the concentration detected in heat‐treated samples. Principal components analysis explained the variations in the observed responses, presenting well‐defined and separated groups. UHPH represents a suitable alternative to reduce cooked‐related compounds presented in heat‐treated milk.Practical applicationsThis study provides more information regarding ultra‐high‐pressure homogenization (UHPH) as an emerging technology with industrial applications. In this case, the UHPH application was able to reduce the amount of volatile compounds such as ketones related to cooked flavor in heat treatments at high intensity, such as UHT processing. For this, several UHPH‐proved safety conditions were compared to the volatile profile obtained in UHT milk.

Characterization of Whey Protein Oil-In-Water Emulsions with Different Oil Concentrations Stabilized by Ultra-High Pressure Homogenization

In this study, the effect of ultra-high-pressure homogenization (UHPH: 100 or 200 MPa at 25 °C), in comparison to colloid mill (CM: 5000 rpm at 20 °C) and conventional homogenization (CH: 15 MPa at 60 °C), on the stability of oil-in-water emulsions with different oil concentrations (10, 30 or 50 g/100 g) emulsified by whey protein isolate (4 g/100 g) was investigated. Emulsions were characterized for their microstructure, rheological properties, surface protein concentration (SPC), stability to creaming and oxidative stability under light (2000 lux/m2). UHPH produced emulsions containing lipid droplets in the sub-micron range (100–200 nm) and with low protein concentrations on droplet surfaces. Droplet size (d3.2, µm) was increased in CH and UHPH emulsions by increasing the oil concentration. CM emulsions exhibited Newtonian flow behaviour at all oil concentrations studied; however, the rheological behaviour of CH and UHPH emulsions varied from Newtonian flow (n ≈ 1) to shear-thinning (n ˂ 1) and thixotropic behaviour in emulsions containing 50% oil. This was confirmed by the non-significant differences in the d4.3 (µm) value between the top and bottom of emulsions in tubes left at room temperature for nine days and also by a low migration velocity measured with a Turbiscan LAB instrument. UHPH emulsions showed significantly lower oxidation rates during 10 days storage in comparison to CM and CH emulsions as confirmed by hydroperoxides and thiobarbituric acid-reactive substances (TBARS). UHPH emulsions treated at 100 MPa were less oxidized than those treated at 200 MPa. The results from this study suggest that UHPH treatment generates emulsions that have a higher stability to creaming and lipid oxidation compared to colloid mill and conventional treatments.

Physicochemical and sensory characteristics of a UHT milk-based product enriched with conjugated linoleic acid emulsified by Ultra-High Pressure Homogenization

Abstract In the past decade, there has been an increasing interest in the incorporation of conjugated linoleic acid (CLA) into foodstuffs. Physicochemical and sensory characteristics of a UHT milk-based product enriched with CLA (0.6% v/v in final product) in a free fatty acid form and emulsified by Ultra-High Pressure Homogenization (UHPH, 200 MPa) was evaluated and compared with conventional homogenization (CH; 25 MPa). Particle size changes were evaluated until the final milk-based products were produced (CH-P and UHPH-P). Rheological properties, colour, pH, physical stability, proteolysis, primary and secondary lipid oxidation and sensory characteristics were analysed during storage. UHPH-P exhibited similar viscosity (≈ 2 mPa × s) but greater physical stability compared to CH-P due to the smaller particle size (≈ 200 nm). UHPH-P also presented lower content of lipid hydroperoxides and less perception of oxidized attributes. Industrial relevance An emulsion containing CLA in a form more prone to lipid oxidation was treated by UHPH or CH. The results in this manuscript address the physicochemical stability and sensory properties improvement of a UHT milk-based product enriched with the CLA-emulsion homogenized by UHPH. Thus, UHPH is suggested as an antioxidant emulsification technique.

Research progress on cloud stability of orange juice

After squeezed, pulp particles, cell wall fragments, orange oil drops, hesperidin crystal, cytochrome and some amorphous material in orange were dispersed in water ununiformly. They contribute to the turbidity of citrus juices, which was known as “cloud”. Quality factors such as flavor, color, texture, and aroma are partly attributable to the cloud. If the cloud particles were too large, cloud will settle down, with the occurrence of loss cloud, leading to cloud loss. In this paper, the main components and characteristics of cloud in orange juice were summarized. The cloud was made of pectin, protein, cellulose, hesperidin, and so on. Simultaneously, the factors affecting the stability of cloud in orange juice were reviewed, including the effect of pectin methylesterase, orange 's varieties and maturity, p H, calcium, and clouding agents. Addition of pectin methylesterase inhibitor, or usage of non-thermal processing technologies, such as ultra-high pressure homogenization technique and ultrasonic treatment, could maintain cloud stability in processing or storage of orange juices.Studying the cloud's component interaction mechanism and the orange juices processing new technology unceasingly in a deep-going way could improve cloud stability of orange juices in processing and storage, making orange juices keep better conditions in its shelflife.

Colloidal emulsion based delivery systems for steroid glycosides

Water insoluble bioactive molecules with limited solubility in common triglyceride are difficult to formulate in colloidal form. We demonstrate the fabrication and characterization of nanoscale diacylglycerol oil-in-water emulsions containing high levels (20wt%) of steroid glycosides stabilized by food grade emulsifiers. The emulsions were produced using ultra high pressure (120MPa) homogenization with average droplet sizes as small as 80nm. The nanoscale emulsions were stabilized using food grade surfactants, surface active biopolymers and proteins. Due to amphiphilic nature of steroid glycosides molecule and higher polarity of the diacylglycerol rich oils used as solvents, it was possible to prepare stable emulsifier-free emulsions. The emulsions displayed very good stability against Ostwald ripening, creaming and coalescence. The emulsions were followed in time and were found stable for more than one year. In the presence of some sugars, the emulsions can be freeze-dried and form readily water dispersible powders without significant coalescence.

Life cycle assessment of emerging technologies: The case of milk ultra-high pressure homogenisation

Milk is becoming a key food commodity as population grows and demand increases. The treatment of milk to extend its shelf life is thus an important step in avoiding losses and optimizing resource use. The drawbacks of the most common treatments for shelf stable milk are the loss of nutritional values and high energy consumption. Ultra-high pressure homogenisation (UHPH) is an emerging technology relying on dynamic pressure up to 400 MPa. The combination of high pressure, temperature, shear, cavitation and impingement can provide commercially sterile milk of higher quality and longer shelf life. A life cycle assessment was performed comparing this emerging technology to the common thermal treatment: indirect ultra-high temperature sterilisation combined with non-aseptic homogenisation. The results show that high-pressure based processing has a lower environmental burden compared to the high-temperature based processing, already at pilot-scale, and this difference is primarily due to the lower electricity consumption. Additionally, upscaling considerations were made using power laws and scenario analysis to simulate future full-scale applications of UHPH. The upscaling shows that a decrease in carbon footprint up to 88% is achievable with improvements in efficiency. UHPH could, therefore, represent a substitute for existing practices considering its technological readiness level and potential synergies when integrated into industrial scale production lines.

Enhanced stability of emulsions treated by Ultra-High Pressure Homogenization for delivering conjugated linoleic acid in Caco-2 cells

Using novel technologies which offer higher protection and release of bioactive compounds is a current challenge in the food industry. Ultra-High-Pressure Homogenization (UHPH) is an emerging technology that produces physico-chemical and microbiological stable emulsions. The ability of oil-in-water emulsions stabilized by soy protein isolates (4%) to deliver conjugated linoleic acid (CLA, 6%), was studied. Emulsions were produced by UHPH at 200 MPa and by conventional homogenization (CH) at 15 MPa. For another batch of CH emulsions, a heat treatment was also conducted applying high-temperature-short-time conditions (72 °C for 20 s; CH-HTST). The physico-chemical properties of the emulsions were determined, as well as microbial, physical, and oxidative stability. The emulsions were subjected to in vitro digestion, and tested on absorptive Caco-2 cells. The presence of CLA isomers was followed throughout the process. When comparing similar formulations, UHPH emulsions showed smaller particle size and a homogeneous microstructure than emulsions prepared by CH or CH-HTST. Moreover, UHPH produced a sterile emulsion and showed better physical stability during storage compared to other treatments, maintaining an optimal oxidative stability until 3 months. After in vitro digestion and delivery in Caco-2 cells, similar percentages of bioavailability of CLA were found for all the emulsion treatments. The study has gone towards enhancing oil-in-water emulsions by using UHPH technology for delivering conjugated linoleic acid in functional foods.

Plant-based milk alternatives an emerging segment of functional beverages: a review.

Plant-based or non-dairy milk alternative is the fast growing segment in newer food product development category of functional and specialty beverage across the globe. Nowadays, cow milk allergy, lactose intolerance, calorie concern and prevalence of hypercholesterolemia, more preference to vegan diets has influenced consumers towards choosing cow milk alternatives. Plant-based milk alternatives are a rising trend, which can serve as an inexpensive alternate to poor economic group of developing countries and in places, where cow's milk supply is insufficient. Though numerous types of innovative food beverages from plant sources are being exploited for cow milk alternative, many of these faces some/any type of technological issues; either related to processing or preservation. Majority of these milk alternatives lack nutritional balance when compared to bovine milk, however they contain functionally active components with health promoting properties which attracts health conscious consumers. In case of legume based milk alternatives, sensory acceptability is a major limiting factor for its wide popularity. New and advanced non-thermal processing technologies such as ultra high temperature treatment, ultra high pressure homogenization, pulsed electric field processing are being researched for tackling the problems related to increase of shelf life, emulsion stability, nutritional completeness and sensory acceptability of the final product. Concerted research efforts are required in coming years in functional beverages segment to prepare tailor-made newer products which are palatable as well as nutritionally adequate.

Applications of High and Ultra High Pressure Homogenization for Food Safety.

Traditionally, the shelf-life and safety of foods have been achieved by thermal processing. Low temperature long time and high temperature short time treatments are the most commonly used hurdles for the pasteurization of fluid foods and raw materials. However, the thermal treatments can reduce the product quality and freshness. Consequently, some non-thermal pasteurization process have been proposed during the last decades, including high hydrostatic pressure, pulsed electric field, ultrasound (US), and high pressure homogenization (HPH). This last technique has been demonstrated to have a great potential to provide “fresh-like” products with prolonged shelf-life. Moreover, the recent developments in high-pressure-homogenization technology and the design of new homogenization valves able to withstand pressures up to 350–400 MPa have opened new opportunities to homogenization processing in the food industries and, consequently, permitted the development of new products differentiated from traditional ones by sensory and structural characteristics or functional properties. For this, this review deals with the principal mechanisms of action of HPH against microorganisms of food concern in relation to the adopted homogenizer and process parameters. In addition, the effects of homogenization on foodborne pathogenic species inactivation in relation to the food matrix and food chemico-physical and process variables will be reviewed. Also the combined use of this alternative technology with other non-thermal technologies will be considered.

Potential application of ultra-high pressure homogenization in the physico-chemical stabilization of tiger nuts' milk beverage

The present study aimed to evaluate the effect of UHPH treatments (at 200 and 300 MPa and 40 °C of inlet temperature) on the physico-chemical characteristics of tiger nuts' milk beverages, in comparison with the raw beverage and the product treated by a conventional homogenization-pasteurization (18 + 4 MPa, 80 °C, 15 s) without stabilizers (H-P1) or with them (H-P2). The long term evaluation of samples showed that UHPH-treated beverages presented the highest colloidal stability, principally against creaming, due to the reduction in particle size and the new particle interactions, even if comparing with H-P2 beverage. Peroxidase activity showed the highest reduction after applying 300 MPa treatment, and regarding fat oxidation reactions, 200 MPa-treated beverage appeared to be the most stable. In this sense, the UHPH is presented as an emerging technology for obtaining tiger nuts' milk beverages free of additives with improved physico-chemical characteristics.

Ultra High Pressure Homogenization of Soy Milk: Effect on Quality Attributes during Storage

The present work analyzed soy milk prepared from whole dehulled soybeans. The traditional method of soy milk preparation leads to wastage of about 35% of soybean solids in the form of okara, which gets filtered out. In the current study, soy milk was prepared with practically 100% recovery of soybean solids and treated with continuous flow high pressure processing (207 and 276 MPa pressure, 121 and 145 °C exit temperatures, and 0.75 and 1.25 L/min flow rates), and the changes in the physical, chemical, microbial, and sensory properties during 28 days of storage at 4 °C were analyzed. The treated soy milk remained stable for 28 days. There was a significant reduction in the particle size of soybean solids which did not change during storage. The pH of the treated soy milk was significantly lower than the untreated soy milk and it reduced further upon storage. The soy milk was pasteurized with high pressure processing coupled with preheating. No lipoxygenase activity was detected. Compared to commercial samples, there was no significant difference in the astringency, bitterness, or chalkiness of soy milk prepared in the study.

Proteolysis of cheese made from goat milk treated by ultra high pressure homogenisation

The effect of ultra high-pressure homogenisation (UHPH) of goat milk (200 MPa, 30 °C) on the proteolytic profiles of cheese was studied and compared to cheeses made with homogenised-pasteurised (18 + 2 MPa, 72 °C for 15 s) and pasteurised (72 °C, 15 s) milk. Cheeses produced by UHPH-treated milk presented higher hydrolysis of αs2-, β- and para-κ-casein than those made with pasteurised milk; however, cheeses made by homogenised-pasteurised milk exhibited the highest hydrolysis of αs1-and para-κ-caseins. The increase in proteolysis by the homogenisation process could be attributed to the increase in the exposure of substrates to proteolytic enzymes. The UHPH-treatment of milk significantly increased the levels of whey soluble nitrogen and hydrophobic and hydrophilic peptides, however, levels of free amino acids were reduced during the first days of ripening as a consequence of the decrease in the aminopeptidase activity. No significant differences were detected in free amino acid profiles of the different cheeses by the principal component analysis.

Ultra-high pressure homogenization for "cleaner" reduced-fat emulsions

Ultra-high pressure homogenization for "cleaner" reduced-fat emulsions

Ultra-high pressure homogenization for "cleaner" reduced-fat emulsions

Ultra-high pressure homogenization for "cleaner" reduced-fat emulsions

Ultra-High Pressure Homogenization improves oxidative stability and interfacial properties of soy protein isolate-stabilized emulsions

Ultra-High Pressure Homogenization (100–300MPa) has great potential for technological, microbiological and nutritional aspects of fluid processing. Its effect on the oxidative stability and interfacial properties of oil-in-water emulsions prepared with 4% (w/v) of soy protein isolate and soybean oil (10 and 20%, v/v) were studied and compared to emulsions treated by conventional homogenization (15MPa). Emulsions were characterized by particle size, emulsifying activity index, surface protein concentration at the interface and by transmission electron microscopy. Primary and secondary lipid oxidation products were evaluated in emulsions upon storage. Emulsions with 20% oil treated at 100 and 200MPa exhibited the most oxidative stability due to higher amount of oil and protein surface load at the interface. This manuscript addresses the improvement in oxidative stability in emulsions treated by UHPH when compared to conventional emulsions.

Super-cooled and amorphous lipid-based colloidal dispersions for the delivery of phytosterols.

Super-cooled and amorphous lipid-based colloids are highly desirable delivery systems because of their ability to encapsulate compounds in a soluble or in a non-crystalline state. In this study, we demonstrate the preparation and characterization of super-cooled and amorphous lipid-based nanoscale colloidal dispersions containing high concentrations of phytosterols (PSs). PSs are highly hydrophobic natural bioactive compounds that are known to significantly reduce blood cholesterol levels in humans, but are insoluble in water and are poorly soluble in common lipids such as triacylglycerols (TAGs). Using the ultrahigh pressure homogenization of pre-heated dispersions, followed by temperature quenching, colloidal dispersions with varying concentrations of PSs in the lipid phase are prepared. Long and medium chain TAGs in combination with a non-ionic surfactant are used. The particle size, morphology and stability are analysed by dynamic and static light scattering, electron microscopy, and X-ray diffraction. Rapid temperature quenching enables the formation of stable colloidal dispersions of 10 wt% PSs, more than five times the equilibrium solubility at room temperature. Super-cooled emulsions are formed using liquid TAG, whereas amorphous particles are formed in the case of solid TAG. In both cases, the complete suppression of the crystallization of both PSs and lipids is observed due to the nanoscale confinement. The colloidal dispersions are stable for at least four months. The insights of this work will help understand the colloid formation and particle morphology control in the development of delivery systems for hydrophobic bio-actives such as drugs, cosmeceuticals, nutraceuticals, nutritional and agricultural nanoscale formulations.