Ultra-high Pressure Homogenization Research Articles

Improvement of the physical stability of oil-in-water nanoemulsions elaborated with Sacha inchi oil employing ultra-high-pressure homogenization

This study focused on assessing the physical stabilization of several oil-in-water nanoemulsions obtained by Ultra-High-Pressure Homogenization (UHPH). For this, several formulations were developed using Sacha inchi oil (~9.3% w/w), ultra-pure water, preservatives (0.44% w/w) and several emulsifier mixtures at 2% w/w, which were combined in different proportions to provide surfactant blends with HLB values (HLBB) of 6, 8, 10, and 12. The conventional emulsions were then subjected to UHPH (40,000 psi) and underwent thermal stability assays for 4 weeks, where changes in creaming index, droplet size, polydispersity, viscosity and zeta potential, were evaluated. The results showed the required HLB (HLBr) for SI oil was approximately 8 and when UHPH was utilized, high physical stability of emulsified systems was achieved. It was also found that the increase in HLBB for the emulsions submitted to UHPH leads to a less viscosity, smaller droplet sizes and more homogeneous system.

Evaluation of Continuous UVC Treatments and its Combination with UHPH on Spores of Bacillus subtilis in Whole and Skim Milk.

The aim of this study was to evaluate the effectiveness of different UVC treatments, alone or in combination with ultra-high pressure homogenization (UHPH) on Bacillus subtilis spores in milk. Spores of B. subtilis (CECT4002) were inoculated in whole and skim milk to an initial concentration about 6 log CFU/mL. Milk was subjected to different ultraviolet radiation treatments at 254 nm (UVC) using a concentric tubular reactor in a dose ranging from 10 to 160 J/mL. Different number of passes were used to adjust the final dose received by the matrix. In general, increasing the number of passes (defined as number of entries to the tunnel-NET) increased the inactivation of spores of B. subtilis. The best lethality results (above 4 Log CFU/mL) were obtained by applying doses from 100 J/mL with several NET. When the same doses were achieved with a single pass lethality in most cases did not exceed 1 log CFU/mL. Increasing the NET also increased the likelihood for the spores to remain longer in the effective distance from the UVC source, estimated as 0.02 mm for whole milk and 0.06 mm for skim milk. Combination of UHPH and UVC did not clearly increase the efficiency of a single UVC treatment, and a lower lethality was even observed in some cases. UHPH treatments increased the turbidity and absorption coefficient (254 nm) of both whole and skim milk.

Impact of oil phase concentration on physical and oxidative stability of oil-in-water emulsions stabilized by sodium caseinate and ultra-high pressure homogenization

In the present study, oil-in-water emulsions were formulated using 5.0% (w/v) of sodium caseinate (SC) and different oil concentrations (10–30%, v/v) by conventional homogenization (CH) and ultra-high pressure homogenization (UHPH, 200–300 MPa). The effect of oil concentration and pressure of treatment on emulsions characteristics and stability was studied. Emulsions were characterized assessing their microstructure, droplet size distribution, rheological properties, emulsifying activity index (EAI), creaming stability by Turbiscan®, and photo-oxidation. UHPH emulsions, especially those treated at 200 MPa, showed smaller droplet size and greater physical stability than CH emulsions. In addition, emulsions containing higher oil volume fractions (20 and 30%) exhibited greater physical and oxidative stability. UHPH emulsions treated at 200 MPa and containing 20% oil content were the most stable emulsions against physical separation and photo-oxidation. These results show that UHPH is a potential technology to enhance the physical and oxidative stability of emulsions containing sodium caseinate as emulsifier for several applications.

Evaluating microalgal cell disruption upon ultra high pressure homogenization

The impact of (ultra) high pressure homogenization on the degree of cell disruption was investigated for Nannochloropsis sp. suspensions. The degree of cell disruption was studied by combining four evaluation methods: turbidity measurement, scanning electron microscopy, hexane:isopropanol extraction efficiency, and fluorescence microscopy using the viability stain SYTOX green. Applying an ultra high pressure of 250 MPa obviously reduced the number of homogenization passes required to obtain a specific degree of cell disruption compared to 100 MPa. However, heating of the sample occurred at 250 MPa, resulting in extensive aggregate formation of the released intracellular material after multiple homogenization passes. Furthermore, cell wall integrity was not necessarily linked to membrane integrity, implying that moderate (U)HPH conditions are possibly sufficient for certain applications by damaging the cell membrane, without achieving full rupture of the cell wall. Once again it was proven that different methods for evaluation of cell disruption should be combined to get comprehensive insight into the disruption of microalgae.

Effect of ultra-high pressure homogenisation of cream on the physicochemical and sensorial characteristics of fat-reduced starter-free fresh cheeses

The objective of the present study was to evaluate the effect of the incorporation of cream treated by ultra-high pressure homogenisation (UHPH) on the physicochemical and sensorial characteristics of fat-reduced fresh cheeses. Light creams treated by UHPH at 300 MPa with or without addition of 1.5 g/100 g sodium caseinate were compared to conventionally treated creams (batch pasteurisation at 65 °C for 30 min or homogenisation at 15 MPa followed by pasteurisation). Reduced-fat cheeses were obtained mixing treated creams with skim milk until 1.5 g/100 g fat, while milk at 3.2 g/100 g were used to made full-fat cheeses. The reduction of fat content of pasteurised cheese-making milk decreased cheese yield by 23%. These cheeses presented greater hardness, elasticity, cohesiveness, gumminess and chewability than full-fat cheeses. However, homogenisation of cream increased cheese yield by 5 and 13% with conventional treatment and UHPH, respectively. The addition of sodium caseinate before UHPH treatment increased cheese yield by 22%, as a consequence of their water retention capacity, obtaining similar values as for full-fat cheeses. These cheeses, which were the most valued on the scale of preference and described as more watery by panellists, were less hard, elastic, cohesive, gummy and chewy than their fat-reduced counterparts, with values similar to full-fat cheeses.

(Ultra) High Pressure Homogenization Potential on the Shelf-Life and Functionality of Kiwifruit Juice.

The increasing competition within the food industry sector makes the requisite of innovation in processes and products essential, leading to focus the interest on the application of new processing technologies including high pressure homogenization (HPH) and ultra high pressure homogenization (UHPH). In this context, the present research aimed at evaluating the effects of two UHPH treatments performed at 200 MPa for 2 and 3 cycles on quality and functionality of organic kiwifruit juice stored at three different temperatures, i.e., 5, 15, and 25°C. The results showed that only the treatment performed at 200 MPa for 3 cycles was able to significantly increase the shelf-life of organic kiwifruit juices when stored at refrigeration temperature, avoiding also phase separation that occurred in the sample treated at 0.1 MPa (control) after 20 days of refrigerated storage. The obtained data showed also that the highest applied pressure was able to increase some quality parameters of the juice such as viscosity and luminosity (L∗) and increased the availability of total phenol content consequently enhancing the juice total antioxidant activity. The application of a treatment at 200 MPa for 3 cycles allowed to obtain a stable kiwifruit juice for more than 40 days under refrigerated storage. A challenge to implement this technology in food process as full alternative to thermal treatment could be represented by the adoption of pressure level up to 400 MPa followed by the packaging in aseptic conditions.

Influence of ultra‐high pressure homogenisation on physicochemical and sensorial properties of orange juice in comparison with conventional thermal processing

SummaryThe effect of different ultra‐high pressure homogenisation (UHPH) treatments on physicochemical and sensorial properties of orange juice was studied in comparison with thermal pasteurisation (90 °C, 1 min). UHPH treatments consisted on combinations of two inlet temperatures (10 or 20 °C) and three pressures (100, 200 and 300 MPa). Effect of treatments was assessed on general quality parameters (colour, pH, °Brix, titratable acidity, reducing sugars and non‐enzymatic browning index), particle size distribution and cloud stability. None of the UHPH treatments caused significant differences in the °Brix, reducing sugars, pH and non‐enzymatic browning index with respect of fresh or pasteurised juice. Only titratable acidity was significantly lower when inlet temperature of UHPH treatments was 20 °C. UHPH treatments significantly reduced the particle size and in consequence the cloudiness and the total colour value (∆E*) increased. The overall consumer acceptability of UHPH and pasteurised juices was similar.

Use of Ultra High Pressure Homogenization to sterilize grape must

Ultra-High Pressure Homogenization Sterilization (UHPHS) allows the sterilization of fluid foods at low temperatures or even in refrigeration. UHPHS is a continuous technique that allows to process 10,000 L/h with a single pump working at 300 MPa with an imbalance of 1 MPa (Ypsicon EP2409583). During the process, fluid temperature increases less than 5 ∘C. The technique is sensory gentle not affecting molecules formed by covalent bonds so aroma and pigments are unaltered. During the process of white musts, the complete elimination of yeasts, bacteria and spores can be achieved and the must may remain unfermented for several months-years if stored in amicrobic conditions. The technique is also effective in the destruction of polyphenol oxidase (PPO) enzymes. Final size particle is 100–300 nm allowing to increase the availability of yeast assimilable nitrogen and opens the opportunity to nano-encapsulate flavours. Destruction of PPOs and elimination of microorganisms help to reduce sulphites in wines. UHPHS facilitates the use of new biotechnologies such as the use of non-Saccharomyces yeasts and yeast-bacteria co-inoculations by enabling a better implantation of the starters in absence of competition with wild grape microorganisms.

Structure and Functional Properties of Antioxidant Nanoemulsions Prepared with Tea Polyphenols and Soybean Protein Isolate.

In this study, tea polyphenols (TP) was added to a soy protein isolate (SPI) to prepare nanoemulsions by ultra-high pressure homogenization (UHPH). The nanoemulsions were characterized by a confocal laser scanning electron microscopy, infrared spectroscopy, dynamic rheometer and size-potential analyzer. The effects of TP on the hydrophobicity, emulsifiability, particle size, potential and antioxidant capacity of the prepared nanoemulsions were investigated. The properties of the nanoemulsions with different concentrations of TP were analyzed. The results indicated that ultra-high pressure homogenization treatment contributed to the formation of the SPI-TP complex that showed higher antioxidant activity. The nanoemulsions with good emulsifying properties and high DPPH scavenging ability at the concentration of TP ranged from 0.15-0.20g / mL. Furthermore, nanoemulsions prepared in this way also had a uniform particle size. Therefore, this nanoemulsions exhibited a good potential to act as an efficient emulsifier.

Effects of dynamic ultra-high pressure homogenization on the structure and functional properties of casein

Effects of dynamic ultra-high pressure homogenization on the structure and functional properties of casein

Inactivation of ascospores of Talaromyces macrosporus and Neosartorya spinosa by UV-C, UHPH and their combination in clarified apple juice

This work addresses the use of a thin-film short wave ultraviolet radiation (UVC) reactor and its combination with ultra-high pressure homogenization (UHPH) for the inactivation of Talaromyces macrosporus (CBS 130.89) and Neosartorya spinosa (CBS 586.90), fungal species that can cause food spoilage in products made of fruits. Ascospores of these microorganisms were inoculated in phosphate buffer solution (PBS) and clarified apple juice at a concentration between 5 and 6 Log10 spores/mL before treatments. Ascospores of both microorganisms were not detected in PBS after UV-C treatments even at the lowest assayed dose (1.8 J/mL), but in apple juice T. macrosporus showed to be significantly more UV-C resistant than N. spinosa. A UV-C dose of 21.5 J/mL in a single pass achieved decimal reductions of 2.15 Log10 and 5.4 Log10 respectively. Decimal reductions of both strains significantly increased in many cases when the same UV-C dose was applied in 2 or 3 passes throughout the UV-C reactor achieving T. macrosporus a maximum reduction of 3.88 Log10 after a UV-C dose of 21.5 J/mL applied in 3 passes. UHPH treatments at 100 and 200 MPa were ineffective in inactivating ascospores of both microorganisms, However, UHPH left ascospores more vulnerable to UV-C resulting in a synergistic effect achieving a maximum reduction of 3.6 Log10 on T. macrosporus after a combined treatment of UHPH at 200 MPa and a single pass of UV-C at 21.5 J/mL. The use of scanning electron microscopy revealed that only UHPH caused small changes in the cell wall structure of ascospores, but that might have left cells better exposed to UV-C.

Use of Ultra-High Pressure Homogenization processing in winemaking: Control of microbial populations in grape musts and effects in sensory quality

Abstract Ultra-High Pressure Homogenization (UHPH) is a fast and efficient technique that can sterilize fluid foods at low temperatures or even under cooling conditions. A white must (Vitis vinifera L.) was processed at 300 MPa (inlet temperature 20 °C, in-valve temperature 98 °C, outlet temperature 25 °C, and time in valve 0.02 s) and their performance was compared with two untreated controls, a must that underwent a spontaneous fermentation (without SO2 addition) and another must that was sulfited with 35 mg/L of total SO2 and inoculated with the same Saccharomyces cerevisiae yeast as the UHPH-treated must. UHPH treatment led to the total elimination of grape microorganisms considering an initial population of 1 × 106 CFU/mL in average of wild yeasts and fungi in must, and approximately 7 × 103 CFU/mL of background bacteria. In a parallel assay, UHPH-processed must without yeast inoculation showed absence of fermentation for eight days at 18 °C. The musts treated with UHPH showed a lighter appearance (10%) before fermentation compared to the control. The triangular test verified the existence of sensory differences between the wines obtained and the preference tests showed that the judges found the wine obtained from the UHPH-treated must more fruity (3.5/5 compared with 1.5–2 in controls) and with better aroma. Industrial relevance UHPH is an interesting way to process the must before fermentation allowing the reduction of sulfite addition while controlling wild and spoilage microorganisms.

Inactivation study of Bacillus subtilis, Geobacillus stearothermophilus, Alicyclobacillus acidoterrestris and Aspergillus niger spores under Ultra-High Pressure Homogenization, UV-C light and their combination

Lethality rates of Bacillus subtilis, Geobacillus stearothermophilus, Alicyclobacillus acidoterrestris, and Aspergillus niger spores were studied into phosphate-buffer saline (PBS) and PBS supplemented with caramel (PBSC) after Ultra-High Pressure Homogenization (UHPH) and UV-C treatments applied separately and combined. UHPH procedures were carried out at different pressures (100, 200 and 300 MPa) and inlet temperatures (20, 50 and 70 °C), while UV-C treatments consisted in a combination of doses (from 0.9 to 21.5 J/mL) and eventually temperatures (20 and 50 °C) or cycles. UHPH treatments were efficient at inactivating A. niger conidiospores in PBS but much less efficient in the inactivation of bacterial spores. Efficacy of UHPH against bacterial spores was increased pre-heating the samples at 70 °C. UV-C was more efficient against bacterial spores in PBS, but much less in PBSC. When UV-C treatments were applied through several cycles their efficacy against B. subtilis spores increased. Combination of UHPH at 200 MPa and UV-C moderately increased the lethal effect on B. subtilis spores than when these treatments were applied separately. Nevertheless, the combination of both technologies has a complementary effect allowing acting on a wide range of microorganisms, increasing the possibilities to obtain a safer and durable product.

Continuous Versus Discontinuous Ultra-High-Pressure Systems for Food Sterilization with Focus on Ultra-High-Pressure Homogenization and High-Pressure Thermal Sterilization: A Review.

High-pressure thermal sterilization (HPTS) and ultra-high-pressure homogenization (UHPH) are two emerging sterilization techniques that have not been implemented in the food industry yet. The two technologies apply different acting principles as HPTS uses isostatic pressure in combination with heat whereas UHPH uses dynamic pressure in combination with shear stress, cavitation, impingement, and heat. Both technologies offer significant benefits in terms of spore inactivation in food production with reduced thermal intensity and minimized effects on sensory and nutritional profiles. These benefits have resulted in relevant research efforts on both technologies over the past few decades. This state of the art of the discontinuous HPTS-based and the continuous UHPH-based sterilization concepts are assessed within this review. Further, various basic principles and promising future preservation applications of HPTS and UHPH for food processing, that are also applicable in the pharmaceutical, biochemical, and biotechnological sectors, are summarized. In addition, the applications and limitations of these technologies in terms of optimizations needed to overcome the identified challenges are emphasized.

Modeling the effect on skim milk during ultra-high pressure homogenization using front-face fluorescence

Abstract This study provides a rapid method to evaluate and control quality changes in skim milk, using front-face fluorescence during ultra-high pressure homogenization (UHPH), for potential inline usage. Tryptophan, dityrosine and Maillard compounds were selected as indicators for their intrinsic fluorescence. The homogenization pressure was from 100 to 300 MPa and inlet temperature was from 23 to 83 °C, both distributed on a central composite design. The selected fluorophores showed good fit to the models as functions of pressure and inlet temperature. However, there was little formation of dityrosine and Maillard compounds when inlet temperature was below 50 °C. Tryptophan and dityrosine fluorescence could provide information on milk protein changes, such as denaturation, reformation and aggregation, while generation of Maillard compounds indicated thermal effects between sugars and amino acids. This work shows a promising potential to monitor and predict structural and functional changes in milk during UHPH processing and decide on its appropriate usage for further dairy production.

Modeling of the changes in bovine milk caused by ultra-high pressure homogenization using front-face fluorescence spectroscopy

Ultra-high pressure homogenization (UHPH) has been considered as an effective method to modify/enhance liquid-food properties in many studies. This research provides an alternative approach to monitor, evaluate and control quality changes induced by UHPH processing of milk using front-face fluorescence spectroscopy for potential inline usage. The fluorescence intensity spectra provided structural, functional and nutritional information of milk compounds diversification. Homogenization pressure and inlet temperature were distributed on a central composite design which covered the range of commonly used UHPH treatment conditions for improving milk technological and sensory characteristics as well as microbiological safety. The indicators showed good fit to the response surfaces as functions of pressure and inlet temperature. Tryptophan and dityrosine fluorescence provided information on milk protein changes, such as denaturation and aggregation, and particle size changes also confirmed protein denaturation and aggregation information from the fluorescence results. Generation of Maillard compounds indicated the thermal effects between reducing sugar and amino acids on milk. The retinol concentration, as a nutrient, could be well predicted by principal components summarized from milk sample spectra, without sample preparation.

Microfiltration and ultra-high-pressure homogenization for extending the shelf-storage stability of UHT milk

Fat separation, gelation or sedimentation of UHT milk during shelf-storage represent instability phenomena causing the product rejection by consumers. Stability of UHT milk is of increasing concern because access to emerging markets currently implies for this product to be stable during shipping and prolonged storage, up to 12 months. The role of microfiltration prior to UHT process in avoiding or retarding the gelation or sediment formation was studied by comparing microfiltered UHT milk to conventional UHT milk. A second trial was set up to study the effects of double ultra-high pressure homogenization in delaying the cream rising and UHT milk homogenized once at lower pressure was taken as control. All milk samples were produced at industrial plant level. Milk packages were stored at 22 °C, opened monthly for visually inspecting the presence of cream layer, gel or sediment and then analysed. Microfiltration markedly delayed the formation of both gel particles and sediment, with respect to the control, and slowed down the proteolysis in terms of accumulation of peptides although no correlation was observed between the two phenomena. The double homogenization, also evaluated at ultra-structural level, narrowed the fat globule distribution and the second one (400 MPa), performed downstream to the sterilization step, disrupted the fat-protein aggregates produced in the first one (250 MPa). The adopted conditions avoided the appearance of the cream layer in the UHT milk up to 18 months. This study contributes important knowledge for developing strategies to delay instability phenomena in UHT milk destined to extremely long shelf storage.

Changes in the shelf life stability of riboflavin, vitamin C and antioxidant properties of milk after (ultra) high pressure homogenization: Direct and indirect effects

Changes in the stability during shelf life of riboflavin, vitamin C and the antioxidant capacity of (ultra) high pressure homogenized ((U)HPH) milk were explored. With increasing pressures, a decrease of up to 50% in the degradation rate of riboflavin was observed, likely due to an indirect effect induced by (U)HPH leading to increased scattering and absorbance of the wavelengths related to riboflavin's photosensitized oxidation. Such mechanism was also confirmed in a model system. Vitamin C presented minimal decrease in concentration immediately after (U)HPH treatment, yet it quickly degraded during shelf life. The antioxidant capacity of (U)HPH treated milk measured by ORAC showed a higher value when compared to pasteurized milk, yet no effect was observed by the ABTS method. The observed changes during shelf life, that can be related to direct and indirect processing effects suggest that (U)HPH can assist in possible improvement of milk nutritional quality. Milk is a highly consumed product worldwide due to its high nutrient content. Novel innovative methods are constantly researched to improve the nutritional qualities of foods including milk. High or Ultra high pressure homogenization ((U)HPH, depending on the maximal pressure) is a novel technology that can possibly provide microbial inactivation in addition to numerous physicochemical changes in the product. The aim of this project was to evaluate the direct and indirect effect of (ultra) high homogenization pressures on nutritional qualities of milk exposed to fluorescent light during shelf life, conditions encountered in retail stores. A better fundamental understanding of the outcomes of novel processing technologies such as (U)HPH on quality parameters such as vitamin content and antioxidant properties can promote further development and acceptance of those technologies by the industry and by the consumers.

Effect of ultra-high pressure homogenization on cream: Shelf life and physicochemical characteristics

The ultra-high pressure homogenization (UHPH) effect on microbial and physicochemical shelf life of cream during storage at 4 °C were studied and compared with a conventional homogenization-pasteurization treatment. Cream samples were processed using UHPH at 300 MPa with an inlet temperature of 40 °C. Furthermore, a sample was also submitted to UHPH after the addition of 1.5% (w/v) of sodium caseinate. Ultra-high pressure homogenized samples were compared with homogenized-pasteurized (15 MPa, 55 °C; 65 °C, 30 min) cream sample and an untreated sample, which was used as a control.UHPH was efficient in reducing the total bacteria, reaching reductions of 6 log cfu/mL compared to raw samples. Enterobacteriaceae were completely eliminated in creams treated by UHPH and conventional homogenization-pasteurization. Microbial results suggest a shelf life between 29 and 36 days for UHPH-treated creams. Furthermore, no creaming was observed in cream samples treated by UHPH with caseinate throughout 29 days of storage, being a very stable cream over time.

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.