Ultra High Pressure Homogenization Treatment Research Articles

Encapsulating capacity of ultra-high-pressure homogenization (UHPH): Replacement of milk fat by vegetable oils using buttermilk as a functional ingredient in yogurt processing

This study investigated the characteristics of yogurts produced by substituting dairy fat with polyunsaturated fatty acids (PUFA)-rich oils encapsulated with buttermilk (BM) in spray-dried emulsions (SDE). Two homogenization methods, conventional (CH) and ultra-high-pressure homogenization (UHPH), were compared to obtain the emulsions for spray drying. Recombined milks (RMs) were formulated using two different concentrations (4 g/100 g and 6 g/100 g) of SDE, followed by fermentation. Yogurt characteristics were evaluated during cold storage using various parameters, including coagulation properties, texture and rheology, microstructure, physicochemical characteristics (color, pH, total acidity, and water holding capacity), oxidative stability, main fatty acid profile, microbial assessment, and sensory evaluation. During cold storage, several parameters significantly influenced the yogurt characteristics. The CH yogurts exhibited higher textural parameters (firmness and consistency) and viscoelastic parameters (G′ and G'') compared to the UHPH yogurts at the same SDE concentration. However, UHPH yogurts generally showed better water holding capacity (WHC) values. UHPH yogurts also demonstrated superior stability to oxidation and higher PUFA content. The observed differences between the CH and UHPH treatments can be attributed to the structuring of fat-protein-BM into colloidal particles based on the homogenization system employed in this study. Neither of the homogenization systems nor the SDE content impacted yogurt flavor.

Application of multiple ultra-high-pressure homogenization to the pasteurization process of Japanese rice wine, sake

Hiire is a pasteurization process in the production of Japanese rice wine (sake), which stabilizes the quality of product; however, it also generates the carcinogen ethyl carbamate (EC). In this study, we investigated the application of ultra-high-pressure homogenization (UHPH) as an alternative sterilization method for sake production. Microbiological analysis revealed that multiple UHPH treatments sterilized hiochi lactobacilli (Lactobacillus fructivorans, L. homohiochii, L. casei, and L. hilgardii) and Saccharomyces cerevisiae. Enzyme activity assays revealed that α-amylase, glucoamylase, and acid-carboxypeptidase activities were reduced to less than 1% of the levels in non-pasteurized sake after four-time UHPH treatment. These results show that UHPH treatment meets the two requirements of the sake sterilization process sterilization and enzyme inactivation. The UHPH-processed sake did not show any significant changes in general properties but had reduced organic acid and aromatic component contents, with ethyl caproate content showing the most significant reduction of approximately 20%. Interestingly, EC was detected in pasteurized sake but not in UHPH-processed sake. These findings indicate that the UHPH technology could be used to inactivate microorganisms and enzymes in sake without generating EC.

Effect of ultra-high pressure homogenization on structural and techno-functional properties of egg yolk granule proteins

The impact of ultra-high pressure homogenization (UHPH) (175 and 300 MPa, 1 and 4 passes) on the structure of egg yolk granule was evaluated to improve the techno-functional properties of the proteins. The UHPH treatment destabilized and modified the structure of egg yolk granule proteins, which was validated by protein profiles from gel electrophoresis. A decrease of free thiol and an increase of disulfide bond content was correlated with a decrease of the surface hydrophobicity, specifically at 300 MPa with 4 passes. The structural modifications induced by UHPH, mainly at 300 MPa (1 and 4 passes), improved the water and oil binding capacities of egg yolk granules with values ranging from 1.30 to 1.55 gwater/ggranule and 3.34 to 3.73 goil/ggranule, respectively as well as their stability index. However, egg yolk granule solubility was not impacted by the application of UHPH. These new insights are key to supporting the development of new egg yolk granule-based ingredients for the food industry.

Effect of reverse osmosis and ultra-high-pressure homogenization on the composition and microstructure of sweet buttermilk

Buttermilk (BM), the by-product of butter making, is similar to skim milk (SM) composition. However, it is currently undervalued in dairy processing because it is responsible for texture defects (e.g., crumbliness, decreased firmness) in cheese and yogurt. One possible way of improving the incorporation of BM into dairy products is by the use of technological pretreatments such as membrane filtration and homogenization. The study aimed at characterizing the effect of preconcentration by reverse osmosis (RO) and single-pass ultra-high-pressure homogenization (UHPH) on the composition and microstructure of sweet BM to modify its techno-functional properties (e.g., protein gel formation, syneresis, firmness). The BM and RO BM were treated at 0, 15, 150, and 300 MPa. Pressure-treated and control BM and RO BM were ultracentrifuged to fractionate them into the following 3 fractions: a supernatant soluble fraction (top layer), a colloidal fraction consisting of a cloudy layer (middle layer), and a high-density pellet (bottom layer). Compositional changes in the soluble fraction [lipid, phospholipid (PL), protein, and salt], as well as its protein profile by PAGE analysis, were determined. Modifications in particle size distribution upon UHPH were monitored by laser diffraction in the presence and absence of sodium citrate to dissociate the casein (CN) micelles. Microstructural changes in pressure-treated and non-pressure-treated BM and RO BM particles were monitored by confocal laser scanning microscopy. Particle size analysis showed that UHPH treatment significantly decreased the size of the milk fat globule membrane fragments in BM and RO BM. Also, pressure treatment at 300 MPa led to a significant increase in the recovery of total lipids, CN, calcium, and phosphate in the BM soluble fraction (top layer) following ultracentrifugation. However, PL were primarily concentrated in the pellet cloud (middle layer), located above the pellet in BM concentrated by RO. In contrast, PL were evenly distributed between soluble and colloidal phases of BM. This study provides insight into the modifications of sweet BM constituents induced by RO and UHPH from a compositional and structural perspective.

Effect of Ultra-High-Pressure Homogenization Processing on the Microbiological, Physicochemical, and Sensory Characteristics of Fish Broth.

The effect of ultra-high-pressure homogenization (UHPH) treatments at 300 MPa at inlet temperatures (Ti) between 45 and 75 °C on the microbiological, physical, and sensorial characteristics of fish broth was evaluated. Before the application of UHPH treatments, different fish broth formulations were tested, selecting the formula with the best organoleptic and nutritional characteristics and the lowest cost, containing 45% monkfish heads and rock fish in the same proportion. The microbiological shelf-life of fish broth during cold storage at 4 and 8 °C was extended by a minimum of 20 days by applying UHPH treatments at inlet temperatures (Ti) between 45 and 65 °C. Fish broth UHPH-treated at Ti = 75 °C was microbiologically sterile during storage at 4 °C, 8 °C, and room temperature. Fish broth UHPH-treated was physically stable, significantly reducing the particle size. Color showed higher luminosity and lower yellowness as the inlet temperature increased. In fish broth UHPH-treated at Ti = 75 °C, selected for its microbiological stability, no differences were observed in the nutritional composition, antioxidant activity, and sensorial perception compared to untreated fish broth. Hence, UHPH treatments showed to be an alternative to preserving fish broth with an improved microbiological shelf-life and good sensorial characteristics.

Impact of Ultra-High Pressure Homogenization on the Structural Properties of Egg Yolk Granule.

Ultra-high pressure homogenization (UHPH) is a promising method for destabilizing and potentially improving the techno-functionality of the egg yolk granule. This study’s objectives were to determine the impact of pressure level (50, 175 and 300 MPa) and number of passes (1 and 4) on the physico-chemical and structural properties of egg yolk granule and its subsequent fractions. UHPH induced restructuration of the granule through the formation of a large protein network, without impacting the proximate composition and protein profile in a single pass of up to 300 MPa. In addition, UHPH reduced the particle size distribution up to 175 MPa, to eventually form larger particles through enhanced protein–protein interactions at 300 MPa. Phosvitin, apovitellenin and apolipoprotein-B were specifically involved in these interactions. Overall, egg yolk granule remains highly stable during UHPH treatment. However, more investigations are needed to characterize the resulting protein network and to evaluate the techno-functional properties of UHPH-treated granule.

Cabernet Sauvignon Red Must Processing by UHPH to Produce Wine Without SO2: the Colloidal Structure, Microbial and Oxidation Control, Colour Protection and Sensory Quality of the Wine

A cryo-macerated must of V. vinifera L. cabernet sauvignon was processed by ultra-high-pressure homogenisation (UHPH) sterilisation without the use of SO2. The UHPH treatment of the must was carried out continuously at a pressure of 300 MPa and reaching a maximum temperature of 77 °C for less than 0.2 s. The colloidal structure of the UHPH must was evaluated by atomic force microscopy (AFM) measuring an average particle size of 457 nm. The initial microbial load was 4-log CFU/mL (yeast), 3-log CFU/mL (bacteria). No yeast and non-sporulating bacteria were detected in 1 mL and 10 mL of the UHPH-treated must, respectively. Furthermore, no fermentative activity was detected in the non-inoculated UHPH-treated musts for more than 50 days. A strong inactivation of the oxidative enzymes was observed, with lower oxidation (≈ × 3) than controls. The antioxidant activity of the UHPH-treated must was much higher (106%) than that of the control must. UHPH had a protective effect in total anthocyanins, and especially in acylated anthocyanins (+ 9.3%); furthermore, the fermentation produces fewer higher alcohol (-44,3%) and more 2-phenylethyl acetate (+ 63%).

Ultra-high-pressure homogenization can modify colloidal, interfacial, and foaming properties of whey protein isolate and micellar casein dispersions differently according to the temperature condition

We investigated how temperature condition during ultra-high-pressure homogenization (UHPH) affects the colloidal, interfacial, and foaming properties of whey protein isolate (WPI) and micellar casein (MC) using the one of UHPH device, Star Burst (SB). While UHPH treatment generally induces both mechanical force and heating under high operating pressure, we differentiated the effects of “mechanical force (below denaturation point of whey proteins)” and “combination of mechanical force and heating (above denaturation point of whey proteins)” on the proteins by controlling the protein dispersion temperature prior to the SB treatment at 240 MPa. For WPI, the combined use of mechanical force and heating induced the exposure of protein hydrophobic regions leading to a more increase in foaming ability while the sole use of mechanical force caused a more decrease in foam stability due to less adsorption efficiency at the interface. For MC, the sole effect of mechanical force strongly increased foaming ability and foam stability due to the large particle size reduction, rather than the combined use. These results suggested that SB treatment can contribute to expand the possibilities of development of new materials possessing unique physicochemical and functional properties by controlling treatment conditions.

Resistance of detached-cells of biofilm formed by Staphylococcus aureus to ultra high pressure homogenization

Staphylococcus aureus is one of the main pathogens contributing to foodborne outbreaks, owing in part to its ability to form biofilms on food-contact surfaces. Cells that can detach from mature biofilms are a source for microbial cross-contamination in liquid food systems. The study was to evaluate and compare the resistance of detached-cells of biofilm formed by S. aureus and planktonic cells to Ultra High Pressure Homogenization (UHPH), a non-thermal technology applied in food processing. The results showed that the survival of both detached-cells and planktonic cells was dependent upon the applied pressure ranging from 30,000 PSI to 40,000 PSI, and cycle numbers with 1 and 3. A significant difference in UHPH resistance was observed at pressures of 35,000 PSI to 40,000 PSI whereby planktonic cell numbers were reduced about 2.0 log CFU/mL compared to a 0.5 log CFU/mL reduction of detached-cells. Cell resistance was further evaluated following UHPH by measuring membrane integrity and potential, as well as observing the cells using scanning electron microscopy (SEM). SEM images revealed more scattered exopolysaccharides in the biofilm after UHPH treatment compared to the control. Additionally, UHPH treatment resulted in planktonic cells having a greater shift to smaller cell size and a wider cell size distribution compared with detached-cells; this indicated a higher resistance of detached-cells to UHPH. This finding suggests that although UHPH has great potential application in food sterilization, the resistance of detached-cells cannot be ignored.

Evaluation of Mycobacterium smegmatis as indicator of the efficacy of high hydrostatic pressure and ultra-high pressure homogenization treatments for pasteurization-like purposes in milk.

The objectives of this study were: to assess the efficiency of high hydrostatic pressure or ultra-high pressure homogenization against Mycobacterium smegmatis in milk and to discuss whether M. smegmatis can be considered a suitable surrogate for other Mycobacterium spp. in high pressure inactivation trials using milk. Three strains of this specie (CECT 3017, 3020 and 3032) were independently inoculated into both skimmed (0.2% fat) and whole milk (3.4% fat) at an approximate load of 6.5 Log CFU/ml and submitted to HHP treatments at 300, 400 or 500 MPa for 10 m at 6°C and 20°C. Evolution of the surviving cells of the inoculated strains was evaluated analysing milk immediately after the treatments and after 5 and 8 d of storage at 6°C. HHP treatments at 300 MPa were seldom efficient at inactivating M. smegmatis strains, but lethality increased with pressure applied in all cases. Generation of sub-lethal injured cells was observed only after 400 MPa treatments since inactivation at 500 MPa was shown to be complete. Significant differences were not observed due to either temperature of treatment or fat content of milk, except for strain CECT3032, which was shown to be the most sensitive to HHP treatments. Milk inoculated with strain CECT3017 was submitted to ultra-high pressure homogenization (UHPH) treatments at 200, 300 and 400 MPa. Maximum reductions were obtained after 300 and 400 MPa treatments, although less than 3.50 Log CFU/ml were inactivated. UHPH did not cause significant number of injured cells. The usefulness of this species as a marker for pressure-based processing seems limited since it showed greater sensitivity than some pathogenic species including other Mycobacteria reported in previous studies.

Effect of single and combined UV-C and ultra-high pressure homogenisation treatments on inactivation of Alicyclobacillus acidoterrestris spores in apple juice

Alicyclobacillus acidoterrestris is a spore-forming bacterium that can survive thermal pasteurization and acidic conditions. It produces changes in the odour and flavour of fruit juices leading to economical loses. A. acidoterrestris CECT 7094 spores were inoculated in clarified and cloudy apple juices (Golden delicious var.) in the range of 5–6 log10 spores/mL and submitted to different short-wave ultraviolet light (UV-C) doses (7.2–28.7 J/mL) and ultra-high pressure homogenisation (UHPH) treatments (100–300 MPa), including their combination. A. acidoterrestris could be inactivated in clarified apple juice at a level of 4.8 log10 CFU/mL by a 300 MPa-UHPH treatment when the inlet temperature was 80 °C. UV-C treatments showed to be more efficient achieving a lethality of 5.5 log10 CFU/mL with a dose of 21.5 J/mL at 20 °C. In cloudy apple juice (2357 NTU) UV-C treatments were less efficient with a maximum lethality of 4.07 CFU/mL after a dose of 28.7 J/mL. A previous application of UHPH contributed with UV-C to obtain higher reductions of A. acidoterrestris spores at the doses of 14.3 and 21.5 J/mL compared with UV-C single treatments. On the other hand, this previous treatment also changed the properties of particles in the matrix which apparently reduced the effectiveness of UV-C at 28.7 J/mL.

Combined use of natural antimicrobial based nanoemulsions and ultra high pressure homogenization to increase safety and shelf-life of apple juice

The present research was aimed to investigate the potentialities of ultra high pressure homogenization (UHPH) to produce stable natural antimicrobial based nanoemulsions. Initially, the nanoemulsions were characterized for their size, stability over time and antimicrobial properties against several pathogenic and spoilage microorganisms. After that nanoemulsions were tested to increase the safety and shelf-life of apple juice deliberately inoculated with pathogenic (Listeria monocytogenes Scott A, Staph. aureus SR231, Escherichia coli 555) and spoilage microorganisms (Saccharomyces cerevisiae SPA, Lactobacillus plantarum 82) and treated with different high pressure homogenization treatments. The analyses performed by dynamic laser light scattering showed that the hexanal and trans-2-hexenal based nanoemulsions were characterized by an average size of 86 and 100 nm, respectively while they were characterized by a stability, over time, of 14 months without separation. Moreover, the nanoemulsions resulted, after the UHPH treatment, colourless. The pathogenic species deliberately inoculated in apple juice decreased their cell loads with different kinetics in relation to the use of hexanal and trans-2-hexenal and high pressure homogenization treatment applied. Regarding spoilage microorganisms, S. cerevisiae cell loads decreased under detection limit (1 log CFU/mL) in juice containing nanoemulsions and treated at 200 MPa for 2 cycles. The data of the present research contribute to support the application of natural antimicrobial based nanoemulsions into complex food system, enlarging the experimental evidence for their use in food sector. In particular, the obtained hexanal and tran-2-hexenal based nanoemulsions have demonstrated great application, due also to their organoleptic compatibility, to the fruit juice sector, promoting also an increase of quality of apple juice.

Effect of dynamic ultra-high pressure homogenization on the structure and functional properties of whey protein.

The effects of dynamic ultra-high pressure homogenization (UHPH) on the structure and functional properties of whey protein were investigated in this study. Whey protein solution of 10mg/mL (1% w/w) was prepared and processed by a laboratory scale high pressure homogenizer with different pressures (25, 50, 100, 150, 200, and 250MPa) at an initial temperature of 25°C. Then, the solution samples were evaluated in terms of secondary structure, sulfhydryl and disulfide bond contents, surface hydrophobicity, average particle size, solubility, foaming capacity, emulsifying activity, and thermal properties. It was found that the secondary structure of whey protein changed with the dynamic UHPH treatment. The interchange reaction between the disulfide bond and the sulfhydryl group was promoted and the surface hydrophobicity significantly increased. The functional properties of the whey protein accordingly changed. Specifically, after dynamic UHPH treatment, the average particle size of the whey protein and emulsion decreased while the solubility, the foaming capability and the emulsification stability increased significantly. The results also revealed that with the dynamic UHPH at 150MPa, the best improvement was observed in the whey protein functional properties. The whey protein solubility increased from 63.15 to 71.61% and the emulsification stability improved from 195 to 467min.

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.

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.

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.

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.