Ultra-high Pressure Homogenization Research Articles

Inactivation of Saccharomyces cerevisiae and Lactobacillus plantarum in orange juice using ultra high-pressure homogenisation

Yeasts and lactic acid bacteria are the usual contaminants in orange juice and responsible for decreasing the shelf life of the product. Ultra high-pressure homogenisation has been shown to be an alternative to the traditional thermal pasteurisation of pumpable foods. The product was pumped through a homogeniser valve at 100 MPa, 150 MPa, 200 MPa, 250 MPa and 300 MPa using two synchronized overlapped intensifiers at a flow rate of approximately 270 mL/min. The inlet temperature was kept at 10 °C, pH at 4.1 and soluble solids at 10.0 °Bx. After processing, the product was immediately cooled to 4 °C and the microbiological count was determined. The study showed that Lactobacillus plantarum and Saccharomyces cerevisiae are sensible to ultra high-pressure homogenisation treatment. The results indicated that pressures higher than 250 MPa were able to completely destroy initial loads of 1.2 × 107 UFC/mL of L. plantarum and 2.9 × 105 UFC/mL of S. cerevisiae in orange juice, making this technology a promising way to nonthermally process orange juices. This paper deals with inactivation of microorganism contaminants of orange juice using dynamic ultra high process technology. It is of industrial interest and relevance to evaluate the use of this non-thermal emerging technology to process fluid foods that may result into better taste, optimum product functionality, safety and quality characteristics.

Effects of Ultra-High Pressure Homogenization on the Cheese-Making Properties of Milk

The effects of single- or 2-stage ultra-high pressure homogenization (UHPH; 100 to 330MPa) at an inlet temperature of 30°C on the cheese-making properties of bovine milk were investigated. Effects were compared with those from raw, heat-pasteurized (72°C for 15s), and conventional homogenized–pasteurized (15 + 3MPa, 72°C for 15s) treatments. Rennet coagulation time, rate of curd firming, curd firmness, wet yield, and moisture content of curds were assessed. Results of particle size and distribution of milk, whey composition, and gel microstructure observed by confocal laser scanning microscopy were analyzed to understand the effect of UHPH. Single-stage UHPH at 200 and 300MPa enhanced rennet coagulation properties. However, these properties were negatively affected by the use of the UHPH secondary stage. Increasing the pressure led to higher yields and moisture content of curds. The improvement in the cheese-making properties of milk by UHPH could be explained by changes to the protein–fat structures due to the combined effect of heat and homogenization.

Limonene encapsulation in freeze-drying of gum Arabic–sucrose–gelatin systems

Encapsulation of limonene in freeze-drying of various matrices consisting of gum Arabic, sucrose and gelatin was studied. Retention of limonene in freeze-drying was observed by measuring absorbance at 252 nm using a spectrophotometer. Two different levels of limonene, in the weight ratios (w/w) of 9:1 and 8.5:1.5 (total solids (TS):limonene) were studied. Highest amount of limonene (75.3±0.3% of initially added amount) in the emulsions homogenised at 25 MPa (4 MPa in second stage) followed by freeze-drying, was retained in a matrix consisting of gum Arabic, in the ratio of 9:1 (w/w). A mixture consisting of gelatin–sucrose–gum Arabic in the w/w ratio of 0.66:0.17:0.17 retained highest amount (71.8±0.1% of initially added amount) of limonene in the ratio (w/w) of 8.5:1.5 (TS:limonene). A matrix consisting of gum Arabic–sucrose–gelatin (1:1:1 w/w/w) with added limonene at a ratio (w/w) of 9:1 (TS:limonene), was used to study the effects of ultra high-pressure homogenisation (50–250 MPa) on limonene encapsulation in freeze-drying. Highest amount (84% of initially added amount) of limonene was retained in the emulsions homogenised at a pressure of 100 MPa. Electron micrograph of freeze-dried matrix of gum Arabic–sucrose–gelatin in the weight ratio of 1:1:1 suggested that it possessed a flake like structure, which was free of dents and shrinkage. A mixture consisting of gum Arabic–sucrose–gelatin is an efficient encapsulant for limonene encapsulation by freeze-drying.

Fate of Staphylococcus aureus in Cheese Treated by Ultrahigh Pressure Homogenization and High Hydrostatic Pressure

We evaluated the influence of ultrahigh pressure homogenization (UHPH) treatment applied to milk containing Staphylococcus aureus CECT 976 before cheese making, and the benefit of applying a further high hydrostatic pressure (HHP) treatment to cheese. The evolution of Staph. aureus counts during 30 d of storage at 8°C and the formation of staphylococcal enterotoxins were also assessed. Milk containing approximately 7.3 log10 cfu/mL of Staph. aureus was pressurized using a 2-valve UHPH machine, applying 330 and 30MPa at the primary and the secondary homogenizing valves, respectively. Milk inlet temperatures (Tin) of 6 and 20°C were assayed. Milk was used to elaborate soft-curd cheeses (UHPH cheese), some of which were additionally submitted to 10-min HHP treatments of 400MPa at 20°C (UHPH+HHP cheese). Counts of Staph. aureus were measured on d 1 (24h after manufacture or immediately after HHP treatment) and after 2, 15, and 30 d of ripening at 8°C. Counts of control cheeses not pressure-treated were approximately 8.5 log10 cfu/g showing no significant decreases during storage. In cheeses made from UHPH treated milk at Tin of 6°C, counts of Staph. aureus were 5.0±0.3 log10 cfu/g at d 1; they decreased significantly to 2.8±0.2 log10 cfu/g on d 15, and were below the detection limit (1 log10 cfu/g) after 30 d of storage. The use of an additional HHP treatment had a synergistic effect, increasing reductions up to 7.0±0.3 log10 cfu/g from d 1. However, for both UHPH and UHPH+HHP cheeses in the 6°C Tin samples, viable Staph. aureus cells were still recovered. For samples of the 20°C Tin group, complete inactivation of Staph. aureus was reached after 15 d of storage for both UHPH and UHPH+HHP cheese. Staphylococcal enterotoxins were found in controls but not in UHPH or UHPH+HHP treated samples. This study shows a new approach for significantly improving cheese safety by means of using UHPH or its combination with HHP.

Inactivation of Staphylococcus spp. strains in whole milk and orange juice using ultra high pressure homogenisation at inlet temperatures of 6 and 20 °C

The objective of this work was to evaluate the inactivation induced by ultra high pressure homogenisation (UHPH) of Staphylococcus aureus ATCC 13565 and Staphylococcus carnosus CECT 4491 inoculated into milk and orange juice considering the effect of inlet temperature of the sample (6 and 20 °C) on the lethality values and on the production of sublethal injuries. Samples of UHT whole milk and UHT orange juice were inoculated at a concentration of approximately 7.0 log (CFU/ml) and pressurized with a dual valve UHPH machine at 300 MPa at the primary homogenising valve and at 30 MPa on the secondary valve. Viable and injured bacterial counts were measured 2 h after UHPH treatment and after 3, 6, and 9 days of storage at 4 °C for milk, and after 3, 6, 9, 12, and 15 days of storage at 4 °C for orange juice. The inlet temperature, the food matrix and the kind of strain influenced significantly ( P < 0.05) the lethality level, which was higher for S. aureus in whole milk at an inlet temperature of 20 °C. No sublethal injuries were detected after treatments. The change over time of viable counts for both strains showed a very strong decreasing tendency during the storage at 4 °C for orange juice, while the strain S. carnosus showed a low decreasing tendency and greater resistance when inoculated in milk and pressurized at 6 °C.

Inactivation by Ultrahigh-Pressure Homogenization of Escherichia coli Strains Inoculated into Orange Juice

The aim of this work was to evaluate the efficacy of ultrahigh-pressure homogenization (UHPH) for inactivation and/or sublethal injury of two strains of Escherichia coli (O58:H21 ATCC 10536 and O157:H7 CCUG 44857) inoculated into orange juice (pH 3.6). The effects of orange juice inlet temperature (6 and 20°C) on the lethality values and the capacity of these strains for survival, repair, and growth during refrigerated storage after UHPH treatment also was evaluated. Samples of orange juice that had been treated with ultrahigh temperatures were inoculated with E. coli in the stationary phase of growth until a final concentration of approximately 7.0 log CFU/ml was reached. These samples were then treated for one cycle with a double-valve UHPH machine, with 300 MPa at the primary homogenizing valve and 30 MPa at the secondary valve. Counts of viable and injured bacterial cells were obtained for samples taken 2 h after UHPH treatment and after 3, 6, 9, 12, 15, 18, 21, 27, and 33 days of storage at 4°C. The inlet temperature and the strain type both influenced significantly (P < 0.05) the lethality effect on E. coli, which was higher when the inlet temperature was 20°C. No sublethal injuries were detected after any treatment. The changes in viable counts over time for both strains in pressurized and control samples were similar. The viable counts remained high from day 0 to day 18 and then tended to decrease. After 27 days of storage at 4°C, E. coli O157: H7 was more resistant in orange juice samples pressurized at inlet temperatures of 6 and 20°C, with viable counts of 3.41 and 3.20 log CFU/ml, respectively.

Inactivation of two strains ofEscherichia coliinoculated into whole and skim milk by ultrahigh-pressure homogenisation

L'inactivation par homogeneisation a tres haute pression (UHPH) d'Escherichia coli ATCC 10536 et d'Escherichia coli O157:H7 CCUG 44857 inoculees au lait entier et au lait ecreme a ete etudiee. Des echantillons de lait entier ou ecreme UHT ont ete inocules avec des souches a une concentration approximative de 7,0 Log 10 (cfu·mL -1 ) et ont ensuite ete mis sous pression dans une machine de UHPH composee de deux pistons, le premier avec un systeme de soupape homogeneisant a 300 MPa, le second avec une soupape a 30 MPa. Les temperatures initiales du lait etaient de 6 °C et 20 °C. Le comptage des microorganismes vivants et ceux ayant subi des dommages a ete fait 2 heures apres le traitement UHPH et au 3 e , 6 e , et 9 e jours de conservation a 4 °C. La nature du lait a influence significativement (P < 0,05) le degre d'inactivation atteint pour les deux souches d' E. coli, et de maniere plus importante dans le lait entier pour une temperature de 20 °C. Le niveau d'inactivation etait similaire pour E. coli ATCC 10536 et E. coli O157:H7 CCUG 44857, atteignant respectivement les valeurs letales de 4,30 et 3,94 Log 10 cfu·mL -1 a une temperature initiale de 20 °C. Aucun dommage subletal n'a ete detecte sur les souches apres les traitements. L'evolution des microorganismes vivants durant la conservation a 4 °C etait similaire dans le lait entier et le lait ecreme. La souche E. coli O157:H7 CCUG 44857 a montre une tendance a la baisse de 0,3 unites logarithmiques et des differences significatives entre le 1 er jour et le 9 e jour de conservation.

Inactivation of Listeria innocua in Milk and Orange Juice by Ultrahigh-Pressure Homogenization

The aim of this work was to evaluate the bactericidal efficacy of ultrahigh-pressure homogenization (UHPH) against Listeria innocua ATCC 33090 inoculated into milk and orange juice. We also intended to study the effect of inlet temperature on the lethality and production of sublethal injuries in this microorganism and its ability to survive, repair, and grow in refrigerated storage after UHPH treatment. Samples of ultrahigh-temperature whole milk and ultrahigh-temperature orange juice inoculated at a concentration of approximately 7.0 log (CFU per milliliter) were immediately pressurized at 300 MPa on the primary homogenizing valve and at 30 MPa on the secondary valve, with inlet temperatures of 6.0 ± 1.0°C and 20 ± 1.0°C. L. innocua viable counts and injured cells were measured 2 h after UHPH treatment and after 3, 6, and 9 days of storage at 4°C for milk and after 3, 6, 9, 12, 15, 18, and 21 days of storage at 4°C for orange juice. Both the inlet temperature and the food matrix influenced significantly (P < 0.05) the inactivation of L. innocua, which was higher in whole milk at the 20°C inlet temperature. The UHPH treatment caused few or no sublethal injuries in L. innocua. During storage at 4°C after treatments, counts increased by approximately 2 logarithmic units from day 0 to 9 in whole milk, whereas in orange juice counts diminished by approximately 2.5 logarithmic units from day 0 to 18.

Functional properties of whey proteins as affected by dynamic high-pressure treatment

An ultra high-pressure homogenizer was used to treat whey protein isolate solutions (3%, w/w). The treated solutions (up to 300 MPa) were characterised for both physico-chemical properties (particle size distribution, surface hydrophobicity and structural conformation) and functional properties (solubility, foaming stability and interfacial rheology). Dynamic high-pressure treatment did not affect the conformation of the proteins (determined by micro-calorimetry, size-exclusion chromatography and electrophoretic technique). This treatment dissociated large protein aggregates leading to unmasking of the buried hydrophobic groups without affecting protein solubility. Interactions may then occur between these groups that enhance the viscoelasticity of air-water interfaces (assessed by drop tensiometry) and improve foam stability (evaluated by sparging method). Dynamic high-pressure-treated whey proteins showed better foaming and stabilising properties.

Effects of ultra-high-pressure homogenization and heating on structural properties of casein micelles in reconstituted skim milk powder

Reconstituted skim milk powder (RSMP) was homogenized at different pressures (41–186 MPa), and with up to six passes. The higher the pressure and the more passes employed, the smaller was the average diameter of the casein micelles. Different combinations of heat and pressure treatments were employed: control (C), homogenization at 186 MPa (H), heat (T) at 85 °C for 10 min, homogenization then heat (HT), and heat then homogenization (TH). The effect of homogenization on the decrease in micelle size was found to be H>TH>HT>T=C. The serum phase of homogenized milks (H) showed different protein size exclusion profiles compared with those from other treatments. The ultra-high-pressure homogenization (UHPH) was found to increase the amount of non-sedimentable caseins (κ, αs1 and αs2) in the serum. Electron microscopy showed formation of smaller particles following treatments H, TH, and HT when compared with C. It was concluded that UHPH was capable of modifying the structural properties of casein micelles and that the sequence of treatments was an important factor in determining the nature of the modifications.

Vitamin E Nanoparticle for Beverage Applications

In beverage fortification, the current vitamin E products on the market have problems with physical stability, turbidity, sensory issues and regulatory concerns. The problems were examined and potential solutions hypothesized. Based on the rationale found, a new product was designed specifically for beverage applications. The new product has an average particle size of around 100 nm, produced by ultra high-pressure homogenization and stabilized by microencapsulation with a food-approval starch. The vitamin E nanoparticle product is stable in beverage and does not visibly alter beverage appearance.

Degradation of methylcellulose during ultra-high pressure homogenisation

Initially developed for the dairy industry, the very high pressure homogenisation (>100 MPa) is now also applied in the pharmaceutical sector and in biotechnology (breaking cells for biomass extraction). The use of this technology to make fine food emulsions and to modify functional properties of macromolecules seems to be promising. Thus the objective of this study was to understand the effect of homogenisation forces on the mechanical degradation of a model polymer extensively used in food, cosmetic and pharmaceutical preparations: the methylcellulose. Degradation of the polymer was studied in a pressure range in the homogenising valve from 20 to 350 MPa. It was observed that as the pressure imposed by the homogeniser increased, the intrinsic viscosity decreased. Intrinsic viscosity decrease was correlated to apparent changes in the average molecular weight of the polymers obtained by size exclusion chromatography coupled on-line with multi-angle laser light scattering and refractive index detection (SEC/MALLS/RI). The strong elongational flow encountered by the polymer at the entrance of the valve of the high pressure homogeniser device may bring sufficient energy to disrupt covalent bonds. Consequently, as shown by flow behaviour the thickening properties of this polymer were also reduced.

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.

Effects of Microfluidizer® Technology on Bacillus licheniformis Spores in Ice Cream Mix

We studied the effect of Microfluidizer® technology (sometimes referred to as “microfluidization”), a new ultra-high pressure homogenization process, on spores of Bacillus licheniformis in ice cream mix. Four batches of pasteurized ice cream mix were preheated to 33, 36, 44, or 50°C, and spores of B. licheniformis were added to yield an inoculum of 2.0×104 spores/ml of mix. Samples were treated at 50,000, 100,000, 150,000, and 200,000 kPa. Respective percentages of spore destruction ranged from 6 to 68%. As process pressure in the Microfluidizer® system increased, the temperature of the product also increased. At the Microfluidizer® system outlet, temperatures ranged from 46 to 88°C. Therefore, a combination of forces, including high pressure and temperature, likely had a multiplier effect on spore destruction during Microfluidizer® processing of ice cream mix. Data suggest that it might be possible to design a pasteurizer-Microfluidizer® system that would inactivate most bacterial spores in dairy foods without the extreme heat treatment currently required in commercial processing operations.

超高圧乳化処理により得られた水溶性高分子／板状無機化合物からなるコロイド分散の特徴と化粧品への応用

超高圧乳化処理により得られた水溶性高分子／板状無機化合物からなるコロイド分散の特徴と化粧品への応用