A la cerca de tecnologies per mantenir les propietats organoleptiques originals dels aliments amb un processament minim que garanteixi alhora la inactivacio de microorganismes, en els ultims anys s'estan investigant solucions no termiques. El Centre d'Innovacio, Recerca i Transferencia en Tecnologia dels Aliments (CIRTTA) de la UAB ha incorporat una d'aquestes tecnologies: un equip de radiacio ultraviolada d'ona curta (UCV), amb que els investigadors han obtingut resultats d'alta efectivitat en sucs, brous i infusions. Ara el centre de recerca prepara una jornada de demostracio que tindra lloc el primer trimestre del proxim any.

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.

Microstructure, physical properties and oxidative stability of emulsions treated by colloid mill (CM), conventional homogenization (CH, 15 MPa) and ultra-high-pressure homogenization (UHPH, 100-300 MPa) by using different concentrations of 1, 3 and 5 g/100 g of sodium caseinate (SC), were evaluated. The application of UHPH treatment at 200 and 300 MPa resulted in emulsions that were highly stable to creaming and oxidation, especially when the protein content increased from 1 to 3 and 5 MOO g. Further, increasing the protein content to 3 and 5 g/100 gin UHPH emulsions tended to change the rheological behavior from Newtonian to shear thinning. CH emulsions containing 1 g/100 g of protein exhibited Newtonian flow behavior with lower tendencies to creaming compared to those formulated with 3 or 5 g/100 g. This study has proved that UHPH processing at pressures (200-300 MPa) and in the presence of sufficient amount of sodium caseinate (5 g/100 g), produces emulsions with oil droplets in nano-/submicron scale with a narrow size distribution and high physical and oxidative stabilities, compared to CM and CH treatments. (C) 2016 Elsevier Ltd. All rights reserved.

Although, the High Hydrostatic Pressure (HHP) technology has been gaining gradual popularity in food industry since last two decades, intensive research is needed to explore the missing information. Bacterial inactivation in food by using HHP applications can be enhanced by getting deeper insights of the process. Some of these aspects have been already studied in detail (like pressure, time, and temperature, etc.), while some others still need to be investigated in more details (like pH, rates of compression, and decompression, etc.). Selection of process parameters is mainly dependent on type of matrix and target bacteria. This intensive review provides comprehensive information about the variety of aspects that can determine the bacterial inactivation potential of HHP process indicating the fields of future research on this subject including pH shifts of the pressure treated samples and critical limits of compression and decompression rates to accelerate the process efficacy.

Oil-in-water pre-emulsions (15% sunflower + 5% olive oils) obtained by colloid mill homogenization (CM) at 5000 rpm using whey protein isolate at different levels (1, 2 and 4%) were stabilized by ultra high-pressure homogenization (UHPH, 100 and 200 MPa) and by conventional homogenization (CH, 15 MPa). Emulsions were characterized for their physical properties (droplet size distribution, microstructure, surface protein concentration, emulsifying stability against creaming and coalescence, and viscosity) and oxidative stability (hydroperoxide content and thiobarbituric acid reactive substances, TBARs) under light (2000 lux/m(2) for 10 days). UHPH produced emulsions with lipid droplets of small size in the sub-micron range (100-200 nm) and low surface protein with unimodal distribution when produced at 4% whey proteins and 200 MPa. All emulsions exhibited Newtonian behavior (n approximate to 1). Long term physical stability against creaming and coalescence was observed in UHPH-emulsions, compared to those obtained by CM and CH. However, CH emulsions were highly stable against creaming (days) in comparison to the CM emulsions (hours). UHPH resulted in emulsions highly stable to oxidation compared to CM and CH treatments, especially when 100 MPa treatment was applied.Industrial relevance: In the food, cosmetic and pharmaceutical sectors, industrial operators are currently interested in developing encapsulating systems to delivery bioactive compounds, which are generally hydrophobic, unstable and sensitive to light, temperature or/and oxygen. Ultra high-pressure homogenization is capable of producing stable submicron emulsions (<1 mu m) with a narrow size distribution, inducing more significant changes in the interfacial protein layer thus preventing droplet coalescence and also inhibit lipid oxidation. The present study suggests that emulsions produced by whey protein (4%) treated by ultra high-pressure homogenization have a good physical stability to flocculation, coalescence and creaming and also high stability to lipid oxidation, opening a wide range of opportunities in the formulation of emulsions containing bioactive components with lipid nature. (C) 2015 Elsevier Ltd. All rights reserved.

Staphylococcus aureus ATCC6538 was inoculated in skimmed milk, orange juice, and Tris buffer samples. Inoculated samples were subjected to high hydrostatic pressure (HHP) treatments at 700 MPa for 5 min at 4 °C starting temperature with fast, medium, and slow rates of compression and decompression. The objective of this study was to determine the effects of changing rates of compression and decompression on inactivation of S. aureus during HHP processing. Immediate effect of different HHP treatments was not significantly different. However, during subsequent storage in refrigeration, highest microbial inactivation was the result of treatments with fast compression and slow decompression rates in all matrices.

The effect of compression and decompression rates of high hydrostatic pressure (HHP) on Escherichia coli O157:H7 was investigated. Samples of orange juice, skimmed milk and Tris buffer were inoculated with E. coli O157:H7 and subjected to 600MPa for 3min at 4 degrees C with fast, medium and slow compression and decompression. Analyses immediately after HHP treatment revealed that E. coli in milk and juice treated with fast compression suffered more than slow compression rates. Slow decompression resulted in higher inactivation of E. coli in all matrices. After overnight storage, highest stress-recovery (1.19logcfu/mL) was observed in Tris buffer. Healthy cells were<1logcfu/mL in milk and buffer samples, but no growth was detected in orange juice for any of the treatments immediately after HHP. After 15 days at 4 degrees C, E. coli cells in skimmed milk and Tris buffer recovered significantly, whereas the recovery of sublethally injured cells was inhibited in orange juice.

Ultra high pressure homogenization (UHPH) is a non-thermal technology capable of producing emulsions, inducing microbial and enzymatic inactivation and confering new functional characteristics, due to changes in the structures of produced foods. Emulsions containing 1.5 % of sodium caseinate (SC) and 20 % oil (15 % sunflower + 5 % olive) were obtained by colloidal mill (CM, 5000 rpm for 5 min) and by ultra-high pressure homogenization (UHPH, 50300 MPa). Emulsions were characterized for their physical properties including rheological behaviour, surface protein concentration, visual stability to creaming and oxidative stability under light (2000 lux/m 2 ). The particle size of the CM emulsions was significantly reduced (P < 0.05) by UHPH treatments, although the differences between UHPH treatments were scarce. All CM emulsions were visually totally separated in 2 h; however, no visual separation was observed in all UHPH emulsions even after 20 days of cold storage. Examination of the rheological properties of emulsions in all cases exhibited Newtonian behaviour (n ≈ 1), showing higher viscosity in UHPH emulsions than CM emulsions, although these differences were only significant in emulsions treated at 50 MPa. The oxidative stability analyses revealed a significant increase (P < 0.05) in both primary and secondary oxidation products in CM emulsions as compared to UHPH emulsions.

The effect of including citrus fruits (CF) and artichoke silage (AS) in the rations of dairy ewes on texture, colour and sensorial characteristics of ripened cheeses was evaluated. This study was carried out over a two-year period. During each lactation period four groups of ewes were fed with rations containing 0, 10, 20 and 30% of either CF or AS in a dry matter basis. Bulk milk samples were collected three times during each experimental period and semi-hard cheeses were manufactured and sampled during ripening. Cheese colour was significantly influenced by the increase of citrus fruits in the ration so that these ripened cheeses presented a "yellower" colour compared to control cheeses. Texture and sensory parameters of ripened cheese were not influenced by the inclusion of citric fruits. Artichoke silage in the rations did not affect colour or texture of ripened cheeses. Sensory evaluation revealed that inclusion of artichoke silage did not reduce the overall impression scores of cheese; on the contrary the highest score was for cheeses corresponding to 10% of artichoke silage in the ration. According to our results, the inclusion of these two by-products in the diet of lactating ewes does not impair the sensory and textural characteristics of 60-day-old cheeses.

We investigated the effect of changing compression and decompression rates of High Hydrostatic Pressure (HHP) treatments on inactivation of spores. Bacillus subtilis (PS832) spores were inoculated in Tris buffer, skimmed milk and orange juice. The samples were subjected to HHP treatments of 600 MPa for 3 min at 60 degrees C and 70 degrees C. Microbiological analyses were carried out at 0, 1, 7 and 15 days of refrigeration storage (4-5 degrees C). Flow cytometery technique was used for the estimation of sublethally injured population. After 15 days, all pressure treated matrices at 70 degrees C showed higher spore inactivation caused by slower compression rates as compared to faster ones. However, at 60 degrees C, the inactivation caused by slower compression was not significantly different from faster rates. Slow decompression was found to be more lethal in 60 degrees C and 70 degrees C HHP treated samples. It is concluded that slow compression combined with slow decompression has a greater impact on inactivation of B. subtilis spores than any combination of fast compression and fast decompression at 60 degrees C and 70 degrees C processing temperatures. However the population of sub-lethally injured cells was found to be higher with fast compression and slow decompression rates. (C) 2011 Elsevier Ltd. All rights reserved.

The use of reduced isomerised hop extracts to achieve both bitterness and light stability became very popular during the last decade. Changes during storage in four hop extracts and seven commercial lager beers are studied using HPLC and spectrophotometric techniques. The degradation of the iso-α-acids and tetrahydro iso-α-acids as a function of time is represented by the ratio, in percentage, of the sum of trans-isomer concentration to the sum of the cis-isomer concentration (T/C). The results provided conclusive evidence that the gradual decreased of bitterness intensity in beer was due to the degradation of iso-α-acids, notably to the instability of the trans-iso-α-acids. When the beers were stored for 14 days at 45°C the decrease of the T/C average varied from 8.6 to 14.0%, except in lemon beer, in which case, T/C decreased 36.9%. The results allowed us to infer that in open storage and/or warm conditions the deterioration of beer was critical above 35°C. On the other hand, the results showed that tetrahydro iso-α-acids remained unaltered.

The effect of including citrus fruits (CF) in the rations of dairy ewes on the milk characteristics and biochemical changes of cheeses during ripening was evaluated. For this purpose, 48 lactating ewes (Guirra breed) were divided into 4 homogeneous groups and fed with isoenergetic and isoprotein rations containing CF at 0, 10, 20, and 30% on a dry matter basis in substitution of dry barley and pelleted beet pulp. During the experimental period, 3 batches of bulk milk were collected from each group and semi-hard cheeses were manufactured. Cheeses were sampled at 15, 30, and 60 d of ripening. Milk coagulation parameters and cheese yield were not negatively affected by the inclusion of CF in the ration. Physicochemical composition of cheeses at 60 d showed statistical differences for lower total solids and fat content of 30% CF cheeses. Proteolysis of cheeses measured by water-soluble nitrogen and total free amino acids content was not influenced by the ration. Differences between rations with respect to free fatty acids were significant for medium- and long-chain free fatty acids, and therefore for total content, but differences did not show a trend related to the increase of CF in the diet. The inclusion of CF in the ration of lactating ewes up to levels of 30% did not negatively affect the properties of milk and the biochemical and sensory characteristics of cheeses.

Plasmin residual activity and its relation to proteolysis of milk subjected to ultra-high pressure homogenisation (UHPH; 200–300MPa, inlet temperature=30°C and 40°C) and to a high-pasteurisation treatment (90°C, 15s) were studied during refrigerated storage. Proteolysis was examined by capillary electrophoresis, HPLC peptide profiles, pH 4.6-soluble nitrogen and free amino acids. Inactivation of plasmin increased as homogenisation pressure did. Extensive proteolysis, was observed in 200MPa 40°C milk, due to its higher native and microbial enzyme contents, compared with the other samples. In general, hydrolysis of β-casein, hydrophobic peptide and pH 4.6-soluble nitrogen levels increased with higher residual plasmin activity, while hydrophilic peptides were not affected by the different treatments applied. β-Lactoglobulin was denatured to a greater extent by thermal treatment than by UHPH treatments. This study provides further insight into how UHPH treatments influence milk properties.

Ewe milk cheeses were submitted to 200, 300, 400, and 500 MPa (2P to 5P) at 2 stages of ripening (after 1 and 15 d of manufacturing; P1 and P15). The high-pressure-treated cheeses showed a more important hydrolysis of beta-casein than control and 2P1 cheeses. Degradation of alpha(s1)-casein was more important in 3P1, 4P1, and P15 cheeses than control and 2P1 cheeses. The 5P1 cheeses exhibited the lowest degradation of alpha(s)-caseins, probably as a consequence of the inactivation of residual chymosin. Treatment at 300 MPa applied on the first day of ripening increased the peptidolytic activity, accelerating the secondary proteolysis of cheeses. The 3P1 cheeses had extensive peptide degradation and the highest content of free amino acids. Treatments at 500 MPa, however, decelerated the proteolysis of cheeses due to a reduction of microbial population and inactivation of enzymes.

The free fatty acid (FFA) profile of high pressure treated ewes' milk cheeses were studied to assess the effect of pressure treatment on cheese lipolysis. Cheeses were treated at 200, 300, 400 or 500 MPa (2P to 5P) at two stages of ripening (after 1 and 15 days of manufacturing; P1 and P15) and FFA were assayed at 1, 15 and 60d ripening. On the first day of ripening, 3P1-cheeses showed levels of FFA twice that of the control cheeses. However, no significant differences were found between 3P1 and control cheeses at 60 d ripening. On the contrary, 4P1 and 5P1-cheeses had the lowest total FFA levels. The point at which pressure treatment was applied influenced the FFA profile of cheeses; cheeses pressurized at pressures < 400 MPa on the first day of ripening were more similar to untreated cheeses than their homologues treated at 15 d.

High-pressure (HP) processing was investigated for determining potential changes induced on textural, rheological, sensory and compositional characteristics of semi-hard ewes’ milk cheeses. Pressures from 200 to 500MPa were applied at day 1 or day 15 after manufacture. Applying pressure on the first day after cheese manufacture caused an increase in pH and also increased the retention of remaining water into the curd after HP treatment. Applying pressure on day 15 of ripening led to chesses with characteristics more similar to control cheeses. Different behavior on mechanical characteristics was observed depending on the pressure conditions applied. Moderate pressures (200 and 300MPa) enhanced the firming of cheeses, which was demonstrated in the increase of fracture stress and G* values. The highest conditions of pressure applied, especially 500MPa, produced a weakening effect in the casein matrix. These cheeses showed the highest deformability and the lowest fracturability and rigidity. The sensory panel also found this treatment to produce the softest, less elastic and less crumbly cheeses. On the other hand, cheeses treated by HP at day 15 were similar to the control and preferred by the panel.

Lactic acid bacteria isolated from raw milk of Guirra ewes were characterised from a technological point of view, in order to select the suitable strains for their use as a cheese starter. Lactococcus lactis subsp. lactis, which represented more than 67% of the fast acid-producer bacteria in raw milk, exhibited no differences in their acidifying activity after 24h of incubation. Most lactobacilli were weak acid-producers, showing a great variation in their acidifying activity. Four strains of Lactobacillus paracasei subsp. paracasei, 1 of Lb plantarum and 1 of Lb. pentosus exhibited high proteolytic capacity. Enzyme activity (API-ZYM assay) of lactococci and lactobacilli was generally low. Lactobacillus spp. all showed esterase and esterase-lipase activity, and in general, they had higher aminopeptidases values than those observed in L. lactis subsp. lactis. There was no endopeptidase activity in any of the lactococci tested, but most lactobacilli showed slight a-chymotrypsin activity. Alkaline phosphatase was not detected among the lactococci and lactobacilli, but acid phosphatase activity was observed.

The extent of primary and secondary proteolysis of cheeses made from raw (RA), pasteurized (PA, 72 degrees C, 15 s) or pressure-treated (PR, 500 MPa, 15 min, 20 degrees C) goats' milk was assessed. Modifications in cheese-making technology were introduced to obtain cheeses with the same moisture content, and thus studied per se the effect of milk treatment on cheese proteolysis. The PR milk cheese samples were differentiated from RA and PA milk cheeses by their elevated beta-lg content, and by the faster degradation of alphas1-, alphas2- and beta-CN throughout ripening. Non-significant differences were found in either pH 4.6 soluble-nitrogen or trichloracetic acid soluble-nitrogen contents of cheeses. However, the pasteurization of milk decreased the free amino acid production in cheese. The RA milk cheeses had the highest amount of proline and the lowest concentrations of serine, tyrosine, arginine and alpha-aminobutyric acid, whereas PR milk cheese showed higher levels of arginine.

Ewe's milk cheeses at different stages of ripening (1 and 15 days) were subjected to high pressure (HP) in the range of 200-500 MPa at 12 degrees C for 10 min in order to study the possibility of cheese ripening acceleration. Microbiological counts (total counts, lactococci and lactobacilli) were reduced as pressure increased, specially those treatments carried out at :400 MPa. Water soluble nitrogen at pH 4.6 expressed as % total N (WSN/TN) and total free amino acids (FAA) were used as index of proteolysis. At the end of ripening, cheeses pressurized at 15 days of ripening had higher WSN/TN values than those treated at day 1, with cheeses treated at 300 MPa obtaining the highest values. The application of 300 MPa treatments led to an increase in the FAA content compared to control cheeses, particularly when HP treatment was applied at day 1. Treatments at 500 MPa resulted in lower FAA contents than control cheeses, suggesting that pressures > 400 MPa delay the FAA formation. Enhancement of proteolysis observed at 300 MPa may be attributed to HP-produced cell lysis and enzymes release, although HP-induced conformational changes in protein cheese matrix could play also a role.