Using High-Pressure Processing for Reduction of Proteolysis and Prevention of Over-ripening of Raw Milk Cheese

High-pressure-processing (HPP) at 400 or 600 MPa was applied to cheeses made from ewe raw milk, on days 21 or 35 after manufacturing, to reduce proteolysis and prevent over-ripening. The characteristics of HPP and non-pressurized (control) cheeses were compared during ripening at 8 °C until day 60 and further storage at 4 °C until day 240. HPP and control cheeses showed similar pH values throughout ripening, but on day 240 pH values remained 0.4–0.6 units lower for HPP cheeses than for the control cheeses. Casein degradation was significantly retarded in the 600 MPa cheeses. Their α-casein concentration was 48–52 % higher on day 60 and 30–33 % higher on day 240 than in the control cheeses while β-casein concentration was 25–26 % higher on day 60 and 100–103 % higher on day 240. No significant differences in para-κ-casein concentration between cheeses were found on day 60, but on day 240, it was 22–35 % higher in the 600 MPa cheeses than in the control cheese. Hydrophilic peptides, hydrophobic peptides and total free amino acids evolved similarly in HPP and control cheeses during the 60-day ripening period. However, on day 240 hydrophilic peptides were at 34–39 % lower levels in the 600 MPa cheeses than in the control cheeses, hydrophobic peptides at 7–16 % lower levels and total free amino acids at 25–29 % lower levels. Flavour intensity scores increased at a slower rate in HPP cheeses than in the control cheese. Flavour quality declined markedly in the control cheeses during refrigerated storage while it did not vary significantly in 600 MPa cheeses.     

High-pressure processing decelerates lipolysis and formation of volatile compounds in ovine milk blue-veined cheese

Enzyme-rich cheeses are prone to over-ripening during refrigerated storage. Blue-veined cheeses fall within this category because of the profuse growth of Penicillium roqueforti in their interior, which results in the production of highly active proteinases, lipases, and other enzymes responsible for the formation of a great number of flavor compounds. To control the excessive formation of free fatty acids (FFA) and volatile compounds, blue-veined cheeses were submitted to high-pressure processing (HPP) at 400 or 600 MPa on d 21, 42, or 63 after manufacture. Cheeses were ripened for 30 d at 10°C and 93% relative humidity, followed by 60 d at 5°C, and then held at 3°C until d 360. High-pressure processing influenced the concentrations of acetic acid and short-chain, medium-chain, and long-chain FFA. The effect was dependent on treatment conditions (pressure level and cheese age at the time of treatment). The lowest concentrations of acetic acid and FFA were recorded for cheeses treated at 600 MPa on d 21; these cheeses showed the lowest esterase activity values. Acetic acid and all FFA groups increased during ripening and refrigerated storage. The 102 volatile compounds detected in cheese belonged to 10 chemical groups (5 aldehydes, 12 ketones, 17 alcohols, 12 acids, 35 esters, 9 hydrocarbons, 5 aromatic compounds, 3 nitrogen compounds, 3 terpenes, and 1 sulfur compound). High-pressure processing influenced the levels of 97 individual compounds, whereas 68 individual compounds varied during refrigerated storage. Total concentrations of all groups of volatile compounds were influenced by HPP, but only ketones, acids, esters, and sulfur compounds varied during refrigerated storage. The lowest total concentrations for most groups of volatile compounds were recorded for the cheese pressurized at 600 MPa on d 21. A principal component analysis combining total concentrations of groups of FFA and volatile compounds discriminated cheeses by age and by the pressure level applied to HPP cheeses.     

Volatile compounds and sensory changes after high pressure processing of mature “Torta del Casar” (raw ewe's milk cheese) during refrigerated storage

The main objective of this paper was to study the changes during refrigerated storage in the volatile compounds and the sensory characteristics of raw ewe's milk mature Torta del Casar cheese High Pressure Processing-treated (200 or 600 MPa for 5 or 20 min) on day 60 after manufacture. Most of the volatile compounds and sensory characteristics were significantly affected by the refrigerated storage and to a lesser extent by the HPP treatment. The 600 MPa HPP treatments caused a decrease in the levels of the most abundant volatile compounds (acids and esters) and in bitterness scores on days 120 and 180. A significant effect was also found for some compounds, the overall flavour, and saltiness on day 240 after manufacture.Industrial relevance textHigh pressure processing treatments at 600 MPa applied to mature raw ewe's milk cheese such as “Torta del Casar” cheese could be an interesting option for the cheese industry to prevent some of the changes that occur during refrigerated storage that are related to over-ripening and excessive bitterness development. In addition, compared to the application of the treatment before maturation is completed, treating mature cheeses is convenient for the cheese industry because it provides the advantage of not requiring any unpackaging steps, which allows the food industry the commercialization of the cheeses without any additional packaging.     

Effect of high-pressure-processing on the microbiology,proteolysis, texture and flavour of Brie cheese during ripening and refrigerated storage

Brie cheeses were high pressure (HP)-treated at 400 or 600 MPa on days 14 or 21 after manufacture to prevent over-ripening. Lactic acid bacteria and Penicillium camemberti numbers declined markedly after HP treatment. In control cheese pH increased 2.0 units from day 21 to day 60, but less than 0.3 units in HP-treated cheeses. Cheeses treated at 600 MPa showed the maximum concentrations of residual caseins during refrigerated storage and control cheese the minimum concentrations. A 7.6-fold increase in hydrophobic peptides was recorded from day 21 to day 60 in control cheese and 0.8–1.6-fold increases in HP-treated cheeses. The maximum aminopeptidase activity was detected in control cheese, the highest free amino acid concentrations in cheeses treated at 400 MPa. The firmest texture was recorded for cheeses treated on day 14 at 400 or 600 MPa. HP-treated cheeses showed higher flavour quality scores than control cheese from day 60 onwards.     

Effects of High Pressure and Heat Treatments on Physicochemical and Gelation Properties of Rapeseed Protein Isolate

High pressure (HP, 200, 400, and 600 MPa)- and heat (60, 80, and 100 °C)-induced gelation, aggregation, and structural conformations of rapeseed protein isolate (RPI) were characterized using gel permeation–size-exclusion chromatography, differential scanning calorimetry, and circular dichroism (CD) techniques. HP treatments significantly (p?<?0.05) increased the content of soluble protein aggregates and surface hydrophobicity of RPI. In contrast, heat treatments at 80 and 100 °C led to significant (p?<?0.05) decreases in the amount of soluble protein aggregates. At pressure treatment of 200 MPa, there was a significant (p?<?0.05) increase in free sulfhydryl group content of RPI, whereas 400- and 600-MPa treatments as well as temperature treatments (60–100 °C) caused significant decreases. Protein denaturation temperature was increased by about 6 °C by HP and heat treatments. The far-UV CD spectra revealed increases in α-helix content of RPI after HP treatments with 400 MPa producing the most increase. Near-UV data showed that HP and heat treatments of RPI led to increasing interactions among the aromatic amino acids (evidence of protein aggregation), and between aromatic amino acids and the hydrophilic environment, which indicates protein unfolding. Least gelation concentration of RPI was significantly (p?<?0.05) reduced by HP and heat treatments, but HP-treated RPI produced gels with better textural properties (hardness increased from ~7.7 to 81.1 N, while springiness increased from ~0.37 to 0.99). Overall, pressure treatments (200–600 MPa) were better than heat treatments (60–100 °C) to modify the structure and improve gelation properties of RPI.     

Assessing the Impact of High-Pressure Processing on Selected Physical and Biochemical Attributes of White Cabbage (Brassica oleracea L. var. capitata alba)

The aim of this study was to investigate the effect of combined pressure/temperature treatments (200, 400 and 600 MPa, at 20 and 40 °C) on key physical and chemical characteristics of white cabbage (Brassica oleracea L. var. capitata alba). Thermal treatment (blanching) was also investigated and compared with high-pressure processing (HPP). HPP at 400 MPa and 20–40 °C caused significantly larger colour changes compared to any other pressure or thermal treatment. All pressure treatments induced a softening effect, whereas blanching did not significantly alter texture. Both blanching and pressure treatments resulted in a reduction in the levels of ascorbic acid, effect that was less pronounced for blanching and HPP at 600 MPa and 20–40 °C. HPP at 600 MPa resulted in significantly higher total phenol content, total antioxidant capacity and total isothiocyanate content compared to blanching. In summary, the colour and texture of white cabbage were better preserved by blanching. However, HPP at 600 MPa resulted in significantly higher levels of phytochemical compounds. The results of this study suggest that HPP may represent an attractive technology to process vegetable-based food products that better maintains important aspects related to the content of health-promoting compounds. This may be of particular relevance to the food industry sector involved in the development of convenient novel food products with excellent functional properties.     

High-pressure processing of Gorgonzola cheese: influence on Listeria monocytogenes inactivation and on sensory characteristics

The presence of Listeria monocytogenes on the rind of Gorgonzola cheese is difficult to avoid. This contamination can easily occur as a consequence of handling during ripening. The aims of this study were to determine the efficiency of high-pressure processing (HPP) for inactivation of L. monocytogenes on cheese rind and to evaluate the influence of HPP treatments on sensory characteristics. Gorgonzola cheese rinds, after removal, were inoculated (about 7.0 log CFU/g) with L. monocytogenes strains previously isolated from other Gorgonzola cheeses. The inoculated cheese rinds were processed with an HPP apparatus under conditions of pressure and time ranging from 400 to 700 MPa for 1 to 15 min. Pressures higher than 600 MPa for 10 min or 700 MPa for 5 min reduced L. monocytogenes more than 99%. A reduction higher than 99.999% was achieved pressurizing cheese rinds at 700 MPa for 15 min. Lower pressure or time treatments were less effective and varied in effectiveness with the cheese sample. Changes in sensory properties possibly induced by the HPP were evaluated on four different Gorgonzola cheeses. A panel of 18 members judged the treated and untreated cheeses in a triangle test. Only one of the four pressurized cheeses was evaluated as different from the untreated sample. HPP was effective in the reduction of L. monocytogenes on Gorgonzola cheese rinds without significantly changing its sensory properties. High-pressure technology is a useful tool to improve the safety of this type of cheese.     

Effects of High-Pressure Processing on the Cooking Loss and Gel Strength of Chicken Breast Actomyosin Containing Sodium Alginate

The effects of high-pressure processing (HPP) (0–400 MPa for 10 min) on the cooking loss (CL), gel strength, and thermal gelling mechanism of chicken breast actomyosin solution containing 0.5 % (w/v) sodium alginate (AS-SA) were investigated. The results showed that HPP could significantly increase (P?相似文献   

Effect of a bacteriocin-producing Lactococcus lactis strain and high-pressure treatment on the esterase activity and free fatty acids in Hispánico cheese

The effect of milk inoculation with a bacteriocin-producing (BP) culture and of high-pressure (HP) treatment of 15-day-old Hispánico cheeses (400 MPa, 5 min, 10 °C), separately or combined, on the release of intracellular esterases and cheese lipolysis was investigated. Esterase activity and free fatty acids (FFAs) content increased during ripening of Hispánico cheese and palmitic, oleic and stearic acids being the most abundant FFAs. On day 15, the highest esterase activity was recorded for HP-treated BP cheese. The activity for HP-untreated BP cheese was the next highest. No difference in the activities was found between HP-treated and untreated cheeses made without BP culture. Total FFAs on day 15 were at a lower concentration in BP cheeses than in cheeses made without BP culture, probably due to the lower pH values of the former. The rate of total FFA accumulation from day 15 to day 50 was higher in BP cheeses (31.1–32.1% increase) than in cheeses made without BP culture (19.3–21.7% increase). The highest total FFA concentration on day 50 (612 mg kg⁻¹) was found for HP-untreated cheese made without BP culture.     

High-pressure effects on the microstructure, texture, and color of white-brined cheese

Abstract: White‐brined cheeses were subjected to high‐pressure processing (HPP) at 50, 100, 200, and 400 MPa at 22 °C for 5 and 15 min and ripened in brine for 60 d. The effects of pressure treatment on the chemical, textural, microstructural, and color were determined. HPP did not affect moisture, protein, and fat contents of cheeses. Similar microstructures were obtained for unpressurized cheese and pressurized cheeses at 50 and 100 MPa, whereas a denser and continuous structure was obtained for pressurized cheeses at 200 and 400 MPa. These microstructural changes exhibited a good correlation with textural changes. The 200 and 400 MPa treatments resulted in significantly softer, less springy, less gummy, and less chewy cheese. Finally, marked differences were obtained in a* and b* values at higher pressure levels for longer pressure‐holding time and were also supported by ΔE* values. The cheese became more greenish and yellowish with the increase in pressure level. Practical Application: The quality of cheese is the very important to the consumers. This study documented the pressure‐induced changes in selected quality attributes of semisoft and brine‐salted cheese. The results can help the food processors to have knowledge of the process parameters resulting in quality changes and to identify optimal process parameters for preserving pressure‐treated cheeses.     

Effects of High-Pressure Processing on the Quality of Sea Bass (Dicentrarchus labrax) Fillets During Refrigerated Storage

The aim of this study was to evaluate the effect of high-pressure processing (HPP) on the quality of fresh sea bass fillets using two pressure levels (250 and 400 MPa; 5 min pressure holding time). Vacuum-packed fillets were used as control samples, and all fillets were stored under refrigerated conditions for 18 days. The microbiological, chemical, physical, and sensory parameters were followed. Both HPP treatments increased the microbiological shelf life of sea bass fillets. In day 14, control samples reached the upper acceptability limit (7 log colony-forming units (CFU)?g^?1), while fillets treated at 250 and 400 MPa had 3.2 and 1.4 log CFU g^?1, respectively. In general, hydrogen sulphide-producing bacteria and Enterobacteriaceae loads were below the detection limit in HPP treatments. Results from nucleotide analysis indicate that HPP treatments reduced the conversion of inosine 5′-monophosphate to inosine. HPP also influenced fillet sensory characteristics. The most evident changes in fillets were the increase in whiteness, the loss of translucency, and a firmer consistency. The effect was more pronounced in the treatment at 400 MPa. Lipid oxidation increased in HPP-treated samples, being more accentuated in the treatment at 400 MPa. Instrumental smell intensity increased in both HPP treatments, though the sensory panel did not detect any rancid or other unpleasant odours. No effect was observed in the amount of volatile bases or in pH values. In conclusion, HPP treatments showed potential application for new fish product development with increased microbiological safety and shelf life, longer freshness, and unique characteristics (e.g. firmer and whitish).     

Effects of High-Pressure Processing with or without Blanching on the Antioxidant and Physicochemical Properties of Mango Pulp

The effects of high-pressure processing (HPP 300 MPa/15 min, 400 MPa/5 min, 500 MPa/2.5 min, and 600 MPa/1 min) and high-temperature/short-time processing (HTST 110 °C/8.6 s), with or without blanching, on mango pulp were comparatively evaluated in terms of the antioxidant compounds, antioxidant capacity, sugars, and color. Blanching treatment significantly increased the total phenol content and the antioxidant capacity of mango pulp, but did not change the levels of L-ascorbic acid, carotenoids, sugars, and visual color (total color difference, △E?<?2.00). Both HPP and HTST treatments significantly increased the total phenol content and antioxidant capacity of un-blanched mango pulp, but no significant changes occurred in the blanched mango pulp. HPP did not affect the levels of L-ascorbic acid, carotenoids, and sugars in mango pulp regardless of blanching. However, HTST significantly decreased the fructose and glucose levels, as well as induced the isomerization of β-carotene, with the increase in 13-cis-β-carotene accompanied by the decrease in all-trans-β-carotene. Moreover, HPP-treated mango pulp consistently showed lower △E values than those HTST-treated samples, regardless of blanching.     

Evolution of lipolysis during the ripening of traditional Feta cheese

Lipolysis was studied during ripening of traditional Feta cheese produced in two small dairies, A and B. The cheeses were made from a thermized mixture of ewes’/goats’ milk by using yoghurt as starter and artisanal rennet from lambs’ and kids’ abomasa (cheese A) or mixed artisanal rennet with calf rennet (cheese B).The acid degree value and the free fatty acids (FFA) contents in both cheeses increased sharply up to 18 d (pre-ripening period at 15 °C) and continued to increase throughout ripening. In both mature cheeses, acetic acid was found at high levels (13–18% of the total FFAs). However, except for this, all FFA contents differed significantly (P < 0.05) between the two cheeses throughout ripening. The levels of individual and total C2:0–C8:0, C10:0–C14:0 and C16:0–C18:2 fatty acids were significantly higher (P < 0.05) in cheese A than in cheese B. Presumably the difference, especially in the C2:0–C8:0 content, was due mainly to the type of the rennet used. Butyric acid was the dominant FFA in cheese A (20% of the total FFAs at 120 d), while the most abundant FFAs in cheese B were capric (18%) and lauric acid (18%). In general, the lipolysis degree of the two cheeses was higher than those reported for the industrially-made Feta cheese.In organoleptic evaluation, cheese A had a piquant taste that was attributed to its high content of butyric acid and showed a significantly (P < 0.05) higher total score than cheese B.     

Proteolysis and biogenic amine buildup in high-pressure treated ovine milk blue-veined cheese

Penicillium roqueforti plays an important role in the ripening of blue-veined cheeses, mostly due to lactic acid consumption and to its extracellular enzymes. The strong activity of P. roqueforti proteinases may bring about cheese over-ripening. Also, free amino acids at high concentrations serve as substrates for biogenic amine formation. Both facts result in shorter product shelf-life. To prevent over-ripening and buildup of biogenic amines, blue-veined cheeses made from pasteurized ovine milk were high-pressure treated at 400 or 600 MPa after 3, 6, or 9 wk of ripening. Primary and secondary proteolysis, biogenic amines, and sensory characteristics of pressurized and control cheeses were monitored for a 90-d ripening period, followed by a 270-d refrigerated storage period. On d 90, treatments at 400 MPa had lowered counts of lactic acid bacteria and P. roqueforti by less than 2 log units, whereas treatments at 600 MPa had reduced lactic acid bacteria counts by more than 4 log units and P. roqueforti counts by more than 6 log units. No residual α-casein (CN) or κ-CN were detected in control cheese on d 90. Concentrations of β-CN, para-κ-CN, and γ-CN were generally higher in 600 MPa cheeses than in the rest. From d 90 onwards, hydrophilic peptides were at similar levels in pressurized and control cheeses, but hydrophobic peptides and the hydrophobic-to-hydrophilic peptide ratio were at higher levels in pressurized cheeses than in control cheese. Aminopeptidase activity, overall proteolysis, and free amino acid contents were generally higher in control cheese than in pressurized cheeses, particularly if treated at 600 MPa. Tyramine concentration was lower in pressurized cheeses, but tryptamine, phenylethylamine, and putrescine contents were higher in some of the pressurized cheeses than in control cheese. Differences in sensory characteristics between pressurized and control cheeses were generally negligible, with the only exception of treatment at high pressure level (600 MPa) at an early ripening stage (3 wk), which affected biochemical changes and sensory characteristics.     

Commercial application of high-pressure processing for increasing starter-free fresh cheese shelf-life

Different non-thermal technologies have been proposed to extend the shelf-life of solid food products, high-pressure processing (HPP) being one of the emerging technologies which has been most extensively studied. In this study, one of the first commercial industrial-scale applications of HPP on a starter-free fresh cheese, with the aim of increasing its shelf-life, is presented. The effect of 500 MPa (5 min, 16 °C) on physico-chemical, microbial, colour, microstructure, texture and sensorial characteristics of starter-free fresh cheeses during cold storage of 21 days was studied. The results showed that pressurised cheeses presented a shelf-life of about 19–21 days when stored at 4 °C, whereas control cheese became unsuitable for consumption on day 7–8. On the other hand, cheese treated at 500 MPa was firmer and more yellow than the untreated one. However, these changes, which were detected by instrumental and sensory analysis, did not affect the preference for pressurised cheese. These results may lead to practical applications of HPP in the food industry to produce microbiologically safe cheese with extended shelf-life and sensory quality.     

Effect of high‐pressure treatments on microbial loads and physicochemical characteristics during refrigerated storage of raw milk Serra da Estrela cheese samples

This work studied the effect of high pressure processing (HPP) at 400, 500 and 600 MPa during 10, 5 and 3 min, respectively, on samples ewe cheese manufactured from raw milk, during storage (100 days) at 5 °C. Total aerobic mesophilic and lactic acid bacteria were slightly affected, decreasing by about 1.0 and 0.82 log CFU g^?1, respectively, immediately after HPP treatment at 600 MPa for 3 min, while Enterobacteriaceae, yeasts and moulds, and Listeria innocua were reduced to below the quantification limits. Lactic acid bacteria decreased further during storage, showing increasing inactivation as the pressure level increased. Physicochemical parameters (water activity, moisture content, pH and titratable acidity) were generally not affected by HPP, while lipid oxidation increased throughout storage, with HPP samples showing lower values (50–66%) at 100 days of storage. The results indicated that HPP has potential to improve cheese microbial safety and shelf‐life, with a lower lipid oxidation level than nonpressurised cheese.     

Effect of hydrostatic high-pressure processing on the chemical,functional, and rheological properties of starter-free Queso Fresco

Queso Fresco (QF), a popular high-moisture, high-pH Hispanic-style cheese sold in the United States, underwent high-pressure processing (HPP), which has the potential to improve the safety of cheese, to determine the effects of this process on quality traits of the cheese. Starter-free, rennet-set QF (manufactured from pasteurized, homogenized milk, milled before hooping, and not pressed) was cut into 4.5- × 4.5- × 15-cm blocks and double vacuum packaged. Phase 1 of the research examined the effects of hydrostatic HPP on the quality traits of fresh QF that had been warmed to a core temperature of 20 or 40°C; processed at 200, 400, or 600 MPa for 5, 10, or 20 min; and stored at 4°C for 6 to 8 d. Phase 2 examined the long-term effects of HPP on quality traits when QF was treated at 600 MPa for 3 or 10 min, and stored at 4 or 10°C for up to 12 wk. Warming the QF to 40°C before packaging and exposure to high pressure resulted in loss of free whey from the cheese into the package, lower moisture content, and harder cheese. In phase 2, the control QF, regardless of aging temperature, was significantly softer than HPP cheeses over the 12 wk of storage. Hardness, fracture stress, and fracture rigidity increased with length of exposure time and storage temperature, with minor changes in the other properties. Queso Fresco remained a bright white, weak-bodied cheese that crumbled and did not melt upon heating. Although high pressures or long processing times may be required for the elimination of pathogens, cheese producers must be aware that HPP altered the rheological properties of QF and caused wheying-off in cheeses not pressed before packaging.     

High-pressure processing of Turkish white cheese for microbial inactivation

High-pressure processing (HPP) of Turkish white cheese and reduction of Listeria monocytogenes, total Enterobacteriaceae, total aerobic mesophilic bacteria, total molds and yeasts, total Lactococcus spp., and total Lactobacillus spp. were investigated. Cheese samples were produced from raw milk and pasteurized milk and were inoculated with L. monocytogenes after brining. Both inoculated (ca. 10(7) to 10(8) CFU/g) and noninoculated samples were subjected to HPP in a high-pressure food processor at 50 to 600 MPa for 5 and 10 min at 25 degrees C. Reductions in L. monocytogenes, total aerobic mesophilic bacteria, Lactococcus spp., and Lactobacillus spp. in both pasteurized- and raw-milk cheese samples and reductions in total molds and yeasts and total Enterobacteriaceae counts in raw-milk cheese samples increased with increased pressure (P < or = 0.05). The maximum reduction of the L. monocytogenes count, ca. 4.9 log CFU/g, was obtained at 600 MPa. Because of the highly inhibitory effect of pasteurization, the total molds and yeasts and total Enterobacteriaceae counts for the cheese samples produced from pasteurized milk were below the detection limit both before and after HPP. There was no significant difference in inactivation of L. monocytogenes, total aerobic mesophilic bacteria, Lactococcus spp., and Lactobacillus spp. under the same treatment conditions for the raw milk and pasteurized milk cheeses and for 5- and 10-min treatment times (P > 0.05). No significant change was detected in pH or water activity of the samples before and after HPP. Our findings suggest that HPP can be used effectively to reduce the microbial load in Turkish white cheese.     

Proteolysis in goat cheese made from raw,pasteurized or pressure-treated milk

Primary and secondary proteolysis of goat cheese made from raw (RA), pasteurized (PA; 72 °C, 15 s) and pressure-treated milk (PR; 500 MPa, 15 min, 20 °C) were examined by capillary electrophoresis, nitrogen fractionation and HPLC peptide profiles. PA milk cheese showed a more important hydrolysis (P<0.05) of α_s1-casein than RA milk cheese at the first stages of ripening (15 days), while PR milk cheese had a level between those seen in PA and RA milk cheeses. Degradation of β-casein was more important (P<0.05) in PA and PR than in RA milk cheeses at 15 days of ripening. However, from thereon β-casein in PR and RA milk cheeses was hydrolyzed at essentially similar rates, but at lower rates (P<0.05) than in PA milk cheeses. Pressure treatment could induce proteolysis of β-casein in a way, which is different from that produced by heat treatment. There was an increase in 4.6-soluble nitrogen (WSN) and in trichloroacetic acid (TCASN) throughout ripening in cheeses, but higher contents (P<0.05) in PA and PR milk cheeses at the end of ripening were observed. PR milk cheeses contained considerably higher content (P<0.05) of free amino acids than RA or PA milk cheeses. In general, heat and pressure treatments had no significant effect on the levels of hydrophobic and hydrophilic peptides.     

Study of Antioxidant Capacity and Quality Parameters in An Orange Juice–Milk Beverage After High-Pressure Processing Treatment

The aim of this study was to obtain a beverage with a high content of bioactive compounds. Therefore, a mixture of orange juice and milk was prepared. The effect of high-pressure processing (HPP), four different pressures (100, 200, 300, and 400 MPa), four treatment times for each pressure (120, 300, 420, and 540 s) on antioxidant compounds, and quality parameters was studied. The effects of HPP treatment were compared with those of thermal treatment (90 °C for 15, 21 s and 98 °C for 15, 21 s). Ascorbic acid retention in the orange juice–milk beverage was higher than 91% in all cases after HPP. There was a significant increase (p < 0.05) in phenolic compounds at 100 MPa/420 s, however at 400 MPa/540 s, it was observed a non-significant decrease. Total carotenoid content was significantly higher in all samples treated by HPP when treatment time was 420 and 540 s. Color changes increased when pressure and treatment times were higher, with the highest difference appearing at 400 MPa/540 s, but HPP had a smaller effect on total color changes than thermal processing. A 5-log reduction of Lactobacillus plantarum CECT 220 was obtained in the orange juice–milk beverage after HPP (200 MPa, 300 s), and this was compared with treatment at 90 °C (15 s), the heat treatment most effective at preserving ascorbic acid.