B. Guamis

Applications of high-hydrostatic pressure on milk and dairy products: a review

Abstract Interest in high-pressure (HP) applications on milk and dairy products has recently increased. Pressures between 300 and 600 MPa have shown to be an effective method to inactivate microorganisms including most infectious food-borne pathogens. In addition to microbial destruction, it has been reported that HP improves rennet or acid coagulation of milk without detrimental effects on important quality characteristics, such as taste, flavour, vitamins, and nutrients. These characteristics offer the dairy industry numerous practical applications to produce microbially safe, minimally processed dairy products with improved performances, and to develop novel dairy products of high nutritional and sensory quality, novel texture and increased shelf life.

Influence of ultra-high pressure homogenisation on antioxidant capacity, polyphenol and vitamin content of clear apple juice

Ultra-high pressure homogenisation (UHPH) is a recently developed technology and is still under study to evaluate its effect on different aspects of its application to food products. The aim of this research work was to evaluate the effect of UHPH treatments on quality characteristics of apple juice such as antioxidant capacity, polyphenol composition, vitamin C and provitamin A contents, in comparison with raw (R) and pasteurised (PA) apple juice. Several UHPH treatments that include combinations of pressure (100, 200 and 300MPa) and inlet temperatures (4 and 20°C) were assayed. Apple juice was pasteurised at 90°C for 4min. Antioxidant capacity was analysed using the oxygen radical antioxidant capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) assay while total phenolic content was determined by the Folin-Ciocalteau assay. According to the FRAP and DPPH assays, UHPH processing did not change apple juice antioxidant capacity. However, significant differences were detected between samples analysed by TEAC and ORAC assays. In spite of these differences, high correlation values were found between the four antioxidant capacity assays, and also with total polyphenol content. The analysis and quantification of individual phenols by HPLC/DAD analytical technique reflects that UHPH-treatment prevented degradation of these compounds. Vitamin C concentrations did not change in UHPH treated samples, retaining the same value as in raw juice. However, significant losses were observed for provitamin A content, but lower than in PA samples. UHPH-treatments at 300MPa can be an alternative to thermal treatment in order to preserve apple juice quality.

Application of high pressure treatment for cheese production

Abstract High hydrostatic-pressure treatment offers the food industry a new technology for food preservation. Interest in high pressure application on milk has recently increased. Pressures between 300 and 600 MPa can inactivate microorganisms including most infectious food-borne pathogens. In addition to microbial destruction, it has been reported that high pressure improves rennet or acid coagulation of milk and increases cheese yield. A lot of work has been published on microorganism inactivation, denaturation of whey proteins, changes in the mineral distribution and coagulating properties on model or real milk systems. However, practical applications of high pressure treatment in the dairy industry have received little attention. This paper examines recent work in this area and summarizes parts of our ongoing work toward the development of high pressure applications for the cheese industry.

Effect of High Hydrostatic Pressure on Listeria innocua 910 CECT Inoculated into Ewe's Milk

Ewes milk standardized to 6% fat was inoculated with Listeria innocua 910 CECT at a concentration of 10(7)CFU/ml and treated by high hydrostatic pressure. Treatments consisted of combinations of pressure (200, 300, 350, 400, 450, and 500 MPa), temperature (2, 10, 25, and 50 degrees C), and time (5, 10, and 15 min). To determine numbers of L. innocua, listeria selective agar base with listeria selective supplement and plate count agar was used. Low-temperature (2 degrees C) pressurizations produced higher L. innocua inactivation than treatments at room temperatures (25 degrees C). Pressures between 450 and 500 MPa for 10 to 15 min were needed to achieve reductions of 7 to 8 log units. The kinetics of destruction of L. innocua were first order with D-values of 3.12 min at 2 degrees C and 400 MPa and 4 min at 25 degrees C and 400 MPa. A baroprotective effect of ewes milk (6% fat) on L. innocua was observed in comparison with other studies using different media and similar pressurization conditions.

Inactivation of Listeria innocua Inoculated in Liquid Whole Egg by High Hydrostatic Pressure

The resistance of Listeria innocua, as a model microorganism for Listeria monocytogenes, to high hydrostatic pressure in liquid whole egg was studied at several pressures (300, 350, 400, and 450 MPa),temperatures (- 15, 2, and 20 degrees C), and times (5, 10, and 15 min). Listeria innocus was added to liquid whole egg at approximately 10(6) CFU/ml. Listeria innocua was not totally inactivated in any of the treatments. In general, reduction was better at 2 degrees than at room temperature, but the greatest inactivation was obtained at 450 MPa at 20 degrees C for 15 min (over 5 log of reduction), The results indicate that microbial inactivation was increased with prolonged exposure to pressure. D values for Listeria innocua were obtained at 400 MPa for two temperatures (2 and 20 degrees C), and different times (0 to 20 min). The microbial inactivation followed apparent first-order kinetics, exhibiting a decimal reduction time of 7.35 min at 2 degrees C and 8.23 min at 20 degrees C.

Combined effect of nisin and high hydrostatic pressure on destruction of Listeria innocua and Escherichia coli in liquid whole egg.

High hydrostatic pressure inactivation of Escherichia coli and Listeria innocua inoculated in liquid whole egg was improved significantly (P < 0.05) with nisin addition at concentrations of 1.25 and 5 mg/1. A reduction of almost 5 log10 units in E. coli counts and more than 6 log10 units for L. innocua was obtained at 450 MPa and 5 mg/l of nisin. For this treatment, the two microorganisms were not detectable after 1 month of storage at 4 degrees C. The amount of nisin added did not affect E. coli inactivation at 300 MPa. For L. innocua, 5 mg/l of nisin was more effective than 1.25 mg/l. Nisin showed no effect when samples were stored at 20 degrees C after pressurization, except for samples with L. innocua containing 5 mg/l of nisin and treated with 450 MPa.

Populations of Aerobic Mesophils and Inoculated E. coli during Storage of Fresh Goat's Milk Cheese Treated with High Pressure

Pasteurized goats milk inoculated with Escherichia coli 405 CECT was manufactured into cheese containing 108CFU/g. The fresh cheese was treated by combinations of pressure (400, 450, and 500 MPa), temperature (2, 10, and 25°C) and time (5, 10, and 15 min). Once treated, cheeses were stored at 2 to 4°C. Counts of surviving Escherichia coli and aerobic mesophilic bacteria were determined 1, 15, 30, and 60 days after treatment. No colonies of surviving E. coli were detected 1 day after pressurization, except in samples treated for 5 min at 25°C at pressures of 400 and 450 MPa. No surviving E. coli were detected at 15, 30, or 60 days in any case. Aerobic mesophilic bacteria counts after treatment were between 2 and 3 log CFU/g in most cases and only a slight increase during refrigerated storage could be detected in samples treated at 400 MPa.

Inactivation of Staphylococcus aureus in raw milk cheese by combinations of high-pressure treatments and bacteriocin-producing lactic acid bacteria

Aims:  To investigate the combined effect of high‐pressure treatments (HPT) and milk inoculation with bacteriocin‐producing lactic acid bacteria (BP‐LAB) on the survival of Staphylococcus aureus during ripening of raw milk cheese.

Influence of Pressurization on Goat Milk and Cheese Composition and Yield

Fresh goat cheese was made from pasteurized (72 °C, 15 s) or HP- treated milk (500 MPa, 15 min, 20 °C). Microbiological quality (i.e. mesophilic aerobic bacteria and enterobacteria) of pressurized milk was comparable to pasteurized milk. Pasteurized and HP-treated milks had different pHs and non-casein nitrogen. During the curd formation, the pH fell faster in pasteurized milk than in HP-treated milk and there was a slightly larger amount of milk fat separated from the curd whey in HP- treated milk. HP treatment reduced the level of whey expelled from the curd making the whey removal process more difficult, and so the time involved in the cheesemaking was increased. The cheese made from HP-treated milk had higher levels of moisture and salt, but a slightly lower fat content than pasteurized milk. Additional retention of whey protein and, especially, the greater moisture led to improvements in cheese yield from HP-treated milk.

Effects of High-Pressure Treatment on the Sensory Quality of White Grape Juice

The effects of high-pressure treatment on the colour (objective measurement) and sensory characteristics of white grape juice were studied during storage at 4 °C for 60 days. Grape juice was subjected to three different treatments: 400 or 500 MPa at 2 u °C, and 400 MPa at 40 °C during 10 min. Untreated juice was used as control. Colour parameters (CIE L * a * b *), hue angle (tan m 1 b */ a *), chroma {( a * 2 + b * 2 ) 1/2 }, luminosity Q *{(10 2 log( L *) + 100} and saturation S *( C */ L *) were measured. Juices were evaluated for sweetness, acidity, off-flavour and aroma. High-pressure treatments did not affect the colour parameters of juice, and similar sensory characteristics were observed in both control and treated samples on the first day. The colour and sensory characteristics of pressure-treated samples remained more stable than those of the control juice during 60 days of storage. The control juice was slightly fermented developing some changes in flavour and colour.