R. Gervilla

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.

Use of ultra-high-pressure homogenization to preserve apple juice without heat damage

Ultra-high-pressure homogenization (UHPH) is a technology for continuous treatment of fluid food products and can be applied to avoid thermal treatment of fruit juices. Treatment of fresh apple juice at homogenization pressures from 100 to 300 MPa and inlet temperatures of 4 °C or 20 °C caused important decreases in microbial counts when treatment pressure reached at least 200 MPa. After the treatment, counts were<1 log cfu/ml when homogenization pressure reached at least 200 MPa, and remained stable for more than 2 months at 4 °C. Hydroxymethylfurfural for thermal-treated juice reached values 100-fold higher than for its UHPH-treated or raw counterparts. Browning index was higher in non-thermal-treated juice, and it had an inverse correlation with the severity of UHPH treatment. Part of this browning occurred during Pilot Plant processing, but it kept on browning during preservation in juices in which PPO was not fully inactivated. UHPH treatment of apple juice may be an alternative to conventional thermal processing.

Microbial inactivation by ultra high-pressure homogenisation on fresh apple juice

The effect of ultra high-pressure homogenisation (UHPH) on the microbial shelf life of fresh apple juice immediately after treatment and storage at 4 °C was studied and compared with fresh raw apple juice and a conventional heat treatment (pasteurised apple juice (PA)) used at industrial level (90 °C for 4 min). Apple juice samples were processed using an ultra high-pressure homogeniser (model FPG11300, Stansted Fluid Power Ltd., Essex, UK), applying treatments of 100, 200 and 300 MPa (single stage) at an inlet temperature of 4 °C. The microbial quality was studied by enumerating total counts (TC), psychrotrophs (PS), moulds and yeasts (MY), lactobacilli (LB), enterobacteriaceae (EB) and faecal coliforms (FC). UHPH samples at 200 and 300 MPa and PA samples reached reductions on PS, MY, LB, EB and FC of at least 3.9, 3.5, 2.4, 3.2 and 3.0 log cycles, respectively, whereas on TC reductions were of 2.6 and 3.6 log cycles on UHPH samples at 200 and 300 MPa, respectively, and at least 4.3 log cycles (not detected) on PA samples. Hence, alternative methods such as UHPH may give new opportunities to develop fresh apple juice with an equivalent shelf life to PA in terms of microbiological characteristics.

Influence of High-Pressure and Ultra-High-Pressure Homogenization on Antioxidants in Fruit Juice

High-pressure homogenization has been applied to stabilize several fruit juices both microbiologically and enzimatically without (or with very little) thermal effect. This treatment also helps to preserve vitamin C, carotenoid, and polyphenol content keeping it quite close to the original value in raw juice. These fruit juices better retain the health-related compounds. Antioxidant activity of juices is also well preserved.