High-pressure processing and antimicrobial biodegradable packaging to control Listeria monocytogenes during storage of cooked ham

The efficiency of combining high-pressure processing (HPP) and active packaging technologies to control Listeria monocytogenes growth during the shelf life of artificially inoculated cooked ham was assessed. Three lots of cooked ham were prepared: control, packaging with alginate films, and packaging with antimicrobial alginate films containing enterocins. After packaging, half of the samples were pressurized. Sliced cooked ham stored at 6 degrees C experienced a quick growth of L. monocytogenes. Both antimicrobial packaging and pressurization delayed the growth of the pathogen. However, at 6 degrees C the combination of antimicrobial packaging and HPP was necessary to achieve a reduction of inoculated levels without recovery during 60 days of storage. Further storage at 6 degrees C of pressurized antimicrobial packed cooked ham resulted in L. monocytogenes levels below the detection limit (day 90). On the other hand, storage at 1 degrees C controlled the growth of the pathogen until day 39 in non-pressurized ham, while antimicrobial packaging and storage at 1 degrees C exerted a bacteriostatic effect for 60 days. All HPP lots stored at 1 degrees C led to counts <100CFU/g at day 60. Similar results were observed when combining both technologies. After a cold chain break no growth of L. monocytogenes was observed in pressurized ham packed with antimicrobial films, showing the efficiency of combining both technologies.     

High pressure treatments on the inactivation of Salmonella Enteritidis and the characteristics of beef carpaccio

The effect of high pressure (HP) on Salmonella enterica subsp. enterica serovar Enteritidis in beef carpaccio stored under temperature abuse conditions (8°C) during 30days was investigated. After treatment, reductions of S. Enteritidis were 3.68 and 5.94 log cfu/g in samples pressurized at 450MPa for 5 and 10min, respectively, whereas the pathogen was only detected after enrichment of samples treated at 450MPa for 15min. During storage, counts of S. Enteritidis decreased 0.26 log cfu/g in non-pressurized carpaccio, 1.33 log cfu/g in carpaccio treated at 450MPa for 5min and were only detected after enrichment in carpaccio pressurized at 450MPa for 10 or 15min. Color (L*, a* and b*) varied with pressurization and storage, with higher changes in carpaccio treated at longer pressurization times. Shear resistance was slightly lower in treated samples just after pressurization, but increased at the end of the storage period. Maximum force was less affected by treatment.     

Effects of combining microbial transglutaminase and high pressure processing treatments on the mechanical properties of heat-induced gels prepared from arrowtooth flounder (Atheresthes stomias)

The objective of this study was to evaluate the effect of setting conditions (25 °C for 2 h or 40 °C for 30 min) and combining of microbial transglutaminase (MTGase) and high pressure processing (HPP) on the mechanical properties of heat induced gels obtained from paste from arrowtooth flounder (Atheresthes stomias). Treatments included fish paste control without added MTGase, fish paste incubated with MTGase but not pressurized (MTGase + cooking), fish paste incubated with MTGase and pressurized at 600 MPa for 5 min (MTGase + HPP + cooking) and fish paste pressurized at 600 MPa for 5 min and incubated with MTGase (HPP + MTGase + cooking). The controls and the treated samples were then subjected to one of two thermal treatments: 90 °C for 15 min or 60 °C for 30 min before cooking at 90 °C for 15 min. Samples of fish paste heated at 60 °C before cooking could not be used to prepare gels for texture profile analysis (TPA). TPA showed that pressurization improved the mechanical properties of gels made from paste treated with MTGase and set at 25 °C. The opposite was observed for samples set at 40 °C. Setting at 40 °C appeared to induce proteolytic degradation of myofibrillar proteins.     

Simultaneous determination of nine lignans using pressurized liquid extraction and HPLC-DAD in the fruits of Schisandra chinensis

The pressurized liquid extraction and HPLC-DAD was developed for extraction and determination of bioactive lignans in Schisandra chinensis. The efficient PLE conditions employed methanol as extraction solvent, 125 °C of extraction temperature, 5 min of static extraction time and only one cycle. A rapid HPLC-DAD method was described for simultaneous determination of nine lignans, including schisandrol A, gomisin J, schisandrol B, tigloylgomisin H, angeloylgomisin H, schisandrin A, γ-schisandrin, gomisin N and schisandrin C. The extraction efficiency of PLE was observed to be comparable with reflux and sonication. In addition, the contents of nine lignans in S. chinensis from different regions were analysed by PLE and HPLC-DAD method.     

Plasmin activity in pressurized milk

The effects of pressure (up to 400 MPa), applied at room temperature, on native proteinase activity of milk were investigated by means of plasmin activity, plasmin-derived activity after plasminogen activation and their distribution in different milk fractions, micelle microstructure, beta-LG denaturation, and casein susceptibility to proteolytic attack. The pressure conditions assayed did not lead to plasmin inactivation and only decreased around 20 to 30% total plasmin activity after plasminogen activation. However, pressure caused severe disruption of the micellar structure, releasing high levels of caseins, plasmin, and plasminogen to the soluble fraction of milk. High levels of soluble denatured beta-LG were also found in the ultracentrifugation supernatants of pressurized milks, particularly in those treated at 400 MPa. Probably as a result of micellar disintegration, caseins became more susceptible to proteolysis by exogenous plasmin. However, no enhanced proteolytic degradation was observed when we compared the evolution of pressurized and unpressurized milks during refrigerated storage. Serum-liberated plasmin may become more vulnerable to the action of proteinase inhibitors leading to a reduced proteolysis on refrigerated storage, despite the increased susceptibility of caseins to proteinase action.     

Optimization of Subcritical Fluid Extraction of Bioactive Compounds Using Hansen Solubility Parameters

ABSTRACT:  Process engineering operations in food and nutraceutical industries pertaining to the design of extraction of value-added products from biomass using pressurized liquids involve a careful selection of the solvent and optimal temperature conditions to achieve maximum yield. Complex molecular structure and limited physical property data in the literature of biological solutes extracted from biomass compounds have necessitated the process modeling of such operations. In this study, we have applied the Hansen 3-dimensional solubility parameter concept to optimize the extraction of molecularly complex solutes using subcritical fluid solvents. Hansen solubility spheres characterized by the relative energy differences (RED) have been used to characterize and quantify the solute–subcritical solvent interactions as a function of temperature. The solvent power of subcritical water and compressed hydroethanolic mixtures above their boiling points has been characterized using the above-mentioned method. The use of group contribution methods in collaboration with computerized algorithms to plot the Hansen spheres provides a quantitative prediction tool for optimizing the design of extraction conditions. The method can be used to estimate conditions for solute–solvent miscibility, an optimum temperature range for conducting extractions under pressurized conditions, and approximate extraction conditions of solutes from natural matrices.     

Optimization and economic evaluation of pressurized liquid extraction of phenolic compounds from jabuticaba skins

The optimization of the extraction of anthocyanins and other phenolic compounds from jabuticaba skins, a promising Brazilian source of these compounds, was studied using pressurized liquid extraction (PLE). An optimization study was performed using ethanol as a solvent and with extraction pressure (5-10 MPa), temperature (313-393 K) and static extraction time (3-15 min) as independent variables. The optimum PLE conditions for all response variables were estimated; however, PLE conditions resulting in the highest recovery of anthocyanins (5 MPa, 553 K and 9 min of static extraction time) were chosen for comparison with a conventional low-pressure solvent extraction (LPSE). The attributes compared were yield, content of anthocyanins and phenolic compounds and economic feasibility. Similar extraction yields were obtained by LPSE and PLE under optimized conditions; however 2.15 and 1.66-fold more anthocyanins and total phenolic compounds, respectively, were extracted using PLE, while the cost of manufacturing (COM) obtained for the PLE extract was 40-fold lower.     

Inactivation of Saccharomyces cerevisiae by equipment pressurizing at ambient temperature after generating CO2 microbubbles at lower temperature and pressure

To improve the inactivation efficiency of low pressure CO₂ microbubbles (MB-CO₂), we developed the MB-CO₂ equipment from batch system to two-stage MB-CO₂ system which was additionally pressurized at ambient temperature after MB-CO₂ was mixed with a solution at lower temperature and pressure. Therefore, the effect of the two-stage MB-CO₂ treatment for inactivating Saccharomyces cerevisiae was investigated. The two-stage MB-CO₂ efficiency for the inactivation of S. cerevisiae dramatically increased by lowering the temperature and by increasing the pressure in the mixing vessel. Furthermore, its effectiveness significantly enhanced by increasing the temperature in the heating coil, although not by the pressure. As a result, using the two-stage MB-CO₂ equipment was suggested as a new effective technique to inactivate S. cerevisiae.     

Pressurized liquids as an alternative process to antioxidant carotenoids' extraction from Haematococcus pluvialis microalgae

In this work, extraction of antioxidant carotenoids from Haematococcus pluvialis microalga, has been studied combining pressurized liquid extraction (PLE), using hexane and ethanol as extracting solvents, and analytical techniques such as thin layer chromatography (TLC) and HPLC with DAD. The effect of the extraction temperature (50, 100, 150 and 200 °C) and the polarity of the solvent have been studied in terms of in vitro antioxidant activity and chemical composition considering two different morphological cells (green vegetative cells and red cysts). Results demonstrate that the extraction temperature had a positive influence in the extraction yield while its effect in the antioxidant activity was negative, lowering the activity of the extracts with an increase of the extraction temperature. The best yields were obtained with ethanol at the higher extraction temperature while the best antioxidant activity was also achieved using ethanol but at lower temperatures. Chemical composition was determined by TLC and HPLC with DAD. Several compounds were identified in the samples and concentration of astaxanthin was obtained. Results pointed out that the extracts contained different carotenoids in both, the green and the red phase, and that depending on its contribution a stronger antioxidant activity would be expected.     

Combined effect of enterocin AS-48 and high hydrostatic pressure to control food-borne pathogens inoculated in low acid fermented sausages

The single and combined effects of enterocin AS-48 and high hydrostatic pressure (HHP) on Listeria monocytogenes, Salmonellaenterica, and Staphylococcus aureus was investigated in fuet (a low acid fermented sausage) during ripening and storage at 7 °C or at room temperature. AS-48 (148 AU g⁻¹) caused a drastic 5.5 log cfu g⁻¹ decrease in L. monocytogenes (P < 0.001) and a significant (P < 0.01) inhibition (1.79 logs) for Salmonella at the end of ripening (10 d). After pressurization (400 MPa) and storage Listeria counts remained below 5 cfu g⁻¹ in all fuets containing AS-48 (pressurized or not). HHP alone had no anti-Listeria effect. HHP treatment significantly reduced Salmonella counts, with lowest levels in pressurized fuets with AS-48. S. aureus showed similar growth for all treatments and storage conditions. These results indicate that AS-48 can be applied alone to control L. monocytogenes and combined with HHP treatment to control Salmonella in fuets.     

Consumer Acceptance of Prerigor Pressurized Versus Conventionally Processed Utility Grade Beef

Consumer tests of institutional prerigor pressurized and conventionally aged shoulder clods and/or inner chucks from utility grade cows were tested in a local soup kitchen, college women's cooperative living group and a university catering or banquet food service. The 318 member panels evaluated the prerigor pressurized beef as being more acceptable than conventionally processed beef. Differences in degree of acceptability at each location may be due to method of preparation.     

弹簧摇架与气加压摇架加压力探析

用不同的测试方法检测弹簧摇架与气加压摇架压力的变化，并分析了两者产生压力变化的王要原因，在分析气加压摇采发展变化的基础上介绍了特克斯帕特斯公司生产的PK3000新型气加压摇架的结构及优点。     

Pressurized solvent extraction of wheat germ oil

This study examined the pressurized solvent extraction of wheat germ oil. The effects of temperature (45–135 °C at 1500 psi), extraction time, sample size and solvent type on the extraction efficiency and oil quality were studied. Extraction efficiency of the normal-hexane was compared to that of the iso- and high purity-hexane, iso-propanol, ethanol and acetone. The extracts were analyzed for n-3 and n-6 polyunsaturated fatty acid content. Pressurized solvent extraction reduced extraction time significantly as compared to Soxhlet extraction. The time required for complete oil recovery was dependent on the amount of wheat germ used for extraction. The amount of extract collected was highest when ethanol was used as a solvent for pressurized solvent extraction. Soxhlet and pressurized solvent extractions resulted in similar oil yields when hexane was used as a solvent. Fatty acid composition of the extracts was not affected by either temperature or extraction method. The experimental results indicate that a pressurized solvent extraction technique reduces solvent consumption and extraction time with no adverse effect on the extraction yield and fatty acid composition of the oil.     

基于机器学习的整体穿刺加压参数预测方法

针对整体穿刺加压密实过程中碳布回弹导致平均层高波动范围较大,影响立体织物性能的问题,提出一种基于机器学习理论的加压参数预测方法,将平均层高与加压参数之间复杂建模转换为多元回归问题,使用适合计算机运算的无约束优化迭代方法求解。基于scikit-learn类库对特征变量进行特征选择,对比6种回归模型的预测性能得分后选择K近邻回归作为基学习器,使用集成算法提升模型的预测性能。预测模型部署到生产环境后的实验结果表明:使用机器学习预测后,加压参数对整体穿刺过程平均层高均值变化的响应速度得到提高,且均值变化幅度得到降低,实验样本平均层高波动范围均值从12.0%降低至6.8%,标准差从0.008 3降低至0.006 6。     

A comparative study on the structure of Saccharomyces cerevisiae under nonthermal technologies: high hydrostatic pressure, pulsed electric fields and thermo-sonication

Nonthermal technologies are becoming more popular in food processing; however, little detailed research has been conducted on the study of the lethal effect of these technologies on certain microorganisms. Saccharomyces cerevisiae is a yeast related to spoilage of fruit products such as juices; novel technologies have been explored to inactivate this yeast. Three nonthermal technologies, high hydrostatic pressure (HHP), pulsed electric fields (PEF) and thermo-sonication (TS), were used to evaluate and to compare the structural damage of yeast cells after processing. Processing conditions were chosen based on previous experiments to ensure the death of cells; HHP was conducted at 600 MPa for 7 min (room temperature, 21 °C); for PEF, 30.76 kV/cm at 40 °C and 21 pulses (2 μs each), and finally for TS the conditions were 120 μm, 60 °C and 30 min in continuous and pulsed modes; all treatments were applied in apple juice. Cells were prepared for electron microscopy using an innovative and short microwave assisted dehydration technique. Scanning electron microscopy showed the degree of damage to the cells after processing and illustrated the important and particular characteristics of each technology. Cells treated with high hydrostatic pressure showed a total disruption of the cell membrane, perforation, and release of the cell wall; scars were also observed on the surface of the pressurized cells. PEF treated cells showed less superficial damage, with the main changes being the deformation of the cells, apparent fusion of cells, the formation of pores, and the breakdown of the cell wall in some cells. Finally, the thermo-sonicated cells showed a similar degree of cellular damage to their structure regardless of whether the TS was applied continuously or pulsed. The main characteristics of cellular death for this technology were the erosion and disruption of the cellular membrane, formation of orifices on the surface, lysis of cells causing the release of intracellular contents, roughness of the cell membrane, and displacement of cell debris to the surface of other cells. This study confirms some theories about cell inactivation and presents new and detailed results about nonthermal technologies, but also shows that after using the above mentioned conditions, recovery of cells, specifically those that are pressurized and thermo-sonicated, it is not possible to do it following the high extent of damage observed in the entire population. Furthermore, a faster methodology that was used in sample preparation for electron microscopy provided high quality resolution images, allowing closer study of the detail of structural lethal effects on treated cells.     

Simultaneous application of microbial transglutaminase and high hydrostatic pressure to improve heat induced gelation of pork plasma

The effects of treating porcine plasma with microbial tranglutaminase (MTGase) under high hydrostatic pressure (HHP) were studied as a means of improving its gel-forming properties when subsequently heated at pH 5.5, near the pH of meats. Plasma containing varying levels of commercial MTGase was pressurized (400MPa, room temperature, pH 7) for different times, and adjusted to pH 5.5 prior to heating to induce gelation. MTGase-treatment under HHP led to greater enhancement of heat-induced plasma gel properties as compared to control samples. The greatest improvements were achieved by pressurising plasma with 43.3U MTGase/g protein for 30min, thereby achieving recoveries of 49% and 63% in fracture force (gel strength) and fracture distance (gel deformability) of the subsequently heat-induced gels, respectively, relative to gel properties obtained by heating untreated plasma at physiological conditions (pH 7.5).     

Design and scale-up of pressurized fluid extractors for food and bioproducts

This article provides an in-depth review of the literature on the design, scale-up, and effects of scale on the extraction of food and bioproducts in pressurized fluid extractors. The design of pressurized fluid extraction systems such as supercritical CO₂, pressurized solvent, and pressurized low polarity water (subcritical water) are similar. Knowledge of phase equilibria, mass transfer rate, and solubility data are important first steps for the scale-up of extraction processes and equipment. The literature for the design, scale-up, and effects of scale on the extraction of bioproducts in pressurized fluid extractors is examined with particular attention to the mass transfer principal and important parameters for extraction as they relate to the design and scale-up of fixed bed pressurized fluid extractors. Often when two scales of an extractor are examined, the scale-up has not been done uniformly, leaving the effects of the scale-up on extraction in doubt. There has been some success in design of a continuous pressurized fluid extractor by utilizing a battery of vessels in series to operate on a quasi-continuous basis, and with the use of screw conveyors to produce a gas-tight plug of material, which allows the extraction to operate at the necessary elevated pressures and temperatures.     

超高压对天然肠衣力学特性的影响

天然肠衣在不同的应用场合具有不同的力学性能要求,将超高压引入肠衣的加工,可改变其力学特性。本研究选择天然猪肠衣作为原料,通过单因素试验方法分别考察加压水平(100～600MPa)、加压介质温度(20～45℃)和保压时间(5～30min)对肠衣剪切强度和抗拉强度的影响。研究结果表明：加压介质温度20℃时,300～600MPa的压力可显著提高肠衣的剪切强度与抗拉强度(p ＜ 0.05);而加压介质温度45℃时,300MPa 的压力可导致肠衣剪切强度与抗拉强度的显著降低(p ＜ 0.05);300MPa 作用下,5～30min 范围内的保压时间对肠衣剪切强度、抗拉强度均无显著性影响(p ＞ 0.05)。因此,超高压导致肠衣剪切强度与抗拉强度的降低,可改善其食用的质构品质;而超高压提高肠衣强度的作用则可增强其在组织工程中应用的可行性。