Radio Frequency Treatment of Food: A Review on Pasteurization and Disinfestation.

Radio frequency (RF) is a novel technology with several food processing and preservation applications. It is based on the volumetric heating generated from the product's dielectric properties. The dielectric properties of each material are unique and a function of several factors (i.e., temperature, moisture content). This review presents a list of dielectric properties of several foods and describes the use of RF as an innovative technology for the food industry. This paper includes several examples of pasteurization, fungi inactivation, and disinfestation in selected food products. The aim of this review is to present the potential applications of RF in pasteurization and disinfestation and research needs that should be addressed. RF has been successfully applied in the inactivation of pathogens such as Salmonella spp., Listeria monocytogenes, and Escherichia coli in low- and high-moisture food. The disinfestation of crops is possible using RF because of selective heating. This process inactivates the insects first because of the different dielectric properties between the pests and the food. The products' final quality can be considerably better than conventional thermal processes. The processing time is reduced compared to traditional heating, and thermal damage to the food is minimized. The main drawback of the technology is the lack of uniform heating, mainly when the product is surrounded by a packaging material with different dielectric properties from the food.

Colombian biodiversity is governed by a rich and diverse policy mix.

We lack an understanding of how diverse policymakers interact to govern biodiversity. Taking Colombia as a focal case, we examined six decades of biodiversity governance (1959-2018). Here we analysed the composition of the policy mix, and how it has evolved over time, how policies differ among lead actors and ecosystems, and whether the policy mix addresses the primary threats to biodiversity. We identified 186 biodiversity-related policies that govern multiple ecosystems, use different instruments and address the main threats to biodiversity (that is, agriculture and aquaculture, and biological resource use). We found policy gaps in the governance of invasive species and wildlife trade. Biodiversity policy integration into some sectoral policies, such as climate change, poverty and pollution, has become more common in the past decade. Our results point to an increased need for effective coordination across sectors and actors, as new ones influence and implement the policy mix.

A review on egg pasteurization and disinfection: Traditional and novel processing technologies.

Salmonella Enteritidis is a pathogen related to many foodborne outbreaks involving eggs and egg products. Regulations about whether eggs should be pasteurized are very different and inconsistent worldwide. In the United States, eggs are not required to be pasteurized. Hence, less than 3% of the eggs in the country are pasteurized. The standard pasteurization method (57°C, 57.5 min) uses a long thermal process that increases the cost of the product and affects its quality. Foodborne outbreaks can be reduced if eggs are properly pasteurized to inactivate Salmonella spp. However, the technology to pasteurize eggs needs to offer a faster and more reliable method that can be scaled up to industry settings at a low cost and without affecting product quality. Several novel technologies have been tested for eggshell disinfection and egg pasteurization. Some thermal technologies have been evaluated for the pasteurization of eggs. Microwave has limited penetration depth and is a technical challenge for egg pasteurization. However, radio frequency can penetrate eggshells effectively to inactivate Salmonella, considerably reduce processing time, and maintain the quality of the product. Nonthermal technologies such as ultraviolet, pulsed light, cold plasma, ozone, pressure carbon dioxide, electrolyzed water, and natural antimicrobials have been explored for surface cleaning of the intact egg as alternatives without affecting the internal quality. This review presents some of these novel technologies and the current challenges. It discusses the possible combination of factors to achieve the egg's internal pasteurization and the eggshell's disinfection without affecting the quality at a low cost for the consumer.

Reconstrucción en amputaciones distales de dedos en niños con injerto compuesto y vendaje semioclusivo / Reconstruction of distal finger amputations in children with composite autograft and semi-oclusive dressing

La reconstrucción de una amputación distal de dedo en un niño es un desafío. Los procedimientos propuestos son muchos, y los resultados no han sido buenos. La reconstrucción con reposición del segmento a modo de injerto compuesto, o con técnicas microquirúrgicas, parece ofrecer la mejor de las posibilidades, pues se conservan estructuras irremplazables, como el lecho ungueal y el hiponiquio, lo que permite que los niños mantengan un pulpejo anatómico y con función normal. Presentamos una serie de tres pacientes pediátricos tratados con una nueva técnica, que combina la reposición del segmento, como un injerto compuesto, y el uso de curación semioclusiva (composite autograft and semi-oclussive dressing, CASOD, en inglés). Hemos observado buenos resultados.

The reconstruction of finger tip amputation in children is challenging. There are many procedures described to treat this injury, none of which present optimal results. Repositioning of the amputated segment as an autograft or with microsurgical techniques seems to offer the best outcome. It enables the preservation of otherwise irreplaceable structures, such as the nail bed and the hyponychium, thus enabling children to mantain an anatomically and functionally normal finger pad. We present a series of three pediatric patients treated with tha new technique, which combines composite autograft and semi-oclusive dressing (CASOD). The results observed so far have been promising.

[Temporal association between the circulation of respiratory viruses and hospitalizations due to Kawasaki disease]. / Asociación temporal entre la circulación de virus respiratorios y hospitalizaciones por enfermedad de Kawasaki.

BACKGROUND: The etiology of Kawasaki disease (KD) is unknown. It is believed that viral infections could trigger the disease in susceptible patients. AIM: To study the temporal association between the circulation of respiratory viruses and KD hospitalizations in the Metropolitan Region (MR), Chile, between 2010-2017. METHODS: Ecologic study consisting of a review of KD cases in children under 18 years of age based on hospital discharges. The circulation of respiratory viruses was analyzed using the report of the metropolitan surveillance network. Moving averages for KD (MAKD) and respiratory viruses (MARV) were used. RESULTS: 14,902 cases of respiratory virus infections were recorded between 2010-2017. A direct correlation was found between MARV-respiratory syncytial virus (RSV) of one month and year and MAKD of the subsequent month (correlation coefficient (ρ) = +0.441; p < 0.001). A similar association was found for MARV-influenza A (FLU A) (ρ = + 0.362; p < 0.001). MARV-influenza B (FLU B) and MARV-metapneumovirus (MPV) had direct correlations with MAKD (ρ = +0.443; p < 0.001 and ρ = +0.412; p < 0.001, respectively), being FLU B contemporary in month and year with KD, and MPV presenting a one-month lag. CONCLUSION: There is a direct temporal correlation between RSV, FLU A, FLU B and MPV circulation and KD in children from RM, Chile.

Displasia del desarrollo de la cadera: tamizaje y manejo en el lactante / Developmental dysplasia of the hip: screening and management in the infant

La displasia del desarrollo de la cadera comprende un conjunto de anormalidades que afectan la articulación coxofemoral: la displasia, subluxación y luxación de la cadera. El concepto de "displasia" describe anormalidades en la estructura femoral, acetabular o ambas. Corresponde a la patología ortopédica más frecuente del recién nacido y lactante, lo que genera mucha preocupación e intranquilidad entre los padres, en los primeros controles sanos de sus hijos. Es una patología en la que un diagnóstico oportuno y precoz son la clave para poder realizar un tratamiento efectivo, obteniendo como resultado una cadera clínica y radiológicamente normal al finalizar el desarrollo esquelético. Para esto es fundamental conocer la patología e ir activamente en su búsqueda. Actualmente existe mucha discusión sobre la manera de pesquisar esta patología. En Chile, se realiza tamizaje universal con imagen -radiografía de pelvis- a todos los niños a los 3 meses de edad. El objetivo de la siguiente revisión, es traer a la práctica clínica actual de todos aquellos profesionales que se enfrentan en distintos escenarios a esta patología: médicos de atención primaria, enfermeras, médicos en etapas de destinación y formación en distintas regiones del país, pediatras y ortopedistas, aquellas características y signos de sospecha propios de esta enfermedad y detallar las herramientas para un correcto diagnóstico y oportuno tratamiento.

Developmental dysplasia of the hip (DDH) comprises a set of abnormalities that affect the hip joint: hip dysplasia, subluxation, and dislocation. It is the most frequent orthopedic pathology of the newborn and infant, and it generates great concern among parents during the first health check-ups of their children. It is a condition in which a timely and early diagnosis is key to be able to carry out an effective treatment, obtaining as a result of a clinically and radiologically normal hip at the end of skeletal development. For this, it is essential to know this orthopedic condition and actively search for it. Currently, there is much discussion about how to screen DDH. In Chile, universal screening with imaging - pelvic radiography - is performed on all children at 3 months of age. The objective of the following review is to bring to the current clinical practice of all those professionals who face this pathology in different scenarios: primary care physicians, nurses, physicians in training stages in different regions of the country, pediatricians and orthopedic surgeons, signs of suspicion typical of the disease and detail the assessment tools for a correct diagnosis and timely treatment.

Asociación temporal entre la circulación de virus respiratorios y hospitalizaciones por enfermedad de Kawasaki / Temporal association between the circulation of respiratory viruses and hospitalizations due to Kawasaki disease

INTRODUCCIÓN: La etiología de la enfermedad de Kawasaki (EK) es desconocida, planteándose que infecciones virales la gatillan en pacientes susceptibles. OBJETIVO: Estudiar la asociación temporal entre la circulación de virus respiratorios y hospitalizaciones por EK en la Región Metropolitana (RM), Chile, entre 2010-2017. METODOLOGÍA: Estudio ecológico retrospectivo de casos de EK en pacientes bajo 18 años de edad, en base a egresos hospitalarios. La circulación de virus se analizó mediante el reporte de la red de vigilancia metropolitana. Se utilizaron promedios móviles para EK (PMEK) y virus respiratorios (PMVR). RESULTADOS: Se registraron 14.902 casos de infecciones virales respiratorias entre 2010-2017. Se observó correlación directa entre PMVR-virus respiratorio sincicial (VRS) de un mes y año y PMEK del mes subsiguiente (coeficiente de correlación (ρ) = +0,441; p < 0,001), y una asociación similar para PMVR-influenza A (FLU A) (ρ = +0,362; p < 0,001). PMVR-influenza B (FLU B) y PMVR-metapneumovirus (MPV) presentan correlaciones directas con PMEK (ρ = +0,443; p < 0,001 y ρ = +0,412; p < 0,001, respectivamente), siendo contemporáneo en mes y año con EK para FLU B, mientras que MPV presenta un desfase de un mes entre PMVR y PMEK. CONCLUSIÓN: Existe correlación temporal directa entre la circulación de VRS, FLU A, FLU B y MPV con EK en niños de la RM, Chile.

BACKGROUND: The etiology of Kawasaki disease (KD) is unknown. It is believed that viral infections could trigger the disease in susceptible patients. AIM: To study the temporal association between the circulation of respiratory viruses and KD hospitalizations in the Metropolitan Region (MR), Chile, between 2010-2017. METHODS: Ecologic study consisting of a review of KD cases in children under 18 years of age based on hospital discharges. The circulation of respiratory viruses was analyzed using the report of the metropolitan surveillance network. Moving averages for KD (MAKD) and respiratory viruses (MARV) were used. RESULTS: 14,902 cases of respiratory virus infections were recorded between 2010-2017. A direct correlation was found between MARV-respiratory syncytial virus (RSV) of one month and year and MAKD of the subsequent month (correlation coefficient (ρ) = +0.441; p < 0.001). A similar association was found for MARV-influenza A (FLU A) (ρ = + 0.362; p < 0.001). MARV-influenza B (FLU B) and MARV-metapneumovirus (MPV) had direct correlations with MAKD (ρ = +0.443; p < 0.001 and ρ = +0.412; p < 0.001, respectively), being FLU B contemporary in month and year with KD, and MPV presenting a one-month lag. CONCLUSION: There is a direct temporal correlation between RSV, FLU A, FLU B and MPV circulation and KD in children from RM, Chile.

Combined Effect of Ultrasound and Mild Temperatures on the Inactivation of E. coli in Fresh Carrot Juice and Changes on its Physicochemical Characteristics.

The combination of ultrasound and mild temperatures to process fruits and vegetables juices is a novel approach that is showing promising results for microbial inactivation and preservation of bioactive compounds and sensory attributes. This study centers on investigating the inactivation of Escherichia coli (ATCC 11755) in carrot juice as a result of the combined effect of ultrasound (24 kHz frequency, 120 µm, and 400 W) with temperature (50, 54, and 58 °C) and processing time (0 to 10 min). In addition, the possible changes in physicochemical properties and the retention of bioactive compounds after processing were analyzed. Microbial inactivation with ultrasound treatment at 50 °C resulted in 3.5 log reduction after 10 min, whereas at 54 °C almost 5 log reduction was attained in the same period of time; meanwhile, for treatment at 58 °C, no viable cells were detected (>5 log reduction) after 2 min. There was no significant difference (P > 0.05) on pH (6.80 to 6.82), °Brix (8.0 to 8.5), titratable acidity (0.29% to 0.30%), total carotenoid (1774 to 1835 µg/100 mL), phenolic compounds (20.19 to 20.63 µg/mL), ascorbic acid (4.8 mg/100 mL), and color parameters between fresh and ultrasound treated samples at the studied temperatures. To predict the inactivation patterns, observed values were tested using 3 different general models: first-order, Weibull distribution, and biphasic. The Weibull and biphasic models show good correlation for inactivation under all processing conditions. Results show ultrasound in combination with mild temperature could be effectively used to process fresh carrot juice providing a safe product without affecting physicochemical characteristics. PRACTICAL APPLICATIONS: The combination of ultrasound and mild temperatures is effective in reducing microbial load in carrot juice to safe levels. This combination would be beneficial in the industrial processing of carrot juice without altering the quality attributes or bioactive compounds.

Conocimiento de los padres sobre la fiebre en niños menores de 5 años que acuden al servicio de emergencias en el Hospital del Niño Dr. Ovidio Aliaga Uría / Parent's knowledge about fever in children under 5 attending emergency department at Dr. Ovidio Aliaga Uría children hospital

OBJETIVO: Determinar el conocimiento sobre la fiebre, de los padres de niños menores de 5 años que acuden al servicio de Emergencias del Hospital de Niño DISEÑO: descriptivo prospectivo de serie de casos. LUGAR: El estudio se realizó entre octubre de 2016 y noviembre de 2016 en el Servicio de Emergencias del Hospital del Niño "Ovidio Aliaga Uría" de la ciudad de La Paz. PARTICIPANTES: padres de niños febriles que acudieron al Hospital del Niño "Ovidio Aliaga Uría" de 0 a 59 meses de edad MEDICIONES PRINCIPALES: el instrumento evaluó la escolaridad de los padres, el punto de corte considerado como fiebre, las consecuencias temidas de la fiebre, la droga usada para la fiebre, la dosis administrada en caso de usarse algún medicamento, la fuente de información de donde se obtuvo el conocimiento de fiebre, si se sabe medir la temperatura, cual es el método más usado para la medición de temperatura y cuáles son los tratamientos alternativos que se utilizan. RESULTADOS. El intervalo de alza térmica que los padres consideran como una fiebre es entre 37 a 37,5°C (52%). El temor de los padres es que la temperatura incremente por más de 39°C con un porcentaje de 59%. El principal temor de los padres frente a un alza térmica es que desencadene convulsiones 46%. El medicamento más utilizado es el paracetamol 53%, las dosis administradas por los padres de antitérmicos son dosis inadecuadas en 50% de los casos. Saben medir la fiebre 64% siendo el principal instrumento utilizado el termómetro oral (36%). CONCLUSIONES. Una gran parte de los padres manejan un concepto errado respecto al punto de corte para considerar fiebre. El principal temor de los padres ante el ascenso de la misma es la presencia de convulsiones. La droga más usada por los padres que participaron en nuestro estudio es el paracetamol. La principal fuente de información de los padres era la información brindada por personal de salud, pero existe una tendencia a usar sobredosis de antitérmicos. Aún son usados métodos caseros y naturales para controlar la fiebre.

OBJECTIVE: To determine knowledge about fever in parents of young children attending to emergency department. DESIGN: Descriptive and prospective study from case series. PLACE: The study was conducted from October to November 2016 in emergency department at Dr. Ovidio Aliaga Uría Children Hospital. PARTICIPANTS: Parents of young children from 0 to 59 months old that showed febrile seizures at attending emergency room in the hospital. MAIN MEASURES: Survey considered parents knowledge about the cut off to consider fever, feared consequences of fever, used drugs to treat, drug doses in case of administrating medicaments, source of information regarding knowledge about fever, how to measure children temperature, the methods to measure temperature and the alternative treatments about fever. RESULTS: Parents considered fever when temperature rises between 37 to 37,5 °C (52%). Parents get afraid when temperature increases higher than 39 °C, in a 59%. The presence of seizures is the main fear in parents (46%). paracetamol is most used drug. 50%the cases displayed an inadequate dose administration of antipyretic. CONCLUSIONS: most of the parents have an inadequate concept about the cut of to consider fever. The mean fear is the presence of fever seizures, paracetamol is the most used drug. The source information of parents is obtained from health staff, but they tend to overdose the administration of antipyretics, and the use of home methods is still common.

Reelin supplementation recovers synaptic plasticity and cognitive deficits in a mouse model for Angelman syndrome.

The Reelin signaling pathway is implicated in processes controlling synaptic plasticity and hippocampus-dependent learning and memory. A single direct in vivo application of Reelin enhances long-term potentiation, increases dendritic spine density and improves associative and spatial learning and memory. Angelman syndrome (AS) is a neurological disorder that presents with an overall defect in synaptic function, including decreased long-term potentiation, reduced dendritic spine density, and deficits in learning and memory, making it an attractive model in which to examine the ability of Reelin to recover synaptic function and cognitive deficits. In this study, we investigated the effects of Reelin administration on synaptic plasticity and cognitive function in a mouse model of AS and demonstrated that bilateral, intraventricular injections of Reelin recover synaptic function and corresponding hippocampus-dependent associative and spatial learning and memory. Additionally, we describe alteration of the Reelin profile in tissue from both the AS mouse and post-mortem human brain.

Physico-chemical parameters, bioactive compounds and microbial quality of thermo-sonicated carrot juice during storage.

Thermosonication has been successfully tested in food for microbial inactivation; however, changes in bioactive compounds and shelf-life of treated products have not been thoroughly investigated. Carrot juice was thermo-sonicated (24 kHz, 120 µm amplitude) at 50 °C, 54 °C and 58 °C for 10 min (acoustic power 2204.40, 2155.72, 2181.68 mW/mL, respectively). Quality parameters and microbial growth were evaluated after processing and during storage at 4 °C. Control and sonicated treatments at 50 °C and 54 °C had 10, 12 and 14 d of shelf-life, respectively. Samples sonicated at 58 °C had the best quality; microbial growth remained low at around 3-log for mesophiles, 4.5-log for yeasts and molds and 2-log for enterobacteria after 20 d of storage. Furthermore, thermo-sonicated juice at 58 °C retained >98% of carotenoids and 100% of ascorbic acid. Phenolic compounds increased in all stored, treated juices. Thermo-sonication is therefore a promising technology for preserving the quality of carrot juice by minimising the physicochemical changes during storage, retarding microbial growth and retaining the bioactive compounds.

Adult stem cell transplantation: is gender a factor in stemness?

Cell therapy now constitutes an important area of regenerative medicine. The aging of the population has mandated the discovery and development of new and innovative therapeutic modalities to combat devastating disorders such as stroke. Menstrual blood and Sertoli cells represent two sources of viable transplantable cells that are gender-specific, both of which appear to have potential as donor cells for transplantation in stroke. During the subacute phase of stroke, the use of autologous cells offers effective and practical clinical application and is suggestive of the many benefits of using the aforementioned gender-specific cells. For example, in addition to being exceptionally immunosuppressive, testis-derived Sertoli cells secrete many growth and trophic factors and have been shown to aid in the functional recovery of animals transplanted with fetal dopaminergic cells. Correspondingly, menstrual blood cells are easily obtainable and exhibit angiogenic characteristics, proliferative capability, and pluripotency. Of further interest is the ability of menstrual blood cells, following transplantation in stroke models, to migrate to the infarct site, secrete neurotrophic factors, regulate the inflammatory response, and be steered towards neural differentiation. From cell isolation to transplantation, we emphasize in this review paper the practicality and relevance of the experimental and clinical use of gender-specific stem cells, such as Sertoli cells and menstrual blood cells, in the treatment of stroke.

Stem cell therapy for neonatal hypoxic-ischemic encephalopathy.

Treatments for neonatal hypoxic-ischemic encephalopathy (HIE) have been limited. The aim of this paper is to offer translational research guidance on stem cell therapy for neonatal HIE by examining clinically relevant animal models, practical stem cell sources, safety and efficacy of endpoint assays, as well as a general understanding of modes of action of this cellular therapy. In order to do so, we discuss the clinical manifestations of HIE, highlighting its overlapping pathologies with stroke and providing insights on the potential of cell therapy currently investigated in stroke, for HIE. To this end, we draw guidance from recommendations outlined in stem cell therapeutics as an emerging paradigm for stroke or STEPS, which have been recently modified to Baby STEPS to cater for the "neonatal" symptoms of HIE. These guidelines recognized that neonatal HIE exhibit distinct disease symptoms from adult stroke in need of an innovative translational approach that facilitates the entry of cell therapy in the clinic. Finally, new information about recent clinical trials and insights into combination therapy are provided with the vision that stem cell therapy may benefit from available treatments, such as hypothermia, already being tested in children diagnosed with HIE.

Therapeutic outcomes of transplantation of amniotic fluid-derived stem cells in experimental ischemic stroke.

Accumulating preclinical evidence suggests the use of amnion as a source of stem cells for investigations of basic science concepts related to developmental cell biology, but also for stem cells' therapeutic applications in treating human disorders. We previously reported isolation of viable rat amniotic fluid-derived stem (AFS) cells. Subsequently, we recently reported the therapeutic benefits of intravenous transplantation of AFS cells in a rodent model of ischemic stroke. Parallel lines of investigations have provided safety and efficacy of stem cell therapy for treating stroke and other neurological disorders. This review article highlights the need for investigations of mechanisms underlying AFS cells' therapeutic benefits and discusses lab-to-clinic translational gating items in an effort to optimize the clinical application of the cell transplantation for stroke.

Advanced retorting, microwave assisted thermal sterilization (MATS), and pressure assisted thermal sterilization (PATS) to process meat products.

Conventional thermal processes have been very reliable in offering safe sterilized meat products, but some of those products are of questionable overall quality. Flavor, aroma, and texture, among other attributes, are significantly affected during such processes. To improve those quality attributes, alternative approaches to sterilizing meat and meat products have been explored in the last few years. Most of the new strategies for sterilizing meat products rely on using thermal approaches, but in a more efficient way than in conventional methods. Some of these emerging technologies have proven to be reliable and have been formally approved by regulatory agencies such as the FDA. Additional work needs to be done in order for these technologies to be fully adopted by the food industry and to optimize their use. Some of these emerging technologies for sterilizing meat include pressure assisted thermal sterilization (PATS), microwaves, and advanced retorting. This review deals with fundamental and applied aspects of these new and very promising approaches to sterilization of meat products.

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.

Milk processed by pulsed electric fields: evaluation of microbial quality, physicochemical characteristics, and selected nutrients at different storage conditions.

UNLABELLED: Pulsed electric fields (PEF) technology was used to pasteurize raw milk under selected treatments. Processing conditions were: temperature 20, 30, and 40 °C, electric field 30.76 to 53.84 kV/cm, and pulse numbers 12, 24, and 30 for skim milk (SM), and 12, 21, and 30 for whole milk (WM) (2 µs pulse width, monopolar). Physicochemical parameters (pH, electrical conductivity, density, color, solids nonfat [SNF]) and composition (protein and fat content) were measured after processing. Shelf life of SM and WM was assessed after processing at 46.15 kV/cm, combined with temperature (20 to 60 °C) and 30 pulses. Mesophilic and psychrophilic loads and pH were evaluated during storage at 4 and 21 °C. Results showed minor variations in physicochemical properties after processing. There was an interesting trend in SM in SNF, which decreased as treatment became stronger; similar behavior was observed for fat and protein, showing a 0.18% and 0.17% decrease, respectively, under the strongest conditions. Protein and fat content decreased in WM samples treated at 40 °C, showing a decrease in protein (0.11%), and an even higher decrease in fat content. During storage, PEF-treated milk samples showed higher stability at 4 °C with minor variations in pH; after 33 d, pH was higher than 6. However samples at 21 °C showed faster spoilage and pH dropped to 4 after 5 d. Growth of mesophilic bacteria was delayed in both milks after PEF processing, showing a 6- and 7-log cycles for SM and WM, respectively, after day 25 (4 °C); however, psychrophilic bacteria grew faster in both cases. PRACTICAL APPLICATION: Pulsed electric fields (PEF) technology in the pasteurization of liquid food products has shown positive results. Processing times can be reduced considerably, which in turn reduces the loss of nutrients and offers important savings in energy. PEF has been used successfully to pasteurize some liquid foods, but it is still not used commercially in milk pasteurization, although several trials have shown the positive effects of PEF milk pasteurization, which could allow for its future use at the industrial level.

Processing of soft Hispanic cheese ("queso fresco") using thermo-sonicated milk: a study of physicochemical characteristics and storage life.

Queso fresco is a handmade cheese consumed in Latin America and some regions of the United States. However, deficient milk processing has affected its microbial quality and it has an extremely short shelf life and low yield. The objective of this work was to process queso fresco using thermo-sonicated milk; physicochemical parameters were evaluated, including microbial quality during storage (4 °C). An ultrasonic processor (UP400S, 400 W, 24 kHz, 120 µm) was used to sonicate raw milk. Seven milk systems (500 mL each) were evaluated: 1 untreated, and 6 treated at 63 °C/30 min; 63 °C/10 min + sonication; 63 °C/30 min + sonication; 72 °C/15 s; 72 °C/15 s + sonication; and 72 °C/1 min + sonication. A conventional cheese-making process was followed for all systems. The effect of sonication on milk was quite noticeable. Curdling times were reduced considerably, cheese yield (20.6%) was almost doubled, and luminosity of cheese was increased (L*). Textural properties and microstructure images matched very well. Queso fresco processed at 63 °C/120 µm/30 min had the best quality. After storage for 23 d at 4 °C mesophilic count was just 4 log; psychrophilic count, 3.5 log; and enterobacteria count, 3 log. The pH and color remained almost constant and a minor degree of syneresis was observed at end of storage. Due to microstructural rearrangement of the milk components such as fat globules and casein micelles, cheese yield was doubled compared to the traditional handmade product. Shelf life was extended considerably and the product had higher quality.

Inactivation of Pseudomonas fluorescens in skim milk by combinations of pulsed electric fields and organic acids.

Pseudomonas fluorescens suspended in skim milk was inactivated by application of pulsed electric fields (PEF) either alone or in combination with acetic or propionic acid. The initial concentration of microorganisms ranged from 10(5) to 10(6) CFU/ml. Addition of acetic acid and propionic acid to skim milk inactivated 0.24 and 0.48 log CFU/ml P. fluorescens, respectively. Sets of 10, 20, and 30 pulses were applied to the skim milk using exponentially decaying pulses with pulse lengths of 2 micros and pulse frequencies of 3 Hz. Treatment temperature was maintained between 16 and 20 degrees C. In the absence of organic acids, PEF treatment of skim milk at field intensities of 31 and 38 kV/cm reduced P. fluorescens populations by 1.0 to 1.8 and by 1.2 to 1.9 log CFU/ml, respectively. Additions of acetic and propionic acid to the skim milk in a pH range of 5.0 to 5.3 and PEF treatment at 31, 33, and 34 kV/cm, and 36, 37, and 38 kV/cm reduced the population of P. fluorescens by 1.4 and 1.8 log CFU/ml, respectively. No synergistic effect resulted from the combination of PEF with acetic or propionic acid.