ABSTRACT
RESUMEN Los métodos de conservación de alimentos no-térmicos han generado un considerable interés en la industria alimentaria como potencial alternativo a los métodos tradicionales de procesamiento. Uno de los métodos no-térmicos más estudiados es el de campos eléctricos pulsados o PEF (Pulsed Electric Fields). La aplicación de PEF en el procesamiento de alimentos permite limitar la exposición a altas temperaturas y reducir la necesidad de aditivos alimentarios. En PEF, se expone al alimento a pulsos eléctricos generando poros en la membrana celular, este fenómeno se le conoce como electroporación. La electroporación promueve la inactivación de organismos patógenos, reduce la actividad enzimática, favorece la transferencia de masa, mantención de color, sabor y contenido de compuestos antioxidantes, mejora la eficiencia en el procesamiento de alimentos y mantiene de cualidades organolépticas que son atractivas tanto para el consumidor como también para la industria. Los antioxidantes son sustancias capaces de proteger a las células de los radicales libres. La acción de los antioxidantes es de interés tanto del punto de vista sanitario, como industrial. Existe abundante evidencia que asocia el consumo de antioxidantes como factor protector ante enfermedades. Por otro lado, los antioxidantes cumplen un rol importante en la duración de los alimentos ya que actúan como conservantes, prolongando su vida útil. La utilización de PEF, respecto a otras tecnologías para el procesamiento de alimentos, ha demostrado un aumento en la extracción, menor pérdida por temperatura y una mayor disponibilidad de compuestos de interés, incluidos antioxidantes.
ABSTRACT Non-thermal food preservation methods have gained considerable interest in the food industry as a potential alternative to traditional processing methods. One of the most studied non-thermal methods is Pulsed Electric Fields (PEF). The application of PEF in food processing allows limiting exposure to high temperatures and reducing the need for food additives. In PEF, food is exposed to electrical pulses generating pores in the cell membrane, this phenomenon is known as electroporation. Electroporation promotes the inactivation of pathogenic organisms, reduces enzyme activity, favors mass transfer, maintains color, flavor and antioxidant compound content, improves food processing efficiency and maintains organoleptic qualities that are attractive to both the consumer and the industry. Antioxidants are substances capable of protecting cells from free radicals. The action of antioxidants is of interest both from a health and industrial point of view. There is abundant evidence that associates the consumption of antioxidants as a protective factor against diseases. On the other hand, antioxidants play an important role in the shelf life of foods as they act as preservatives, prolonging their shelf life. The use of PEF, compared to other food processing technologies, has shown an increase in extraction, lower temperature loss and greater availability of compounds of interest, including antioxidants.
ABSTRACT
Nanosecond pulsed electric field (nsPEF) is a novel, nonthermal, and minimally invasive modality that can ablate solid tumors by inducing apoptosis. Recent animal experiments show that nsPEF can induce the immunogenic cell death of hepatocellular carcinoma (HCC) and stimulate the host's immune response to kill residual tumor cells and decrease distant metastatic tumors. nsPEF-induced immunity is of great clinical importance because the nonthermal ablation may enhance the immune memory, which can prevent HCC recurrence and metastasis. This review summarized the most advanced research on the effect of nsPEF. The possible mechanisms of how locoregional nsPEF ablation enhances the systemic anticancer immune responses were illustrated. nsPEF stimulates the host immune system to boost stimulation and prevail suppression. Also, nsPEF increases the dendritic cell loading and inhibits the regulatory responses, thereby improving immune stimulation and limiting immunosuppression in HCC-bearing hosts. Therefore, nsPEF has excellent potential for HCC treatment.
Subject(s)
Animals , Carcinoma, Hepatocellular/therapy , Cell Line, Tumor , Immunity , Liver Neoplasms/therapy , Neoplasm Recurrence, LocalABSTRACT
Objective To investigate acute cell damage and delayed inhibition effects by pulsed electric fields(PEFs)with different frequencies on human ovarian carcinoma cell line SKOV3 in vitro and in subcutaneous transplanted tumor of human SKOV3 in BALB/c nude mice,and evaluate the potential use of relatively higher frequency PEFs to reduce unpleasant sensations without decreasing therapeutic effects in clinical electrochemotherapy.Methods Firstly,SKOV3 cell suspension were exposed to PEFs with gradient increasing frequencies(1,60,1 000,5 000 Hz)and voltages(50,100,150,200,250,300,350,400 V),respectively.MTT assay was used to determine the acute cell damage.Then PEFs with gradient increasing frequencies(1,60,1 000,5 000 Hz)and fixed voltage (250 V)were applied to the subcutaneously transplanted tumor,in vivo antitumor assay was used to observe the delayed inhibition effect;histological changes were observed by light and electron microscope. Results The 1 Hz PEFs has similar cytotoxic effects with 5 kHz,and no significant difference of delayed tumor inhibition effect on subcutaneous transplanted tumor among all groups exposed to different frequencies of PEFs(P＞0.05).Histological observation showed acute damage in all exposed groups.and only in 5 kHz group was induced apoptotic effect observed.Conclusions PEFs with relatively higher frequency can achieve similar tumor killing effect with the low frequency PEFs,and it can also induce apoptosis.Relatively higher frequency PEFs show therapeutic potentials for reducing unpleasant sensations in clinical electrical treatment of tumor.
ABSTRACT
Different natural antimicrobials affected viability of bacterial contaminants isolated at critical steps during a beer production process. In the presence of 1 mg/ml chitosan and 0.3 mg/ml hops, the viability of Escherichia coli in an all malt barley extract wort could be reduced to 0.7 and 0.1% respectively after 2 hour- incubation at 4 °C. The addition of 0.0002 mg/ml nisin, 0.1 mg/ml chitosan or 0.3 mg/ml hops, selectively inhibited growth of Pediococcus sp. in more than 10,000 times with respect to brewing yeast in a mixed culture. In the presence of 0.1mg ml chitosan in beer, no viable cells of the thermoresistant strain Bacillus megaterium were detected. Nisin, chitosan and hops increased microbiological stability during storage of a local commercial beer inoculated with Lactobacillus plantarum or Pediococcus sp. isolated from wort. Pulsed Electric Field (PEF) (8 kV/cm, 3 pulses) application enhanced antibacterial activity of nisin and hops but not that of chitosan. The results herein obtained suggest that the use of these antimicrobial compounds in isolation or in combination with PEF would be effective to control bacterial contamination during beer production and storage.
Diferentes antimicrobianos naturales disminuyeron la viabilidad de bacterias contaminantes aisladas en etapas críticas del proceso de producción de cerveza. En un extracto de malta, el agregado de 1 mg/ml de quitosano y de 0,3 mg ml de lúpulo permitió reducir la viabilidad de Escherichia coli a 0,7 y 0,1%, respectivamente, al cabo de 2 horas de incubación a 4 °C. El agregado de 0,0002 mg/ml de nisina, 0,1 mg/ml de quitosano o de 0,3 mg/ml de lúpulo inhibió selectivamente (10.000 veces más) el crecimiento de Pediococcus sp. respecto de la levadura de cerveza en un cultivo mixto. El agregado de 0,1 mg/ml de quitosano permitió disminuir la viabilidad de una cepa bacteriana termorresistente, Bacillus megaterium, hasta niveles no detectables. Por otra parte, el agregado de nisina, quitosano y lúpulo aumentó la estabilidad microbiológica durante el almacenamiento de cervezas inoculadas con Lactobacillus plantarum y Pediococcus sp. aislados de mosto de cerveza. La aplicación de campos eléctricos pulsantes (CEP) (3 pulsos de 8kV/cm) aumentó el efecto antimicrobiano de la nisina y del lúpulo, pero no el del quitosano. Los resultados obtenidos indicarían que el uso de antimicrobianos naturales en forma individual o en combinación con CEP puede constituir un procedimiento efectivo para el control de la contaminación bacteriana durante el proceso de elaboración y almacenamiento de la cerveza.