En este trabajo se ha realizado en quesos canarios un estudio comparado entre algunos modelos de prediccion para el calculo de la actividad del agua. En la aplicacion generica la ecuacion que obtiene unos resultados que mas se ajustan a los experimentales es la propuesta por Marcos et al. (1983a): aw = 1,0234 - 0,007 g cenizas/100 g H2O. No obstante es en la aplicacion restringida a quesos con un porcentaje de agua igual o superior al 40 por ciento, donde se obtienen mejores ajustes. La ecuacion de regresion (Millan et al., 1991) en la que se combinan los efectos depresores de la fraccion del nitrogeno no proteico (NNP) y de la modalidad del cloruro sodico en el agua toal (m), obtiene buenos ajustes en el 100 por cien de las muestras: aw = 1,00343 - 0,00055 NNP - 0,03280 m.

Se ha determinado la Aw y el pH en cincuenta y dos muestras de queso: 12 frescos (menos de 20 dias de maduracion), 15 semicurados (entre 20 y 45 dias) y 25 curados (mas de 45 dias de maduracion) elaborados con distintos tipos de leche (vaca, oveja, cabra y mezcla) procedentes de la region sur de Espana (Granada, Jaen, Cordoba, Sevilla, Badajoz, Albacete y Ciudad Real.

Viticulture in Baja California (Mexico), located in a semi-arid region, is limited by the availability of water. Treated wastewater (TWW), however, could be used to irrigate some crops. Therefore, the objective of this study was to assess the effect of irrigating grapevines with TWW on the microbiological and chemical quality of grapes in the Guadalupe Valley. Five-year-old Tempranillo grapevines were irrigated with 10 or 20 L week-1 of TWW from the El Sauzal wastewater treatment plant; for the control treatment, water from the Guadalupe Valley aquifer was used. The analysis showed that TWW satisfied all the parameters of the norms NOM-001-SEMARNAT-1996 and NOM-003-SEMARNAT-1997 for restricted and non-restricted irrigation, as well as for direct and indirect contact during the study. No significant differences (p>0.05) were observed in pH, titratable acidity, the concentration of soluble solids (sugar) or yeast assimilable nitrogen in the grapes, regardless of the type of water used for irrigation. The concentrations of the Ca, Mg, Na and K ions were not affected by the irrigation treatments (p> 0.05). This study shows that TWW from the El Sauzal treatment plant did not cause short-term negative impacts on the quality of grapes for vinification, and that treated water could be used to irrigate this crop. | La viticultura está limitada en Baja California por la disponibilidad del agua debido a que es una zona semidesértica, peto las aguas residuales tratadas (ART) se podrían utilizar pata regar algunos cultivos. Por tanto, el objetivo de este estudio fue evaluar el impacto del riego de la vid con ART sobre la calidad microbiológica y química de las uvas en el Valle de Guadalupe, México. Entre 10 a 20 L semana-1 de ART de la planta de tratamiento de El Sauzal fueron aplicados a vides Tempranillo de 5 años de edad y para los testigos se usó agua del acuífero Valle de Guadalupe. El análisis mostró que las ART de la planta de tratamiento cumplieron con todos los parámetros de las normas NOM-001-SEMARNAT-1996 y NOM-003-SEMARNAT-1997 para el riego restringido y no restringido, así como para el contacto directo e indirecto durante el estudio. No se observaron diferencias significativas (p>0.05) en pH, acidez titulable, concentración de sólidos solubles (azúcar) y nitrógeno asimilable por las levaduras de las uvas, independientemente del tipo de agua aplicada como riego. Las concentraciones de los iones de Ca, Mg, Na y K no fueron afectadas por los tratamientos de riego (p> 0.05). Este estudio muestra que el ART de la planta de tratamiento de El Sauzal no tuvo un impacto negativo a corto plazo sobre la calidad de la uva para vinificación y el agua tratada podría usarse para regar este cultivo.

The efficacy of postharvest hot-dip treatment on Redblush grapefruit was investigated by 3-min dips in water at 50°C and 20°C, with and without 1500 ppm imazalil (IMZ) or thiabendazole (TBZ). Fruits were stored for 16 weeks in cold rooms at 8°C and then held at 20°C for 1 week to simulate shelf life. IMZ and TBZ treatment at 20°C considerably reduced the incidence of chilling injury (by about 50-60%) and the percentage (by 20%) of fungal infections. The effectiveness of the two fungicides was found to be considerably increased at 50°C. However, the beneficial effect of hot-dip treatment was noted, whether or not associated with the use of fungicides. The chilling index was threefold lower in fruit dipped in water at 50°C. Similar results were obtained by IMZ treatment and mold decay was decreased by about 50%. IMZ treatment at 50°C proved to be phytotoxic, thus resulting in reddish peel pitting, starting on the fourth week of storage. No further detrimental heat-related effect was detected in the remaining cases. Fruit treated with the two fungicides exhibited no significant differences in respiration rate under cold storage, when compared to control. By contrast, by the end of shelf life, sharply increased values were found in fruit treated with IMZ at 20°C. Endogenous ethylene production and internal quality attributes (juice%, total soluble solid content, juice acidity, and ripening index) did not reveal important differences between treatments. Ethanol concentration in the juice was remarkably lower in fruit treated with the two fungicides, whereas differences due to dip temperature were negligible in most cases.