5 research outputs found
Yeasts and wine off-flavours: a technological perspective
Review article. Part of the special issue "Wine microbiology and safety: from the vineyard to the bottle (Microsafety Wine)", 19-20 Nov. 2009, ItalyIn wine production, yeasts have both beneficial
and detrimental activities. Saccharomyces cerevisiae is the
yeast mainly responsible for turning grape juice into wine
but this species and several others may also show
undesirable effects in wines. Among such effects, technologists
are particularly concerned with the production of offflavours
that may occur during all stages of winemaking.
Typical spoiling activities include the production of ethyl
acetate by apiculate yeasts before fermentation, hydrogen
sulphide by S. cerevisiae during fermentation phases,
acetaldehyde by film-forming yeasts during bulk storage,
and volatile phenols by Dekkera bruxellensis during storage
or after bottling. The occurrence of these hazards depends
on the technological operations designed to obtain a given
type of wine and most can be avoided by current preventive
or curative measures. On the contrary, good manufacturing
practices must be strengthened to deal with the problem of
volatile phenol production in red wines. Appropriate
monitoring of D. bruxellensis populations and quantification
of 4-ethylphenol is advised during storage, particularly
when oak barrels are used, and absence of viable cells must
be guaranteed in bottled wines. This work, which is based
on our experience at winery level, aims to provide
information on appropriate technological strategies to deal
with the problem of off-flavours produced by yeasts
Anoxia in a coastal bay: case study of a seasonal event
Bahía Concepción (Gulf of California) was studied to describe some extremely low dissolved-oxygen values at the bottom of the bay. Surveys included measurements of vertical distribution of temperature, dissolved oxygen, nitrate, nitrite, phosphates and hydrogen sulfide. Thermal stratification from early spring to autumn and a well-mixed water column during the winter were present. Dissolved-oxygen concentration was homogeneous in the water column from winter to spring (5-7 mg L-1). From summer to autumn, bottom dissolved oxygen ( 20 m) decreased to reach conditions of hypoxia (1-2 mg L-1) or anoxia; nitrate, nitrite, and phosphates increased (up to 13, 1.7 and 2.2 *M) followed by a last short period of a deep hydrogen sulfide layer (up to 3.1 mg L-1). A back calculation to estimate the input of organic matter in the deep layer showed that 18 g C m-2y-1 needed to be trapped in the bottom to induce such an oxygen depletion. This period is thought to be unfavorable for bottom infauna in this bay.<br>Se midió seis variables físico-químicas en Bahía Concepción (Golfo de California, 1993 y 1994) para explicar el origen de valores muy bajos de oxígeno disuelto en el fondo. La estructura hidrográfica mostró una fuerte estratificación térmica vertical del inicio de la primavera hasta el otoño, mientras que durante el invierno se observa una columna de agua homogénea. Las concentraciones de oxígeno disuelto siguen el mismo patrón: homogéneas de invierno a primavera (5-7 mg L -1), mientras que del verano al otoño disminuyen en la capa de fondo ( 20-m) hasta alcanzar condiciones de hipoxia (1-2 mg L-1) o anoxia. Las concentraciones de nitrato, nitrito y ortofosfatos también aumentan en la capa de fondo (13, 1.7 y 2.2 *M respectivamente), seguido de un corto período de formación de sulfuro de hidrógeno (hasta 3.1 mg L-1). Por cálculos indirectos se establece que 18 g C m-2 a-1 de materia orgánica son atrapados en el fondo provocando la severa disminución del oxígeno disuelto. Este período se considera crítico para la fauna bentónica de esta bahía
Artisanal fisheries in La Paz Bay and adjacent oceanic area (Gulf of California, Mexico)
We analyzed the artisanal fishery capture data for La Paz Bay (Baja California Sur, Mexico) from 1998 to 2005. Capture data were related to the reproductive cycle of each species. Complete fishing records for 18 species of commercial importance belonging to eight families were identified. The most frequently captured species in La Paz Bay was the Pacific red snapper Lutjanus peru, with 43% of the total capture. This species was followed in importance by the spotted rose snapper Lutjanus guttatus, other groupers (Serranidae), and the jacks (Carangidae), with 18.8%, 15%, and 7.3% of the capture, respectively. Other commercial species captured in smaller amounts included the yellowfin tuna Thunnus albacares, the California flounder (or California halibut) Paralichthys californicus, the flathead mullet Mugil cephalus, the goliath grouper Epinephelus itajara, and different species of mojarra (Gerreidae). With few exceptions, catches outside the bay were higher than in the inner bay. All species were caught throughout the year regardless of their reproductive season. We recommend the implementation of fishery regulations for La Paz Bay, especially in the case of the Pacific red snapper, since it is the most exploited. Currently, overexploitation and possible local shortage of species may occur at any time and without warning in the near future. Aside from fishery management, an attractive option for increasing the supply of marine resources in the area is to use the inner bay for marine fish farming.