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[(2)H(10)]-4-Mercapto-4-methylpentan-2-one (d(10)-1), [(2)H(2)]-3-mercaptohexan-1-ol (d(2)-2), and [(2)H(5)]-3-mercaptohex-1-yl acetate (d(5)-3), deuterated analogues of impact odorants of wines, were used to determine quantitatively the natural compounds in white wines (Muscadet, Sauvignon, and Bacchus) with a stable isotope dilution assay using gas chromatography coupled either with ion trap tandem mass spectrometry (GC-ITMS-MS) or with atomic emission detection monitored on sulfur-selective acquisition (GC-AED). The thiol compounds were recovered from wines by liquid-liquid extraction, then purified from the wine extracts by covalent chromatography, and analyzed. The quantitative determination of 4-mercapto-4-methylpentan-2-one 1 in the wines that were analyzed was performed better with GC-AED than with GC-ITMS-MS under the conditions that were used. However, the detection limit of the method was higher than the odor threshold of 4-mercapto-4-methylpentan-2-one 1 in wine (5 vs 0.8 ng/L). The levels of this compound in the Sauvignon and Bacchus wines were much higher than its odor threshold, but it was not detectable in the Muscadet wines. On the contrary, GC-ITMS-MS was much more sensitive than GC-AED for detection of 3-mercaptohexan-1-ol 2 and 3-mercaptohex-1-yl acetate 3, and the detection limits were much lower than their odor thresholds in wine. The former compound was detected in all of the Muscadet wines that were analyzed at levels always higher than its odor detection threshold, while the latter occurred at levels higher than its odor threshold in only one Muscadet wine.  相似文献   
2.
This study describes broad-scale spatial variations in sardine growth across the northeastern Atlantic and Mediterranean waters using opportunistic samples collected in recent years. More detailed information on spatial, decadal and seasonal growth variations is provided for the Iberian-Biscay region using data collected in acoustic surveys since the mid-1980s. Growth curves are fitted to annual or monthly length-at-age data using a robust Von Bertalanffy model; parameters for recent samples are compared with literature information using an auximetric plot while differences between areas within the Iberian-Biscay region are tested by log-likelihood ratio tests. Sardine growth performance is generally lower in the Mediterranean and declines across the northeastern Atlantic from the English Channel to north Morocco but increases sharply off Mauritania. Lower growth of Mediterranean sardines is possibly associated to the overall oligotrophy of this Sea while differentiation from the Atlantic is likely sustained by reproductive isolation between populations from the two areas. Within the northeastern Atlantic, size- and age related migrations may partly explain differences in maximum length/age and mean length-at-age between neighbouring areas but the broad-scale latitudinal decline in growth is consistent with adaptation to the north–south decline in seasonal temperature gradients and to the annual cycles of plankton production. Within the Atlantic Iberian waters, sardine grows and improves in condition during spring and summer when the allocation of energetic resources for gonad development cease, temperature is close to the annual maxima and plankton production is high. Variation in sardine length-at-age and growth within the Atlanto-Iberian stock area has implications for stock structure and needs to be taken into account in the calculation of weight and maturity-at-age for assessment purposes. No evidence of broad temporal changes in sardine growth within the Iberian-Biscay region is obtained.  相似文献   
3.
More than 120 surveys over 25 years suggest that appropriate use of the daily egg production method (DEPM) provides unbiased but rather imprecise estimates of spawning biomass (coefficient of variation generally above 30%). Knowledge of species reproductive biology and early life history and a survey design adapted to local population dynamics are required to optimize DEPM performance in terms of bias, precision and cost. Clupeoid applications dominate worldwide (mainly for anchovies and sardines) and estimates are often used to tune indirect assessment models or to calibrate other fisheries‐independent methods. The method seems better adapted to the life history of anchovies than of sardines, leading to more precise estimates of anchovy spawning biomass and facilitating extensions of the method to estimate total biomass and numbers at age. The continuous underway fish egg sampler is often used as a secondary sampler in the ichthyoplankton survey of the DEPM to reduce the cost and improve the precision of egg production. Multinomial models were recently developed to analyse egg incubation data and used in a Bayesian procedure for egg ageing and delimitation of daily cohorts. These were incorporated in model‐based estimators to get spatially explicit estimates of egg production, daily fecundity parameters and spawning biomass that can improve the precision of DEPM. Uncertainty in daily fecundity estimation of clupeoids is mainly because of spawning fraction estimation by the post‐ovulatory follicle (POF) method. Exploration of recent histological and molecular techniques for POF characterization and laboratory experiments to test the effect of temperature on POF degradation can help to improve spawning fraction estimation. Available estimates of egg production and mortality, daily fecundity, spawning area and biomass from different populations, species and ecosystems are being used to improve the understanding of clupeoid spawning dynamics, their relation with ecosystem productivity and to build comprehensive population models. Finally, a counter‐intuitive finding of this review is that, although the DEPM is almost exclusively applied to clupeoids, recent evidence indicates that it may be easier and cheaper to use in other teleost families, including demersal species.  相似文献   
4.
A study of the volatile fraction of Assyrtiko wines, using gas chromatography coupled with olfactometry, was realized. Twenty-seven volatile compounds were identified as potent odorants, most of them originating from the fermentation process. Quantification of the major volatile compounds was realized developing a rapid analytical method based on fractionation of a 50 mL wine aliquot using C 18-reversed phase adsorbent. After elution of the volatile compounds with pentane-diethyl ether and concentration under nitrogen, the final wine extract was injected in a gas chromatography-flame ionization detection system. The method allows satisfactory determination of more than 15 volatile compounds of wine. The linearity of the method gave a typical r (2) between 0.990 and 0.999, while reproducibility ranged from 5.1 to 12.2% (as relative standard deviation) with 9.5% as the average. The method was applied to wines produced by Assyrtiko grapes (AOC Santorini), for two consecutive years, to compare the effect of skin contact prior to fermentation and the must clarification process. Direct press and skin contact wines were differentiated analytically; however, highly significant differences were not. Inversely, the differences found between direct press/clarified and nonclarified wines were significant. Wines produced by direct press and clarified must presented significantly higher levels of ethylic esters and fusel alcohol acetates but lower fusel alcohol levels, leading probably to more fruity wines. This difference, between clarified and nonclarified grape musts, was not significant in the case of the wines produced by skin contact of Assyrtiko berries. These findings were validated by preference sensory analysis tests.  相似文献   
5.
The influence of site on grape and wine composition was investigated for Vitis vinifera L. cv. Agiorgitiko in the Nemea appellation area in southern Greece. Three nonirrigated plots were studied during the 1997 and 1998 vintages, which were typically very hot and without summer rainfall. Vines were subjected to different water regimens as a result of the variation of soil water-holding capacity and evaporative demand. Vine water status was determined by means of predawn leaf water potential. Differences in vine water status between sites were highly correlated with the earliness of shoot growth cessation and veraison. Grape composition was monitored during fruit ripening. Water deficit accelerated sugar accumulation and malic acid breakdown in the juice. Early water deficit during the growth period was demonstrated to have beneficial effects on the concentration of anthocyanins and total phenolics in berry skins. A similar pattern was observed for the phenolic content of wines elaborated after vinification of grapes harvested on each plot, in both seasons. Limited water availability seemed to increase glycoconjugates of the main aromatic components of grapes as a quantitative increase in levels of bound volatile compounds of the experimental wines was observed under water deficit in both years. Wines produced from grapes of stressed vineyards were also preferred in tasting trials.  相似文献   
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7.

Purpose  

The impact of wildfire on (a) slope hydrological processes, (b) soil erodibility, and (c) post-fire hillslope sediment and phosphorus (P; dissolved and particulate) yields are quantified for natural forest areas of the burned Evrotas River basin, Peloponnese, Greece. Further, the geochemical partitioning of P in burned and unburned sediment is evaluated by sequential extraction to assess potential bioavailability of particulate P (PP) in downstream aquatic ecosystems.  相似文献   
8.
This paper describes the study of 19 wines of the Grenache Noir cultivar obtained from representative soils of the Rhone Valley according to their geographical site, climatic conditions, hydrological regulation, and soil profile. Among the volatile compounds analyzed by GC/MS/FID, the concentrations of the varietal compounds (i.e., beta-damascenone, beta-ionone, and geraniol) and those of the compounds without direct influence on the wine aroma (i.e., hexenols and methanol) indicated the existence of two groups of wines. These concentrations were correlated with grape maturity due to the ecosystem and particularly the soil.  相似文献   
9.
Generalized additive models (GAMs) were fitted to sardine (Sardina pilchardus) egg distribution data from three daily egg production method surveys. The results showed that the area of egg cover off Portugal decreased significantly from 11 800 km2 in 1988 to 7000 km2 in 1997 and 7400 km2 in 1999. This is because of a significant reduction in sardine egg presence off northern Portugal, GAM estimated areas being similar or higher in the late 1990s for southwestern and southern Portugal. The distributional area covered by larvae was not estimated for 1988 (larval distribution extended beyond the survey area), although it was probably higher than the 9600 km2 for 1997 and 5500 km2 for 1999. In 1997 and 1999, the Gulf of Cadiz was also sampled, indicating extensive areas with sardine eggs and larvae (more than 50% of the total area of distribution off Portugal). Standardized data from 15 ichthyoplankton surveys between 1985 and 2000 show a decline in the mean probability of egg presence within the Portuguese continental shelf from the mid‐1980s to the late‐1990s, because of a marked reduction in egg presence off northern Portugal. Sardine larval data from the same surveys suggest that the reduction in mean probability of presence in the north is less marked than for eggs (although this comparison ignores the presence of sardine larvae beyond the continental shelf in the 1980s). Similar changes off northern Portugal and western Galicia are observed in commercial sardine catches and the acoustically estimated area of fish distribution. It is possible that the observed decline in spawning area off northwestern Iberia during the 1990s is indirectly reflecting the prevalence of environmental conditions detrimental to sardine recruitment (northerly winds during winter that favour coastal upwelling and offshore transport), which have reduced the spawning contribution of young fish in that area.  相似文献   
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