Influence of SO<Subscript>2</Subscript> on the evolution of volatile compounds through alcoholic fermentation of must stabilized by pulsed electric fields

The aim of this work was to study the influence of sulphur dioxide (SO₂) on the formation of volatile compounds by yeast through wine alcoholic fermentation. Thus Parellada must was microbiologically stabilized using a pulsed electric field (PEF) treatment and inoculated with Saccharomyces cerevisiae Na33 strain. Fermentation was carried out with or without SO₂ and the results showed that the evolution of the volatile compounds profile throughout the process was similar. The content of volatile acids in wine obtained by using sulphur dioxide was not significantly different from that fermented without adding the compound. However, the final content of total alcohols and esters was significantly different even thought the differences were small. Consequently, when grape must is treated by PEF the sulphur dioxide concentration usually used in winemaking could be reduced to safer levels or even eliminated without an important effect on the volatile compounds content of the final product. Therefore, the absence of sulphur dioxide should not have a negative impact on the sensory characteristics of wine.     

Multivariate cluster analysis to study motility activation of Solea senegalensis spermatozoa: a model for marine teleosts

Computer-assisted sperm analysis (CASA) and clustering analysis have enabled to study sperm subpopulations in mammals, but their use in fish sperm has been limited. We have used spermatozoa from Senegalese sole (Solea senegalensis) as a model for subpopulation analysis in teleostei using two different activating solutions. Semen from six males was activated using 1100 mOsm/kg solutions: artificial seawater (ASW) or sucrose solution (SUC). Motility was acquired at 15, 30, 45, and 60 s post-activation. CASA parameters were combined into two principal components, which were used in a non-hierarchical clustering analysis, obtaining four subpopulations (CL): CL1 (slow/non-linear), CL2 (slow/linear), CL3 (fast/non-linear), and CL4 (fast/linear). We detected spermatozoa lysis, especially in ASW. Sperm motility was higher for SUC and decreased with time. The subpopulation proportions varied with time and activating treatment, showing both an increase in CL1 and CL2 and a decrease in CL3 and CL4 with time. Both CL3 and CL4 were higher in samples activated with SUC, at least in early post-activation. Proportions of CL3 and CL4 at 15 s were associated with higher quality at 60 s and with lower lysis. A second clustering analysis was conducted, classifying the males accordingly to their motility subpopulations. This analysis showed a high heterogeneity between samples. Subpopulation analysis of CASA data can be applied to Solea spermatozoa, allowing identification of potentially interesting sperm subpopulations. Future studies might benefit from these techniques to establish the relationship of these subpopulations with fish sperm quality and fertility, helping to characterize males according to their reproductive potential.     

Quantification of heterocyclic amines from thermally processed meats selected from a small-scale population-based study

Heterocyclic amines (HAs) are potent mutagens that form at high temperatures in cooked, protein-rich food. Due to their frequent intake, these compounds are considered a risk factor for human cancer. Cooking conditions and eating habits strongly influence the level of HA exposure. Thus, it is difficult to assess the intake of HAs in a large population. Food-frequency questionnaires (FFQs), designed to provide data on parameters that affect HA formation, were used to survey a small population (459 persons) from Barcelona (NE Spain). Subsequently, the most-consumed food items named were cooked according to the preferences of the population surveyed and analyzed for HAs using SPE and LC-MS/MS. In the population studied, the estimated intake via consumption of 13 meat dishes was 285.6 ng of mutagenic HAs per capita and day. PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) was the HA to which the population was most exposed, mainly from fried chicken and griddled beef. When the co-mutagens norharman and harman are included, the mean daily intake of HAs rises to 475.6 ng per capita and day. A novel putative DMIP regioisomer was detected in the cooked meats, which was analyzed in the present study by multistage MS.