Effect of drying on tartric acid and malic acid in Shiraz and Merlot berries

Background and Aims: Grape berries are dried to concentrate sugar and aroma compounds to produce specific wine style. This work aimed to characterise biochemical changes during drying of two different cultivars, considering in particular tartaric acid and malic acid evolution. Methods and Results: Shiraz and Merlot grapes were dried at nine, 15, 21 and 27°C and berries were sampled every 2 to 3 days and sorted by density using NaCl solutions to account for berry heterogeneity. Mass loss of up to 45%, increase in sugar concentration of 71% and decrease in malic acid concentration of 64% were observed. The TA declined by up to 49%. Conclusion: The decline in tartaric acid could be explained by enhanced potassium hydrogen tartrate precipitation inside the berry or during sampling. Significance of the Study: The tartaric acid precipitation causes important analytical biases in physiological experiments. This study illustrates that common analytical methods are often inappropriate and are the reason for inconsistent tartaric acid values in many studies

Attraction of <i>Frankliniella occidentalis</i> Females towards the Aggregation Pheromone Neryl (<i>S</i>)-2-Methylbutanoate and Kairomones in a Y-Olfactometer

An understanding of insect olfaction allows for more specific alternative methods of pest control. We evaluated the responses of the western flower thrips (WFT, Frankliniella occidentalis) in a Y-olfactometer to estimate gas-phase concentrations of the aggregation pheromone neryl (S)-2-methylbutanoate and known kairomones such as methyl isonicotinate, (S)-(-)-verbenone, and p-anisaldehyde. The gas-phase concentrations of these compounds were obtained from the release rates measured in dynamic headspace cells. The compounds were collected from the headspace using dried solid-phase extraction (SPE) cartridges and analyzed with a triple quadrupole GC-MS/MS. We observed that the aggregation pheromone significantly attracted WFT females at doses of 10 and 100 µg, whereas methyl isonicotinate and p-anisaldehyde significantly attracted WFT females at the highest dose. Verbenone did not produce any significant results. A completely different picture was obtained when the gas-phase concentrations were considered. The minimal gas-phase concentrations of the pheromone required to attract WFT females was 0.027 ng/mL, at least 100 times lower than that of the other two compounds. The relevance and implications of our results are discussed in light of the insect’s biology and pest management methods

Development of distillation sensors for spirit beverages production monitoring based on impedance spectroscopy measurement and partial least-squares regression

During spirit beverages production, the distillate is divided into three parts: the head, the heart, and the tail. Acetaldehyde and ethanol are two key markers which allow the correct separation of distillate. Being toxic, the elimination of the head part, which contains a high concentration of acetaldehyde, is crucial to guarantee the consumer’s health and security. Plus, the tail should be separated from the heart based on ethanol concentration. Nowadays, online or in-line sensors for acetaldehyde monitoring during distillation do not exist, and the online sensors for alcohol monitoring, based on density measurement, remain expensive for producers. In this work, we demonstrate the development of distillation monitoring sensors based on electrical impedance spectroscopy (EIS) measurements, combined with PLS-R (partial least-squares regression) modeling. Four types of sensors are proposed and tested with wine-based distillates. Using PLS-R, the best correlations were found for one electrode, named “SpotsSym”. With an R2 up to 89.9% for acetaldehyde concentration prediction and an R2 up to 86.8% for ethanol, the obtained results indicate the promising potential of the proposed approach. To our knowledge, this is the first report of sensors capable of simultaneously measuring ethanol and acetaldehyde concentrations. Furthermore, these sensors offer the advantages of being low cost and nondestructive. Based on these results, the development of an in-line distillation monitoring system is possible in the near future, providing a promising tool for spirit beverages producers

Sport nutritional supplements: quality and doping controls

Proceedings of the 1st International Meeting of the congress on nutrition and athletic performance, Edmonton, Alberta, Canada, August 8-11, 2001 - Communication lors du congrès 'Nutrition et performance sportive', Edmonton, 8-11 aout 1551

Robinia pseudoacacia (Black Locust) – An Invasive Species with Unsuspected Potential in Grappa Ageing: Highlights of Analytical Sciences in Switzerland

No abstract

Characterisation of stem extracts of various grape varieties obtained after maceration under simulated alcoholic fermentation

The removal of stems prior to maceration during red winemaking is generally associated with an improvement in wine quality. However, in recent years, increased interest in the use of stems in winemaking has been observed among winegrowers. Different advantages of this practice have been listed in the literature. In order to better understand their role during winemaking, stems of ten red grape varieties from different winegrowing regions of Switzerland were studied to determine which minerals, acids and polyphenols are extracted under simulated alcoholic fermentation. The composition of the extracts revealed differences between the grape varieties. In addition, the growing conditions and the terroir seem to have an influence on the compounds extracted from the stems, especially the mineral composition such as potassium and copper. Among the extracted polyphenols, phenolic acids and proanthocyanidins were mostly found in the stem extracts, especially caftaric acid, catechin and procyanidin B1. Their concentrations were significant compared to the average values found in wines

Metabolism of Schizosaccharomyces pombe under reduced osmotic stress conditions afforded by fed-batch alcoholic fermentation of white grape must

Strains of Schizosaccharomyces pombe are being increasingly investigated with regards to their grape winemaking potential either in combination with the typical production yeast, Saccharomyces cerevisiae, or in monoseptic fermentations. Their ethanol tolerance and ability to degrade L-malic acid is oenologically convenient but contrasts with the comparatively high acetic acid and acetaldehyde formation potential which is considered undesirable, especially in white winemaking. The purpose of this work was to investigate the performance of a selected S. pombe strain in monoseptic femerntations of white grape must. Traditional batch fermentations were compared with an innovative and automated fed-batch fermentation technique were sugar concentrations are kept low during fermentations to decrease sugar induced osmotic stress. Because of its known effect on growth and ethanol tolerance, the effect of Mg was also tested. While Mg supplementation was not shown to significantly influence residual values of sugars, ethanol, glycerol, organic acids and acetaldehyde, the application of the fed-batch technique led to a fundamental change in yeast physiology. While glycerol values were only slightly reduced, the fed-batch approach allowed obtaining wines devoid of acetic acid whose levels were considerable in wines produced by the traditional batch technique (0.6 g/L). The work demonstrates that the acetic acid metabolism of S. pombe is associated to sugar induced osmotic stress such as for S. cerevisiae, too, and may be controlled by application of suitable fermentation techniques for winemaking

Dosage en continu des sucres et de l'alcool pendant les fermentations par spectroscopie proche infrarouge ::une opportunité pour l'automatisation des vinifications et les défis oenologiques actuels

La spectroscopie infrarouge à transformée de Fourier (IRTF) est fréquemment utilisée pour l’analyse d’échantillons oenologiques en laboratoire. Le but de ce projet était de développer et valider une méthode d’IRTF permettant le dosage automatique des sucres et de l’éthanol en continu, c’est-à-dire directement dans la cuve de fermentation. Pour cela, une sonde de transflectance submersible a été reliée à un spectromètre IRTF proche infrarouge. Des modèles de calibration pour le glucose, le fructose, les sucres totaux (définis comme glucose + fructose) et l’éthanol ont été développés avec des échantillons d’apprentissage issus de plusieurs fermentations en blanc et en rouge. Une fois validés, ces modèles se sont avérés efficaces pour le dosage en continu des sucres totaux et de l’éthanol pendant les fermentations en conditions de turbidité pratiques, rapprochant ainsi le laboratoire de la cave. La méthode de dosage en ligne permet aussi de réaliser des fermentations fed-batch pour réduire le stress des levures et la production de métabolites secondaires tels que l’acide acétique. Son application sera évaluée pour la fermentation de moûts chargés en acide acétique

Insights on the Structural and Metabolic Resistance of Potato (Solanum tuberosum) Cultivars to Tuber Black Dot (Colletotrichum coccodes)

Black dot is a blemish disease of potato tubers caused by the phytopathogenic fungus Colletotrichum coccodes. Qualitative resistance (monogenic) that leads to the hypersensitive response has not been reported against black dot, but commercial potato cultivars show different susceptibility levels to the disease, indicating that quantitative resistance (polygenic) mechanisms against this pathogen exist. Cytological studies are essential to decipher pathogen colonization of the plant tissue, and untargeted metabolomics has been shown effective in highlighting resistance-related metabolites in quantitative resistance. In this study, we used five commercial potato cultivars with different susceptibility levels to black dot, and studied the structural and biochemical aspects that correlate with resistance to black dot using cytological and untargeted metabolomics methods. The cytological approach using semithin sections of potato tuber periderm revealed that C. coccodes colonizes the tuber periderm, but does not penetrate in cortical cells. Furthermore, skin thickness did not correlate with disease susceptibility, indicating that other factors influence quantitative resistance to black dot. Furthermore, suberin amounts did not correlate with black dot severity, and suberin composition was similar between the five potato cultivars studied. On the other hand, the untargeted metabolomics approach allowed highlighting biomarkers of infection, as well as constitutive and induced resistance-related metabolites. Hydroxycinnamic acids, hydroxycinnamic acid amides and steroidal saponins were found to be biomarkers of resistance under control conditions, while hydroxycoumarins were found to be specifically induced in the resistant cultivars. Notably, some of these biomarkers showed antifungal activity in vitro against C. coccodes. Altogether, our results show that quantitative resistance of potatoes to black dot involves structural and biochemical mechanisms, including the production of specialized metabolites with antifungal properties

BRIEF COMMUNICATION Open Access

Daytime pattern of post-exercise protein intake affects whole-body protein turnover in resistance-trained male