Mechanical tests and definition of new indexes of grape berry firmness. Evolution of berry skin hardness during alcoholic fermentation

The mechanical strength or firmness of a fruit is considered an important parameter to characterise its state of ripeness or conservation, as well as other parameters such as sugar level or color. The mechanical hardness of grapes influences the integrity and sanitary quality of the harvest. In this study, the mechanical characteristics of grapevine berries were studied at harvest time in order to determine their rheological properties (firmness and hardness of the berry skin) during alcoholic fermentation. Special indexes were defined measuring the energy needed to crush the berries to 50 % of their initial diameter, and applied successively to two different varieties. The entire berry firmness and the skin hardness were both different. Mechanical indexes linked to grape firmness were defined. Using these indexes, a significant effect on the firmness behavior due to variety was recorded: the skin of 'Grenache Noir' was found firmer and harder than 'Carignan Noir'. Furthermore, during the alcoholic fermentation, no change in skin hardness was observed for both varieties, despite changes in the composition of the must. These results give new information on mechanical properties of berries and could be used as an aid in the winemaking process. Indeed, they would probably help the winemaker to better choose the type of fermentation and maceration adapted to his grapes according to the type of wine he wishes to produce

Informatisation de l'identification varietale des cereales par electrophorese: une premiere etape.

National audienc

Utilisation des paramétres physiques pour la caractérisation de la véraison des baies de raisin

National audienc

Sampling size for determination of adenine nucleotide contents in mature grape berries: application to reference samples analysis

International audienc

Fermeté et maturation du raisin. Définition et évolution de différents paramètres rhéologiques au cours de la maturation

National audienc

Firmness and grape berry maturation. Definition of different rheological parameters during the ripening

Mechanical properties of Shiraz and Gamay grape berries were studied in relation with their maturity state using the PenelaupTM rheometer. The analysis of the constrains registered during berry crushing with the flat tool of the device, up to the pellicular tearing, allowed the definition of different rheological parameters and the characterisation of mechanical behaviour of grape and its evolution with the degree of ripening. The analysis of the deformability curves shows, independently of the cultivar, that berry behaviour is not elastical except for some berries at the beginning and at the end of the ripening. This behaviour can be characterised by two indexes expressing the curvature sense of deformability curves, the curvature degree in a way reflecting the turgescence state of the grape. Berry firmness was also considered in two different ways: the initial firmness which represents the elasticity coefficient of the fruit at the beginning of the deformation, and the bursting firmness which can be considered as the pellicular elasticity coefficient. Others parameters, as the pellicular strength which can be expressed from the value of the displacement at berry bursting and the energy used for the deformation were also defined. The evolution of these different parameters during ripening confirms that berry softening at the véraison time depends on the cultivar and on environmental conditions as the vintage. The analysis of the evolutions also indicates that pellicular strength is maximum at this crucial period of berry development

Involvement of some small GTPases in grape berry ripening

National audienc

A Bayesian Network to Prevent Mite Infestations in Rose Greenhouses

Mite infestation is a big threat for rose greenhouses. It is much easier to halt and destroy them if their future development can be predicted. Taking into account temperature, humidity, cropping practices, plant vigour and some other influent parameters, an expert is able to predict the future development of the mites. Unfortunately, not all greenhouses can call on an expert permanently to help them in their fight against mites. To help them we have developed a novel model to assess and anticipate mite invasions in greenhouses in the short term. The model, based on a Bayesian network, takes into account the environment and the parameters defining invasion status with their interactions Data have been collected using knowledge from horticultural experts. The model has been validated in real situations emanating from the field. We obtained a good correlation between forecasts and expert predictions for the 18 cases used in this study. Thus, using this model should help the growers to protect against mite outbreaks. It constitutes a framework for studies of other harmful pest invasions

A Model for Predicting Wine Quality in a Rhône Valley Vineyard

A model was developed as a tool to evaluate wine quality via submodels that represent soil, plants, meteorology, agronomic variables, various vineyard parameters, grape (Vitis vinifera L.) characteristics, and enological practices. The model is based on a highly extensive and unique dataset collected from a single Rhone Valley vineyard (Domaine de Beaurenard) in southern France and the expertise of its winemaker. This modeling study is a first step toward simulating the quality of a wine on the basis of 88 variables in the vineyard and 56 enological variables. The model was validated by comparing the scores predicted by the model with actual scores given by the international press for 49 modeled wines. At the end of the study, the model was compared against other statistical models. Through this model, winemakers can predict future wine quality early and develop improved business strategies. This modeling study was created for and applied directly to the studied situation (Chateauneuf du Pape, Cotes du Rhone, and Rasteau) and is not directly transferable to other situations. Nonetheless, it can serve as a basis for studies in other vineyards because, with the development of precision farming and the multiplication of sensors in agronomy, most wineries will soon have access to the necessary data to model the quality of their wine

Molecular characterization and expression analysis of the Rab GTPase family in Vitis vinifera reveal the specific expression of a VvRabA protein

International audienceAs a first step to investigate whether Rab GTPases are involved in grape berry development, the Vitis vinifera EST and gene databases were searched for members of the VvRab family. The grapevine genome was found to contain 26 VvRabs that could be distributed into all of the eight groups described in the literature for model plants. Genetic mapping was successfully performed; VvRabs were mostly located on independent chromosomes, apart from eight that were located on the as yet unassigned portions of the genome clustered in the ChrUn_Random chromosome. Conserved and divergent regions between VvRab protein sequences were identified. Transcript expression of 11 VvRabs was analysed by real-time quantitative RT-PCR. Except for VvRabA5b, transcript expression was detected, in general, in all the organs investigated, but with different patterns. In grape berries, VvRab transcripts were expressed at all stages of fruit development, with different profiles, except in the case of members of the A family which displayed generally similar patterns. The response to growth regulators in cell cultures was generally specific to each VvRab, with a differential pattern of expression for ethylene, auxin, and abscisic acid according to the VvRab. Interestingly, and unexpectedly considering transcript expression, western blotting using a monoclonal antibody raised against AtRabA5c (ARA4) showed a specific expression in the exocarp of ripe grape berries, in all seven red and white berry varieties tested. By contrast, no expression was detected in any of the other organs or tissues investigated. This paper contains the first description of Rab GTPases in V. vinifera. The involvement of a specific VvRab in grape berry late development and the potential role of this Rab GTPase are discussed in relation to literature dat