Innovations in the Use of Bentonite in Oenology: Interactions with Grape and Wine Proteins, Colloids, Polyphenols and Aroma Compounds

Bentonite is used in oenology to improve the limpidity and the stability of wine and to predict the formation of deposits in the bottle. The exchangeable cations in its lamellar structures strongly influence some properties, such as the specific surface, the exchange capacity and the adsorption behavior. The unintended use of bentonite for juice settling and/or for wine fining produces jeopardized effects on colloidal and protein stability, the aroma compounds and sensory profiles. The interactions with haze-forming proteins, other colloids, as well as aroma compounds and phenols would have been to discover as the modulation of wine colloids by an adjuvant severely affects the wine resilience and the sensory profile. This chapter reviews several studies that focus on the impact of commercial bentonite samples used for both juice clarification and wine fining on the colloids, proteins, phenols and aroma compounds of white and red wines. Some parameters of practical value, such as the wine heat stability, the concentrations of total and haze-forming proteins and the content of the most relevant aromas, have been assessed to track the effects of bentonite and to achieve findings that are applicable to the field of oenology

Assessement of sensory firmness and crunchiness of table grapes by acoustic and mechanical properties.

Background and Aims The instrumental measurement of crunchiness in tablegrapes has been the subject of little research in spite of the great relevance of this sensory texture trait to consumer preference. Therefore, our aim was to evaluate the potential of several mechanical and acoustic properties to assess the perceived firmness and crunchiness of tablegrape cultivars. Methods and Results The ripening effect was minimised by densimetric sorting of the berries before testing. The textural quality of seven tablegrape cultivars was evaluated by sensory analysis. Furthermore, three mechanical tests (texture profile analysis, cutting and denture) were performed on the berry flesh or on whole berries, and the acoustic emission produced was recorded simultaneously. Correlation studies showed strong and significant relationships between sensory texture attributes and instrumental parameters, particularly for the denture test. Nevertheless, satisfactory predictive accuracy for the perceived crunchiness required multivariate linear regression involving both mechanical and acoustic properties resulting from the denture test performed on whole berries. In this case, residual predictive interquartile amplitude was higher than 2. Most of the reliable models developed for perceived firmness are fairly recommended not for quantitative purposes but for fast screening (1.6 < residual predictive interquartile amplitude < 2). Conclusions The standardised protocol proposed permits more objective and quantitative sensory data to be obtained for firmness and crunchiness of tablegrapes. Significance of the Study A combined mechanical–acoustic strategy has not previously been used in tablegrapes and represents a powerful tool for a more complete and exhaustive texture characterisation, particularly firmness and crunchiness, by means of a more objective and standardised protocol

SACCHAROMYCES CEREVISIAE BIODIVERSITY IN MONFERRATO, NORTH WEST ITALY, AND SELECTION OF INDIGENOUS STARTER CULTURES FOR BARBERA WINE PRODUCTION

The aim of this study was to examine the biodiversity of Saccharomyces cerevisiae isolates from Barbera grapes and musts, from the Monferrato area, in the Piedmont region – North West Italy. An interdelta element PCR analysis was used to identify and discriminate 636 S. cerevisiae isolates at a strain level. Ninety-six S. cerevisiae that showed different molecular fingerprints were characterized through physiological tests and laboratory scale fermentations. A chemical analysis of experimental wines obtained from inoculated fermentations showed significant differences between the wines. The main variables considered in the strain differentiation were the residual sugars and the production of acetic acid, which ranged from 148.64 to 3.44 g/l and from 0.20 to 0.60 g/l, respectively. As a consequence, strain variability should be considered as a relevant resource to select suitable starter cultures in order to improve or characterize wines with a close bond to the geographic region