Abstract

CATARINO, Sofia; SOARES, José; CURVELO-GARCIA, A.S.  and  SOUSA, R. Bruno de. Influence of bentonites on mineral composition of wine: potassium, sodium, calcium, aluminium, lead. pH effect . Ciência Téc. Vitiv. [online]. 2004, vol.19, n.1, pp.29-45. ISSN 0254-0223.

Bentonites are enological products widely utilised on clarification and proteic stabilization of musts and white wines. The risk of mineral contamination, associated with hygienic, sensory and legal quality of wines, should not be neglected. The knowledge of extraction and mineral elements release phenomena and influence factors are very important to prevent this contamination. The aim of the present work was to investigate the extraction phenomena, the nature of extraction solution and pH level. 6 different bentonites, in wine and tartaric acid solution, at 3 pH levels (2,9 to 3,6), were studied. The analysis of extraction solutions were realised by FAAS, GFAAS and ICP-MS. More than 50 mineral elements (major, minor and trace elements) were analysed. The results were obtained at specific experimental conditions, so, they should not be directly applied to wine, concerning the mineral contents. Bentonite-treated wines showed higher Ca, Na and Al contents, while K contents decreased. The influence of bentonite on Pb contents was very important: some bentonites increased this metal content, while others decreased it. The pH effect showed to be significant on Ca, Al and Pb releases: higher Ca contents were found at pH 3,6. On the other hand, Al and Pb extraction and release decreased with pH increase. Bentonite factor was determinative on mineral elements amounts released, depending on pH value.

Keywords : wine; bentonites; pH; K; Ca; Na; Al; Pb.

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