Protein haze formation in wines revisited. The stabilising effect of organic acids |
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Authors: | Luís Batista Sara Monteiro Virgílio B Loureiro Artur R Teixeira Ricardo B Ferreira |
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Affiliation: | 1. Departamento de Botânica e Engenharia Biológica, Instituto Superior de Agronomia, Universidade Técnica de Lisboa, 1340-017 Lisboa, Portugal;2. Disease & Stress Biology Laboratory, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal;3. CEV – Biotecnologia das Plantas, S.A., Rua José Vicente Gonçalves n°8 H, Parque Industrial do Seixal, 2840-068 Aldeia de Paio Pires, Portugal |
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Abstract: | The effect on the wine protein haze potential of five organic acids commonly encountered in wines (l(+)-tartaric, l(−)-malic, citric, succinic and gluconic acids) was assessed. All five acids, tested at 20 mM, reduced dramatically the haze potential of proteins, either in wine or dissolved in water, throughout the range of pH values typical of wines (i.e., from 2.8 through 3.8). Subtle differences among the acid effects did not correlate with the number of their carboxyl groups, but were attributed to electrostatic interactions that depend upon the acid pKa values, the protein pI values and the medium pH. These results invalidate or question the validity of all experiments on wine proteins involving wine model solutions containing organic acids. Overall, the results obtained in the present work clearly indicate that organic acids with a common occurrence in wines exhibit a stabilising effect upon the haze potential of the wine proteins. |
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Keywords: | Haze Organic acids Tartaric acid Wine proteins X factor |
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