Analytical, Nutritional and Clinical Methods Prediction of tartrate stability of sherry wines by a conductimetric system with rapid response J. Go´mez Benı ´ tez a, *, V.M. Palacios Macı ´ as a , R. Veas Lo´pez b , L. Pe´rez Rodrı ´ guez a a DepartmentofChemicalEngineering,FoodTechnologyandEnvironmentalTechnologies,SciencesFaculty,UniversityofCa ´diz,CampusRı´oSanPedro,P.B. 40. 11510 Puerto Real, Cadiz, Spain b Bodegas Osborne S.A., Ferna ´n Caballero, 3, 11500 El Puerto de Santa Marı´a (Ca ´diz), Spain Received 15 May 2002; received in revised form 10 October 2002; accepted 10 October 2002 Abstract The particular production process of Sherry wines means that an appropriate level of tartrate stability is not always reached. The objective of the work described here was to find a rapid and reliable method to determine the tartrate stability of this type of wine. After a broad initial characterization, it was shown that cold-treated Sherry wines remain more oversaturated with potassium bitartrate than white and red table wines. The saturation temperature (Ts) and the result of the minicontact test (Mc) have been correlated with the tartrate stability of different Sherry wines, with the conclusion that wines having Mc values lower than 10 mS/cm remain stable at 4  C during 1 week. In contrast, a direct relationship between stability and Ts was not found. The minicontact test is therefore proposed as a method for the rapid and reliable determination of the tartrate stability of Sherry wines. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Potassium bitartrate; Tartrate stability; Sherry wines; Saturation temperature; Minicontact test 1. Introduction Sherry wines are liquor wines produced in the south of Spain (C.E. 1988, 1999) and there is a wide range of sherry types that are significantly different in nature (Jerez-Xe´ re` z-Sherry, 1977). The production methods for these types of wines have been widely described in the bibliography (Gonza´ lez Gordon, 1972; Martı´nez, Pe´rez & Benı´tez, 1997; Pe´rez, Flores, Ramı´rez, & Navarete, 1980). Sherry wines show numerous peculiarities in terms of their composition in relation to tartrate stabi- lity and the efficacy of stabilization treatments. The alcohol strength can vary from 15 % vol. in the ‘‘Fino’’ wines to 22 % vol. in some old ‘‘Oloroso’’ wines and as the alcohol content increases the solubility of the potassium bitartrate (KHT) decreases (Ratsimba, Laguerie, Biscans, & Gaillard, 1989). The effect of the high sugar content in some types of wines, which can exceed 100 g/l in the Cream wines, acts in addition to the effect of the alcohol content. These sugars come from the natural sweet wines used in blending processes and are produced with sun-concentrated grape (Gonza´ lez Gordon, 1972). The natural sweet wines also contain a high colloid content (Usseglio-Tomasset, Bossia, Del- fini, & Ciolfi, 1980), which inhibits the growth of the KHT crystals and hinders stabilization by cold treat- ment (Celotti, Bornia, & Zoccolan, 1999; Guitard, 1983). The addition of ‘‘Vinos de Color’’ (obtained by flame-heating wines directly) in blends has the same effect and such blending is often carried out to adjust the final color of some wines (Gonza´lez Gordon, 1972). The presence of peptides and glycoproteins should also be considered for Fino and Manzanilla wines as these are released from dead yeast settled in the bottom of the casks during the biological ageing. These compounds have an inhibitory effect on KHT crystallization (Ger- baud, Gabas, Blouin, Pellerin, & Moutounet, 1997; Gerbaud et al., 1996; Lubbers, Leger, Charpentier, & Feuillat, 1993). Likewise, both extraction from the wood of the casks and the concentration effect by evaporation during prolonged ageing increase the potassium concentration in the wines with physical- chemical ageing; e.g. as occurs in Oloroso wines (Pe´ rez Rodrı´guez, 1991). All of these characteristics of Sherry wines hinder tartrate stabilization by cold treatment. 0308-8146/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0308-8146(02)00511-3 Food Chemistry 81 (2003) 457–462 www.elsevier.com/locate/foodchem * Corresponding author. E-mail address: juangomez.benitez@uca.es (J. Go´mez Benı´tez).