The relationship between heat-unstable wine proteins and bentonite fining is still unclear: whether bentonite removes selectively some protein classes [1] or this removal changes as a function of matrix parameters [2] [3] [4] [5] is a matter of debate. This work intended to quantify and identify the protein fractions of two international white wines (Chardonnay and Sauvignon blanc), and to characterize the fining effect of five different types of activated sodium bentonite. The physical properties (elemental analysis, surface charge density, swell index and specific surface area) of the bentonite samples and the general wine characteristics were determined. Preliminary tests revealed that 100 g/hL and 50 g/hL of any type of bentonite were sufficient to gain colloidal stability for the Chardonnay and the Sauvignon wine, respectively. The performances of each clay type on the different wine protein fractions were evaluated by 8-16% gradient SDS-PAGE, protein quantification with QuantityOne software (Biorad), and subsequent band identification by MALDI TOF mass spectrometry. Results revealed differences in the physical properties of the different clays, e.g. swell index and specific surface area. The protein profiles of the two unfined white wines were quite similar, but major differences were found after bentonite fining. Both the low (LMW) and the medium molecular weight protein fractions were prone to removal by clay particles in Chardonnay. Only the LMW bands were removed in Sauvignon after fining instead. This behavior could thus explain the contradictory data found in previous reports [1] [2]: bentonite action is specific in Sauvignon for LMW protein fractions, while, on Chardonnay, it removes all the protein fractions. In addition, on Chardonnay we can easily appreciate differences in the degree of removal among different bentonite labels, while on Sauvignon all the clay types showed similar performances. Protein identification is currently underway.
Selective heat-unstable protein removal by different bentonite labels.
Giribaldi M;Giuffrida MG
2010
Abstract
The relationship between heat-unstable wine proteins and bentonite fining is still unclear: whether bentonite removes selectively some protein classes [1] or this removal changes as a function of matrix parameters [2] [3] [4] [5] is a matter of debate. This work intended to quantify and identify the protein fractions of two international white wines (Chardonnay and Sauvignon blanc), and to characterize the fining effect of five different types of activated sodium bentonite. The physical properties (elemental analysis, surface charge density, swell index and specific surface area) of the bentonite samples and the general wine characteristics were determined. Preliminary tests revealed that 100 g/hL and 50 g/hL of any type of bentonite were sufficient to gain colloidal stability for the Chardonnay and the Sauvignon wine, respectively. The performances of each clay type on the different wine protein fractions were evaluated by 8-16% gradient SDS-PAGE, protein quantification with QuantityOne software (Biorad), and subsequent band identification by MALDI TOF mass spectrometry. Results revealed differences in the physical properties of the different clays, e.g. swell index and specific surface area. The protein profiles of the two unfined white wines were quite similar, but major differences were found after bentonite fining. Both the low (LMW) and the medium molecular weight protein fractions were prone to removal by clay particles in Chardonnay. Only the LMW bands were removed in Sauvignon after fining instead. This behavior could thus explain the contradictory data found in previous reports [1] [2]: bentonite action is specific in Sauvignon for LMW protein fractions, while, on Chardonnay, it removes all the protein fractions. In addition, on Chardonnay we can easily appreciate differences in the degree of removal among different bentonite labels, while on Sauvignon all the clay types showed similar performances. Protein identification is currently underway.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
