Astringency has been defined by the American Society for Testing Materials as “the complex of sensations due to shrinking, drawing or puckering of the epithelium as a result of exposure to substances such as alums or tannins”. Regarding the importance of astringency in wine consumer acceptance, elucidating the molecular mechanisms underpinning this complex sensation represents an important goal for scientists. Although different mechanisms have been described (Gibbins & Carpenter, 2013), the salivary protein precipitation is still the most accepted theory. According to this, wine astringency perceived in the oral cavity is originally attributed to the interaction and subsequence precipitation of salivary proteins by wine tannins –mainly flavanols–.
Human saliva is rich in different types of peptides and proteins: histatins, statherin, P−B peptide, cystatins and proline-rich proteins (PRPs), being the latter ones the most studied regarding the development of astringency (Ramos-Pineda et al., 2019; Soares et al., 2018). However, other high molecular weight (HMW) proteins like albumin, α-amylase and mucins are the major components of the human salivary proteome (Cheaib & Lussi, 2013; Castagnola et al., 2011) and little research has been reported in relation to their implication in the astringency development. Here, the molecular interactions between the HMW salivary proteins, namely, albumin from human serum, α-amylase from human saliva (Type XIII-A) and mucin from bovine submaxillary glands (Type I-S), and a seed flavanol extract with a composition similar to that found in red wine have been characterized by Fluorescence Quenching and Isothermal Titration Calorimetry (ITC). Moreover, in order to obtain further insights into the specific flavanols that are involved in the interactions with HMW salivary proteins, each binding assay has been analysed by HPLC–MS. The obtained results suggested that HMW salivary proteins could be implicated in the astringency development, since these proteins were able to interact and to precipitate wine flavanols, although with different involvement depending on the HWM protein assayed since a clear ligand preference was observed.
Authors: Manjón Elvira1, García-Estévez Ignacio1 and Escribano-Bailón Mará Teresa1
1Department of Analytical Chemistry, Nutrition and Food Science, Universidad de Salamanca.
*corresponding author: elvira87@usal.es
References:
Castagnola et al., 2011. Trends in Biotech., 29(8), 409–418.
Cheaib & Lussi, 2013. J. Biosci., 38(2), 259–265.
Gibbins & Carpenter, 2013. J. Texture Stud., 44(5), 364−375.
Ramos-Pineda et al., 2019. Food Chem., 272, 210−215.
Soares et al., 2018. Food Chem., 243, 175−185.
Keywords: mucin, albumin, amylase, molecular interactions, ITC
