Liudis L. PINO, V. Felipe LAURIE
University of Talca, Chile
Email contact: liudislpino[@]gmail.com
AIM: Quinoa (Chenopodium quinoa) is a non-allergenic pseudocereal with a high protein content. The aim of this work was to determine the phenolic fining ability of quinoa protein extracts (QP), and to compare them against commercial proteinaceous fining agents.
METHODS: Quinoa seeds of the variety Regalona-Baer, cultivated in Santa Rosa Experimental Center (Chillán, Chile) and red wine samples (Petit Verdot and Malbec) from the Maule Region of Chile were used for this study. QP were obtained by alkaline extraction and isoelectric precipitation. The protein content of quinoa samples and QP was determined by the Dumas method with a nitrogen to protein conversion factor of 5.85. SDS-PAGE profile of QP was analysed by electrophoresis, according to the Laemmli method (1). The fining efficacy of QP was evaluated at 20°C at different doses and contact times (48 and 96 h) and compared against three commercial fining agents of animal and vegetal origin (Vegefine, Vegecoll and Gelatin). The total tannin content in wines were measured spectrophotometrically by the methyl cellulose precipitable (MCP) tannin assay (2) and the Harbertson-Adams tannin assay (3). The total phenolics were quantified by the Folin-Ciocalteu assay (4). The
anthocyanin content was determined according to the HPLC-DAD method OIV-MA-AS315-11 for the analysis of major anthocyanins in red and rosé wines.
RESULTS: QP showed a content of 60% protein with molecular weight distribution of ? 35 kDa, ? 22 kDa and ? 10 kDa. QP treatments significantly reduced turbidity, total tannin and total phenolics in Petit Verdot wine at the two doses tested (30 and 50 g/hL) and in a similar proportion than the commercial fining agents. For all fining agents it was observed that tannin content decreased more after 96 hours of contact time (11-16%) than after 48 hours (5-11%) of treatment. Like so, QP fining resulted in a significant reduction of the tannin content in Malbec fined wine (20-25%), more so than when using the commercial fining agents (3-10%). For both wines, the color of the fined samples (measured as malvidin-3-glucoside equivalent at 520 nm) was not significantly affected by the treatments with QPs.
CONCLUSIONS: The results obtained suggest that QP could be an interesting alternative for wine fining with plant derived proteins; therefore, more studies on this subject are being performed.
1. Laemmli, U. K. (1970). Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature, 227(5259), 680-685.
2. Mercurio, M. D., Dambergs, R. G., Herderich, M. J., & Smith, P. A. (2007). High throughput analysis of red wine and grape phenolics adaptation and validation of methyl cellulose precipitable tannin assay and modified somers color assay to a rapid 96 well plate format. Journal of agricultural and food chemistry, 55(12), 4651-4657.
3. Harbertson, J. F., Picciotto, E. A., & Adams, D. O. (2003). Measurement of polymeric pigments in grape berry extract sand wines using a protein precipitation assay combined with bisulfite bleaching. American journal of enology and viticulture, 54(4), 301-306.
4. Waterhouse, A. L. (2002). Polyphenolics: determination of total phenolics. On RE Wrolstad. Current protocols in food analytical chemistry, 257-326.