Anthocyanin profile variability : changes in Sangiovese pigments acylation related to growing condition and viticoltural management

The traceability of the varietal origin was recently discussed for Sangiovese grapes in the “Brunello di Montalcino” production. The alarm for the hypothetical scandal produced an important economical and marketing impact. Following the events, experts and scientists discussed the use of the anthocyanin profile as index of the varietal purity of the wine. In our opinion the interesting specificity of the anthocyanins biosynthetic pathway should not be confused with the possibility of its utilization in the wine origins identification concerning grape variety. As demonstrated, many factors can influence the final proportions between the molecules. The variability of anthocyanin profile was studied during the last three years (2008, 2009, 2010), focusing on acylations, in Sangiovese cultivated in Montalcino (Toscana, Italy). In the same vineyard, 5 clones, in 2 exposure conditions, harvested in 3 ripening time were studied. Three clones, ripened in the two exposure, were selected for microvinification tests in 2009 and 2010, to be analyzed after fermentation, 6 months and 1 year aging. Considering the grapes, the 255 HPLC profiles showed a high variability in the percentage of acylated compounds, ranging between 1.00 and 9.84%, an average value of 3.52%, a median 3.17%, and a standard deviation of 1.53. The year is responsible of the 49% of the explained variability, but also the other factors had an interesting effect (bunch exposure = 8%, harvesting time = 6%, clone = 5%). The interactions of the year with the bunch exposure and the harvesting time explained respectively the 9% and 14% of the variability. Even though the seasonal weather course strongly influenced the percentage of acylation, with the lower proportion in 2010, and the higher in 2009, the results indicated a reproducible influence of the vineyard management. The clones 83 and VCR4 always showed the higher proportion of acylated compounds, while the 2110 clone had a smaller percentage of these compounds. An early harvesting produced grapes with a lower proportion of acylated compounds. The same effect was obtained with the bunch directly exposed to the solar radiation compared to the shaded ones. Also the relative proportions of the acids involved in the esterification were significantly affected by the year and the vineyard management. In general, the esterification with acetic acid interested an average of 28% of the acylated pigments. Wines were made from 500-1200 kg of grapes, depending on the productions. In 2010, the skin pigments profiles were analyzed during the maceration. No specific trends were observed during the maceration, indicating a non specific extraction of the acylated molecules, when compared to the non esterified ones. During wine aging, the differences related to the vineyard management seems to be maintained, at least in the first year of wine maturation. As expected, the genotype influenced the anthocyanins biosynthetic pathway, producing a typical pigments profile. The Sangiovese grapes profile was confirmed to be characterized by low acylated pigments percentage. At the same time, according to our survey, it demonstrated a wide range of variability in response environmental and cultural factors. In conclusion anthocyanin profiling is significantly affected by the environmental conditions, clone diversity and harvesting timing. Consequently it is possible to manage the pigment biosynthesis, trying to obtain an anthocyanin profile more useful for the enological objectives. Because of their properties (color hue, stability), acylated pigments are usually better considered than the non esterified compounds. Significant profile changes can be obtained with different vineyard management, and these differences can be maintained during wine making. As a consequence the use of anthocyanin profiles for the traceability of the grape varietal origin, should be carefully considered.