Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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SUMMER 2012
WINEMAKING
Sensory analysis of wines made from the unsupplemented Chardonnay juice (160 mg/L YAN) reveals a complex aroma profile with the more prominent sensory descriptors being “acetic,” “bruised apple,” “stale beer,” “cheese,” and “sweat,” whereas the fruity and floral descriptors received generally lower ratings (Figure 4). The low concentration of acetate and ethyl esters together with relatively high alcohol concentration suggests a chemical rationale for the sensory profile of the low YAN wines (Figure 3). The “sweat” and “cheese” attributes are likely to have resulted from volatile fatty acids that are more readily perceived in wines having a relatively low aroma intensity, which typically results from low juice YAN content.7
Moderate nitrogen supplementation (320 mg N/L) produces cleaner and more intense fruitier/floral wines, with prominent descriptors including “floral,” “tropical,” ”fruit ester,” and “banana” (Figure 4). These wines were characterized by increased total ester and reduced higher alcohol content compared to wines made from unsupplemented juice (Figure 3).
Perhaps surprisingly, whether inorganic or organic nitrogen supplements were used, the aroma profiles of the moderate nitrogen (320 mg N/L) wines were almost indistinguishable. This result suggests that winemakers have great flexibility in choice of products for moderate nitrogen supplementation, bearing in mind that some commercial organic nutrient products have very low YAN content.
Sensory profiles of wines made from high nitrogen supplemented juices, however, strongly depend on the type of nitrogen supplement used (Figure 4). Organic nitrogen (480 mg N/L) produced wines with the greatest intensity of fruitiness, in which the “floral,” “tropical,” “fruit ester,” and “banana” descriptors were most highly rated.
On the other hand, wines produced from high nitrogen juices supplemented
with inorganic nitrogen (480 mg N/L), were dominated by descriptors for volatile off-odors, giving a strong solvent character. The concomitant high concentration of ethyl acetate (100 mg/L) appears to be responsible for the masking- solvent odor (Figure 3).8 This result clearly shows that only moderate additions of DAP should be made and that repeated additions of DAP, such as can occur during fermentatio rescue procedures, can substantially increase perceived wine “volatile acidity” due to excessive ethyl acetate production (N.B. the odor of
ethyl acetate is often incorrectly referred to as volatile acidity).
The high aromatic impact of the organic nitrogen supplement is suggestive that grapes with naturally very high amino nitrogen might also have aromatic intensity. Further research is needed to show whether the grape-derived aroma compounds are likewise enhanced or, in fact, simply masked by the intense yeast aroma compounds.
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