Comparison of inorganic and organic nitrogen supplementation of grape juice – Effect on volatile composition and aroma profile of a Chardonnay wine fermented with Saccharomyces cerevisiae yeast Diego Torrea a,b , Cristian Varela a , Maurizio Ugliano a , Carmen Ancin-Azpilicueta b , I. Leigh Francis a , Paul A. Henschke a,⇑ a Australian Wine Research Institute, P.O. Box 197, Glen Osmond (Adelaide), SA 5064, Australia b Universidad Pubica de Navarra, Department of Applied Chemistry, Campus Arrosadia S-N, E-31006 Pamplona, Spain article info Article history: Received 2 September 2010 Received in revised form 10 December 2010 Accepted 21 January 2011 Available online 28 January 2011 Keywords: Fermentation Wine Chardonnay Yeast Saccharomyces cerevisiae Aroma Flavour Nitrogen abstract Inorganic nitrogen salts, and to a growing extent organic nitrogen preparations, are widely used to ameliorate a nitrogen deficiency in wine fermentation, but the impact of nitrogen supplementation on perceived wine sensory profile is essentially unknown. Supplementation of a low nitrogen Chardonnay grape juice with either ammonium nitrogen or combined amino acid and ammonium nitrogen showed that the type of nitrogen and concentration in the range 160–480 mg N/l had a substantial impact on the formation of yeast volatile compounds and perceived wine aroma. Addition of amino acid and ammo- nium nitrogen increased both acetate and medium chain fatty acid esters to a greater extent and decreased higher alcohols to a lesser extent than ammonium nitrogen alone whereas ammonium nitro- gen substantially increased ethyl acetate and acetic acid. Low nitrogen wines were rated relatively low in floral/fruity aroma descriptors, while moderate nitrogen wines showed a good balance between desirable and less desirable attributes, whereas high nitrogen produced either an acetic/solvent character or high- est ratings for floral/fruity attributes, depending on nitrogen type. These results show that amount and type of nitrogen supplement can substantially modulate Chardonnay wine volatiles composition and perceived aroma. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The yeast assimilable nitrogen (YAN) content of grape must is a critical nutrient that has been identified as being suboptimal in many viticultural regions surveyed world-wide (see for example: Butzke, 1998; Hagen, Keller, & Edwards, 2008; Henschke & Jiranek, 1993; Nicolini, Larcher, & Versini, 2004). A concentration exceed- ing 140 mg N/l is generally considered the threshold concentration for low risk completion of fermentation for low solids, low temper- ature, anaerobic musts of moderate sugar content (reviewed by Bell & Henschke, 2005). Higher concentrations of nitrogen are gen- erally required for the reliable fermentation of musts containing a combination of risk factors including higher sugar concentrations (reviewed by Colombié, Malherbe, & Sablayrolles, 2005; Cramer, Vlassides, & Block, 2002; Henschke & Jiranek, 1993; Jiranek, Langridge, & Henschke, 1995a). The main sources of assimilable nitrogen present in grape juice include ammonium, a-amino acids, and, to a lesser extent, small peptides. During the early stages of fermentation, these com- pounds are rapidly accumulated by yeast, thus fulfilling the bio- synthetic requirements for amino acids needed for protein synthesis and growth, and any surplus is then stored in the cell vacuole (Henschke & Jiranek, 1993; Salmon, 1996). Insufficient assimilable nitrogen results in lower biomass yields and conse- quently slower fermentation rates (Salmon, 1989; Varela, Pizarro, & Agosin, 2004), which increase the risk of slow or stuck fermenta- tions (reviewed by Alexandre & Charpentier, 1998; Bisson, 1999; Henschke, 1997). Supplementation of musts with inorganic nitro- gen in the form of ammonium salts, such as diammonium phos- phate (DAP), can decrease such risks and may also affect the formation of undesirable volatile sulphur compounds (Bell & Henschke, 2005; Jiranek, Langridge, & Henschke, 1995b; Vos & Gray, 1979). As a result, DAP addition to grape must, in many cases without knowledge of initial YAN content, is common practice in the wine industry. Besides its effect on yeast growth and fermentation kinetics, YAN can regulate yeast metabolism at several levels including 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.01.092 ⇑ Corresponding author. Tel.: +61 8 8303 6600; fax: +61 8 8303 6601. E-mail addresses: paul.henschke@awri.com.au, cristian.varela@awri.com.au (P.A. Henschke). Food Chemistry 127 (2011) 1072–1083 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem