Abstract
Amino acid contents and their derived volatile compositions in Cabernet Sauvignon grapes and wines after regulated deficit irrigation (RDI) were investigated during the 2015 and 2016 growing seasons in Yinchuan (NingXia, China). High-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) were used for amino acid and volatile compound analyses. Three RDI strategies were tested: 60% (RDI-1), 70% (RDI-2), and 80% (RDI-3) of grapevine estimated evapotranspiration (ETc), and 100% ETc was used as the control group (CK). RDI-treated vines had lower yields and berry weights with higher total soluble solids than the control treatment. RDI-1 increased proline levels in berries and wines. RDI-2 enhanced tyrosine and asparagine levels in wines. RDI-3 enhanced arginine, alanine, valine, leucine, and isoleucine levels in berries and wines. RDI-2 and RDI-3 increased the concentrations of 2-methyl-1-butyl acetate, benzaldehyde, 3-methyl-1-pentanol, and 3-methyl-1-butanol in wines. The accumulation of volatile compounds was closely related to the amino acid concentrations—especially isoleucine, valine, and leucine—in grapes. Our results showed that RDI treatments altered amino acid concentrations and their derived volatile compositions in wines.
Highlights
Amino acids present in grapes serve as a nitrogen source for yeasts during alcoholic fermentation [1]
The weather during the years of this study was typical of a semiarid continental climate, which is very suitable for cultivation of Cabernet Sauvignon (V. vinifera L.) [26]
The results showed that the level of phenylalanine in the berries from the regulated deficit irrigation (RDI)-3 treatment was significantly higher than that in the other treatment groups (Table 2) and, promotes the production of polyphenol [2]
Summary
Amino acids present in grapes serve as a nitrogen source for yeasts during alcoholic fermentation [1]. Amino acids in grapes are precursors of volatile compounds, such as leucine, valine, isoleucine, and phenylalanine [2]; and the branched-chain amino acids (valine, leucine, and isoleucine), aromatic amino acids (phenylalanine, tyrosine, and tryptophan), and methionine in grapes can be converted into α-ketoacids and metabolized into higher alcohols and higher acids in yeast cells through the Ehrlich pathway [2,3]. These compounds can be further metabolized into alcohol esters and acetates [3]. Many previous studies have reported how changes in grape amino acid content can affect wine volatile composition [1,5,6]
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