Albuquerque, F.

Câmara, J. S.

Ferreira, A. C.

Marques, J. C.

Pereira, V.

Pontes, M.

English

Repositório Institucional da Universidade Católica Portuguesa

Evolution of Free Amino Acids in Young Madeira Wines Submited to Controlled Heating Conditions 1 Centro de Química da Madeira, Departamento de Química da Universidade da Madeira, Campus da Penteada, 9000-390 Funchal, Portugal. 2 Madeira Wine Company, Rua dos Ferreiros, 9000-082 Funchal, Portugal. 3 Escola Superior de Biotecnologia da Universidade Católica, Rua Dr. António  B. Almeida, 4200-072 Porto, Portugal. *marques@uma.pt Results Objectives Introduction Methodology Amino acids represent the main fraction of non volatile nitrogen compounds in wines. They are an importante source of nitrogen during yeast fermentation and are directly involved in the formation of aroma compounds.  They can also be used for the characterization of grape varieties and the evaluation of the impact of processing changes introduced in the vinification process. Madeira wines are currently submitted to controlled oxidising conditions, known as estufagem, after fermentation and fortification, which are responsible for the aroma characteristics of these fortified wines. The purpose of this study was:   to determine the typical distribution of amino acids in sweet and dry young Madeira wines;   to evaluate the changes in composition when these wines are heated under controlled condictions in order to detect any influence in the formation of the aroma. A: pH: 6.65, 57,4 mM Na2HPO4, 50 mM propionic acid, 2 % DMS, 5.5 CH3CN, 92,5% H2O  B: 33 % MeOH, 7 % DMS, 40 % CH3CN, 20 % H2O Sweet wines (Malvasia) were submited to a partial fermentation and dry wines (Sercial) to a complete fermentation.  After fortification, the wines                      were heated at: -  30 ºC -  40 ºC -  50 ºC Samples were collected from the vats every 30 days and preserved under refrigeration before used. Amino acids were determined in a Waters HPLC system  equipped with a fluorescence detector (Fig. 1). The method used was based on the method proposed by A. C. Ferreira and L. Pripis-Nicolau et al. Involving a pre-column derivatisation with iodoacetic acid (IDA) and o-phthaldialdehyde (OPA). Fig. 1 – HPLC system used on the determination of amino acids. Fig. 2 – Gradient programme used in the study and composition of mobile phases. 8th International Enology Symposium, Bordeaux, 25-27 June, 2007 Conclusions Acknowledgements References The main amino acid observed before heating is arginine (116 mg/l), followed by serine, aspartic acid and cysteine (~10 times lower content). The study carried out allowed the implementation of a routine amino acid determination. Significant changes in the composition of amino acids were detected not only in sweet and dry wines but also when similar wines are fermented under slightly different conditions, showing the importance of complete and uniform control of fermentation conditions for high quality Madeira wines.  The results also show that some amino acids play na important role in the formation of complex aroma during the heating step of the vinification process, which can affect colour, aroma and final organoleptic perception of commercial wines.  P. Hernadez-Orte, J. Cacho and Vicente Ferreira; J. Agric. Food Chem., 50 (2002) 2891;  C. Ferreira; PhD thesis, Université Victor Segalen Bordeaux (1998);  L. Pripis-Nicolau, G. Revel, S. Marchand, A. A. Beloqui and A. Bertrand; J. Sci. Food Agric., 81 (2001) 731.   This research work was supported by Agência da Inovação (projecto IMPACT).   The authors are grateful to Madeira Wine Company for the wines used in the study. Fig. 4 – Amino acid composition (mg/l) in sweet wine samples (Malvasia), before and after the heating step (4 months) at the considered temperatures. Fig. 5 – Amino acid composition (mg/l) in dry wine samples (Sercial), before and after the heating step (4 months) at the considered temperatures. The initial amino acid profile is quite diferent from Malvasia wine, namely in what concerns the content of arginine, cysteine and alanine. Major aminoacids are aspartic acid, arginine and phenylalanine.  Glutamic acid, tyrosine and phenylalanine show higher amounts then those obtained in sweet wines. Table 1 – % decrease of amino acids content in Malvasia sweet wines. In Malvasia Sweet wines, cysteine, aspartic acid and asparagine have the main decrease in the estufagem, followed by arginine.  In Sercial Dry wines cysteine, phenylalanine and tyrosine have the main decrease in estufagem, followed by aspartic acid and arginine. Pontes, M.1, Pereira, V.1, Albuquerque F.2, Câmara J. S.1, Ferreira A. C.3, Marques J.C.1* 

Evolution of Free Amino Acids in Young Madeira Wines Submited to Controlled Heating Conditions

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Evolution of Free Amino Acids in Young Madeira Wines Submited to Controlled Heating Conditions

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