Abstract
The current study was focused on the impact of accelerated ageing (heating step) on the amino acid and biogenic amine profiles of fortified wines. In this sense, three Madeira wines from two commonly used grape varieties (one red and the other white) were analysed during the heating, at standard (45°C, 3 months) and overheating (70°C, 1 month) conditions, following a precolumn derivatization procedure using iodoacetic acid,o-phthaldialdehyde, and 2-mercaptoethanol, carried out in the injection loop prior to RP-HPLC-FLD detection. Eighteen amino acids were identified, with arginine being the most abundant. An important decrease of the amino acid levels was detected during the standard heating (up to 30%), enhanced up to 61% by the temperature increase. Cysteine, histidine, and asparagine revealed the greatest decreases at 45°C. Conversely, some amino acids, such as asparagine, slightly increased. Four biogenic amines were identified but always in trace amounts. Finally, it was observed that the accelerated ageing did not favour the biogenic amine development. The results also indicate that the heating process promotes the amino acid transformation into new ageing products.
Highlights
Amino acids are an important fraction (25–30%) of the nitrogenous source released in the crushing and pressing practices during winemaking, constituting a relevant source to yeast growing and vitality during the alcoholic fermentation [1, 2]
The Tinta Negra (TN) variety presented the highest content in total amino acids, in particular the sweet style
It was demonstrated that the amino acid decreases with fermentation
Summary
Amino acids are an important fraction (25–30%) of the nitrogenous source released in the crushing and pressing practices during winemaking, constituting a relevant source to yeast growing and vitality during the alcoholic fermentation [1, 2]. Free amino acids present in wine may have different origins, namely, from the degradation of grape proteins, metabolism of yeasts, and lactic acid bacteria, and from yeast and bacteria autolysis [3, 4] Their profile and concentration in wines can be affected by several factors, such as grape variety (including rootstock), environment, and growing conditions (mainly nitrogen fertilization), and from the winemaking techniques employed, including the ageing procedure, such as biological ageing. Amino acids have motivated researchers to study their profile and influence in wine production, for their importance in the fermentation step but essentially due to their important effect on wine’s flavour development (as metabolic precursors of higher alcohols), and as criteria for differentiation and authenticity studies [5,6,7,8,9,10,11] Their metabolism affects the aroma complexity and can be responsible for the concentration increase of biogenic amines and ethyl carbamate precursors in wine
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