Chemiomics: A systems chemistry approach to unravel the interface pathways between oxidation and Maillard mechanism responsible for flavour modulation during wine storage.

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Response surface methodology: a tool to minimize aldehydes formation andoxygen consumption in wine model system

Publication . Monforte, Ana Rita; Oliveira, Carla; Martins, Sara I. F. S.; Ferreira, António César Silva

A response surface methodology was applied to study the effect of precursors on o-quinone and phenylacetaldehyde formation in wine model systems stored at 40 °C during 24 h. The results confirmed that glucose plays an important role in reducing aldehyde formation by inhibiting the formation of o-quinone. The regression equations showed that oxygen consumption followed a 2nd polynomial equation whereas phenylacetaldehyde and o-quinone were best fit with a polynomial function containing quadratic terms. These behaviors indicate that different pathways are involved in the respective aldehyde formation and oxygen consumption. RSM has been shown to be a powerful tool to better understand key chemical reactions. By considering a number of factors, individually and in combinations, the derived equations predicted that the best combination to minimize phenylacetaldehyde was achieved for high glucose levels and low amounts of gallic acid and metals. This is valuable information when trying to improve wines sensorial properties during shelf-life.

2019Journal article

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Impact of phenolic compounds in strecker aldehyde formation in wine model systems: target and untargeted analysis

Publication . Monforte, A.R.; Martins, S.I.F.S.; Ferreira, A.C. Silva

The Strecker degradation of phenylalanine has been studied in a phenolic compound/phenylalanine wine model system. Six phenolic compounds (3,4-dihydroxybenzoic acid, gallic acid, caffeic acid, ferulic acid, catechin, and epicatechin) were compared in the formation of phenylacetaldehyde when in the presence of glucose or methylglyoxal (MG). The addition of glucose reduced the formation of Strecker aldehyde, independently of the phenolic compound. The addition of MG, on the other hand, increased phenylacetaldehyde formation for hydroxybenzoic acids and decreased phenylacetaldehyde formation for flavan-3-ols, confirming their capacity to trap the dicarbonyl compound. As a target phenolic compound, catechin was chosen to perform kinetic studies to further understand the reaction intermediates involved in the mechanism of phenylacetaldehyde formation, in particular, catechin o-quinone and catechin–MG adduct. The addition of glucose and MG increased the consumption of catechin, while a reduction in the respective o-quinone was observed, suggesting that these substrates have an impact in other reactions involving catechin. In that regard, for the first time, it was demonstrated that the catechin–MG adduct was capable of oxidizing and forming a new o-quinone, contributing to wine instability promoted by oxidation reactions.

2020Journal article

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Strecker aldehyde formation in wine: new insights into the role of gallic acid, glucose, and metals in phenylacetaldehyde formation

Publication . Monforte, Ana Rita; Martins, Sara I. F. S.; Ferreira, António C. Silva

Strecker degradation (SD) leading to the formation of phenylacetaldehyde (PA) was studied in wine systems. New insights were gained by using two full factorial designs focusing on the effects of (1) pH and (2) temperature. In each design of experiments (DoE) three factors, glucose, gallic acid, and metals at two levels (present or absence), were varied while phenylalanine was kept constant. The obtained results gave a clear indication, with statistical significance, that in wine conditions, the SD occurs in the presence of metals preferentially via the phenolic oxidation independent of the temperature (40 or 80 °C). The reaction of the amino acid with the o-quinone formed by the oxidation of the gallic acid seems to be favored when compared with the SD promoted by the reaction with α-dicarbonyls formed by MR between glucose and phenylalanine. In fact, kinetics results showed that the presence of glucose had an inhibitory effect on PA rate of formation. PA formation was 4 times higher in the control wine when compared to the same wine with 10 g/L glucose added. By gallic acid quinone quantitation it is shown that glucose affects directly the concentration of the quinone. decreasing the rate of quinone formation. This highlights the role of sugar in o-quinone concentration and consequently in the impact on Strecker aldehyde formation, a promising new perspective regarding wine shelf-life understanding.

2018Journal article

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