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- Unveiling the evolution of Madeira Wine key metabolites: a three-year follow-up studyPublication . Pereira, Vanda; Leça, João M.; Freitas, Ana I.; Pereira, Ana C.; Pontes, Marisela; Albuquerque, Francisco; Marques, José C.Madeira wine (MW) encompasses an unusual oxidative ageing process that makes it distinc tive. Several metabolites have been related to its quality and safety, such as 5-hydroxymethylfurfural (HMF), furfural, sotolon, and ethyl carbamate (EC). These compounds were quantified over a three year period to assess their formation rate according to the ageing procedure used: canteiro vs. estufagem. Estufagem, which includes thermal processing of young MWs, promoted greater HMF, furfural, and sotolon accumulation, especially in sweet wines, in which sotolon contributed significantly to aroma (odour active values up to 17.5). Tinta Negra revealed a higher predisposition to form EC while Malvasia and Sercial were less prone to its formation. The formation of furfural, HMF, and EC strongly correlated with the ageing time. Sotolon had a strong correlation with the ageing time in canteiro (r = 0.79) and a moderate correlation in estufagem (r = 0.65). In both ageing procedures, sotolon, furfural, and HMF formation trends strongly correlated with each other (r = 0.74–0.90). In turn, EC also correlated with all furans (r = 0.51–0.85). Yellow tones (b*) correlated with these metabolites only when wines undergo estufagem. This study provides valuable insights to improve MW quality and safety management procedures.
- Micro-oxygenation in Madeira WinePublication . Freitas, Ana Isabel Camacho de; Marques, José Carlos Antunes; Pereira, Vanda Nulita GomesA micro-oxigenação consiste na adição deliberada e controlada de pequenas quantidades de oxigénio durante o processo de vinificação, com o intuito de melhorar as características organoléticas do vinho. Tendo em conta o carácter oxidativo do processo de envelhecimento do vinho Madeira, avaliou-se o impacto de três tratamentos de microoxigenação (t1- 66 mg/L por mês, antes da estufagem; t2 - 66 mg/L por mês, durante a estufagem; t3 – oxigénio dissolvido acima de 7 mg/L, durante a estufagem) no conteúdo de oxigénio dissolvido, parâmetros enológicos básicos, cor, polifenóis, furanos, composição volátil e características sensoriais. Em geral, a adição de um fluxo padrão de oxigénio não teve um impacto notável na cor, na composição polifenólica, nos furanos ou no perfil volátil, favorecendo, no entanto, o desenvolvimento de sotolon (até 97%) e de acetais heterocíclicos (até 95% para o trans-dioxolano). Já as condições de sobreoxigenação (t3) diminuíram consideravelmente a intensidade da cor (cerca de 41%) e o conteúdo polifenólico (até 29% durante a estufagem). Adicionalmente, este tratamento desacelerou a formação de furanos e de sotolon até cerca de 36%, comparativamente ao controlo. Para tal, foi desenvolvida uma metodologia para a determinação simultânea de sotolon e acetais heterocíclicos (cis- e trans-dioxano e cis- e trans-dioxolano), tendo por base a miniaturização da extração líquido-líquido e análise por GC-MS/SIM. Após otimização, o procedimento de extração foi validado relativamente ao sotolon, demonstrando ter boa sensibilidade (LOD e LOQ de 2,3 e 6,8 μg/L, respetivamente), linearidade (R2 de 0,999), precisão (desvios padrão para repetibilidade e reprodutibilidade inferiores a 8% e 10%, respetivamente) e exatidão (recuperação média de 105,4%), recorrendo a uma abordagem ecológica, rápida e de baixo custo. Relativamente aos acetais heterocíclicos, a metodologia foi avaliada em termos de precisão, com desvios padrão inferiores a 13% para a repetibilidade e a 17% para a reprodutibilidade.
- A simple emulsification-assisted extraction method for the GC–MS/SIM analysis of wine markers of aging and oxidation: application for studying micro-oxygenation in Madeira WinePublication . Freitas, Ana I.; Pereira, Vanda; Leça, João M.; Pereira, Ana C.; Albuquerque, Francisco; Marques, José C.Sotolon and the heterocyclic acetals of glycerol are known as potential aging and oxidation markers in fortified wines such as Madeira, Port, and Sherry. Thus, determining the evolution of these compounds under different oxidative aging conditions is important for fortified wine quality purposes. This study proposes a new methodology based on a miniaturized emulsification extraction followed by GC–MS/SIM, which was developed and optimized to follow the formation of sotolon and heterocyclic acetals in fortified wines that were submitted to traditional accelerated aging and micro-oxygenation. The optimization was achieved by means of a mixed-level factorial design, considering 3 factors: sample volume, extractant volume, and concentrated extract volume, by performing 19 experiments in duplicate. The extraction was optimized using 8 mL of wine sample, 5 mL of dichloromethane, concentrating the extract up to 10-fold. The method performance was evaluated for sotolon, using a matrix matched calibration between 10 and 2000 μg/L. The selectivity was confirmed through the analysis of real samples. The methodology showed good linearity (R2 = 0.999), high sensitivity (LOQ = 6.8 μg/L), recovery about 105%, and good precision (less than 8 and 9%, evaluated by the variation of intra- and inter-day measurements, respectively). This is the first methodology that revealed to be an excellent tool to simultaneously follow the formation of sotolon and heterocyclic acetals in Madeira wines, using an inexpensive, simple, efficient, and effective experimental layout. Indeed, it was shown that traditional accelerated aging and micro-oxygenation have impact on the formation of such molecules.
- Profiling of passion fruit volatiles: an effective tool to discriminate between species and varietiesPublication . Porto-Figueira, Priscilla; Freitas, Ana; Cruz, Catarina J.; Figueira, José; Câmara, José S.The aim of this work was to gain insights on the volatile composition of nine passion fruits grown at Madeira Island (Portugal) – Yellow, Purple, Lemon, Orange, Pineapple, Peach, Melon, Banana and Tomato – and discriminate between them. The volatile composition of these fruits has been investigated using the same analytical technique, HS–SPME/GC–MS and multivariate analysis (MVA). The selected SPME methodology (DVB/CAR/PDMS fiber at 40 ± 1 °C for 30 min and 10% (w/w) of NaCl under stirring mode (47 × g)) was applied in the profiling of nine different passion fruit samples by GC–MS, allowing the identification of up to 169 volatile compounds belonging to different chemical groups, namely linear and branched esters, terpenes, alcohols and others. Esters were found to be the dominant metabolites regardless of passion fruit sample, with hexyl hexanoate (ranging from 6 to 31%), methyl hexanoate (14–75%) ethyl hexanoate (12–53%) and hexyl butanoate (11–26%) being the principal volatile compounds found, followed by cis-β-ocimene (from 8 to 55%), (E)-2-hexenal (4 to 10% for Banana and Tomato passion fruit samples) and eucalyptol (18% for Tomato passion fruit). The results revealed that the differences in the volatile profile among the studied passion fruits were essentially qualitative, with only 7 common volatiles found in all samples, in different abundance. Advanced statistical techniques (PCA and PLS-DA) were used to explore data. Characteristic markers were successively identified using the NIST library, thus showing that the volatile profile was able to differentiate all nine species and varieties. Profiling of passion fruit volatile metabolites can provide an effective tool to characterize the product and to extract useful information concerning its quality or geographic origin.
- Is sotolon relevant to the aroma of Madeira Wine blends?Publication . Gaspar, João M.; Freitas, Ana I.; Zhao, Qianzhu; Leça, João M.; Pereira, Vanda; Marques, José C.Madeira wine (MW) oxidative aging results in the formation of several key aromas. Little is still known about their odor relevance to the aroma of the most commercialized MWs. This report presents an in-depth study of the odor impact of sotolon in MW blends. First, its odor perception was estimated in MWs according to ASTM E679, testing different 3-year-old (3-yo) commercial blends. The odor relevance of sotolon in the aroma of 3-, 5-, and 10-yo commercial blends (89 MWs) was then appraised by calculating its Odor Activity Value (OAV), after determining its content by RP-HPLC-MS/MS. The sotolon odor perception in MW was as low as 23 µg/L, although it was found that little differences in the wine matrix influenced its perception. OAVs varied between 0.1 and 22, increasing with the blend age. Considering that 16% of the OAVs are higher than 10 (mostly ≥ 10-yo), sotolon was found to be a key contributor to the overall aroma MW blends.