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- Impact of indigenous non-saccharomyces yeasts isolated from Madeira Island vineyards on the formation of ethyl carbamate in the aging of fortified winesPublication . Leça, João Micael; Pereira, Vanda; Miranda, Andreia; Vilchez, José Luis; Malfeito-Ferreira, Manuel; Marques, José CarlosThe impact of selected non-Saccharomyces yeasts on the occurrence of ethyl carbamate (EC) was evaluated. Hanseniaspora uvarum, Starmerella bacillaris, Pichia terricola, Pichia fermentans and Pichia kluyveri isolated from Madeira Island vineyards were inoculated in Tinta Negra musts. Urea, citrulline (Cit) and arginine (Arg) were quantified when the density of musts attained the levels to obtain sweet (1052 ± 5 g/L) and dry (1022 ± 4 g/L) Madeira wines. The urea concentration varied between 1.3 and 5.3 mg/L, Cit from 10.6 to 15.1 mg/L and Arg between 687 and 959 mg/L. P. terricola and S. bacillaris generated lower levels of urea (<2.5 mg/L), Cit (<11.0 mg/L) and Arg (<845.6 mg/L). The five resulting fortified wines, individually fermented by the selected non-Saccharomyces yeast, were exposed to laboratory-accelerated aging at 70 °C for 1 month. From the studied yeasts, P. terricola and S. bacillaris revealed a lower potential to form EC (<100 µg/L); therefore, both yeasts can be a useful tool for its mitigation in wines.
- New insights into ethyl carbamate occurrence in fortified winesPublication . Leça, João M.; Pereira, Vanda; Miranda, Andreia; Vilchez, José Luis; Marques, José C.The occurrence of ethyl carbamate (EC) in fortified wines was studied testing different model wines under accelerated ageing (45 °C for 4 months and 70 °C for 1 month), to investigate the possibility of arginine (Arg) being a direct precursor of EC in fortified wines, comparing it with known major precursors, urea and citrulline (Cit). Wine main sugars were appraised as possible catalysts, as previously pointed out. Model wines showed that: Arg can induce the EC formation under accelerated ageing, even without being metabolised by microorganisms; although much less reactive, Arg can play a significant role since high residual levels can occur in young fortified wines; glucose (Glc) and fructose (Fru) suppressed the EC formation from urea and Cit pathways, in about 11–26%. Moreover, Madeira wine samples were investigated in order to appraise the eventual contribution of the alcoholic fortification. The results revealed that this step can promote a decrease of the amount of these EC precursors up to 46%. Despite preliminary, additional information about the EC formation in fortified wines was obrained namely for designing new mitigation strategies, which can pass through the reduction of residual Arg.
- Impact of Non-Saccharomyces Yeast Fermentation in Madeira Wine Chemical CompositionPublication . Miranda, Andreia; Pereira, Vanda; Jardim, Humberto; Malfeito-Ferreira, Manuel; Marques, José CarlosMadeira wine is produced via spontaneous alcoholic fermentation arrested by ethanol addition. The increasing demand of the wine market has led to the need to standardize the winemak ing process. This study focuses on identifying the microbiota of indigenous yeasts present during Madeira wine fermentation and then evaluates the impact of selected indigenous non-Saccharomyces as pure starter culture (Hanseniaspora uvarum, Starmerella bacillaris, Pichia terricola, Pichia fermentans, and Pichia kluyveri) in the chemical and phenolic characterization of Madeira wine production. Re sults showed that the polyphenol content of the wines was influenced by yeast species, with higher levels found in wines produced by Pichia spp. (ranging from 356.85 to 367.68 mg GAE/L in total polyphenols and 50.52 to 51.50 mg/L in total individual polyphenols through HPLC methods). Antioxidant potential was higher in wines produced with Hanseniaspora uvarum (133.60 mg Trolox/L) and Starmerella bacillaris (137.61 mg Trolox/L). Additionally, Starmerella bacillaris stands out due to its sugar consumption during fermentation (the totality of fructose and 43% of glucose) and 15.80 g/L of total organic acids compared to 9.23 g/L (on average) for the other yeasts. This knowledge can be advantageous to standardizing the winemaking process and increasing the bioactive compounds, resulting in the production of high-quality wines.
- Indigenous yeasts in Madeira wines: impact on the physicochemical and sensorial characterizationPublication . Miranda, Andreia Fátima Santos; Marques, José Carlos AntunesO Vinho Madeira é produzido pela fermentação espontânea através de leveduras indígenas presentes em uvas e adegas. A crescente exigência dos consumidores leva à necessidade de uniformizar o processo de vinificação. O presente trabalho visa avaliar a composição química de vinhos Madeira produzidos em diferentes adegas e com uvas colhidas de diferentes localizações (sul e norte). Depois, isolar e identificar as leveduras indígenas de mostos da casta Tinta Negra de diferentes localizações e adegas, e avaliar o impacto do uso de 5 leveduras indígenas não-Saccharomyces selecionadas (Hanseniaspora uvarum, Starmerella bacillaris, Pichia terricola, Pichia fermentans e Pichia kluyveri) na produção de vinho Madeira, como culturas puras iniciadoras, na composição química, perfil volátil e características sensoriais. Os resultados mostraram variabilibidade na composição química nas diferentes adegas, e baixa reprodutibilidade entre lotes da mesma adega. Uvas da região sul apresentaram níveis mais elevados de açúcares (196.32 g/L), polifenóis totais (270.18 mg GAE/L) e potencial antioxidante (128.48 mg Trolox/L). Os estudos da microflora de leveduas indígenas envolvidas na produção de vinho Madeira permitiram identificar 11 espécies nas adegas (Hanseniaspora uvarum, Starmerella bacillaris, Pichia kluyveri, Pichia fermentans, Saccharomyces cerevisiae, Torulaspora delbrueckii, Candida apicola, Cystobasidium minutum, Pichia terricola, Cystobasidium slooffiae, e Wicheramomyces anolalus) e 6 espécies nas uvas (Hanseniaspora uvarum, Starmerella bacillaris, Pichia kluyveri, Pichia fermentans, Saccharomyces cerevisiae, and Hanseniaspora opuntiae). Os vinhos produzidos por Pichia spp. demonstraram níveis mais elevados de polifenóis totais (367.68 mg GAE/L), enquanto os vinhos produzidos por Starmerella bacillaris demonstraram maior acidez (9.23 g/L) e menor conteúdo de voláteis (11.26%). O vinho produzido por Pichia kluyveri destacou-se na concentração total de volatéis (24.50%), dos quais 77.35% são estéres, obtendo 37% de preferência dos consumidores, com notas intensas de caramelo e especiarias. Portanto, Pichia kluyveri demonstrou potencial para ser utilizada como cultura iniciadora de fermentação na produção de vinho Madeira.