Pinking em vinhos da Beira Interior, sub-região de Castelo Rodrigo: contributo na pesquisa do(s) composto(s) responsáveis pelo pinking
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2016-06-03
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O pinking é a terminologia utilizada para descrever o fenómeno de aparecimento de uma
cor rosa-salmão em vinhos produzidos exclusivamente de uvas de castas brancas. Este defeito
visual dos vinhos brancos é recente, sendo o seu aparecimento atribuído à introdução da
vinificação em condições redutoras. Este fenómeno tem uma implicação económica
importante para as adegas já que acarreta custos acrescidos na produção do vinho branco, e a
nível da sua comercialização, o aparecimento desta cor no vinho branco é mal percepcionada
pelos consumidores. Em Figueira de Castelo Rodrigo observa-se este fenómeno há pelo
menos 12 anos desde a introdução da vinificação em condições redutoras na referida adega.
Tendo em conta a importância desta problemática na produção e comercialização dos vinhos
brancos de Figueira de Castelo Rodrigo, foi objectivo deste trabalho estudar a origem do
aparecimento do pinking em vinhos brancos produzidos nesta adega.
Os compostos responsáveis pelo aparecimento do pinking foram isolados a partir de vinhos
brancos da casta Síria e foram analisados e caracterizados por cromatografia líquida de
elevada eficiência (HPLC) em fase reversa e um detector de ultravioleta-visível de conjunto
de fotodíodos (DAD) e por espectrometria de massa tandem após ionização por electrospray,
tendo-se verificado que se trata de antocianinas, maioritariamente a malvidina-3-Oglucosídeo.
A análise dos bagos da casta Síria permitiu verificar que as antocianinas, contrariamente ao
observado nas castas tintas, se encontram maioritariamente na polpa, embora também existam
em quantidades reduzidas na película.
Em Figueira de Castelo Rodrigo, bem como noutras regiões do mundo, a severidade do
pinking é variável de ano para ano, sugerindo uma relação com as condições climáticas em
cada um dos anos. Para explorar esta possível relação, foram utilizados os dados climatéricos da sub-região de Castelo Rodrigo cedidos pela Direcção Regional de Agricultura e Pescas
(DRAP) Centro que incluíram a temperatura mínima, máxima e média diária, humidade do ar
mínima, média e máxima e a precipitação diária nos doze meses de cada ano, tendo-se
verificado uma correlação significativa entre a severidade do pinking, inferida pela quantidade de polivinilpolipirrolidona (PVPP) adicionado ao vinho branco, e a temperatura média dos 10
primeiros dias de Outubro, que coincide com o período final de maturação das uvas nesta
região.
A quantidade mínima de antocianinas necessária para a visualização do pinking no vinho
branco foi de cerca de 0,3 mg/L. O aparecimento do pinking nos vinhos brancos após
engarrafamento é devido à diminuição do teor de dióxido de enxofre livre, que leva a um
aumento da quantidade relativa de antocianinas na forma corada de catião flavílio bem como
à sua polimerização em vinhos já engarrafados após um certo período, resultando na formação
de compostos corados resistentes a alterações de pH e à descoloração pelo dióxido de enxofre.
Pinking is the terminology used for the salmon-red blush color that may appear in white wines produced exclusively from white grape varieties. This visual defect of white wines is recent, and its appearance attributed to the introduction of vinification under reducing conditions. This phenomenon has important economic implications for wineries as it increases production costs, and also, the appearance of this pink color in white wine is poorly perceived by consumers. In Figueira de Castelo Rodrigo this phenomenon has been observed for at least the last 12 years since the introduction of vinification under reducing conditions in this winery. Given the importance of this issue in the production and marketing of white wines of Figueira de Castelo Rodrigo, the purpose of this work was to study the origin of the pinking appearancing in white wines produced in this winery. The compounds responsible for the appearance of pinking were isolated from Síria white wines and grapes and were analyzed and characterized by high performance liquid chromatography (HPLC) on reverse phase with a photodiode array ultraviolet-visible detector (DAD) and by tandem mass spectrometry after electrospray ionization, and it was found that these compounds are anthocyanins, mainly malvidin-3-O-glucoside. The analysis of the Síria grape berries showed that anthocyanins, contrary to that observed in the red grape varieties, are found mainly in the pulp, although small amounts are found in the skins. In Figueira de Castelo Rodrigo, as well as worldwide, the severity of the pinking phenomena is variable from year to year, suggesting a relationship with the climatic conditions in each year. To explore this possible relation, the climatic data of the Castelo Rodrigo subregion, supplied by DRAP Center, that included the maximum, minimum and average daily temperature, maximum, minimum and average air humidity and precipitation of the 12 months of each year, it was found a significant correlation between the pinking severity, inferred by the amount of PVPP added to white wine, and the average temperature of the first 10 days of October, which is coincident with the final period of grape maturation. The minimum amount of anthocyanins needed for the pink color visualization in wine was nearly 0.3 mg/L. The appearance of pinking in white wines after bottling is due to the lowering of free sulfur dioxide, which leads to an increase of the relative amount of the anthocyanins red flavilyum form and due to their polymerization after bottling for a certain period, resulting in the formation of colored compounds resistant to pH changes and sulfur dioxide bleaching.
Pinking is the terminology used for the salmon-red blush color that may appear in white wines produced exclusively from white grape varieties. This visual defect of white wines is recent, and its appearance attributed to the introduction of vinification under reducing conditions. This phenomenon has important economic implications for wineries as it increases production costs, and also, the appearance of this pink color in white wine is poorly perceived by consumers. In Figueira de Castelo Rodrigo this phenomenon has been observed for at least the last 12 years since the introduction of vinification under reducing conditions in this winery. Given the importance of this issue in the production and marketing of white wines of Figueira de Castelo Rodrigo, the purpose of this work was to study the origin of the pinking appearancing in white wines produced in this winery. The compounds responsible for the appearance of pinking were isolated from Síria white wines and grapes and were analyzed and characterized by high performance liquid chromatography (HPLC) on reverse phase with a photodiode array ultraviolet-visible detector (DAD) and by tandem mass spectrometry after electrospray ionization, and it was found that these compounds are anthocyanins, mainly malvidin-3-O-glucoside. The analysis of the Síria grape berries showed that anthocyanins, contrary to that observed in the red grape varieties, are found mainly in the pulp, although small amounts are found in the skins. In Figueira de Castelo Rodrigo, as well as worldwide, the severity of the pinking phenomena is variable from year to year, suggesting a relationship with the climatic conditions in each year. To explore this possible relation, the climatic data of the Castelo Rodrigo subregion, supplied by DRAP Center, that included the maximum, minimum and average daily temperature, maximum, minimum and average air humidity and precipitation of the 12 months of each year, it was found a significant correlation between the pinking severity, inferred by the amount of PVPP added to white wine, and the average temperature of the first 10 days of October, which is coincident with the final period of grape maturation. The minimum amount of anthocyanins needed for the pink color visualization in wine was nearly 0.3 mg/L. The appearance of pinking in white wines after bottling is due to the lowering of free sulfur dioxide, which leads to an increase of the relative amount of the anthocyanins red flavilyum form and due to their polymerization after bottling for a certain period, resulting in the formation of colored compounds resistant to pH changes and sulfur dioxide bleaching.
Descrição
Dissertação de Mestrado em Enologia
Palavras-chave
Uva (branca) , Vinho branco , Antocianinas , Casta síria