Mold on late harvested Cabernet sauvignon grapes and their effect on must and wine quality.

Ph. Pszczólkowski, B. A. Latorre, C. Ceppi Di Lecco

Abstract


Wine grapes (Vitis vinifera L.) have been historically harvest according to their soluble solid contents, (>22.5%) and tartaric acidity (6-7 g·L-1). However, the phenolic content has been proposed and used lately as a better index to determine harvest date. This has implied to delay harvest significantly which has favoried the development of molds that can affect must and wine qualities. The mold incidence found in 13 Cabernet sauvignon vineyards at harvest varied from 4.7 to 66.7%, and were identified as olive green molds (Cladosporium herbarum, Alternaria alternata, Ulocladium sp.), gray mold (Botrytis cinerea), dark brown mold (Aspergillus niger), and Phoma sp. These fungi species, with the exception of B. cinerea,          were not necessarily associated to rotten berries. C. herbarum and A. alternata were the most frequently species, found in 11 and 7 of 13 sample sites studied, respectively. Weight of moldy grapes was significantly lower than weight of apparently healthy grapes (p < 0.05), with 32.8% overall mean weight loss of the 13 Cabernet sauvignon vineyards. Wines produced with moldy grapes had consistently lower color capacity, a yellowish tint, and had lower contents in antocianins and total phenol. These wines had lower free sulfur dioxide content but combined sulfur dioxide content increased considerably. Additionally, relative to must from apparently healthy grapes, fermentation was delayed at least 12 days when moldy grapes were used. Therefore, the relative high incidence of molds found on wine grapes at harvest reduced yields and had a negative effect on wine qualities, particularly reducing wine color, and affecting smell and flavor. Consequently, the present tendency of Chilean wineries to postpone harvest to obtain a better wine quality does not necessarily fulfill this goal.En Chile, tradicionalmente la cosecha de la vid (Vitis vinifera L.) para vinificación se ha determinado según el contenido de azúcar (>22,5 %) y la acidez total (6-7 g·L-1), expresada como ácido tartárico. Sin embargo, en los últimos años se ha privilegiado la madurez fenólica como criterio de cosecha. Esta situación ha determinado postponer considerablemente la fecha de cosecha lo que ha favorecido el desarrollo de mohos superficiales en las bayas al momento de vinificar. Los mohos identificados en uvas Cabernet sauvignon provenientes de 13 viñedos comerciales a la cosecha correspondieron a mohos verde oliváceos (Cladosporium herbarum, Alternaria alternata, Ulocladium sp.), moho gris (Botrytis cinerea), moho negro (Aspergillus niger) y Phoma sp. Con la excepción de B. cinerea, estos hongos no necesariamente estuvieron asociados a pudriciones. Cladosporium herbarum y A. alternata fueron las especies mas frecuentes, las que se identificaron en 11 y 7 de 13 muestras de uvas Cabernet sauvignon, obtenidas en viñedos comerciales a la cosecha. En promedio, la pérdida de peso se estimó en 32,8%, siendo siempre significativamente (p<0,05) inferior el peso de las uvas mohosas. El vino obtenido con uvas mohosas presentó menor intensidad colorante, un matiz más amarillo, menor contenido de antocianos y de polifenoles totales. A su vez disminuyó el contenido de anhídrido sulfuroso libre y aumentó el anhídrido sulfuroso combinado. Además la fermentación alcohólica se retardó en al menos 12 días en relación con la fermentación de un mosto con uvas aparentemente sanas cosechadas en el mismo viñedo. En consecuencia, se concluye que la alta incidencia de mohos superficiales presentes en las uvas al momento de la cosecha afecta negativamente el peso de la cosecha y las cualidades sensoriales de los vinos obtenidos, particularmente el color, olor y sabor. La tendencia generalizada de la industria chilena a cosechar tardíamente en busca de una mejor calidad del vino resultante no necesariamente permitiría cumplir con este objetivo.

Keywords


mold, Vitis vinifera, wine quality.

Full Text:

Untitled


DOI: http://dx.doi.org/10.7764/rcia.v28i3.447