Whole bunch fermentation: adding complexity, or just making ‘green’ wine?

Certain grape varieties contain negligible levels of isobutyl methoxypyrazine (IBMP) in grapes. However, it has long been known that grape stems may have a high concentration of IBMP. The study aimed to discover the extent to which whole bunch addition during fermentation contributes to ‘capsicum’ (green) flavour and aroma in wine by imparting IBMP. It was also of interest to determine whether additional tannin could be extracted from stem contact, which was expected to impact wine astringency.

Two varieties, Pinot noir and Shiraz, were studied. Fermented either completely crushed, or as 100% whole bunches, as well as other treatments that had proportional whole bunch addition at 25%, 50% or 75%. Wines were put through descriptive sensory analysis after 10 months and multiple volatile and non-volatile compounds were analysed at the same time. 

Were the sensory scores for ‘green capsicum’ and the concentration of IBMP highly correlated with the proportion of whole bunches in the ferment? Were volatile compounds other than IBMP increased by whole bunch fermentations? What differneces were detected between Pinot noir and Shiraz?

Find out how this study showed that winemakers can substantially alter wine volatile and non-volatile composition through whole bunch fermentation, achieve potential wine style outcomes for the respective grape varieties, and whether whole bunch inclusion might improve the complexity of a wine, or simply introduce unwanted ‘green capsicum’ attributes.

Video of the seminar held during Macrowine virtual (June 23-30, 2021)

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