Abstract:
The Impact of the Multicolor Asian Lady Beetle (Harmonia axyridis) on Niagara Wine
Quality
The possible influence of Harmonia axyridis (the Multicolored Asian Lady Beetle) on the
sensory properties of wine was investigated. H. axyridis beetles were added to white and
red grape musts at a rate of 0, 1 or 10 per L, and a trained panel evaluated the finished
wines using flavor-profiling techniques. Significant modification of both wine aroma and
flavor characteristics were observed in the 10 beetlelL treatments, with smaller effects
noted at the 1 beetlelL rate. Vinification in the presence of H. axyridis gave higher
intensity scores for peanut, bell pepper and asparagus aromas and flavors in the white
wines, and peanut, asparagus/bell pepper, and earthy/herbaceous aromas and flavors in
the red wines. In addition, sweet, acid and bitter tastes were affected in red wines, and a
general trend of decreasing fruit and floral intensities with increasing beetle rate was
observed in both white and red wines. 15 ngIL Isopropylmethoxypyrazine was added to
control wines and sensory profiles similar to high beetle treatments were obtained,
supporting the hypothesis that methoxypyrazines from beetles are implicated in the taint.
A trained panel evaluated the treated wines after 10 months of aging using the same
sensory methods described above. Sensory profiles were very similar.
Fennenting in the presence of Harmonia Axyridis (HA) had little influence on the
chemical composition of the ftnished wine. The notable exception IS
Isopropylmethoxypyrazine content, which was assessed usmg GC-MS analysis and
showed increased concentration with increasing beetle nwnber for both white and red
wmes.
The influence of potential remedial treatments on the sensory properties of white and red
wines tainted by Harmonia axyridis were also investigated. Bentonite, activated charcoal,
oak chips, de-odorized oak chips, and UV or light irradiation were applied to tainted
wine, and these wines evaluated chemically and sensorially. Both white and red wines
treated with oak chips had strong oak characteristics, which masked the Harmonia
axyridis-associated aroma and flavour attributes. In red wine, asparagus/bell pepper
characteristics were decreased by bentonite and charcoal treatments. Only activated
charcoal significantly decreased methoxypyrazine levels and only in white wine.
