The introduced biological control agent Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) has attained pest status in North America as its presence in vineyards during harvest may compromise the quality of the resulting wine. Control of H. axyridis in vineyards is difficult as their populations may fluctuate daily, and there are few products registered to control this pest. Sulfur dioxide, in the form of potassium metabisulfite (KMS), is commonly used in wine as both an antimicrobial and an antioxidant. In this study, the effectiveness of KMS as a repellent against H. axyridis was measured. In a Y-tube olfactometer, H. axyridis spent significantly less time in the treatment arm (KMS 2.5, 5, and 10 g/liter) than in the control arm during a 10-min period. When sprayed in a vineyard, KMS significantly reduced the number of H. axyridis on grape vines. KMS is an effective repellent against H. axyridis and may be suitable for use in vineyards to control this pest. KMS (5 g/liter) applied to Riesling grapes at 2 wk, 1 wk, 3 d, or 1 d before harvest did not affect free sulfur dioxide in either freshly processed or settled juice. This study lays the foundation for the development of a pest management strategy incorporating repellents for H. axyridis in vineyards.

This project aims to characterize and define an autochthonous yeast, Saccharomyces bayanus CN1, for wine production from partially dehydrated grapes. The yeast was identified via PCR and Basic Local Alignment Search Tool (BLAST) analysis as Saccharomyces bayanus, and then subsequently used in fermentations using partially dehydrated or control grapes. Wine grapes were dried to 28.0°Brix from the control grapes at a regular harvest of 23.0°Brix. Both the partially dehydrated and control grapes were then vinified with each of two yeast strains, S. bayanus CN1 and S. cerevisiae EC1118, which is a common yeast used for making wine from partially dehydrated grapes. Chemical analysis gas chromatography-flame ionization detector (GC-FID) and enzymatic) of wines at each starting sugar level showed that CN1 produced comparable ethanol levels to EC1118, while producing higher levels of glycerol, but lower levels of oxidative compounds (acetic acid, ethyl acetate, and acetaldehyde) compared to EC1118. Yeast choice impacted the wine hue; the degree of red pigment coloration and total red pigment concentration differed between yeasts. A sensory triangle test (n = 40) showed that wines made from different starting sugar concentrations and yeast strains both differed significantly. This newly identified S. bayanus strain appears to be well-suited for this style of wine production from partially dehydrated grapes by reducing the oxidative compounds in the wine, with potential commercial application for cool climate wine regions.

Abstract:The purpose of this study was to investigate the effect of wine style and cane sugar addition in the liqueur d'expedition (dosage) solution on volatile aroma compounds (VOCs) in traditional method sparkling wine. There were 24 bottles of each treatment produced. Treatments were sparkling wine zero dosage (ZD); NV sparkling wine + sugar (BS); unoaked still Chardonnay wine + sugar (UC); Pinot noir 2009 sparkling wine + sugar (PN); Niagara produced Brandy + sugar (B) and Icewine (IW). The control treatment in the sensory analysis was an oaked still Chardonnay wine + sugar (OC) because the zero-dosage wine was not suitable for a difference test that compared wines with sugar to one without. Standard wine chemical parameters were analysed before disgorging and after liqueur d'expedition was added and included; pH, titratable acidity (TA g/L), alcohol (v/v %), residual sugar (RS g/L), free and total SO 2 and total phenolics (A.U.). Volatile aroma compounds (VOCs) analysed by Headspace Solid-Phase Micro-Extraction Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) included two alcohols, and six ethyl esters. ZD wines had the highest foam height and highest dissolved oxygen level. Sugar affected VOC concentrations in all treatments at five weeks post-disgorging, but by 15 weeks after liqueur d'expedition addition, the wine with added sugar had similar VOC concentrations to the ZD wines. The type of wines used in the dosage solutions had more influence on VOC concentrations than sugar addition.

Background and Aims: Modification of important odorants induced by Botrytis cinerea has been reported in dry red wine (Amarone) made from withered grapes, but the impact on wines produced in other regions remains to be elucidated. Methods and Results: Cabernet Franc grapes from Ontario were dried to 28.0 Brix and fermented with either nonbotrytised grapes or a combination of non-botrytised and botrytised grapes (10% infection). The metabolites, including volatile compounds, were analysed and sensory evaluation including consumer preference were assessed. Gluconic acid, glycerol and acetic acid were significantly higher in the B. cinerea wines. Differences in some ethyl esters, isoamyl acetate and hexanol were observed between the Control and botrytised wines. These wines were differentiated by only one sensory attribute. A consumer preference test (n = 153) comparing liking scores of wines from this study to wines previously made from withered grapes fermented with an autochthonous yeast showed no difference in preference. Conclusions: Inclusion of 10% B. cinerea infection in wines vinified from withered Cabernet Franc grapes makes little chemical or sensory difference, suggesting culling at this infection rate may be unnecessary and does not negatively impact consumer liking. Significance of the Study: Red wine made from withered grapes may tolerate 10% botrytised fruit without adversely affecting consumer liking.

Aim: A Saccharomyces uvarum isolate was assessed for its ability to metabolize acetic acid present in juice and during the fermentation of partially dehydrated grapes. The impact on other yeast metabolites was also compared using an S. uvarum isolate and an S. cerevisiae wine yeast. The upper limit of fruit concentration that allowed the S. uvarum isolate to ferment wines to < 5 g/L residual sugar was defined.Methods and results: Cabernet franc grapes were partially dehydrated to three different post-harvest sugar targets (24.5 °Brix, 26.0 °Brix, and 27.5 °Brix) along with non-dehydrated grapes (21.5 °Brix control). Musts from all treatments were vinified with either the S. uvarum isolate CN1, formerly identified as S. bayanus, or S. cerevisiae EC1118. All wines were successfully vinified to less than 5 g/L residual sugar. Fermentation kinetics between the two yeasts were similar for all wines other than 27.5 °Brix, where CN1 took three days longer. During fermentation with CN1, acetic acid peaked on day two, then decreased in concentration, resulting in final wine acetic acid lower than that measured on day two. Wines fermented with EC1118 showed an increase in acetic acid over the time-course of fermentation. Significantly lower wine oxidative compounds (acetic acid, acetaldehyde and ethyl acetate) and higher glycerol resulted in wine produced with CN1 in comparison to EC1118. Both yeasts produced comparable ethanol at each Brix level tested. Further studies showed that CN1 lowered acetic acid seven-fold from 0.48 g/L in juice to 0.07 g/L in wine whereas EC1118 reduced acetic acid to 0.18 g/L.Conclusions: The autochthonous S. uvarum yeast isolate successfully fermented partially dehydrated grapes to < 5 g/L sugar up to 27.5 ºBrix. The consumption rate of acetic acid was faster than its production during fermentation, resulting in low acetic acid, acetaldehyde and ethyl acetate in wine in comparison to a commercial S. cerevisiae yeast while consistently producing higher glycerol.Significance and impact of the study: The S. uvarum yeast isolate can metabolize acetic acid during fermentation to significantly lower acetic acid, ethyl acetate and acetaldehyde in wine. It can also reduce acetic acid by seven-fold from the starting juice to the finished wine, which could have potential application for managing sour rot arising in the vineyard or during the dehydration process in making appassimento-style wines.