D. Inglis

Upregulation of ALD3 and GPD1 in Saccharomyces cerevisiae during Icewine fermentation

Aims:  To determine acetic acid, acetaldehyde and glycerol production by wine yeast throughout Icewine fermentation. The expression of yeast cytosolic aldehyde dehydrogenases (ALD3 and ALD6) and glycerol‐3‐phosphate dehydrogenase (GPD1) were followed to relate metabolites in the wines to expression patterns of these genes.

Response of wine yeast (Saccharomyces cerevisiae) aldehyde dehydrogenases to acetaldehyde stress during icewine fermentation

Aims:  We previously reported that the aldehyde dehydrogenase encoded by ALD3 but not ALD6 was responsible, in part, for the increased acetic acid found in Icewines based on the expression profile of these genes during fermentation. We have now completed the expression profile of the remaining yeast aldehyde dehydrogenase genes ALD2, ALD4 and ALD5 during these fermentations to determine their contribution to acetic acid production. The contribution of acetaldehyde stress as a signal to stimulate ALD expression during these fermentations was investigated for all ALD genes. The expression of glycerol‐3‐phosphate encoded by GPD2 was also followed during these fermentations to determine its role in addition to the role we already identified for GPD1 in the elevated glycerol produced during Icewine fermentation.

Designing and creating Saccharomyces interspecific hybrids for improved, industry relevant, phenotypes

To remain competitive in increasingly overcrowded markets, yeast strain development programmes are crucial for fermentation-based food and beverage industries. In a winemaking context, there are many yeast phenotypes that stand to be improved. For example, winemakers endeavouring to produce sweet dessert wines wrestle with fermentation challenges particular to fermenting high-sugar juices, which can lead to elevated volatile acidity levels and extended fermentation times. In the current study, we used natural yeast breeding techniques to generate Saccharomyces spp. interspecific hybrids as a non-genetically modified (GM) strategy to introduce targeted improvements in important, wine-relevant traits. The hybrids were generated by mating a robust wine strain of Saccharomyces cerevisiae with a wine isolate of Saccharomyces bayanus, a species previously reported to produce wines with low concentrations of acetic acid. Two hybrids generated from the cross showed robust fermentation properties in high-sugar grape juice and produced botrytised Riesling wines with much lower concentrations of acetic acid relative to the industrial wine yeast parent. The hybrids also displayed suitability for icewine production when bench-marked against an industry standard icewine yeast, by delivering icewines with lower levels of acetic acid. Additionally, the hybrid yeast produced wines with novel aroma and flavour profiles and established that choice of yeast strain impacts on wine colour. These new hybrid yeasts display the desired targeted fermentation phenotypes from both parents, robust fermentation in high-sugar juice and the production of wines with low volatile acidity, thus establishing their suitability for wine styles that are traditionally troubled by excessive volatile acidity levels.

Concentration effect of Riesling Icewine juice on yeast performance and wine acidity

Aims:  The objective of this study was to determine the effect of increasing juice soluble solids above 40°Brix on wine yeast’s ability to grow and ferment the juice, with particular focus on acetic acid production, titratable acidity (TA) changes and the maximum amount of sugar consumed by the yeast.

A novel method for controlling multicolored Asian lady beetle (Coleoptera: Coccinellidae) in vineyards.

ABSTRACT 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.

Osmoadaptation of wine yeast (Saccharomyces cerevisiae) during Icewine fermentation leads to high levels of acetic acid

Volatile acidity (VA) production along with gene expression patterns, encoding enzymes involved in both acetic acid production and utilization, were investigated to relate gene expression patterns to the production of undesired VA during Icewine fermentation.

Good Bugs Gone Bad:Coccinellidae, Sustainability And Wine

Coccinellidae (‘ladybeetles’) are generally known as beneficial insects. Many are voracious predators feeding upon harmful pests such as aphids, scale insects, mealy bugs and mites. Coccinellidae species have been introduced into many regions around the world as bio-control agents for a range of grains, fruit and other crops. However, in part because of a northerly migration due to global warming, introduced species are now displacing native Coccinellidae species in some areas, and reaching densities that pose significant challenges for the grape and wine industries. Harmonia axyridis and Coccinella septempunctata are increasingly found in vineyards, and when they are inadvertently incorporated with grapes at harvest they produce a very potent odorant that taints the subsequent wine (‘ladybug taint’). This has significantly devalued grapes and wine from many regions over the last decade, and the beetles responsible now represent one of the greatest threats to the industry. Approaches for dealing with this novel pest have focused on repellency or exclusion of the beetle from the fruit or vineyard, and on remediation of juice and wine affected by ladybug taint. To date, the use of insecticidal sprays in the vineyard – including the synthetic pyrethroid, cypermethrin, and the organophosphate, malathion – has been the treatment of choice, but their use raises issues related to residues, phytotoxicity and wine quality. We present data from our labs on two alternative options. The first involves the use of potassium metabisulphite – commonly used in wine as an antimicrobial and antioxidant. Y-tube olfactometry and field studies show significant repellency effects (up to 50%) on Coccinellidae. In the second study, a range of grape-derived non-toxic compounds were assessed for their potential Sustainability Today 239 www.witpress.com, ISSN 1743-3541 (on-line) WIT Transactions on Ecology and The Environment, Vol 167,

Investigating the use of partial napping with ultra-flash profiling to identify flavour differences in replicated, experimental wines

ABSTRACT Experimental wine studies with three or more treatments, over multiple years with replicated wines, often require sensory analysis to describe treatment effects on the resultant wines. This scientific approach can result in a large number of samples for sensory analysis, which can be time-consuming, and problematic for the design of descriptive analysis (DA). The aim of this study was to establish whether partial napping (PN) combined with ultra-flash profiling (UFP) could identify a subset of replicate wines that were similar enough in flavour profile that they could be used as representative samples for descriptive analysis (DA). Pinot noir wines from three field treatments (T1, T2, and T3), were produced in triplicate (a, b and c) and analysed by PN and UFP. Multiple factor analysis (MFA) using a citation frequency method showed that two similar replicate wines could be identified for each treatment wine. These results show that UFP allows for small sample sets to be used for subsequent and more resource intensive DA methods, and provides greater insight into the use of rapid sensory analysis in wine research.