Mouthfeel is one of the most important quality parameters of Chardonnay wines. Malolactic fermentation (MLF) is an important process in wine production, and influential to wine mouthfeel, with the reduction in acidity being particularly important for cool climate wines that generally have higher acidity such as Chardonnay. MLF is typically induced by the addition of Oenococcus oeni after the completion of the alcoholic fermentation (AF) but can occur concurrent with AF by inoculating O. oeni simultaneously with the fermentative yeast Saccharomyces cerevisiae. We investigated the effect of MLF inoculation timing as well as the temperature of MLF and the presence of the non-Saccharomyces yeast Torulaspora delbrueckii on Chardonnay wine mouthfeel. Chardonnay wines were produced in 2014 with AF and MLF inoculated for simultaneous or sequential fermentations, and temperatures 15 and 21°C, with or without the addition of T. delbrueckii. Mouthfeel attributes of the wines produced were assessed by a winemaker panel, using Napping® and Ultra-flash profiling. Significant differences in mouthfeel perception were found based on timing and inoculation conditions, as well as between temperatures. Treatment type and temperature also effected the chemical composition of finished wines. Additionally, there are many interactions that occur between taste and aroma that may impact mouthfeel perception. This led us to investigate whether the aroma fraction of Chardonnay wine should be considered when investigating relationships between chemical composition and sensory perception of mouthfeel. Chardonnay wines were determined to have mouthfeel differences by altering the fermentation temperature of the alcoholic and malolactic fermentation as well as the timing of MLF and the presence of a non-Saccharomyces yeast during AF. Napping® and Ultra-flash-profiling were conducted using a panel of white winemakers. Each procedure was conducted twice: once with retro-nasal aroma and once without retronasal aroma. Napping® results showed that retronasal aroma impacted mouthfeel perception. Ultra-flash profiling displayed similar descriptive terms used with and without retronasal aroma, but terms were not consistently used for the same wine treatments with and without retronasal aroma. It is unclear if these differences are due to interactions or due to associated learning. These results suggest that for some mouthfeel terms the volatile fraction is playing a role and to establish relationships with chemical composition and mouthfeel perception it is important to consider both the volatile and nonvolatile wine fractions. We then investigated the impact of pre-fermentation juice treatments on mouthfeel characteristics of Chardonnay wine. Chardonnay grapes were harvested from Oregon State University’s vineyard in September, 2015. After destemming and pressing the juice was subjected to various treatments. These treatments included high, medium, and low turbidity level, as well as hyper-oxidation, two-hour skin contact, and two-hour skin contact + hyper-oxidation. All treatments went through alcoholic and malolactic fermentations. Total phenolics and hydroxycinnamic acids differed between skin contact and hyper-oxidation treatments. Wines that underwent hyper-oxidation contained the lowest total phenolics. Hyper-oxidation following skin contact reduced total phenolics but retained more than the hyper-oxidation treatment. Sensory analysis using citation by frequency procedure showed that all treatments modified the mouthfeel of finished wines. However, chemical analysis did not fully elucidate the cause of these differences. Pre-fermentation juice treatments can be utilized to develop stylistic differences in finished Chardonnay wine. The combined findings of this research demonstrate the usefulness of various enological practices to influence the sensory qualities of a Chardonnay wine, as well as emphasizing the importance of retro-nasal aroma’s influence on the mouthfeel experience of Chardonnay wine.

In an attempt to determine the impact of various oxidative conditions on fermentations inoculated with strains of Saccharomyces cerevisiae containing the MET10-932 allele, a pilot experiment was carried out. A total of twenty-five small-scale fermentations were carried out in a commercial setting using Alexander Valley Chardonnay juice in the 2012 vintage. A total of five different yeast strains and five different juice and wine treatments were performed. The yeast strains included three MET10-932, Phyterra strains: P1Y0, P2Y3, and P7Y9, as well as two strains of the MET10 wildtype allele; CY3079 and EC1118. The MET10 allele is known to be responsible in Saccharomyces cerevisiae strains for low basal levels of sulfite reductase activity. Thus, the MET10-932 yeast strains do not produce hydrogen sulfide in primary fermentation. Experimentation with these yeast strains in various juice conditions is beneficial to understand optimization of fermentative behavior. The oxidative conditions of the juice were altered at various points in the fermentation to determine optimal production conditions as well as to determine fermentative behavior of the MET10-932 and MET10 wildtype yeast strains given various production approaches and techniques. The oxidative treatments ranged from aeration prior to fermentation, sparging with nitrogen pre-fermentation, and aerations at specific time points in the fermentation. In this pilot experiment, no noticeable impacts of aeration treatments were observed on the fermentation behavior. Additionally, the MET10-932 yeast strains illustrated a significantly higher bound SO2 content upon completion of fermentation in the large-scale fermentations. Potential causes for the higher yields of bound SO2 in the MET10-932 yeast strains include use of specific vineyard treatments, nutrients utilized during the fermentation and other fermentative conditions. In order to investigate the source of the higher bound SO2 in the MET10-932 yeast strains, small-scale fermentations were carried out in MMM medium using a treatment of Fermaid K and no nutrient addition. Results indicate that nutrient addition in the form of Fermaid K did not impact the total sulfite production as compared to the fermentation that did not receive nutrient addition. However, the MET10-932 strains did express a higher bound sulfite production as compared to the MET10 wildtype strains. It can be concluded that although various aeration impacts did not greatly impact the fermentation behavior there are still certainly benefits in understanding the optimization of these strains for production purposes. Ruling out Fermaid K nutrient addition as the source of high bound SO2 helps in learning what might be responsible. Further, it can be determined that the high bound SO2 is not solely linked to varietal characteristic of Chardonnay as the high levels were also observed in MMM.

Wineries are facing new challenges due to actual market demands for the creation of products exhibiting more particular flavors. In addition, climate change has lead to the requirement for grape varieties with specific features, such as convenient maturation times, enhanced tolerance towards dryness, osmotic stress, and resistance against plant-pathogens. The next generation of yeast starter cultures should produce wines with an appealing sensory profile and less alcohol. This Special Issue comprises actual studies addressing some of the problems and solutions for the environmental, technical, and consumer challenges of wine making today: Development of sophisticated mass spectroscopic methods enable the identification of the major metabolite spectrum of grapes/wine and deliver detailed insights in terroir and yeast-specific traits;Knowledge of the origin and reactions of reductive sulphur compounds facilitates the avoidance of unpleasant wine odors;Innovative physical–chemical treatments support effective and sustainable color extraction from red grape varieties;Enological enzymes from yeasts used directly or in the form of starter cultures are promising tools to increase the juice yields, color intensity, and aroma of wine;Natural and artificial Saccharomyces hybrids as well as collections of adapted wild isolates from various ecological niches will extend winemakers repertoire, allowing individual fermentations;Exact process control of wine fermentations by convenient computer programs will guarantee consistently high product quality.

Fining is a common practice used in the wine industry which assists with clarification and/or provides corrective treatment for the aroma, taste or aftertaste of a juice or wine. During this thesis project the fining agents activated carbon (AC), gelatin (G), gelatin with silicon dioxide (GSi), polyvinylpolypyrrolidone (PVPP), and a mixed agent consisting of bentonite, PVPP, and isinglass (M) where investigated for their ability to influence the concentration of several aroma compounds in Marlborough Sauvignon blanc. Sensory trials were also conducted to investigate if any chemical changes impact the sensory aspect of the wines. Although both free run and press fraction juice fining was considered, a stronger emphasis was placed on the production of press fraction wines. The focus of this thesis was conceived in direct collaboration with a winery which noted anecdotally that press fraction juices require severe fining regimes thought to be due to the extended skin contact and oxygen exposure they undergo. Therefore, the project set out to explore if pre-fermentation juice fining could modulate aroma compounds present in Marlborough Sauvignon blanc press fraction wines. The first fining trial conducted was to survey the potential for the chosen commercially available agents (AC, G, PVPP, and M) to induce a change in the aroma chemistry of the experimental wines. Both free run and press fraction juices of two vineyards (Awatere valley and Wairau valley) were fined and the resulting wines analysed. Results showed that several aroma compounds may be influenced by prefermentation fining. For instance, there was a significant (p 0.05) reduction in linalool and hexan-1-ol across each vineyard and juice combination when AC fining was employed, compared to their respective controls. Moreover, it was also demonstrated that juice origin (vineyard and fraction) was of a high priority when determining the aroma compound content of the experimental wines. Sensory analysis showed that the panel indicated lower counts of the aroma attribute Green vegetables for the Awatere valley wines which had been fined using AC, compared to the respective control wines. Following on from this experiment, another trial using excessive amounts of juice fining was conceived to provide information regarding part batch fining, a strategy used by some winemakers. Wairau valley press fraction juice was fined using AC, G, and PVPP at rates of 5, 6, and 8 g/L, respectively. Again, a significant (p

Molecular Wine Microbiology features rigorous scientific content written at a level comprehensible for wine professionals as well as advanced students. It includes information on production and spoilage issues, the microbial groups relevant for wine production and microbial wine safety. Microbiology has long been recognized as a key tool in studying wine production, however only recently have wine microbiology studies been addressed at a molecular level, increasing the understanding of how microbiology impacts not only the flavor quality of the wine, but also its safety. Understanding, at a molecular level, how a starter culture can impact ethanol, glycerol, volatile phenols, mannoproteins, biogenic amines or ochratoxin A of a wine are just some of the core points that must be considered in order to achieve maximium consumer acceptability while addressing safety concerns during processing and storage. While other books offer insights into the technological aspects of enology, this book is written by expert microbiologists, who explore the positive and negative impacts of gene function in the production of wine, from a microbiological point of view. - Winner of the 2012 Jury Award in Enology from the International Organisation of Vine and Wine - Presents the most current methods of studying the microbiology of wine - Includes latest identification and typing methods, reducing identification time from days and weeks to minutes and hours - Provides important knowledge about the impact of microbiological factors at the molecular level for reduction of wine spoilage and increased wine quality and safety