Tess Snyder | Jacob Martin | Bjarne Bartlett | James Osborne | Chris Curtin

Digging deeper into Microbial Terroir: Biogeography of Hanseniaspora in Oregon’s Willamette Valley Wine Region

Tess Snyder, Jacob Martin, Bjarne Bartlett, James Osborne, and Chris Curtin*
*Oregon State University – Department of Food Science and Technology, 100 Wiegand Hall, Corvallis, OR, 97331 (christopher.curtin@oregonstate.edu)

The apiculate yeast genus Hanseniaspora has appeared frequently in enological research for over a century, mostly focused upon the species Hanseniaspora uvarum because of its notable capacity to cause spoilage. Recently, there has been more research into the potential benefits of other Hanseniaspora species, such as Hanseniaspora vineae, in producing more complex wines. Furthermore, large-scale, DNA sequencing-based (metabarcoding) vineyard ecology studies have suggested that Hanseniaspora species may not be evenly distributed. Does this mean that fruit from different vineyards could yield spoiled or complex wines depending on which Hanseniaspora species are present? To address this, we sampled extensively from 12 vineyards within the Willamette Valley AVA, across two sub-AVAs (Eola and Yamhill). We then used metabarcoding to assess the contribution of Hanseniaspora to the grape berry fungal community and their relative abundance in cold-soak and early stages of fermentation.

Our results show that while six of the 23 recognized Hanseniaspora species were present on Pinot noir grapes in the Willamette Valley AVA, differences between vineyards were driven by the abundance of H. uvarum. On the other hand, fungal community differences between sub-AVAs were not related to Hanseniaspora species. We observed significant positive correlation between the amount of H. uvarum present in must and at cold-soak, and then cold-soak to early fermentation. While intuitive, it is worth noting that no prior studies have observed this across so many grape samples from different vineyards. Our results provide clear evidence that the amount of H. uvarum on grapes may be an important predictor of potential effects on wine quality, particularly if performing cold-soak, which acts as an enrichment step. H. uvarum isolates have been recovered from almost every must sample for whole genome sequencing and are being evaluated for genetic and phenotypic differences to determine whether vineyard and/or sub-AVA populations vary.

Funding Support: Oregon Wine Research Institute, Agricultural Research Foundation and Oregon State University

Valentina Civa | Marco Ongaro | Matteo Bosaro | Paolo Antoniali | Paola Domizio

Saccharomycodes ludwigii Yeast Derivatives: Novel Potential Bio-Adjuvants for the Winemaking Process

Valentina Civa, Marco Ongaro, Matteo Bosaro, Paolo Antoniali, and Paola Domizio*
*Universita’ Studi di Firenze, Via Donizetti, Firenze, 50144, Italy 
(paola.domizio@unifi.it)

To promote more sustainable production methods and greater respect for the natural characteristics of wines, this study evaluated the impact of non-conventional yeast derivatives on the chemical and physical properties of wines. In particular, various types of yeast derivatives obtained from Saccharomycodes ludwigii were used. This is an osmophilic yeast whose affect on wine has so far been evaluated only as a function of its metabolic activity. However, recent studies have indicated that yeasts belonging to the Saccharomycodes genus can release significant amounts of polysaccharides, particularly mannoproteins, into the medium both during growth and after inactivation. These macromolecules are known to interact with various compounds in wine, contributing to its colloidal stability. Thus, after optimizing the growth conditions favoring production of S. ludwigii biomass, innovative techniques for yeast inactivation were employed and the effect of different derivatives on the final chemical and physical characteristics of white wine was assessed. All fermentation tests conducted with S. ludwigii derivatives exhibited better fermentation kinetics than the control. Basic parameters were consistent across all wines. However, there were significant differences in the aromatic profiles. Wines treated with S. ludwigii derivatives showed higher polysaccharide content compared to the control. Further analysis is warranted to evaluate the influence of these macromolecules on wine colloidal stability and sensory characteristics over time.

Funding Support: Enartis

Matt Garcia | James Osborne | Elizabeth Tomasino

Effect of Malolactic Fermentation Timing and Cold Soaking with Torulaspora delbrueckii on Pinot noir Sensory Properties

Matt Garcia,* James Osborne, and Elizabeth Tomasino
*Oregon State University, 421 NW 4th St, Apt B, Corvallis, OR, 97330 (matthew.garcia@oregonstate.edu)

This study investigated the influence of malolactic fermentation (MLF) timing on Pinot noir color and sensory properties. The addition of a non-Saccharomyces yeast, Torulaspora delbrueckii, during cold soak was also investigated due to potential interactions with the malolactic bacteria and production of acetaldehyde. Pinot noir wines were produced with and without cold soaking, with and without T. delbrueckii, and with a concurrent or sequential MLF. Cold soaking with T. delbrueckii yielded higher acetaldehyde concentrations at the end of cold soak and during alcoholic fermentation, but did not result in significant color differences at the end of MLF. Concurrent MLFs decreased color density and polymeric pigment content, but only if a cold soak had also been undertaken. After nine months of aging, differences in wine color and polymeric pigment content noted at the end of MLF were no longer present. Wines were assessed by a sensory panel to determine liking and sensory characteristics. Panelists were asked to rate their liking of each wine in clear and opaque glasses and to complete rate-all-that-apply descriptive analyses for aroma, taste, and mouthfeel. Wines produced without cold soaking had a significantly different aroma than those produced with a cold soak, while non-cold soak wines were significantly different from each other due to MLF timing. When not paired with cold soak, the concurrent MLF wine was described as having woody and spiced aromas, while the sequential MLF wine was described as having cedar, fruity, and herbal aromas. Use of T. delbrueckii during cold soaking resulted in wines described as having a more balanced and softer mouthfeel than their counterparts. Overall, MLF timing did not affect color once wines had been aged, but did result in wines with different aroma and mouthfeel properties. Cold soaking and use of T. delbrueckii also resulted in wine sensory changes.

Funding Support: Oregon Wine Board, American Vineyard Foundation

Jessica Noble | Marion Bastien | Anthony Silvano | Anne Ortiz-Julien

Revealing Aromatic Thiols in Red Wines

Jessica Noble,* Marion Bastien, Anthony Silvano, and Anne Ortiz-Julien
*Lalemand Oenology, 19 Rue des Briquetiers, 31702 Blagnac, France 
(jnoble@lallemand.com)

Volatile thiols are a well-known family of aroma compounds that, even at low levels, can have a significant affect on the fruity quality of wines. 3MH, 3MH-A, and 4MMP are some of the more well-known aromatic thiols. These compounds confer grapefruit, passion fruit, and boxwood notes in thiolic white and rosé wines when revealed from their odorless form. However, thiol precursors are now known to be present in important red grape cultivars (e.g., Syrah, Cabernet Sauvignon, Merlot, Pinot noir). When revealed, the descriptors used to describe the same thiolic compounds in red wines are black fruits, red fruits, and spice. The aromatic profile of thiols in red wines is complex and is thought to be due to interactions between thiols and other molecules, such as terpenes and esters.

The enzymatic action of yeast is essential to cleave the non-volatile, odorless precursors and release the volatile, aromatically active thiols. Using a cell division approach, we selected a new Saccharomyces yeast with the full potential for thiol revelation due to its highly efficient β-lyase enzyme activity. This enzyme activity is due to the yeast possessing the correct form of the IRC7 gene. The sequence of the IRC7 gene is not identical among all yeasts. Some yeasts have a truncated version of this gene, missing 38 base pairs. This version encodes a non-functional enzyme. Other strains can have a point mutation, close to the enzyme’s active site, which has a strong negative effect on its activity.

For maximum β-lyase activity, the yeast must possess the right combination of the gene, which is the long, unmutated form (IRC7L/L Ref/Ref). This new yeast strain shows very significant thiol revelation, well above average concentration, with a very significant increase in aromatic freshness and black and red fruit notes.

Funding Support: Lallemand Oenology

Stéphanie Rollero | Anne Flesch | Laura Chasseriaud | Etienne Dorignac | Marina Bely | Arnaud Delaherche

Is Complex Nutrition More Advantageous than Mineral Nitrogen for the Fermentative Capacity of Saccharomyces cerevisiae?

Stéphanie Rollero,* Anne Flesch, Laura Chasseriaud, Etienne Dorignac, Marina Bely, and Arnaud Delaherche
*Fermentis, 137 Rue Gabriel Péri, 59700 Marcq-en-Baroeul, France 
(s.rollero@fermentis.lesaffre.com)

During alcoholic fermentation, nitrogen is an essential nutrient for yeast as it plays a key role in sugar transport and biosynthesis of wine aromatic compounds (thiols, esters, and higher alcohols). The main issue of a lack in yeast assimilable nitrogen (YAN) in winemaking is sluggish or stuck fermentations that promote growth of alterative species and lead to economic losses. However, correcting the N deficiency is sometimes not enough to restore proper fermentation performance. This suggests the existence of other nutritional shortages.

The aim of this work was to study the effect of the timing and the nature of nutrient addition (mineral N [100% yeast derivative] or mixed complete [mineral N and yeast derivative]) on alcoholic fermentation. First, 16 commercial strains were inoculated into Sauvignon blanc grape must deficient in YAN (110 mgN/L) and with reducing sugars concentration adjusted to 240 g/L (potential alcohol content of 14.3% vol.). Fermentation kinetics of strains were then classified into three groups: stuck, sluggish, or complete alcoholic fermentations. New experiments were carried out in the same grape must supplemented in YAN with ammonium (mineral) or yeast derivative products (100% organic or mixed) to get 200 mgN/L. Nutrient additions were made at the beginning of alcoholic fermentation (single addition) or in two additions (50% at the beginning + 50% at the middle of alcoholic fermentation).

Our results show that supplementation with mixed nutrients was more beneficial for fermentation performance than mineral N alone. Fractionated addition was also more effective than single addition. This study highlights the need to think about yeast nutrition from a holistic perspective (N and lipid addition, timing of addition).

Funding Support: Fermentis, division of S.I. Lesaffre

Esther Wanjohi | Elizabeth Tomasino | James Osborne

Effect of Pediococcus on Wine Chemical and Sensory Properties

Esther Wanjohi, Elizabeth Tomasino, and James Osborne*
*Oregon State University, 3051 SW Campus Way, Corvallis, OR, 97331 
(james.osborne@oregonstate.edu)

Pediococci have been isolated from wines worldwide, but their specific effect on wine quality is not well described. Due to warmer growing seasons leading to higher-pH grapes and winemakers looking to reduce sulfur dioxide (SO2) use, the risk of Pediococci growth in wines is increasing. Therefore, this project aimed to characterize the sensory impact of Pediococcus on wine and investigated the effect of wine lees and nutrient additions on biogenic amine (BA) production. Nineteen Pediococcus isolates from Oregon, Washington, and California wines were inoculated into sterile filtered Pinot noir and growth was observed for 56 days, followed by the addition of SO2 and bottling. Differences in growth were observed, with many isolates maintaining a population similar to the initial inoculation rate (105 CFU/mL), while others declined in viability before recovering to higher populations. Experienced wine tasters using a modified napping method and ultra-flash profiling assessed the wines. No strong groupings of treatments based on aroma were observed, but there were two distinct groupings based on mouthfeel. One grouping was described as “Light,” “Thin,” and “Sharp,” while the other group was described as “Sticky,” “Medium,” and “Sharp.” These descriptors will be used to define additional chemical analysis. To explore factors affecting BA production by Pediococcus, different nutrient additions were made to Chardonnay juice prior to fermentation. The three nutrient addition treatments were control, high DAP, and high organic N. After completion of alcoholic fermentation, wines were cold-settled prior to racking (no-lees) or no racking (lees) treatments. Dimethyl-dicarbonate was added to kill background microorganisms and after 48 hrs, two BA-producing Pediococcus strains were inoculated into the wines. Growth was monitored for 60 days, after which samples were collected for analysis. BA will be assessed by liquid chromatography-mass spectrometry to determine the effect of nutrients and lees aging on BA production by Pediococcus.

Funding Support: This works was funded by the Northwest Center for Small Fruits Research (59-2072-1-008)