Wines & Vines Home
   
 
Welcome Guest
LOGIN |  CREATE ACCOUNT
 
 
July 2014 Issue of Wines & Vines
 
SUBSCRIBE   »
 

Role of non-Saccharomyces yeasts in wine production

 
by Neil P. Jolly, Cristian Varela, Glen Osmond, and Isak S. Pretorius
 
 
practical winery vineyard
 

An uninoculated fermentation is often referred to as “natural” or “spontaneous” fermentation that involves the sequential action of different non-Saccharomyces and a diversity of indigenous Saccharomyces yeasts. The first fermentation, looking at the 7,000 years of winemaking history, was more likely the result of serendipity than design.

Natural yeast and natural wine: a rather unnatural tale
Spontaneously, ambient yeasts fermented damaged grapes in harvesting pots, mystifying hunter-gatherers who established agriculture and the first great civilization in Mesopotamia around the Tigris-Euphrates river system and tasted wine for the first time.

However, even during those early “vintages” it was clear that, without human intervention, the result of “naturally” fermenting grapes is variable, unreliable and can be undrinkable. It did not take long before the ancients realized that the completely “natural” end result of fermenting grapes is vinegar.

There is heated argument as to whether today’s wine is of higher quality (increased flavor profile and absence of faults and taints) due to the contribution of scientific knowledge, technology and research—or whether so-called natural wine is better. There is a new-found nostalgia for the wine of yesteryear made with a minimalist approach and variable outcomes. The reality is that winemaking is both art and science and always has been.

History taught us that the best outcome for both winemaker and consumer is achieved when the wine industry harnesses what nature, human ingenuity and cutting-edge science offer in harmony with the unique “artistic” nature of wine. Here we summarize what nature’s treasure of “wild” yeasts has to offer and how inventive winemakers can use them in a scientifically controlled manner to craft wine styles that match consumer expectations in a diverse range of market segments.

Non-Saccharomyces yeasts: origin and wine flavor contribution
Non-Saccharomyces yeasts were originally seen as responsible for microbe-related problems in wine production due to their isolation from spoiled wines. Although it was known that some non-Saccharomyces yeasts could form beneficial metabolites for wine quality, this was outweighed by the high levels of volatile acidity and other negative compounds produced.

At the same time, non-Saccharomyces yeasts were considered to be sensitive to SO2, known to be poor fermenters of grape must and intolerant to ethanol. Therefore it was accepted that those non-Saccharomyces yeasts, not initially inhibited by the SO2, died during fermentation due to the combined toxicity of the SO2 and alcohol.

However, research has highlighted the high numbers (106 to 108 cells/mL) and sustained presence of non-Saccharomyces yeasts in modern wine fermentations leading to revisiting the role of these yeasts in winemaking.

Newer research showed that concentrations between 50 and 100 ppm SO2, while effective in white wine fermentations, do not prevent growth of non-Saccharomyces in red wine fermentations. Generally, SO2 concentrations between 0 and 50 ppm have been successfully used for wild fermentation.

During crushing, the non-Saccharomyces yeasts on the grapes, on cellar equipment and in the cellar environment (air- and insect-borne) are carried over to the must. However, cellar surfaces play a smaller role than grapes as a source of non-Saccharomyces yeasts, as S. cerevisiae is the predominant yeast inhabiting such surfaces. Dominant yeasts in must after crushing should therefore be the same as those that are found on grapes.

Despite all the variables in grape harvest and wine production, the yeast species generally found on grapes and in wines are similar throughout the world. However, the proportion or yeast population profile in various regions show distinct differences.

The contribution by non-Saccharomyces yeasts to wine flavor will depend on the concentration of metabolites formed. This in turn is affected by how active the non-Saccharomyces yeasts are.

The specific environmental conditions in the must include high osmotic pressure, equimolar mixture of glucose and fructose, presence of SO2, non-optimal growth temperature, increasing alcohol concentrations, anaerobic conditions and decreasing nutrients. All these factors play a role in determining what species can survive and grow.

The clarification of white must (centrifugation, enzyme treatments and cold settling) can reduce the initial population of yeasts.

In red must, wild yeasts are usually encouraged by cold soaking. In general, wild fermentation benefits from being initially protected from air, but once the ferment is active, aeration is advantageous for yeast activity. Similarly to inoculated fermentation, wild fermented musts containing low yeast assimilable nitrogen (YAN) will deliver wines with more complex “mineral” and “funky” styles, while nitrogen addition will produce wines with a cleaner and more fruity style.

The range of flavor compounds produced by different non-Saccharomyces yeasts includes terpenoids, esters, higher alcohols, glycerol, acetaldehyde, acetic acid and succinic acid. Although far less studied, wine color can also be affected by non-Saccharomyces yeast.

Various research articles have reported on deliberate inoculation of selected non-Saccharomyces yeasts for wine production. These included Torulaspora delbrueckii, Metschnikowia pulcherrima (Candida pulcherrima), Candida zemplinina (Candida stellata), Hanseniaspora species, Zygosaccharomyces species, Schizosaccharomyces species, Lachancea thermotolerans (formerly Kluyveromyces thermotolerans), Pichia species, Hansenula anomala, Williopsis saturnus, Candida cantarellii, Issatchenkia orientalis and Saccharomycodes ludwigii.

Combinations of more than one species of non-Saccharomyces yeasts have also been investigated. Most of these yeasts are poor fermenters, therefore S. cerevisiae (either indigenous or inoculated) is always needed to complete wine fermentatio n. Typically, non-Saccharomyces yeasts have been used in sequential fermentation where these yeasts are allowed to grow or ferment between one hour and 15 days before inoculation with S. cerevisiae.

Wines fermented with non-Saccharomyces yeast have shown different chemical composition and/or different flavor and aroma when compared to wines fermented only with S. cerevisiae.

Although many of these trials were conducted on a laboratory scale utilizing small volumes of grape juice, and the results may not be the same as what could be expected in larger commercial fermentations, they demonstrate the potential of non-Saccharomyces yeast to produce distinctive wines. As a result, a few non-Saccharomyces yeasts have already been commercialized.

Conclusions
The diverse array of yeast available to a winemaker through the cellar environment, in the air, on the grape or through inoculation remains a crucial element to wine production with a wide range of complex flavors and aromas. Harnessing the performance of fermentation for a desired outcome tantalizes and challenges.

Research undertaken in S. cerevisiae can make great contributions to understanding the role and uses of non-Saccharomyces yeast in spontaneous and “inoculated multi-species” ferments. The management of “mixed-ferments” is more complex than “single-species” ferments because so many things can go wrong.

Therefore, a modern approach to “multi-species” wine ferments backed by frontier science and rigorous research is essential to help winemakers achieve their primary objective of a better than 98% conversion of grape sugar to alcohol and carbon dioxide at a controlled rate and without the development of off-flavors. Therein lies wine’s magic blend of art and science.

This article is a summary of findings reported in: N. Jolly et al. “Not Your Ordinary Yeast: non-Saccharomyces Yeasts in Wine Production Uncovered,” FEMS Yeast Research (2014) 14: 215–237.

 
SHARE   »
Print this page   PRINTER-FRIENDLY VERSION   »
E-mail this article   E-MAIL THIS ARTICLE   »
Close
 
Currently no comments posted for this article.
 
CURRENT MONTH'S FEATURES INDEX »


 
Wines & Vines Home
 
866.453.9701 | 415.453.9700 | Fax: 415.453.2517
65 Mitchell Blvd., Ste. A San Rafael, CA 94903
info@winesandvines.com
Wine Industry Metrics
 
Off-Premise Sales » Month   12 Months  
February 2015 $643 million
7%
$7,954 million
5%
February 2014 $601 million $7,560 million
     
Direct-to-Consumer Shipments » Month   12 Months  
February 2015 $132 million
4%
$1,823 million
14%
February 2014 $126 million $1,598 million
     
Winery Job Index » Month   12 Months  
February 2015 275
26%
238
16%
February 2014 219 206
     
 
MORE » Released on 03.13.2015
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Direct To Consumer
Wine Shipping Report
2015
 
Download full report »
 
 

Practical Winery & Vineyard Library
 
Search the PWV archive »
 
 

CALENDAR
  • April 17
     
    Newsom Grape Day
     
  • April 17-19
     
    Earth Day Food & Wine Festival
     
  • April 21
     
    Ahead of the Curve
     
  • April 25-27
     
    World Wine Meetings America
     
  • MORE »
 

READER COMMENTS
 
Article: Is Organic Grape Growing Possible in the East? »
 
Some Long Island, NY, vineyard farmers are already using nearly organic methods. They have worked...
Reader: envcat
 
Article: Loosening AVA Regulations »
 
When I see 'Napa Valley'on a wine label, it doesn't only suggest the flavors I...
Reader: Guest
 
Article: Loosening AVA Regulations »
 
I should be able to live in MA, buy Napa, CA grapes, truck them across...
Reader: Guest
 
Article: The Stark Disparity in Critical Tastes »
 
The disparity is all well and good for consumers. More opinions and a kind of...
Reader: Guest
 
Article: Commercial Teaching Winery for the Midwest »
 
Please visit www.lakemichigancollege.edu/wine for more information about the program.
Reader: Guest
 
 


Directory/Buyer's Guide — Your Wine Industry Marketplace
 
 
WINERY SEARCH
 
 
Advanced Search »
SUPPLIER SEARCH
   by Product
 by Company Name or Brand
 
Browse by Category »
2015 Directory/Buyer's Guide
The Wines & Vines Directory and Buyer's Guide
 
 
EXPANDED ONLINE SEARCH INCLUDED WITH PURCHASE
 
ORDER NOW »
 
LEARN MORE »
 
 
Wines & Vines Magazine
 
 
LEARN MORE »
 
SUBSCRIBE »
 
Digital Edition Now Available!
Wines & Vines Digital Edition Now Available
 
LEARN MORE »
 
ORDER NOW »
 
 
The Wines & Vines Online Marketing System
 
The Industry Standard winery marketing application
 
FREE LIVE DEMO »
 
VIEW VIDEO »
 
 
 
 
Latest Job Listings
 Staff Accountant
 Rutherford, CA
General Administration and
 Harvest Cellar Worker
 Healdsburg, CA
Cellar, Lab and Production
 Harvest Cellar Hands 2...
 Dundee, OR
Cellar, Lab and Production
 Territory Sales Rep-Ri...
 Riverside/San Bernardino, CA
Sales and Marketing
 Area Sales Manager - S...
 Sacramento, CA
Sales and Marketing
 Sales Representative
 New York, NY
Sales and Marketing
 Concierge And Host
 St. Helena, CA
DTC, Tasting Room and Retai
 Fine Wine/Spirits Sale...
 Hudson Valley, NY
Sales and Marketing
 Sales Representatives
 Various, MA
Sales and Marketing
 Accountant
 Saint Helena, CA
Finance
 
More Job Listings >>
Follow Us On:
 
 





Home  |  About Us  |  Editors  |  Subscribe  |  Print Edition  |  Digital Edition

Advertise  |  Site Map  |  Contact Us  |  Privacy Policy
 
 
Copyright © 2001-2015 by Wine Communications Group, Inc. All Rights Reserved.
No material may be reproduced without written permission of the Publisher.
Wines&Vines does not assume any responsibility for any unsolicited manuscripts or materials.