An Introduction on Low Temperature
Fermentation in Wine Production
Many notable wine regions have been
recognized with an integrated use of
temperature control, as this processing aid has
been shown to improve wine quality
dramatically.
Introduction
The Role of Fermentation
Temperature control in the winery involves manipulating
temperature to slow down or accelerate winemaking processes
or control chemical changes in the wine. Since wine is easily
influenced by temperature, this technique is frequently
employed for processes such as fermentation, cold settling,
aging, and storage.
Temperature is a vital part of fermentation in winemaking.
Fermentation occurs when yeast convert sugar to alcohol and
carbon dioxide (Figure 1). Due to the exothermic nature of
fermentation, temperature increases as sugars are metabolized.
Heat production can be managed with the usage of external
temperature control. This typically involves controlling tank
or cellar temperature to keep the wine at a relatively lower
temperature than it would reach naturally. Temperature
manipulation changes the dynamics of the fermentation
system and can be a beneficial source of control in
winemaking.
Figure 1. Chemical equation of alcoholic fermentation (Pavia
2015).
Desirable fermentation temperatures vary for red and white
wines. Red wine fermentation temperatures are optimally
between 68-86°F (20-30°C), while white wine fermentation
temperatures are recommended at or below 59°F (15°C)
(Reynolds et al. 2001). Higher temperatures are favorable in
red winemaking to enhance extraction of color, phenolics, and
tannins from skins (Reynolds et al. 2001). The goal of white
wine fermentation temperature control is to preserve
compounds that contribute to aroma and flavor (Molina et al.
2007).
Experimenting with parameters of fermentation temperature
can be beneficial, particularly when fermenting at lower
temperatures for white, rosé, fruit, or aromatically delicate
varieties. Lowering the temperature of the system causes
fermentation to occur at a slower rate and contributes to
several additional benefits. With modern technology and
enhanced production methods, temperature control is
attainable and manageable for wineries of any commercial
size. The following paper will review the advantages of low
temperature fermentations and how small (<10,000 cases)
commercial wineries can implement this technique in their
production.
Benefits of Temperature Control in
the Winery
Primary Fermentation
Fermentation temperature affects many chemical and sensory
properties of wine. Low temperature fermentation is
advantageous because it preserves an array of aromas and
flavors produced during primary fermentation (Torija et al.
2003). While wine aroma and flavor originates in the grape
berry, Saccharomyces cerevisae yeast cells give off various
aromatic compounds through fermentation as secondary
byproducts (Sweigers et al. 2005). The significant aromatics
produced during fermentation are esters from fatty acids,
organic esters, and higher alcohols (Gil et al. 1996). This class
of aromatic compounds is influenced by fermentation
temperature due to their low molecular weight, which makes
them easily volatile (Sumby et al. 2010). In general, esters
contribute fruity and floral aromas and flavors to wine. For
example, ethyl hexonate is an ethyl ester that produces
strawberry and green apple notes, and isoamyl acetate is an
acetate ester that produces banana and pear aromas
(Pambiachi, 2007).
The preservation of wine aroma and flavor due to lower
fermentation temperatures has been well documented by
research. Molina et al. (2007) found that higher concentrations
of esters are developed at lower temperature fermentations due
to a reduction of evaporative (volatile) loss, which increases
stability of flavor and aroma compounds in wine. This study
found that two aroma profiles were created in the same base
wine when fermented at two different temperatures: 15°C
versus 28°C. These findings exemplify that temperature
creates differences in flavor and aroma.
Temperature control has also been shown to prevent the
development of off-flavors, specifically volatile
sulfur-containing compounds like hydrogen sulfide. Higher
(above 30°C/86°F) fermentation temperatures increase the rate
of fermentation, which may enhance production of undesirable
byproducts produced by the yeast (Reynolds et al. 2001). The
most common off-flavors associated with high temperature
and rapid fermentation are sulfur-derived compounds
including hydrogen sulfide, mercaptans (thiols) and
disulphides (Gladish 1999). These compounds have been
associated with aromas or flavors reminiscent of rotten eggs,
cooked cabbage, skunk, and landfill, amongst other
descriptors. While some of these off-aromas may be
remediated with copper additions, use of clean lees, or other
product additions, these techniques can be challenging to
achieve a clean wine and time consuming on cellar personnel.
Furthermore, additional flavor stripping of desirable aromatics
may occur (Pickering et al. 2005).
Cooler fermentations have been shown to improve the clarity
of wine (Comfort 2012). Clarity is typically achieved through
racking, cold settling, cold stabilization, and fining, but low
temperature fermentation may be an alternative option for
enhanced clarity. At lower temperatures, yeast cells are less
likely to give off colloids, thus improving clearness (Jackson
2014). Colloids derive from yeast and pectin, which form
polysaccharides and aggregates after a physiochemical change
(i.e. temperature), diminishing clarity (Drioli et al. 2010).
Therefore, the use of lower temperature fermentation may
minimize potential for cloudy or hazy wines by the end of
primary fermentation.
Lowering fermentation temperature can also better control
microbial growth and minimize potential spoilage (Jackson
2014). For example, at higher fermentation temperatures
(above 21°C), some bacteria can produce undesirable amounts
of diacetyl, creating a buttery flavor that may be unwanted
(Bartowsky 2009). Also, spoilage yeasts such as Pichia
membranifaciens, Pichia anomala, and Candida species can
develop in the absence of proper temperatures, contaminating
wine surfaces and producing unwanted acetic acid or ethyl
acetate volatiles (Loureiro and Malfeito-Ferreira 2003). The
growth of spoilage organisms is dependent on various factors,
such as oxygen exposure. But, the use of temperature control
can be an effective hurdle in minimizing their presence. This
can potentially reduce the need for higher doses of sulfur
dioxide through production. As consumer perception
encourages limited sulfur dioxide use (Pretorius and Bauer
2002), such practices can be advantageous to wineries’ brands.
for varieties with unique anthocyanin profiles (e.g. Pinot Noir)
or minimal tannin concentrations (e.g. Concord, Chambourcin,
Noiret, Chancellor) that struggle to develop color (Reynolds et
al. 2001). However, the use of temperature control for red
wine making is beneficial to ensure the temperature does not
get too hot (>30°C, 86°F), which can lead to rapid
fermentation, a stuck fermentation, or off-flavor development.
Fermentation temperature has also been shown to influence
red wine flavor (Sacchi et al. 2005). Maintaining fermentation
temperatures close to 15-20°C (59-68°F) is ideal for fruity,
light red wines (Reynolds et al. 2001). If fermentation
temperatures reach 30°C (86°F), aromas and flavors
associated with earthy descriptors become more dominant in
the finished wine (Reynolds et al. 2001).
Malolactic Fermentation
Temperature has implications on malolactic fermentation
(ML) in wine production. ML is a secondary fermentation
where malic acid is converted to lactic acid by lactic acid
bacteria (Lui 2002). Since this process requires a temperature
range of 16-25°C, storage temperature of tanks and barrels are
pertinent. Increasing cellar temperature for varieties in barrels
going through ML may be required. However, winemakers
can preserve other wines in the cellar by maintaining
temperature independently in each tank.
Temperature can be manipulated for other purposes in ML, as
well. For example, temperature is sometimes lowered for
increased stability or for inhibiting ML (Davis et al. 1985).
Additionally, some evidence shows that temperature may have
an effect on the quantity of byproducts from ML bacteria, such
as diacetyl production (Martineau et al. 1995). Diacetyl
imparts a buttery flavor, which can be desirable in some wines
(i.e. Chardonnay) but can be undesirable in other varieties or
lead to spoilage (Bartowsky and Henschke 2004). At about
21°C (69.8°F), this byproduct accumulates to noticeable
amounts (NPCS Board of Consultants & Engineers 2011).
White wines, especially aromatic varieties (e.g. Reisling,
Gewürztraminer, Traminette, Vidal Blanc), rosés, and fruit
wines benefit from the effects of lower temperature
fermentations (below 15°C or 59°F) to help retain their
delicate aroma and flavor described previously. Red wines
traditionally require higher temperature fermentation (~28°C,
82.4 °F) to achieve color and tannin extraction from the skins
(Molina et al. 2007). Color extraction is particularly important
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An Introduction on Low Temperature Fermentation in Wine Production
Other Production Opportunities for
Temperature Control
restart a fermentation.
Concerns with Stuck Fermentation
One of the greatest concerns in low temperature fermentations
is the risk of an increased lag phase and a decreased growth
rate of yeast (Blateryon and Sablayrolles 2000). This is
sometimes referred to as a “sluggish” or “stuck” fermentation.
In these situations, yeast are minimally consuming sugar to
convert it to ethanol (Bisson 1999). However, sluggish and
stuck fermentations differ from slow fermentations. In stuck or
sluggish fermentations, the rate of sugar consumption
decreases dramatically toward the end of primary
fermentation, while slow fermentations have a decreased sugar
consumption rate throughout the entire duration of primary
fermentation (Blateyron and Sablayrolles 2000). Stuck and
sluggish fermentations do not directly result from the low
temperature, but rather from other yeast stressors including,
but not limited to: nitrogen deficiency, lack of oxygen,
excessive clarification, microbial spoilage growth, pH, and
fatty acid development (Van de Water 2000). However, the
use of temperature control should be regularly monitored as
cooler temperature can inflict some of these properties on the
wine during fermentation.
When a stuck or sluggish fermentation occurs, winemakers are
encouraged to test the wine to determine the cause and
develop options for treatment. Delle Units are one way to
evaluate a sluggish wine. With this method, it is first
necessary to test alcohol and reducing sugar separately. Delle
Units can be calculated using the equation [(4.5 x % alcohol)
+ % reducing sugar]. If the Delle Unit is at or above 65,
restarting the fermentation is possible but will be difficult
(Van de Water 2000). At or above 80, the chances of restarting
fermentation are slim to none (Delfini 2001). When
fermentation cannot be restarted, several measures can be
taken to get the fermentation out of its sluggish state, such as
introducing oxygen or re-inoculating with a hardy yeast strain
(Sablayrolles et al. 1996).
Testing for Lactobacilli is another way to provide insight on a
sluggish wine. A presumptive confirmation of Lactobacilli can
be made using a phase contrast microscope to look for
rod-shaped bacteria (Figure 2). Some species of Lactobacilli
can produce acetic acid, and growth can occur during a time
when S. cerevisae growth is stuck and wine is generally
unprotected by sulfur dioxide (Edwards et al. 1999). The
presence and growth of Lactobacilli can make restarting
fermentation challenging. If no Lactobacilli or other spoilage
bacteria are present, it is possible to take measures and get the
fermentation progressing by slightly increasing wine
temperature to more optimal ranges for yeast growth. If
temperature increase alone does not restart the fermentation,
re-inoculation of a hardy wine yeast is typically recommended
(Van de Water 2000). Winemakers may need to ensure that all
other conditions, including oxygen content, are optimal for
their selected yeast to finish the fermentation to dryness. Many
suppliers offer stuck or sluggish fermentation protocols to
Page 3
Figure 2. Image of Lactobacilli (surrounded by round yeast
cells) in juice (Image provided by: Enartis Vinquiry, Wine
Microbiology CD)
Implementing Temperature Control
One way to implement temperature control is through the use
of controlled cellar temperature. A traditional cellar is about
55°F (15°C), but 50-60°F are acceptable cellar temperatures
(Butzke 2010). Insulation of the facility can greatly assist with
maintaining temperatures and minimizing energy costs,
especially if the cellar is cooled by natural means (Smyth
2011). However, ambient temperature does not provide
optimal control over internal tank temperatures. While red
wine fermentations can generally suffice in cellar temperatures
alone, white wines are best kept in tanks with more adequate
temperature control (Butzke 2010).
Refrigeration systems are a more accurate way to control tank
temperatures. In these systems, a refrigerant and a computer
system are used to set the exact temperatures of the tanks
internally. This is extremely helpful for regulating
temperatures during fermentation and storage. These systems
utilize jacketed tanks (Figure 3), a glycol refrigeration and
heating unit, thermostats, pipes, and a chilling unit to the tank
(Pisoni and White 2002). While the input of this system is
relatively expensive at approximately $10,000, these systems
offer winemakers the capability to make small and accurate
temperature changes inside the tank.
An Introduction on Low Temperature Fermentation in Wine Production
method requires either a glycol system or a source of cold or
hot water for temperature fluctuations. A snake unit ranges in
price, but is about a $200-500 investment depending on the
style and size selected, in addition to supplier. The flexible
snake variety (Figure 6) can easily be inserted through the top
of a fermenter or small tank. For barrel usage, a bar-type snake
can be employed (Figure 5).
Figure 3. Two jacketed tanks cooled by refrigeration via glycol
system at Keuka Spring Vineyards in the Finger Lakes, NY
(Photo by Allison Miller)
Tank insulation is a basic form of temperature control that can
be useful when purchasing jacketed tanks is too high of an
initial investment. The most common form of insulation is a
~75 mm thick polystyrene insulation (Nordestgaard 2011), as
shown in Figure 4. Insulation helps maintain internal tank
temperatures and prevents condensation from forming on
exterior tank surfaces (Smyth 2011). Condensation occurs
when the tank surface temperature is below dew point
temperature of the cellar (Delfini and Formica 2001). The
reduction of condensation lowers latent heat, or energy
absorbed or released during a phase change (i.e. gas to liquid,
liquid to solid). Since state changes absorb a great amount of
energy, this will decrease the stress on the refrigeration system
and increase the efficiency of maintaining temperature (Smyth
2011). While insulation systems may not be ideal, they offer
an alternative solution for wineries committed to improving
wine quality by use of temperature management.
Figure 4. Reflective polystyrene insulation on a tank (Photo by
Denise Gardner).
Figure 5. Stainless steel snake compatible for barrel use
(Image from morewinemaking.com)
Figure 6. Stainless steel snake (8 m long) compatible for tanks
and fermenters (Image from morewinemaking.com)
Stainless steel snakes (Figures 5 and 6) are another alternative
way to control internal tank temperature at a reasonable cost.
The snake, composed of vinyl tubing within corrugated
stainless steel tubing, is placed in the wine tank. Glycol or
chilled water flows through one tube and back through the
other, and this recirculation alters wine temperature. This
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An Introduction on Low Temperature Fermentation in Wine Production
Conclusion
Many notable wine regions have been recognized with an
integrated use of temperature control, as this processing aid
has been shown to improve wine quality dramatically.
Temperature control is an essential tool when crafting
high-quality wines, but winemakers are encouraged to monitor
its use. White, rosé, fruit, and aromatically delicate wines have
a greater need for temperature control during fermentation to
enhance aroma and flavor retention. Red wines require higher
temperature fermentations for color and tannin extraction, but
can still benefit from temperature control throughout wine
production.
There are a number of solutions for temperature control, based
upon winery size and financial flexibility. These options
provide incremental improvement steps directly related to
wine quality, overall. Over time, wineries can slowly enhance
temperature control steps to impact wine quality as economic
means are retained.
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An Introduction on Low Temperature Fermentation in Wine Production
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Prepared by Allison E. Miller, Penn State Food Science
Undergraduate student
Contact Information
Denise M. Gardner
Extension Associate
[email protected]
610-489-4315
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An Introduction on Low Temperature Fermentation in Wine Production