2. Refrigerating necessities on prefermentative operations

The temperature control can be done from the first stages of winemaking, by cooling the freshly squeezed grape or the must at the exit of the press. Most authors recommend the entry of red wine vintage at 20�C due to an inlet temperature of 26–28�C, this can lead to a difficult start of fermentation and higher production of volatile acidity [1–3]. The prefermentative maceration applied to certain varieties (Pinot Noir) for the extraction of polyphenols needs to bring the crushed-grapes to temperatures below 13�C, to avoid starting fermentation [4].

In white wines, the pellicular maceration of aromatic grapes (Moscatel, Gewürztraminer, Verdejo, Sauvignon Blanc and Chardonnay) at low temperatures enables the extraction of aromatic compounds. The static debourbage is a slow process, which allows in its course the proliferation of microorganisms. Cold helps to stop or slow the start of fermentation, and the low temperatures increase the speed of sedimentation. Time and temperature are the keys for a quality debourbage. The use of pectolytic enzymes allows a considerable reduction of debourbage times, but on the other hand, the cold slows down the enzymatic phenomena of despectination. Therefore, in the debourbages with addition of enzymes, the temperature of the must should not be less than 10�C [5, 6]. The promptness of enzymatic debourbage is doubled when the temperature rises to 10�C, at the expense of risks of grater microbial proliferation, and is discouraged for vintages with poor sanitary quality. Temperatures under 8�C promote the inactivation of the enzymes and lengthen the fermentative latency phase. In any of the above cases, the refrigeration needs to cool the must or the crushed-grapes to the operating conditions are defined by the fundamental equations of the energy balance (Eq. (1)) [3, 7–10]:

$$\mathbf{d}Q/\mathbf{d}t = m \times \mathbb{C}\_{\varepsilon} \times \Delta t \tag{1}$$


2. Refrigerating necessities on prefermentative operations

Importance

76 Refrigeration

Fermentation thermal

Thermal control of fermentation and meccanization

Cold storage of finished wines

Second fermentation

in bottle

on must/wine.

Amicrobic stabilization

control

Operation V. in white

wine

V. in red wine

Optimum temperature

Cold extraction + 5/10C Must sugar concentration by elimination of frozen

Cold maceration ++ ++ 5/10C Extraction of aromatic precursors

Musts Refrigeration +++ +++ 10/18C Enable the debourbage in white wines

Deboubarge +++ 10/15C Accelerate the sedimentation process

Colloidal stabilization +++ <5–10C Hasten unstable coloring matter

Aging in oak +++ +++ 15–20C Decrease volume losses

Bottle store +++ +++ 12–18C Enhance wine stability

Pellicular maceration ++ ++ <15C Extraction of polyphenolic fraction and aromatic

+++ 25/30C Decrease aromatic losses

+++ 13/20C Aromatic enhancement in white wines

+++ +++ 10/15C Slow down microorganisms metabolism

+++ 12/15C Control the alcoholic fermentation. Refinement of

autolysis products.

+++ ++ <5–10C Filtration process improvement

Tartaric stabilization +++ +++ 5/1C Hasten tartaric salts of calcium and potassium

Bottling + + 15C Reduce loss of aroma and enable the process

Effects on wine/must

Fermentation delay

of fermentation

Delay the start of fermentation

Avoid fermentation stops

Avoid fermentation losses

precursor in red wines before fermentation

Decrease oxidation and aromatic losses

Control the oxidation-reduction process and cession

sparkling wine by slow transfer of fermentation and

Avoid undesirable microbial development

In red wines lower the temperature until the optimum

water

The temperature control can be done from the first stages of winemaking, by cooling the freshly squeezed grape or the must at the exit of the press. Most authors recommend the entry

Table 1. Applications of cold engineering in a wine cellar: optimum working temperatures in wine cellars and the effect

	- Ce = 4.18 kJ/kg �C [11,12].
	- Ce = 3.8 kJ/kg �C for musts with a density of 1090 kg/m3 [13].
	- Ce = 4.5 kJ/kg �C for wines with a density of 995 kg/m3 [13].
	- Ce = 3.65 kJ/kg �C for musts and 4.15 kJ/kg �C for wine [14, 15].
