3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P76 ThE INFLuENCE OF ChOICE FACTORS ON
FERMENTATION OF RED wINE
JIřInA OMELKOVá and LUCIE ZECHMEISTROVá
Faculty of Chemistry, Brno University of Technology, Purkyňova
118, 612 00 Brno, Czech Republic,
omelkova@fch.vutbr.cz
Introduction
Winemaking can be summarized as the biotransformation
of must into wine, which performed principally by Saccharomyces
cerevisiae strains during the primary alcoholic
fermentation. A secondary fermentation, the so-called malolatic
fermentation is biodeacidifacation that is often encouraged,
since it improves wine stability and quality. Malolatic
fermentation (MLF) usually occurs either spontaneously or
after inoculation with selected bacteria after fermentation.
MLF, the enzymatic decarboxylation of L-malic acid to Llactic
acid, is an important secondary fermentation process
carried out by lactic acid bacteria (LAB) during the vinification
of red must, and certain white and sparkling wine styles.
In addition to deacidification, MLF can increase microbiological
stability and enhance the flavour and aroma of wine. The
study was focused on the composition of microflora during
the extraction of flavour components from grape solids and
during fermentation as well. In this way the two technology
processes for the production of red wine from Velké Pavlovice
region were monitored.
Experimental
Three different media were applied for the cultivation
of microorganisms; first for monitoring of total volume of
microorganisms, second for yeasts and third for lactic acid
bacteria. The indirect method was used for the determination
of the amount of viable cells. This method consists of the
enumeration of visible macroscopic colonies grown up on
agar plates. When the cells grew up, the forms of colonies
were analyzed visually and the morphology of microorganisms
was microscopically detected.
Cultivation media:
• Plate Count Agar. Suitable for the determination of total
number of microorganisms in foodstuffs.
• Malt Agar with the addition of antibiotics. Into the cultivation
medium streptomycine 80 µg/l and propionic
acid 0, 25 ml/l was added. Suitable for the isolation and
identification of yeasts and fungi.
• Tomato Juice Medium Base (for Lactobacillus from
wine).Suitable for the isolation and identification of lactic
acid bacteria occurring in wine.
Results
Two technological procedures in wine manufacturing,
which differ in technological steps shown in the Table I, were
compared.
Since the start of wine manufacturing, till the last addition
of SO 2 , the total number of yeasts in wine factory no. 1
s742
Table I
Technological Preliminary Alcoholic
procedure fermentation fermentation
Application SO2 CE CY CB Mode of SO 2
heating
Wine factory – × × – regulated ×
no. 1
Wine factory × × × × non
no. 2 regulated
CE – Commercial Enzymes
CY – Commercial Yeasts
CB – Commercial Bacteria
was monitored. number of cells in dependence on time is
shown in Fig. 1. It is known 1 , that the yeasts Saccharomyces
cerevisiae do not start the fermentation. The yeasts starting
the fermentation are Hanseniaspora (Kloeckera), Candida
Metschnikowia. From Fig. 1. follows that the number of
starting yeasts and yeast microorganisms reached the value
1.2 × 10 6 ± 1.3 × 10 5 cells in 1 ml. Other yeasts than Saccharomyces
growing at the start of the fermentation, utilize
aminoacids and vitamins for their growth and reduce the
growth of Saccharomyces cerevisiae. These play an important
role in the second half of the fermentation time 1 . From
the Fig. 1. it is evident that even though the commercial culture
of Saccharomyces cerevisiae was inoculated into the
mash during the day of crushing, the increase of total number
of yeasts occurred 4 days after the inoculation. The whole
period of preliminary fermentation lasted 8 days and the highest
value of total number of yeasts was achieved in a day
of pressing. After that the decrease was observed. This effect
can be attributed to the autolysis of yeasts after the alcoholic
fermentation 1 . The decrease is also caused by the inhibition
of starting population of bacteria Oenococcus oeni and malolactic
fermentation, as shown in Fig. 2. After the alcoholic
fermentation the autolysis of yeasts occurs, followed by the
liberation of nutrients important for the growth of bacteria
and the growth of present yeasts, as well. The decrease is
also caused by the inhibition of starting population of bacteria
Oenococcus oeni and malolactic fermentation, as shown
Fig. 1. Number of yeasts – wine factory No. 1
×