3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
Experimental
Following yeast strains were isolated from the grape
must: Rhodotorula mucilaginosa (2 strains), Sporobolomyces
pararoseus, Pichia membranefaciens, Pichia anomala (2
strains), Candida intermediata, Torulospora delbruecki, and
Issatchenkia orientalis. For comparison 4 Saccharomyces
cerevisiae yeast strains were also used. Two of them were
isolated from the grape must; two of them were commercial
active dry yeast strains (Lallemand).
Fermentation media: grape must or semisynthetic
medium (10 g dm –3 glucose, 5 g dm –3 (nH4 ) 2SO4 , 2 g dm –3
KH2PO4 , 1 g dm –3 MgSO .
4 7H2O, 0.1 g dm –3 CaCl .
2 2H2O, 0.1 g dm –3 naCl, 3 g dm –3 yeast autolysate, were used. The
fermentation processed under semiaerobic and anaerobic
conditions at the temperature 10 and 25 °C, respectively.
At the end of fermentation process the samples were
sensorially evaluated by a group of degustators.
The identical samples were subsequently analysed by
gas chromatography for the aroma compounds production.
Each sample was analysed on the GC MS (Shimadzu QP
2010) equipment and also on the GC FID equipment (GC
8000 CE Instruments).
Two methods of sample preparation were done:
Samples (20 ml) were extracted by ether (2 ml), and centrifuged
prior to analysis. The etheric extract was used
for analysis. (liquid – liquid extraction). This method
was used for higher alcohols (propanol, isoamylacohol,
ethyl esterand esters determination.
Samples were extracted by Tenaq (solid phase microextraction)
and than 10 min sampled in the GC according
to5 •
•
.
The same column and the same conditions were used by
both analysis: Column: DB WAX 30 m, 0.25 × 0.25, temperature
programme: 30 °C, hold 2 min, increase by 4 °C min –1
up to 230 °C, hold 10 min, 1 ml of sample was injected to
injection port at 200 °C, detector temperature 220 °C, carrier
gas: helium, injektion mode: split 1 : 100, flow control mode:
pressure 70 kPa
Results
MAnOVA test was used to explain the variation in the
aroma compounds produced by various yeast strains under
aerobic/anaerobic conditions. The aerobic conditions influ-
s600
enced the variance in several compounds like ethylacetate,
izoamylacete, and propanol.
The other important factor was the temperature. When
the temperature increased more compounds were produced
by all yeast strains, but the effect of higher temperature was
negative. From the statistical view point the less important
factor was evaluated by the media composition, interpreting
only 5 % of data variance.
Table I shows the sensorial evaluation of fermented
grape must by various yeast strains. There were differences in
the specific aroma in several cases. For example Rhodotorula
mucilaginosa was recognized as fruity aroma in fermenting
grape must, and as vanillic aroma fermenting the synthetic
media under semiaerobic conditions, however socks smelly
and yeasty under anaerobic ones. Similar results were obtained
by Torulospora delbruecki, fermenting semiaerobically
grape must, however “only” honey and fruity aroma fermenting
synthetic medium.
Conclusions
Using statistical data, we confirmed that the aroma compounds
production is strongly influenced by the presence of
oxygen. The temperature affected the production of aroma
compounds to the lower extend and the media composition
had the minor impact.
The changes in the sensorial evaluation of aroma are
more intensive and important than changes in the chemical
composition.
Under defined conditions the apiculate microflora can
produce aromas which directly contribute to the variety or
origin character and highly improve them.
REFEREnCES
1. Granchi L., Ganucci D., Messini A, Vincenzini M.:
FEMS Yeast Res. 2, 403 (2002).
2. Romano P., Fiore C., Paraggio M., Caruso M., Capece
A.: Int. J. Food Microbiol. 86, 169 (2003).
3. Rojas V., Gil J.V., Pinaga F., Manzanares P.: Inter. J.
Food Microbiol. 70, 283 (2001).
4. Pátková-Kaňuchová J., nemcová K., Vajcziková I., Breierová
E.: In proceedings from 36 th Annual Konference
on Yeasts, (2008).
5. Kruzlicova D., Mocak J., Hrivnak J.: J. Food nutr.. Res..
47, 37 (2008).