исках да ви заинтригувам вниманието с нешо друго.Няма да отвръщам ,моето момче ли си или момиче не знам . Това е част от един учебник ,които ти не си сънувал и едва ли си прочел толкова ,колкото аз .Колеги ,исках да ви пусна една статия за Совиньон блана ,но нямам скенер в момента.Няма да обръщам внимание.След време ще ви я пусна ,наистина си заслужава да се прочете.А сега ще продължа да ви пускам нешо от този учебник.Може би е интересно за Brettanomices ,не знам.Ето ви .Сигурно този Аламбик е много компетентен ,направо паднах при обяснението му za домашното вино.Личи си че е слушал Бамбалов много добре .елементарно ,Уотсън .А ,виното ,което прави сигурно има достатъчно оцет за туршииките
WINE
MICROBIOLOGY
Practical Applications
and Procedures
Kenneth C. Fugelsang
Charles G. Edwards
Second edition- цената му е около 400 долара ,но може да се намери и по-евтино от Интернет
Това е учебника ,от който пускам тези елементарни неща .Той е издаден от Davis University и ако го намерите ,наистина си заслужава .Доста добре написан и което е много полезно има доста неща за дезинфекция и почистване на съдове ,бутилкови линии ,контрол на вината при бутилиране ,което доста ни куца на нас в Б-я.А сега ще ви копирам нешо за Brett. На някой може и пък да му е интересно- то глупаците няма да престанат с простотиите си.
11.2.2 Dekkera/Brettanomyces
Various sensory descriptors have been used to characterize Dekkera/
Brettanomyces–tainted wines. These range from “cider,” “clove,” “spicy,”
“smoky,” “leather,” and “cedar” to “medicinal,” “Band-Aid®,” “mousy,”
“horsy,” “wet wool,” “rodent-cage litter,” “barnyard,” or even “sewage.”
These odors are due to synthesis of a number of volatile compounds
including 4-ethyl guaiacol and 4-ethyl phenol (Fugelsang et al., 1993;
Licker et al., 1999). 4-Ethyl guaiacol has been sensorially described as
“clove” or “spice” and 4-ethyl phenol is “smoky” or “medicinal.” Given the
wide range in sensory descriptors of infected wines, more “sensory-neutral”
strains of Brettanomyces may exist, and use of these strains may improve the
quality of some wines without imparting off-odors or fl avors.
The sensorial impact of Brettanomyces depends on the wine as well as
preferences of the winemaker and consumer. For instance, Loureiro and
Malfeito-Ferreira (2003) noted that some consumers would fi nd wines
objectionable if the concentration of 4-ethyl phenol exceeded 620 μg/L
whereas others would not. If present at concentrations less than 400 μg/L,
the authors suggested that this compound contributes complexity by
imparting sensory descriptors of “spice,” “leather,” “smoke,” or “game.” In
contrast, Licker et al. (1999) described a “high Brett” wine that contained
3000 μg/L 4-ethyl phenol, a “medium Brett” wine as having 1700 μg/L,
and a “no Brett” wine with 690 μg/L. Volatile phenol production varies
with the strain of Brettanomyces as found by Fugelsang and Zoecklein
(2003) who reported 120 μg/L 4-ethyl guaiacol and 440 μg/L 4-ethyl
phenol produced by one strain but <10 μg/L by another.
Biochemically, 4-ethyl guaiacol and 4-ethyl phenol originate from
ferulic acid and p-coumaric acid, respectively. The reaction is a two-step
process with an initial decarboxylation of the hydroxycinnamic acids
catalyzed by cinnamate decarboxylase and the reduction of the vinyl
phenol intermediates by vinyl phenol reductase (Fig. 11.1). Although the
specifi c coenzyme involved remains unknown, one possible metabolic
benefi t of the second reaction to Brettanomyces could be reoxidation of
NADH. Under low oxygen conditions such as those found in wines, the
availability of NAD+ can be limited so that carbohydrate metabolism is
inhibited (Section 1.5.1). Reduction of the vinyl phenols to the ethyl
phenols would allow the cell to increase the availability of NAD+ and thus
maintain metabolic functions.Spoilage Microorganisms 165
Although many wine microorganisms like Acetobacter, O. oeni, L.
hilgardii, L. plantarum, L. brevis, P. pentosaceus, P. damnosus, and Saccharomyces
can synthesize 4-vinyl guaiacol or 4-vinyl phenol from ferulic and pcoumaric
acids, respectively, most are not able to reduce the vinyl166 11. Wine Spoilage
Besides volatile phenols, Brettanomyces synthesizes a number of odoractive
compounds, many of which have yet to be identifi ed (Licker et al.,
1999). For instance it is known that Brettanomyces produces isovaleric acid,
an odoriferous compound described as “rancid” (Wang, 1985; Licker et
al., 1999). In addition, some strains can impart “mousy” off-fl avors to wine
through synthesis of various nitrogen-containing compounds (Section
11.3.3).
Controlling the growth of Brettanomyces during vinifi cation is not an
easy task. The yeast is relatively tolerant to SO2 as indicated by Sponholz
(1993) who suggested the use of 100 mg/L total or 30 to 50 mg/L free SO2
for control in wine.
Maintenance of 0.4 to 0.6 mg/L molecular SO2 is effective in limiting
growth. Du Toit et al. (2005) suggested that Brettanomyces may enter a
“viable-but-not-culturable” state in the presence of SO2 (Section 6.1). As
such, the yeast may escape detection by conventional microbiological
methods (i.e., plating) prior to bottling, potentially resulting in sudden
“blooms” during bottle aging if conditions permit.
Other control measures have included fi ning and fi ltration (Section
5.3), and recent research has investigated the use of dimethyl dicarbonate
(Section 5.2.2). Although the research looks promising (Brettanomyces was
inhibited at a concentration of 25 mg/L), Daudt and Ough (1980) only
used one culture (species not reported). Furthermore, the combined use
of DMDC and SO2 against Brettanomyces has not yet been explored although
a synergy between DMDC and SO2 against Saccharomyces was noted by
Ough et al. (1988a). Another option is temperature control. Lowering the
cellar temperature to less than 13ºC/55ºF can also be used to slow the
growth of Brettanomyces. Heat resistance of the yeast has also been reported
(Couto et al., 2005).
Once established in wood cooperage, elimination of these yeasts are
diffi cult partially due to the physical properties of wood. Unlike polished
stainless steel or glass, inside surfaces of barrels are diffi cult to clean due
to the many irregular cracks and crevices where particulates, including
spoilage yeasts, can settle.
11.2.3 Film Yeasts
The visual manifestation of oxidative yeast activity is the formation of a
fi lm, sometimes referred to as “mycoderma.” The fi lm results from repeated
budding of mother and daughter cells that, rather than separating, remain
attached, forming chains that branch and rebranch to eventually cover the
surface of the wine (Section 1.2.2.4). Initially, the yeasts can appear as
fl oating “fl owers.” If allowed to continue, growth may rapidly develop into
intermediates to 4-ethyl guaiacol or 4-ethyl phenol (Chatonnet et al., 1992;
1995; Shinohara et al., 2000). Given this, Brettanomyces could theoretically
reduce vinyl phenols synthesized by other wine microorganisms and
thereby benefi t from the growth of other microorganisms (e.g., lactic
acid bacteria). In support, Dias et al. (2003b) found that Brettanomyces
could use 4-vinylphenol as a precursor to 4-ethylphenol in the absence of
p-coumaric acid.
As only Brettanomyces produces signifi cant amounts of ethyl phenols,
wineries have attempted to use measurement of 4-ethyl phenol as an indicator
for infections. However, synthesis of ethyl phenols varies with strain
(Fugelsang and Zoecklein, 2003). Some lactic acid bacteria, most notably
L. plantarum (Chatonnet et al., 1992; 1995; Cavin et al., 1993) as well as
Pichia guilliermondii (Dias et al., 2003a) are reported to produce small
amounts of ethyl phenols. Because of these reasons, direct comparisons
between concentrations and viable cell concentration can be diffi cult.
Processing methods are currently being sought to remove 4-ethyl
guaiacol and 4-ethyl phenol from wines after an infection of Brettanomyces. For example, Ugarte et al. (2005) noted some success using reverse osmosiscoupled to an adsorption system to remove these volatile phenols from wine. Perhaps a simpler method was that described by Chassagne et al.(2005) where yeast lees were used to remove volatile phenols. Compared with active dry yeasts, the authors reported that yeast lees from fermentation were especially strong at removing 4-ethyl phenol. Sorption of these volatile phenols depended on wine conditions, in particular pH, temperature,and ethanol concentration.
1.1. Formation of volatile phenolics from hydroxycinnamic acids. Copyright ©Society of Chemical Industry. Adapted from Chatonnet et al. (1992) and reprinted with the kind permission of John Wiley & Sons Ltd. on behalf of the SCI.Spoilage Microorganisms 167a thick pellicle, which appears “mold-like.” Baldwin (1993) described thefi lm as a chalky or fi lamentous white substance that was dry enough to appear “dusty.” Candida vini (formerly Candida mycoderma) is a relativelycommon fi lm yeast capable of producing a thick pellicle. Besides formation of a fi lm, these yeasts can synthesize sensorially active compounds such asethyl acetate and acetoin among others (Clemente-Jimenez et al., 2004).
Because fi lm formation by certain non-Saccharomyces yeasts refl ects oxidativegrowth, the best preventative measure is to maintain topped tanksand barrels, thereby depriving the yeasts of air (oxygen) needed for
growth. Baldwin (1993) suggested that addition of dry ice to barrels of
wine and subsequent release of CO2 may also help limit the infl ux of O2.
Because some non-Saccharomyces yeasts (e.g., Pichia membranefaciens and Candida krusei) are resistant to molecular levels of more than 3 mg/L, reliance on SO2 is generally ineffective once a fi lm has formed in the barrel (Thomas and Davenport, 1985). Furthermore, one of the major metabolites of fi lm yeasts is acetaldehyde, which can effectively bind SO2 and decrease its antimicrobial properties (Section 5.2.1). Some winemakersh ave had success placing a few grams of potassium metabisulfi te onto a small plastic Petri dish that is allowed to fl oat on wine in a barrel (Baldwin,1993).
Use of lower cellar temperatures (<15ºC/60ºF) can slow the growth of
fi lm yeasts because the alcohol content and temperature interactively
inhibit growth. As support, Dittrich (1977) reported no growth of fi lmforming yeasts in wines of 10% to 12% alcohol when stored at 8ºC/47ºF
to 12ºC/54ºF, whereas growth was observed in other wines up to 14%
alcohol at warmer temperatures.
Приятно четене .те глупаците по принцип няма какво да научат ,ама човек и от най-дребнитенеща може да извлече полза .Сигурна съм ,че за Brett .има някои неща ,които не сме чули от Бамбалов ,така ,че четете.Има и други по-интересни неща като за манопротеините ,диацетила и т.н Ако ме насочите какво ви е необходимо ,ще ви пусна неща ,които ви интересуват.Ок .