Newsgroup: it.scienza.medicina
Titolo: Frigorifero spento per un giorno

Per una svista la spina del frigorifero � rimasta staccata per una
trentina di ore, con i cibi all'interno. A questo punto il dilemma �
se
1. buttare via
2. consumare rapidamente (quanto rapidamente?)
In particolare, nello scomparto dei surgelati (4 stelle), piuttosto
pieno, ci sono filetti di sogliola e varie verdure (spinaci, bacelli
di soia, minestroni...).
Nel frigo invece c'era del latte microfiltrato aperto (assaggiato, ha
un sapore che non mi convince, anche se non propriamente andato a
male, l'ho gi� buttato), una scatola di uova (rischio formazione
condensa quando sono tornate a temperatura ambiente?), dei formaggi e
della pasta fresca ripiena e non.

condensa quando sono tornate a temperatura ambiente?), dei formaggi e
Io cercherei di mangiare solo le cose che si possono cuocere
adeguatamente (es.uova sode o pesce al forno)
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 della pasta fresca ripiena e non.
boh, vedi tu, io scalderei a temperatura adeguata e consumerei :-p
ciao
luh
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 scadenza e regolati ...
Ma non sono rimaste a temperatura ambiente: sono state raffreddate e
poi sono tornate a temperatura ambiente. Per dirla con l'EFSA,
L'interruzione della catena del freddo � un fattore che aumenta il
rischio di condensa e questo potrebbe aumentare la penetrazione
batterica nell'uovo.

 batterica nell'uovo.
se hai un rifermento a questo ipotetico rischio magari postalo, a me 
sembra un'esagerazione, sopratutto se riferito a uova integre


 sembra un'esagerazione, sopratutto se riferito a uova integre
Citavo da
http://www.efsa.europa.eu/EFSA/efsa_locale-1178620753820_1211902325412.htm
 "L'interruzione della catena del freddo � un fattore che aumenta il
 rischio di condensa e questo potrebbe aumentare la penetrazione
 batterica nell'uovo."
ma in effetti, come dici tu, e come si capisce andando a leggere il
report integrale, questo ipotetico rischio pare riguardare in realt�
soprattutto le uova non perfettamente integre, cio� quelle con
fratture nel guscio, se ben capisco. Il report distingue l'analisi tra
penetrazione di salmonella e quella di altri possibili microorganismi.
[...]
Interruption of the cooling chain may lead to condensation on the
shell (Kaess, 1960 in
Kiefer, 1976) and penetration of bacteria through the shell. Ernst et
al. (1998) divided
commercial shell eggs into intact and cracked groups. Half the eggs
were inoculated by S.
Enteritidis, air dried, and returned to refrigeration. Half of each
group was removed from
refrigeration and allowed to sweat for 3 h. The eggs were then
quantitatively cultured to
determine levels of S. Enteritidis penetration. Sweating did not seem
to increase the number
of S. Enteritidis-positive eggs or the number of S. Enteritidis
present. Dramatically higher
numbers of S. Enteritidis were found in S. Enteritidis-contaminated
cracked eggs than in
sound eggs. This suggests that sweating for 3 h does not increase egg
contamination with S.
Enteritidis; however, bacterial penetration through the shell is more
likely to occur in cracked
eggs.
In the study by De Reu et al. (2006) the condensate group was stored
at 6�C for 24 h followed
by storage for 20 days at 20�C and 60% RH (giving 30 min of condensate
on the eggs) while
the control group was continuously stored at 20�C. Using eggs filled
with agar to visualise
penetration, more frequent egg shell penetration of S. Enteritidis was
observed following
condensation on eggs, but no effects could be shown using intact eggs.
A higher Salmonella
shell contamination was observed for the agar filled eggs of the
condensate group compared
to the control group which may explain the higher probability of
penetration. In an earlier
study (Fromm and Margolf, 1958) penetration was observed more
frequently in the eggs
allowed to sweat. In this study however, wet eggs kept at 22-24�C were
subsequently stored
at 10-12�C and 80% RH. The higher probability of penetration in the
condensate group could
be due to the negative pressure in the eggs allowing contaminated
moisture to be drawn into
the egg contents.
[...]
4.4. Possible side effects of refrigeration on microorganisms other
than Salmonella
[...]
When the egg is being laid there is a natural temperature gradient
between the warm egg
(around 40�C) and the relatively cold environment (ambient
temperature). When free water is
present, with help of capillary action and temperature differences
bacteria can move into the
pores and colonize on the shell membrane (Board et al., 2008). Pfennig
(1974) observed that
motile coliform bacteria could easily penetrate the shell, but Board
and Tranter (2008) have
not seen direct evidence to support this observation. They merely
observed that a very motile
strain of Proteus increased the possibility for other (non motile)
bacteria to pass through the
shell. However, penetration of bacteria through the shell is a
possible side effect of
refrigeration. Kaess (1960 in Kiefer, 1976) states that the presence
of water facilitates the
invasion of bacteria and fungi. This may happen when the refrigeration
chain of eggs is
interrupted and condensation on eggs appears. Vedehra et al. (1970)
found that the exposure
to Pseudomonas of the blunt end of the egg caused more spoilage than
other areas.
In a study already mentioned above Dolman and Board (1992) Pseudomonas
became the
dominant bacteria on inoculated air cell membranes which where stored
at 4�C and at 37�C
for 20 days. In the albumen S. Enteritidis and Staphylococcus xylosus
were prevalent.
De Reu et al. (2006) compared the eggshell penetration of 7 selected
bacterial strains
(Staphylococcus warneri, Acinetobacter baumannii, Alcaligenes sp.,
Serratia marcescens,
Carnobacterium sp., Pseudomonas sp. and S. Enteritidis, recovered from
egg contents) using
the agar and whole egg approach. Results of the first approach
indicated that the Gramnegative,
motile and non-clustering bacteria penetrated the eggshell most
frequently;
Pseudomonas sp. and Alcaligenes sp. were primary invaders followed by
S. Enteritidis.
However, particularly S. Enteritidis was a primary invader of whole
eggs.
Per� poi dicono anche, pi� avanti (cap.6)
It is recognised that the interruption of the cold chain during trade
(collection, sorting,
grading, packaging and distribution) can lead to condensation on the
eggshell. This
condensation can occur under certain combinations of actual eggshell
temperature on one
hand and temperature and relative humidity of subsequent storage on
the other hand.
Consequently there may be an increased risk of growth and penetration
of microorganisms,
including Salmonella spp., present on the surface of the eggshell.
It has also been demonstrated that Salmonella spp. can survive longer
on the egg shell at
lower temperatures depending on the relative humidity.
http://snurl.com/py9it
http://www.efsa.europa.eu/cs/BlobServer/Scientific_Opinion/biohaz_op_ej957_cooling_eggs_en,4.pdf