JARLSBERGOSTEN JARLSBERG CHEESE - UMB

som var vanlig i Norge. Forskere ved Iowa
State College (4) hadde rapportert om et
utviklingsarbeid av en ostetype som fikk betegnelsen
Iowa Swiss. Ystingsteknikken som
ble rapport for denne osten, minner mye om
en goudaostteknologi, men deler av forsøksarbeidet
benyttet ettervarmingstemperatur
på 41,1˚C. Dette er for høyt for Goudaost.
Hovedoppgavearbeidet til Sakshaug
omfattet 24 ystekar à 400 liter melk, der
den samme ystingsteknikken ble benyttet
for alle karene. Fra hvert kar ble det formet
16 runde oster. Hver ost hadde en vekt på
ca. 2,5 kg. Det vil føre for langt å gjennomgå
hele ystingsteknikken her, men det er viktig
å nevne at det ble benyttet en vanlig blandingskultur
av mesofile melkesyrebakerier.
Dette var den samme blandingskulturen av
melkesyrebakterier som ble benyttet for
smør- og osteproduksjon i Norge. Ettervarmingstemperaturen
var på 37˚C.
Det eksperimentelle opplegget omfattet
tilsetting av en stamme av propionsyrebakterien
Propionibacterium freudenreichii subsp.
shermanii i tre forskjellige mengder i tre ystekar.
Ystekarene ble også tilsatt én prosent
av den mesofile blandingssyrekulturen av
melkesyrebakerier. I det fjerde ystekaret ble
Gouda. Before that, a variant with very small eyes
had been produced. However, for several years
leading up to 1955, achieving sufficient numbers
of large eyes in the cheese became an increasing
problem.
In his Masters research, Sakshaug began with
the hypothesis that in the original Norwegian
Gouda cheese, propionibacteria were probably
an important aid to achieving satisfactory eye
formation. Propionibacteria are principally gut
bacteria and would therefore be a part of the
normal flora of the milking parlor. Sakshaug specu-
lated that because parlor and milking hygiene
had improved, the incidence of propionibacteria
had been reduced. These factors, combined with
pasteurization of the cheese milk, could have
resulted in minimal amounts of propionibacteria
in the cheese milk.
The formation of very large eyes in Emmental-
type cheese is primarily due to propionibacteria
which form large amounts of carbon dioxide (CO 2 )
by metabolizing the lactic acid that has been
formed from lactose in the milk by the lactic acid
starter bacteria in the cheese. Propionibacte-
ria metabolize the salt of lactic acid (lactate) to
propionic acid, acetic acid and CO 2 . Sakshaug’s
hypothesis was that the eye formation in Gouda would
be improved and more like that in cheese produced
earlier if a pure culture of propionibacteria was added
to the cheese milk following pasteurization. A review
of the literature showed that many research groups
had previously studied the effect of adding propi-
onibacteria to Emmental cheese milk. However, no
reports could be found referring to the addition
of propionibacteria to pasteurized cheese milk
for Gouda production using the technology that
was common in Norwegian dairies. Research-
ers at Iowa State College (4) had reported the
development of a cheese they called Iowa Swiss.
The technology used for this cheese was similar
to that used for Gouda, but some of the research
used a cooking temperature of 41.1˚C, which is
too high for Gouda.
Sakshaug’s MSc research project comprised
24 cheese vats, each with 400 liters of milk. The
same cheesemaking technology was used for all
vats. Sixteen round cheeses were made from each
vat, each weighing 2.5 kg. To detail the cheese-
making technology used would take too long, but
it is important to mention that an ordinary mixed
mesophilic culture of lactic acid bacteria was used,
the same as is used for butter and cheese produc-
tion in Norway. The cooking temperature was 37˚C.
The experimental setup involved the addition of
a strain of Propionibacterium freudenreichii subsp.
shermanii at three different levels to three cheese
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