Fetatype ost av geitemelk
Master thesis
Permanent lenke
http://hdl.handle.net/11250/295173Utgivelsesdato
2015-08-06Metadata
Vis full innførselSamlinger
- Master's theses (KBM) [891]
Sammendrag
Feta has been produced in Greece since Homer's days and the original Feta cheese is made
from sheep's milk mixed with a maximum of 30 % goat`s milk. One aim of this study was to
investigate whether goat's milk was suitable as the main ingredient for Feta type cheese. This
was done by comparing two types of milk – goat`s milk and cow`s milk – with regard to
cheese making properties and cheese quality. The other aim of this study was to investigate
whether the concentration of casein would lead to savings in cheese manufacture and if it
would have a positive impact on cheese quality. This was done by using microfiltration to
separate the casein fraction in the proteins. The concentrated retentate was then used as part of
the cheese milk in manufacture of cheese from concentrated milk. Two types of milk –
concentrated (microfiltrated) goat milk and non concentrated goat milk – were compared with
regard to cheese making properties and cheese quality.
3 types of Feta type cheese were produced and the production took place over a period of 10
weeks. Type 1 cheese was produced with skimmed, non concentrated cow`s milk and cream
from cow`s milk, type 2 cheese was produced with skimmed, non concentrated goat's milk
mixed with cream from cow`s milk, and type 3 cheese was produced from the retentate from
microfiltrated, skimmed goat's milk mixed with cream from cow`s milk. All types of cheese
was manufactured in 2 blocks with 2 vats (2 replicates) in every block with exception of one
of the blocks with non concentrated goat`s milk - where only one vat (1 replicate) was
produced. All of the 3 types of cheese were following the same cheese making procedure.
In order to investigate the meaning of the experimental variables cow`s milk / goat's milk and
concentrated goat's milk / non concentrated goat`s milk, regarding cheese manufacture and
cheese quality, it was performed multiple chemical analysis. The analysis was performed
during the cheese making, in fresh cheese and in matured cheese. In the matured cheese there
were also conducted texture analysis and a sensory test conducted by a trained taste panel at
TINE.
The results showed that there were significant differences both between goat- and cow's milk
and between concentrated goat's milk and non concentrated goat`s milk when comparing the
cheese milk, cheese making process, fresh and mature cheese. Cheese milk from goat proved to have lower pH, the shortest acidification rate and the
shortest renneting time compared to cheese milk from cow. It was observed that the coagulum
from goat`s milk was very fragile and was more easily broken than cow's milk coagulum.
Cheeses that were made of goat's milk had the lowest dry matter content both in fresh and
matured cheese. pH levels in fresh and mature cheese of goat`s milk showed no significant
differences compared to fresh and mature cheese of cow's milk. The salt content was highest
in the matured cheese from cow's milk. When analyzing the carbohydrates it showed that
mature cheese from goat had significantly higher content of lactose. Texture analysis
regarding hardness and fracture point showed no differences between cheese from cow's milk
and goat's milk.
The only significant difference that were found in cheese milk from concentrated and non
concentrated goat`s milk was the protein concentration and it was highest in the concentrated
milk. Observations of the whey and cheese curd in the vat showed that it was clearly less
whey after cutting of the curd of the concentrated milk and the coagulum clumped together
quickly when the stirring started.
There were found no differences between the two types of milk regarding pH of cheese milk,
acidification rate or renneting time. Cheese made from the concentrated goat milk had the
highest pH and the highest level of total solids. The cheese made from the concentrated goat's
milk had the highest values of ash content, fat content, protein content and content of soluble
nitrogen in percentage of total nitrogen. The salt content was not significantly different
between the two types of cheese.
The results also showed that it was most galactose in the cheese from the non concentrated
milk. In this cheese it was found lactose, but no lactose was detected in the cheese from the
concentrated milk. Texture analysis of hardness and fracture point showed that cheese from
the concentrated milk was the hardest one and also the one with the highest fracture point.
After sensory evaluation by a trained panel of sensory judges from TINE the cheese from the
non concentrated goat milk was considered the best, both regarding taste and consistency.
There was consensus among the judges that the use of goat milk has a positive effect on
flavour and aroma.
Conclusion: Goat`s milk is a suitable raw material for Feta type cheeses; these cheeses
received good feedback from the sensory panel regarding the taste and aroma. Goat`s milk has 8
satisfactory cheese making properties for this type of cheese. Microfiltration can be a suitable
process for the production of Feta type cheese if some operations of the cheese making
process are adjusted. If the stirring time after the cutting of the coagulum is shortened and the
stirring done more gently it will lead to a lower dry matter content and the cheese will be less
hard and dry. Fetaost har blitt produsert i Hellas siden Homers dager og råstoffet i den originale Fetaosten
er sauemelk iblandet maksimum 30 % geitemelk. I dette prosjektet ble det undersøkt om
geitemelk var egnet som hovedråstoff til Fetatype ost ved å sammenligne ost og ysteprosess
ved bruk av geitemelk og kumelk. Det ble også undersøkt om oppkonsentrering av kaseinene
ville være besparende i ysteprosessen og ha en positiv innvirkning på ostekvaliteten. Dette ble
gjort ved å benytte mikrofiltrering til proteinfraksjonering for så å sammenligne ost og
ysteprosess ved bruk av retentatet fra filtrert geitemelk kontra ufiltrert geitemelk.
Det ble produsert 3 typer Fetatype ost og produksjonen foregikk over en periode på 10 uker.
Type 1 ble produsert på skummet, ufiltrert kumelk iblandet fløte fra ku, type 2 ble produsert
med skummet, ufiltrert geitemelk iblandet fløte fra ku, og type 3 ble produsert av retentatet fra
filtrert, skummet geitemelk blandet med fløte fra ku. I alle typene ost ble det ystet i 2 blokker
med 2 kar (2 gjentak) i hver blokk med unntak av den ene blokken til ufiltrert geitemelk –
hvor det kun ble ystet ett kar (1 gjentak). Alle ystingene fulgte samme ystingsopplegg.
For å undersøke betydningen av forsøksfaktorene kumelk/geitemelk og filtrert
geitemelk/ufiltrert geitemelk i forhold til ysteprosessen og ostekvaliteten ble det utført flere
kjemiske analyser underveis; under selve ystingen, på fersk ost og på lagret ost. På den
lagrede osten ble det i tillegg utført teksturanalyser og en sensorisk test utført av et trenet
smakspanel hos TINE.
Resultatene viste at det var signifikante forskjeller ved sammenligning av ystemelk,
ysteprosess, fersk og lagret ost – både mellom geitemelk og kumelk og mellom ukonsentrert
geitemelk og konsentrert geitemelk.
Ystemelk fra geit viste seg å ha lavere pH, kortere syrningstid og løpningstid enn ystemelk fra
ku. Det ble observert at geitemelk-koagelet var skjørere og gikk lettere i stykker enn kumelkkoagelet.
Ost som ble ystet av geitemelk hadde lavest tørrstoffinnhold, både i fersk og lagret
ost. pH-verdiene i fersk og lagret ost av geitemelk visste ingen signifikante forskjeller i
forhold til fersk og lagret ost av kumelk. Saltinnholdet var høyest i den lagrede osten fra
kumelk. Målinger av karbohydrater viste at lagret ost fra geit hadde det signifikant høyeste
innholdet laktose. Teksturanalyse av hardhet og bruddpunkt viste ingen forskjell mellom ost
fra kumelk og geitemelk.