| Sažetak | Natrij iz hrane utječe na mehanizam regulacije krvnog tlaka, a time i na zdravlje
krvožilnog sustava čovjeka. Kako se sir smatra jednim od značajnijih izvora natrija, u mnogim
istraživanjima koriste se zamjenske mineralne soli kao što je primjerice KCl kako bi se
reducirao udio natrija u siru, a da sir zadrži potrebnu slanost i ostala važna svojstva. Neupitno
je da NaCl koji se u sir dodaje postupkom soljenja u proizvodnji sira izravno utječe na mnoge
značajne karakteristike sira kao što su njegov sastav i reološka svojstava. Međutim, sir
škripavac karakterizira nizak udio soli (oko 1%), pa je za pretpostaviti da zamjena dijela NaCl
s KCl neće imati negativan utjecaj na njegov kemijski sastav i reološka svojstva. Cilj rada je
bio utvrditi utjecaj zamjene dijela NaCl s KCl na kemijski sastav i reološka svojstva sira
škripavca.
Sir škripavac proizveo se u pilot pogonu Zavoda za mljekarstvo. Ukupno 60 kg mlijeka
podijelilo se na tri podjednake mase po 20 kg u pet ponavljanja. U svakom ponavljanju
proizvedena su tri sira škripavca različitog udjela natrija kako slijedi: 100% NaCl (kontrolna
grupa), sir škripavac sniženog sadržaja natrija zamjenom 50% NaCl s KCl, sir škripavac
sniženog sadržaja natrija zamjenom 75% NaCl s KCl. Analize sira provedene su standardnim
metodama, a obuhvatile su određivanje sadržaja masti, proteina, suhe tvari, soli, natrija i kalija
te pH vrijednost i aktivitet vode. Za mjerenje teksture koristio se teksturni analizator (TA Plus
Lloyd Instruments) na kojem su se utvrdila slijedeća reološka svojstva: čvrstoća, lomljivost,
deformacija u točki loma, adhezivnost i kohezivnost.
Utvrđeno je da nema značajnih razlika u fizikalnom-kemijskom sastavu sira škripavca
kada je dio NaCl zamijenjen s KCl, osim za vrijednost pH koja se povećala za 0,1 (P<0,001),
dok se sadržaj natrija značajno (P<0,001) smanjio kada se dio NaCl zamijenio s KCl. Nije došlo
do značajnih promjena u reološkim svojstvima sira uslijed zamjene dijela NaCl s KCl, osim za
kohezivnost koja je bila veća (P = 0,099) u siru koji je proizveden s 50% NaCl i 50% KCl.
Koeficijenti korelacija između reoloških svojstava i fizikalnog-kemijskog sastava sira
škripavca pokazali su da lomljivost, deformacija u točci loma i gumenost sira rastu kao
posljedica porasta suhe tvari, a što podrazumijeva i veći udio masti i proteina u siru. Svojstvo
škripavosti posljedica je činjenice da sir škripavac ima specifičnu gumenu strukturu, pri čemu
je utvrđena visoka i negativna korelacija između gumenosti i sadržaja vode u bezmasnoj tvari
sira (P<0,05; r = -0,704). |
| Sažetak (engleski) | Sodium from food affects the mechanism of blood pressure regulation, and thus the
health of the human cardiovascular system. As cheese is considered one of the most important
sources of sodium, many studies use substitute mineral salts such as KCl to reduce the sodium
content of the cheese while maintaining the required salinity and the other cheese properties.
There is no doubt that NaCl added to cheese in the salting process during cheese production
directly affects many significant characteristics of the cheese such as its composition and rheological
properties. However, Škripavac cheese is characterized by a low salt content (about 1%),
so it is to be assumed that replacing part of NaCl with KCl will not have a negative impact on
its chemical composition and rheological properties. The aim of this paper is to determine the
impact of the replacement of a part of NaCl with KCl on the chemical composition and rheological
properties of škripavac cheese.
Škripavac cheese will be produced in the pilot plant of the Department of Dairy Science.
A total of 60 kg of milk was divided into three equal masses of 20 kg in five batches.In each
iteration, three Škripavac cheeses with different sodium contents were produced as follows:
100% NaCl (control group), Škripavac cheese with reduced sodium content by replacing 50%
NaCl with KCl, Škripavac cheese with reduced sodium content by replacing 75% NaCl with
KCl. Cheese analyses were included determination of fat, protein, dry matter, salt, sodium and
potassium content and pH and water activity.A texture analyser (TA Plus Lloyd Instruments)
was used to measure the texture, on which the following rheological properties were determined:
strength, brittleness, fracture point deformation, adhesiveness and cohesiveness.
It was found that there are no significant differences in the physico-chemical composition
of the hard cheese when part of the NaCl is replaced by KCl, except for the pH value which
increased by 0.1 (P <0.001), while sodium content decreased significantly (P <0.001) when part
of NaCl was replaced by KCl. There were no significant changes in the rheological properties
of the cheese due to the replacement of part of NaCl with KCl, except for the cohesiveness
which was higher (P = 0.099) in the cheese produced with 50% NaCl and 50% KCl.
The correlation coefficients between the rheological properties and the chemical-physical
composition of the Škripavac cheese showed that fracture, deformation at the breaking
point, and gumminess of the cheese increase as a result of the increase in dry matter, which
means higher fat and protein content in cheese. The squeaking property of Škripavac cheese is
a consequence of the fact that Škripavac cheese has a specific rubber structure which was in a
high and negative correlation with water content in the fat-free solids of cheese (P <0.05; r = -
0.704). |
