| Abstract | Randman sira se može definirati kao količina sira koja se može proizvesti od određene količine mlijeka i jedan je od najvažnijih ekonomskih parametara u sirarstvu. Na vrijednost randmana, između ostalog može utjecati i vrsta korištene soli. U proizvodnji sira škripavca uobičajeno se koristi NaCl. Kako prekomjeran unos natrija (Na) iz hrane nepovoljno utječe na mehanizam regulacije krvnog tlaka čovjeka, pred sirarsku industriju i znanost postavlja se pitanje kako proizvesti sir sniženog udjela natrija, a koji će zadržati svoja svojstva. U istraživanjima se to često provodi zamjenom dijela NaCl s KCl kako bi zadržali potrebnu slanost i ostale značajke sira. U ovom radu pretpostavlja se da zamijena dijela natrija neće značajno utjecati na randman sira. Cilj rada je bio utvrditi utjecaj smanjenja udjela natrija u proizvodnji sira škripavca kroz zamjenu 50% i 75% NaCl s KCl na njegov randman.
Sir škripavac proizveden je u pilot pogonu Zavoda za mljekarstvo Agronomskog fakulteta Sveučilišta u Zagrebu. Ukupno 60 kg mlijeka podijeljeno je na tri podjednake mase po 20 kg u deset ponavljanja. Kod svakog ponavljanja 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 mlijeka i sira određene su standardnim metodama. Fizikalno-kemijske analize mlijeka obuhvaćale su određivanje sadržaja masti, proteina, kazeina, laktoze, bezmasne suhe tvari te pH vrijednosti, dok su analize sira uključivale određivanje sadržaja masti, proteina, suhe tvari, soli i pH vrijednosti. U radu je također određen stvarni i naravnati randman na željeni udio vlage i soli u siru, te iskoristivost masti i proteina.
Prema rezultatima istraživanja, zamjenom NaCl s 50% i 75% KCl, nije došlo do značajnih promjena fizikalno-kemijskog sastava sira škripavca. Međutim, utvrđen je najveći stvarni i naravnati randman sira škripavca proizvedenog s 75% KCl i 25% NaCl. Stvarni randman za navedeni sir je iznosio 14,98 kg sira iz 100 kg mlijeka za sirenje i bio je veći (P = 0,095) u odnosu na sireve iz druge dvije istražene skupine dok je naravnati randman iznosio 15,20 kg sira za istu količinu mlijeka te je također bio veći u odnosu na druge dvije skupine istraženih sireva. Međutim ta razlika nije bila statistički značajna (P = 0,286). Dobivene korelacije ukazuju na činjenicu da sirevi s većim randmanom imaju veći udio vlage u siru, ali je sadržaj masti, proteina i suhe tvari pri tom bio manji, a time i iskoristivost masti. |
| Abstract (english) | Cheese yield can be defined as the amount of cheese that can be produced from definite quantities of milk and is one of the most important economic parameters in cheese-making. The value of the yield, among other things, can be affected by the type of salt used in the production of the cheese. NaCl is commonly used, but too much intake of Na from food adversely affects the mechanism of regulation of human blood pressure, the cheese industry and science are faced with the question of how to produce cheese with a reduced content of Na, which will retain its properties. In research, this is often done by replacing part of NaCl with KCl to maintain the required salinity and other characteristics of the cheese. In this study, it is assumed that the replacement of part Na will not significantly affect the yield. The aim of this study was to determine the impact of reducing the part of sodium in the production of škripavac cheese by the replacement of 50% and 75% NaCl with KCl on its yield.
Škripavac cheese was produced in the pilot plant of the Department of Dairy Science, Faculty of Agriculture, University of Zagreb. A total of 60 kg of milk was divided into three equal masses of 20 kg in ten replicates. At each replicate, 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. Milk and cheese analyses were performed by standard methods. Physico-chemical analyses of milk included determination of fat, protein, casein, lactose, non-fat dry matter and pH values, while cheese analyzes included determination of fat, protein, dry matter, salt and pH values. In this study the actual and adjusted yield on the desired moisture and fat content in cheese were determined, as well as the fat and protein recovery.
According to the results of this work, where the replacement of NaCl was with 50% and 75% KCl, there were no significant changes in the physico-chemical composition of škripavac cheese. However, these studies showed that the highest actual and adjusted yield was obtained for the cheese produced with 75% KCl and 25% NaCl. The actual yield for this cheese was 14.98 kg of cheese obtained from 100 kg of milk and was close to significantly higher (P = 0.095) compared to other cheeses, and the adjusted yield was 15.20 kg of cheese produced from 100 kg of milk, which is also higher than for other two analyzed cheeses. But this differences were not significant (P = 0,286). The correlations confirmed, among the rest, confirmed that cheeses with higher yield had a higher moisture content in the cheese, but the content of fat, protein and dry matter were loweras well as fat recovery. |
