Utjecaj koncentrata proteina i produkata pročišćavanja sirutke na prinos i kakvoću ovčjeg sira

The effects of the addition of whey protein concentrates and clarification by-products obtained from ovine cheese whey and deproteinized whey (Sorelho) on the yield and quality of the whey cheese (Requeijão) have been evaluated. Whey protein concentrates were obtained by ultrafiltration of skimmed whey and Sorelho. The clarification by-products were obtained after the treatment of the skimmed whey and Sorelho by thermocalcic precipitation and microfiltration with two membranes (0.20 and 0.65 μm pore size). Next, the liophilization of the corresponding retentates was carried out. Each powder was added in three different mass ratios: 0.5, 1.0 and 1.5 %. The addition of the powders caused higher yields of the whey cheese – mainly the one with the additional whey powder – but it did not affect the strength of the products. The retention of water and other components of whey and milk in the whey cheese was influenced by the protein composition of the powders. In relation to colour parameters, the whey cheese manufactured with ultrafiltration and microfiltration retentate powders showed lower values of ligthness than the control whey cheese – mainly the whey cheese with 1.5 % of added powders. The microstructure constituted of small aggregates in the whey cheese manufactured with ultrafiltration and 0.20-μm microfiltration retentate powders and also by large, smooth structures in the other whey cheeses, especially in batches with added Sorelho powders.Istražen je utjecaj koncentrata proteina i produkata pročišćavanja sirutke ovčjeg mlijeka i deproteinizirane sirutke (Sorelho) na prinos i kakvoću sira Requeijão. Koncentrat proteina dobiven je ultrafiltracijom obrane i deproteinizirane sirutke. Produkti pročišćavanja obrane i deproteinizirane sirutke dobiveni su grušanjem i mikrofiltracijom kroz 2 membrane veličine pora 0,20 i 0,65 μm. Nakon toga je provedena liofilizacija dobivenih retentata. Prah dobiven liofilizacijom dodan je siru u masenom omjeru od 0,5; 1,0 i 1,5 %. Dodatak praha povećao je prinos sira dobivenog iz sirutke, osobito onog s dodatkom koncentrata proteina, ali nije utjecao na čvrstoću sira. Zadržavanje vode i ostalih sastojaka iz sirutke i mlijeka u siru ovisilo je o proteinskom sastavu praha. Pri određivanju boje sir iz sirutke, proizveden ultrafiltracijom i mikrofiltracijom retentata, imao je nižu L vrijednost od kontrolnog uzorka, osobito sir s dodatkom 1,5 % praha. Analizom mikrostrukture utvrđeno je da se sir proizveden s dodatkom retentata, dobivenih ultrafiltracijom i mikrofiltracijom kroz membrane veličine pora 0,2 μm, sastoji od malih agregata dok su ostali uzorci sira, posebno oni s dodatkom deproteinizirane sirutke (Sorelho) sadržavali velike agregate glatke površine