The influence of the ultrafiltration on the yield and quality of cottage cheese

U ovom radu proizvedeni su uzorci Cottage sira od kontrolnog obranog mlijeka (s ≈ 3,5% proteina), te od ultrafiltriranog (UF) obranog mlijeka s različitim udjelom proteina ( ≈ 5, 6 i 8%) podešenog uz pomoć permeata. Fermentacija svih uzoraka mlijeka provedena je na 22 °C, dodatkom 0,5% mezofilne kulture,“O” tipa, (DVS- kulture, Chr. Hansen ′s Lab., Danska) bez dodatka sirila. Porast udjela proteina u mlijeku utjecao je najviše na dulje trajanje fermentacije (od 17 do 24; 27 i 29,5 sati) i na povećanje prinosa sira (od 15,2 do 25,3; 26,4 i 37,7%). Primjenom ultrafiltracije postignut je u sirevima veći udjel proteina (18,8-19,7%), pepela (0,86-0,99%), kalcija (115- 137 mg/100g) i suhe tvari ( 21,4-23,5%) u odnosu na kontrolne uzorke sira (17,26% proteina; 0,75% pepela te 105 mg/100g kalcija i 20,7% suhe tvari). Eksperimentalni sirevi posjedovali su bolja senzorska svojstva u odnosu na kontrolne koji su imali nešto mekšu konzistenciju, te nešto manja i više izmrvljena zrna. Najveća djelotvornost prinosa sira izračunata na bazi proteina u mlijeku postignuta je u uzorcima od UF-obranog mlijeka s ≈ 5% proteina. Najbolja senzorska svojstva, tijekom ukupnog perioda čuvanja u hladnjaku (14 dana pri +5°C), zapažena su kod uzoraka Cottage sira proizvedenih od UF-obranog mlijeka s ≈ 6% proteina.In this paper the Cottage cheese samples, from controlled skimmed milk (with 3.5 % proteins), ultrafiltered (UF) and skimmed milk with different protein content (≈ 5%, 6% and 8%) adjusted with permeates, have been produced. Fermentations are obtained at 22 °C, by the addition of 0.5 % mesophilic culture, „O“ type (DVS-culture, Chr. Hansen’s Lab., Denmark) and without rennet addition. The increased protein content has the greatest influence on the fermentation time (from 17 to 24; 27 and 29.5 hours) as well as on the cheese yield (from 15.2 to 25.3; 26.4; and 37.7 %). By the ultrafiltration applied, an increased protein content (18.8-19.7 %), ash (0.86- 0.99 %), calcium (115-137 mg/100g) and dry matter (21.4-23.5 %) have been obtained in comparison with control sample (17.26 % protein, 0.75 % ash, 105 mg/100g calcium, and 20.7 % dry matter). Better sensory characteristics of the experimental cheeses have been obtained in comparison with control samples. The control sample showed slightly softer consistency, and more smaller and more crumbly grains. The most efficient cheese yield, calculated on the basis of milk protein content, is obtained with UF-skimmed milk with ≈5 % protein. The best sensory characteristics, during entire storage time in refrigerator (14 days at +5 °C), are obtained with Cottage cheese produced from UF-skimmed milk with ≈ 6 % protein content