Svrha rada bila je istražiti utjecaj probiotičke kulture Lactobacillus acidophilus i enzima transglutaminaze (TG) na kvalitetu i senzorska svojstva autohtonog svježeg sira iz okolice Zagreba. Svježem, nepasteriziranom, obranom mlijeku dodan je enzim transglutaminaza (TG), a na različitim temperaturama i trajanju aktivacije (8 sati na 11 ºC i 4 sata na 25 ºC). Inaktivacija enzima provedena je postupkom pasterizacije (65 ºC/30 min). Nakon hlađenja na 25 ºC, mlijeko za proizvodnju svježeg sira inokulirano je mezofilnom kulturom bakterija mliječne kiseline MM101 i probiotičkom kulturom L. acidophilus LAC-1. Uz pokusne uzorke, s dodatkom TG i probiotičke kulture, proizvedeni su i kontrolni uzorci bez dodatka TG i probiotika te uzorci bez TG, ali uz dodatak probiotika. Uzorci svježeg sira proizvedeni uz dodatak TG, posebno oni gdje je TG djelovala 8 sati na 11 ºC, imali su veću masu od uzoraka proizvedenih bez dodatka enzima, pa je stoga i prinos sira bio veći, a pokazali su i manju sinerezu tijekom 10 dana čuvanja svježeg sira na 10 ºC negoli uzorci koji su proizvedeni bez dodatka enzima. Isti su uzorci dobili najviše ocjene senzorskih svojstava. Metabolička aktivnost mezofilne kulture MM101 i probiotičkog soja L. acidophilus LAC-1 utjecala je na bolji okus i miris svježeg sira, a broj živih stanica probiotičkog soja L. acidophilus LAC-1 u priređenim uzorcima bio je cca 5 x 106 cfu/g nakon 10 dana čuvanja na 10 ºC, što je više od minimalnog preporučenog broja u probiotičkim proizvodima. Dodatak transglutaminaze doprinosi boljoj konzistenciji i općem izgledu svježeg sira.The aim of this research was to examine the influence of probiotic culture Lactobacillus acidophilus and enzyme transglutaminase (TG) on quality and sensory properties of autochthonous fresh cheese from Zagreb region. Fresh, unpasteurized, skimmed milk was inoculated with TG at different temperatures and activation time (8 h at 11 ºC and 4 h at 25 ºC). Inactivation of the enzyme was carried out during the process of pasteurization (65ºC/30 min). The milk for fresh cheese production was further inoculated with mesophilic culture of lactic acid bacteria MM101 and probiotic strain Lactobacillus acidophilus LAC-1. Besides the trial samples with addition of TG and probiotic bacteria, control samples without addition of TG and probiotic were produced, as well as the samples without addition of TG but with probiotic bacteria addition. Samples of fresh cheese produced with addition of TG, especially in which TG was active at 11 ºC, had greater weight then samples produced without the enzyme addition. Therefore, their yield was also greater then yield of cheese produced without the addition of the enzyme. Furthermore, the samples of fresh cheese produced with addition of TG have shown lesser syneresis than other samples during 10 days of storage at 10 ºC. The same samples also had the best sensory properties. Metabolic activity of mesophilic culture MM101 and probiotic culture L. acidophilus LAC-1 has resulted in better taste and odour of fresh cheese. The viable cell number of probiotic strain L. acidophilus LAC-1 in prepared samples was around 5 x 106 cells/g after 10 days of storage at 10 ºC, which is higher than the minimal dose required for 27 probiotic products. Addition of transgultaminase contributed to better consistency and general appearance of produced fresh cheese
