Influence of the transglutaminase and probiotic culture Lactobacillus acidophilus on the properties of stirred yoghurt

Cilj ovog diplomskog rada je bio istražiti utjecaj transglutaminaze (TGaze) i probiotičke kulture Lactobacillus acidophilus na kvalitetu i senzorska svojstva tekućeg jogurta. Za proizvodnju jogurta je korišteno svježe homogenizirano mlijeko s 3,2 % mliječne masti kojemu je dodan Lactobacillus acidophilus L10 te enzim transglutaminaza aktiviran 1,5 h pri 55 °C. Inaktivacija enzima provedena je postupkom pasterizacije 15 min pri 85 °C. Nakon hlađenja na 42 °C, mlijeko za proizvodnju tekućeg jogurta inokulirano je zamrznutom starter kulturom (BT10X i 100F) te provedena fermentacija. Uzorci su ohlađeni na 20 °C i dodana je probiotička kultura Lactobacillus acidophilus L10. Uz opisane uzorke jogurta, proizvedeni su i kontrolni uzorci bez dodatka TGaze i probiotičke kulture. U radu je određivan fizikalno-kemijski sastav mlijeka i jogurta, broj živih stanica probiotičke kulture Lactobacillus acidophilus kao i senzorska svojstva proizvedenog tekućeg jogurta. Utvrđeno je da proizvedeni tekući jogurti s probiotičkom kulturom Lactobacillus acidophilus i transglutaminazom imaju veću čvrstoću, pokazali su manju sinerezu te su dobili više ocjene senzorskih svojstava. Broj živih stanica Lactobacillus acidophilus je ostao visok tijekom svih 28 dana čuvanja jogurta (cca 108 stanica po mililitru).The aim of this graduated thesis was to investigate influence of transglutaminase and probiotic culture Lactobacillus acidophilus on the quality and sensoric properties of stirred yoghurt. Fresh homogenised milk with 3,3 % of milk fat has been used for the yoghurt production,with addition of Lactobacillus acidophilus L10, and transglutaminase activated during 1,5 h at 55 °C. The enzyme inactivation was completed by pasterization of milk during 15 minutes at 85 °C. Milk was inoculated with the yoghurt starter culture (BT10X and 100F), afer cooling to the temperature of 42 °C, and fermentation has been performed at this temperature of stirred yoghurt. The samples were cooled to the temperature of 20 °C, when probiotic culture Lactobacillus acidophilus L10 was added. Beside the experimental samples, control samples were also made, without addition of transglutaminase and probiotic culture. Physico-chemical parameters of milk and stirred yoghurt, as well as viable count of probiotic culture Lactobacillus acidophilus L10, and sensoric properties of produced stirred yoghurt have been determined. It has been shown that produced stirred yoghurts with probiotic culture Lactobacillus acidophilus L10 and transglutaminase had higher firmness, less syneresis, and better sensoric properties. The viable count of Lactobacillus acidophilus L10 stayed high during all 28 days of storage (cca 108 cells per ml)