Influence of the probiotic culture Lactobacillus helveticus M92, milk proteins and transglutaminase on the properties of set-style yoghurt

Cilj ovog diplomskog rada bio je istražiti utjecaj probiotičke kulture Lactobacillus helveticus M92, mliječnih proteina i transglutaminaze na kvalitetu i senzorska svojstva čvrstog jogurta. Za proizvodnju jogurta je korišteno svježe homogenizirano mlijeko s 1,5 % mliječne masti kojemu je dodana kultura Lactobacillus helveticus M92, mliječni proteini, te enzim transglutaminaza, aktiviran 1,5 h pri 55 °C. Inaktivacija enzima provedena je postupkom pasterizacije 15 min pri 85 °C. Nakon hlađenja na 43°C, mlijeko za proizvodnju čvrstog jogurta inokulirano je zamrznutom starter kulturom (BT10X i 100F) i probiotičkom kulturom Lactobacillus helveticus M92. Proizvedeni su i kontrolni uzorci bez dodatka transglutaminaze, mliječnih proteina i probiotičke kulture Lactobacillus helveticus M92. Dodatak probiotičke kulture smanjuje trajanje fermentacije čvrstog jogurta za ca 30 min u odnosu na kontrolni jogurt, dok dodatak mliječnih proteina i transglutaminaze nije utjecao na trajanje fermentacije. Utvrđeno je da proizvedeni čvrsti jogurti s probiotičkom kulturom Lactobacillus helveticus M92, mliječnim proteinima i transglutaminazom te čvrsti jogurti s mliječnim proteinima i transglutaminazom imaju veću čvrstoću, pokazali su manju sinerezu te su dobili višu ocjenu senzorskih svojstava u odnosu na kontrolne jogurte. Broj živih stanica Lactobacillus helveticus M92 je ostao visok tijekom svih 28 dana čuvanja jogurta (cca 108 CFU/ml).The aim of this graduate thesis was to investigate the influence of the probiotic culture Lactobacillus helveticus M92, milk proteins and transglutaminase on the quality and sensoric properties of set-style yoghurt. Fresh homogenised milk with 1,5 % of milk fat was used for the yoghurt production, with addition of Lactobacillus helveticus M92, milk proteins and transglutaminase activated during 1,5 h at 55 °C. 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) and probiotic culture Lactobacillus helveticus M92, after cooling to the temperature of 43 °C. Beside the experimental samples, control samples were also made, without addition of transglutaminase, milk proteins and probiotic culture Lactobacillus helveticus M92. Addition of probiotic culture reduces the duration of set-style yoghurt fermentation for approximately 30 min compared to the control yoghurt, while the addition of milk proteins and transglutaminase did not affect the duration of fermentation. It has been shown that produced set-style yoghurts with probiotic culture Lactobacillus helveticus M92, milk proteins and transglutaminase and set-style yoghurts with milk proteins and transglutaminase had higher firmness, less syneresis, and better sensoric properties than control yoghurts. The viable count of Lactobacillus helveticus M92 stayed high during all 28 days of storage (cca 108 CFU/ml)