Applaying of high pressure to yoghurt preservation

Effects of the high pressure treatment in the range of 200 - 1000 MPa/15 min., at the room temperature, on survivability of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus was investigated. Sensorial characteristics of yoghurt was conducted by a panel of experts. Influence of yoghurt acidity on the effect of pressurization was also determined. In the experiment, we also attempted to extend shelf-life of yoghurt, subjecting it to the pressure of 550 MPa/15 min. Pressure treated yoghurt was stored for 4-weeks at room and refrigerated temperature; every seven days microbial number, acidity and sensory attributes of the beverage was determined. Addition of fruit jam on the effect of pressurization was also checked. Survivability of microorganisms depends on the value of pressure used in the experiment. The research displayed that yoghurt acidity did not influence the effect of pressurization. During 4-weeks of storage, yoghurt processed at 550 MPa maintained its beneficial characteristics longer compared to the non-pressurized one. Addition of fruit jam beneficially affected consistency of the pressure treated yoghurt. The conducted studies showed that there was possibility of preserving yoghurt by the method of high pressures. Thus, to preserve yoghurt, the complete inactivation of microflora is not necessary.