*2.2. Yoghurt Preparation*

Commercial homogenized pasteurized milk (3.2% *w*/*w* protein and 3.5% *w*/*w* fat) was placed into 2000 mL glass beakers and subjected to thermal treatment consisting of a rapid microwave assisted pre-heating step at 85 ◦C and a batch heating step at 85 ◦C for 20 min in a water-bath (Memmert, Guechenbach, Germany). Subsequently, milk was cooled to fermentation temperature (43.0±0.2 ◦C) and inoculated with 0.2% *v*/*v* commercial starter culture comprising *Streptococcus salivarius* subsp. *thermophilus* and *Lactobacillus delbrueckii* subsp. *bulgaricus* in a ratio of 4:1 (prepared as a 1:5 *w*/*w* dilution of Christian–Hansen freeze-dried YC-X11 culture in commercial UHT skim milk) and 0.3% *w*/*w* commercial probiotic cultures of *Bifidobacterium lactis* and *Lactobacillus acidophilus* (direct inoculation of Christian–Hansen BB12 and LA-5 probiotic cultures) according to the supplier's instructions. The inoculated milk was placed in a water-bath maintained at the desirable fermentation temperature (43.0±0.4 ◦C) until the acidification end point (pH = 4.80) was achieved. Afterwards, the coagulum was manually stirred and divided in three batches. Two of the batches were single stage homogenized at 10 bar in a laboratory high-pressure homogenizer (APV1000, Kolding, Denmark) and packed in 180 g sterile multilayer pouches (laminate film: PP-aluminum-PE); one batch was stored at 5.0 ± 0.2 ◦C (**Control samples**), while the other was subjected to HP treatment (homogenized and HP-treated samples, coded as **Homo-HP**) and then stored under the same chilling conditions. A third batch prepared by directly packing the yoghurt in sterile multilayer pouches of 180 g for HP experiments (HP-treated samples, coded as **HP**) was also prepared. For cherry-flavored samples, 10% (*w*/*w*) of cherry syrup (Olympic Foods S.A., Athens, Greece) was blended with the yoghurt base until homogeneous dispersion of the syrup (68.6±1.57% *w*/*v* total sugars content of the syrup). The day after the production of the samples was considered to be the zero time point, while all quality characterization analysis were carried out in triplicate on a week time intervals for an overall of 28 days.

#### *2.3. High-Pressure Processing*

The experiments were performed using a pilot-scale HP equipment (Food Pressure Unit FPU 1.01, Resato International BV, Assen, Netherlands), as previously described in Tsevdou et al. [12]. For kinetic experiments, 5 mL of the inocula were placed into pouches (laminate film: PP-aluminum-PE) and the viability loss experiments were conducted in the multi-vessel system, in duplicate at various combinations of pressure (100−400 MPa) and temperature (20−40 ◦C) for appropriate process times. For product batch experiments, 180 g of yoghurt were placed into multilayer pouches (laminate film: PP-aluminum-PE) and, the experiments were conducted in triplicate at various combinations of pressure (100−400 MPa) and ambient temperature (26.1±0.3 ◦C) for 10 min.
