Characterization of Streptococcus thermophilus microencapsulated with α-tocopherol addition at different temperatures

This study aims to enhance the survival, shelf life, and controlled release properties of Streptococcus thermophilus, a probiotic with significant health benefits, by spray-drying the bacterium with the addition of α-tocopherol. The goal was to improve its characteristics, such as viability, extended shelf life, and controlled release in the digestive system. To achieve this, the strain Streptococcus thermophilus (NCFB 2392) was spray-dried at a laboratory scale under three different temperatures (100°C, 120°C, and 140°C) with the addition of 0, 100 ppm, and 200 ppm α-tocopherol. In the study, the lowest microencapsulation efficiency (ME) was observed in the MSt-3 group (200 ppm α-tocopherol at 100°C), with a value of 85.98%, while the highest ME was found in the MSt-8 group (100 ppm α-tocopherol at 140°C), with a value of 98.87%. The morphology of the microcapsules obtained after the spray-drying process was examined using scanning electron microscopy (SEM). According to SEM images, the best results were observed in the following groups: MSt-6 (120°C, 200 ppm α-tocopherol), MSt-7 (140°C, 0 ppm α-tocopherol), and MSt-8 (140°C, 100 ppm α-tocopherol). An in vitro digestion test was performed to assess the viability of the microencapsulated bacteria in the digestive system. To evaluate the effects of both the coating material and α-tocopherol, control groups consisting of uncoated live bacteria (CB) and microcapsules without α-tocopherol (KMSt-8) were also studied. The results indicated that the most successful group was MSt-8, with a survival rate of 52.22%. The CB group exhibited a survival rate of 31.42%, while the KMSt-8 group had a slightly higher survival rate of 34.59% compared to the CB group. The viability of the microencapsulated bacteria, particularly from the MSt-8 group, was monitored during storage under two different conditions: room temperature (26°C) and cold storage (+4°C) for three months. After the three-month storage period, MSt-8 microcapsules maintained 78.31±1.21% viability under cold conditions. In conclusion, it was determined that Streptococcus thermophilus can be successfully spray-dried at 140°C with the addition of 100 ppm α-tocopherol, showing favorable characteristics in terms of moisture content, surface morphology, microencapsulation efficiency, resistance in digestive environments, and stability during a three-month storage period. Keywords: Probiotics, Alpha tocopherol, Spray drying, Microencapsulation