Optimization of the capsulation of yoghurt bacteria byelectrospray method and investigation of usingpossibilities of encapsulated yoghurt bacteria in yoghurtproduction

Yoghurt which is produced by fermentation of milk using starter cultures containing Streptococcus thermophilus and Lactobacillus delbrueckii bulgaricus as yoghurt bacteria is one of the most consumed dairy products, especially by individuals with lactose intolerance. Yoghurt bacteria cannot resist against various stress conditions (such as temperature and pH, etc) encountered during production, storage and consumption. Various methods are being developed to provide resistance of microorganisms against various stress conditions. Electrospray encapsulation technique is one of the methods that increases the resistance of microorganisms against environmental conditions. In this study, it is aimed to obtain capsules with the highest capsule loading efficiency, capsules with the highest resistant to low pH media (pH 2.5) and capsules with these two features together by optimizing variables in the coating solution such as whey protein isolate/inulin ratio, distance of the needle tip from the plane and voltage value. In addition in this study, the possibilities of using the obtained capsules in yoghurt production were investigated. In order to produce the capsules with the highest loading efficiency, the whey protein isolate/inulin ratio of 16/8, the voltage value of 19.60 kV and the distance of the needle tip from the plane of 8.00 cm; in order to produce the capsules containing S. thermophilus and L. delbrueckii subsp. bulgaricus with their highest survival in low pH media, the whey protein isolate/inulin ratio of 23.84/1.16, the voltage value of 10.01 kV and the distance of the needle tip from the plane of 16.82 cm; in order to produce the capsules containing S. thermophilus and L. delbrueckii subsp. bulgaricus with their highest survival in low pH media and with highest loading efficiency, the whey protein isolate/inulin ratio of 16/8, the voltage value of 22.07 kV and the distance of the needle tip from the plane of 8.00 cm were determined. It was determined that the pH and titration acidity values were higher and the viscosity and hardness values were lower, of the yoghurt samples with added the capsules containing the yoghurt bacteria than those of the control sample, and no significant difference (P>0.05) was detected in syneresis values of all yoghurt samples. As a result of the sensory analysis of the yoghurt samples, it was found that the appearance and taste scores of the control samples were higher compared to those of the yoghurt samples with added to the capsules containing yoghurt bacteria; however, no significant difference (P<0.05) was found in the odour and general acceptability scores of all yoghurt samples. It was detected that the encapsulation process significantly protected the viability of S. thermophilus and L. delbrueckii subsp. bulgaricus in the yoghurt samples during passage through a dynamic in vitro gastrointestinal model.