Laktik asit bakterileriyle portakal suyu benzeri fonksiyonel içecek üretimi

Orange juice is rich in healthy and nutritive compounds but it contains high levels of sugars and represented a high source of calories. In this thesis, it was tried to diminish its sugars content by using a probiotic strain combined with Lactic Acid Bacteria (LAB) strain that converts the sugars of the juice to lactic acid and polysaccharides (inulin and dextran) of prebiotic features without altering the organoleptic properties. Two groups of LAB able to synthesize polysaccharides from sugars were investigated. The first is represented by Lactobacillus (L.) johnsonii (probiotic strain) and L. gasseri which synthesize inulin. The second is represented by L. satsumensis and L. sakei strains which synthesize dextran. After their characterization in MRS medium, the precited species were grown in orange juice to select the most proficient bacteria. In freshly prepared orange juice (FPorange), the best cell viability was recorded by L. johnsonii and L. satsumensis where they exceeded a cell viability of 9.32 log CFU mL-1 after 22 h fermentation. This level of cell viability was compromised by using commercial orange juice as a fermentation matrix, particularly for L. johnsonii and its cell viability could not exceed 8.32 log CFU mL-1. In commercial orange juice, the cell viability of L. johnsonii was seen to be improved tremendously when it is in co-culture with L. satsumensis or in the presence of 10 mM sodium acetate during fermentation. The pre-culture initial pHs of 6.75 and 7.25 were seen to positively influence the cell viability of the probiotic strain and its sugars' consumption potential and to preserve the bacterium during the storage phase. In FPorange the co-culture of L. johnsonii with L. satsumensis maintained its cell viability higher than 9.42 log CFU mL-1. Moreover, it abated the sugar content of the FPorange by at least 21.6% and produced exopolysaccharıde compounds with a minimum level of 15,66 g/L. Additionally, this mixed culture boosted the overall sensory acceptance score of the fermented beverage higher than 7.22 particularly when L. satsumensis was added after 6 h of fermentation (C3 treatment). Thus, under the fermentation condition C3, the FPorange represented a propitious food matrix for the production of functional beverages with prebiotic and dietetic properties and a good vector for probiotic delivery. Key Words: Lactic Acid Bacteria, probiotic, prebiotic, orange juice, reduced sugars