AuthorNiamah, Alaa Kareem
MetadataShow full item record
Ultrasound treatment (low frequency) effects on probiotic bacteria growth in fermented milk
The effect of ultrasonic treatment at 40 kHz for 0, 5, 10, 15 and 20 minutes on the growth of five different strains of probiotic bacteria (Lactobacillus acidophilus LA-5, Lactobacillus casei LC, Lactobacillus reuteri LR-MM53, Bifidobacterium bifidum Bb-12 and Bifidobacterium loungm BB-536) in fermented milk was investigated. The study findings indicate that ultrasound treatment (10 minutes) increased the viable cells and total acidity for LA-5, LC and LR-MM53 samples but decreased viable cells and total acidity in the Bb-12 and BB-536 samples. All probiotic bacteria strains were ruptured by ultrasound treatment causing an increase in the extracellular release of β-galactosidase enzyme. Increased exposure time led to higher enzymatic activity. 2.9 unit/ml of β-galactosidase was measured in LR-MM53 after ultrasonic treatment for 20 minutes. The fermentation time of LA-5, LC and LR-MM53 samples were reduced after 10 minutes of ultrasound treatment compared with the control sample. Added 5 percent (10⁸ CFU/ml) of probiotic bacteria led to reduce at the fermentation time during ultrasonic treatment compared with control sample. The optimal time span of ultrasound treatment (40 kHz, 116 W) was 10 minutes for all fermented milk samples, which can be applied to increase the number of viable cells of probiotic bacteria and β-galactosidase enzyme.