Study on the Biochemical and Microbiological Characteristics of Several Probiotic Strains in Non-Alcoholic Beer during Storage Period

In this research, the effects of addition of different probiotic strains (L. acidophilus, L. casei, L. reuteri, L. fermentum or L. plantarum) as well as initial pH values (4.3 or 4.8) on the biochemical and microbiological characteristics of non-alcoholic beer drink were studied during 21 days in the refrigerated storage (5°C).
Probiotics identification and incubation were done with gram staining and MRS-broth medium, respectively. pH and redox potential values were measured by pH-meter. Titrable acidity value was determined by titration with 0.1 N NaOH. Probiotic bacteria were enumerated using MRS-agar medium.
The highest biochemical changes were observed in treatments with L. casei and L. acidophilus. The second 7-day interval showed the highest amount of biochemical changes in the treatments with initial pH of 4.3 along with L. casei, L. fermentum and L. reuteri throughout the 21 days of storage; however, other species showed such characteristics only at pH=4.8. The viability of probiotic strains in all treatments, especially in those with initial pH of 4.3, decreased dramatically during the refrigerated storage. L. acidophilus and L. fermentum showed the lowest viability during refrigerated storage. While the highest viability belonged to L. reueri in the treatments with initial pH of 4.3 and to L. plantarum in those with pH=4.8.
The results showed that different initial pH values as well as different types of inoculated probiotic strains in non-alcoholic beer drink had effects on the amount of the biochemical changes and the viability of probiotic strains in non-alcoholic beer drink; therefore, non-alcoholic beer drink can be a good choice for growth of probiotic.