Production and packaging of fermented functional beverage from date syrup by lactobacillus rhamnosus

In this research, production of date palm extract based functional beverage through its fermentation by lactobacillus rhamnosus during 12 weeks storage was assayed.
Fermentation was done at 37°C for 48h.Growth kinetics, pH, acidity, total phenolic content, and antioxidant activity were investigated during the fermentation process.In the next step fermented date extract which was mixed with sugar and citric acid, wasused to produce the functional drink. Pasteurized drinks were packed in the glass and polyethylene terephthalate bottles which were transparent and opaque to indicate the light effect and then storage stability of the beverages was studied. Packages were stored at ambient and refrigerator (4oC) temperature. The samples of each treatment had been withdrawn after two weeks, up to a period of 12 weeks. Afterward following tests were performed on the samples: pH, color intensity, acidity, phenolic compounds, antioxidant activity, aerobic mesophilic and yeasts and moulds colony count. Panel test was performed at the end of the preservation.
The results of growth curve showed that bacterial population of L. rhamnosus reached to 108 CFU/ml after 20 h. In addition pH of date syrup decreased to about 4.3 after fermentation, which is important because of the inhibition of undesirable bacteria growth and technological aspect.
Because of the preservation of phenolic compounds and antioxidant activity, storage at 4oC, in the glass and opaque bottles is suggested. Sensory evaluation showed no significant organoleptic changes in the samples and no moulds, yeasts and aerobic mesophilic bacteria contamination were observed with microbial tests.
These findings suggest that date palm extract drinks should be treated as short shelf life (6 weeks as optimal) products to get the most potential health benefits of antioxidant polyphenols.