Development of a New Milk Drink Containing Dates-immobilized Probiotic Bacteria
Date fruit has been a staple food in North Africa, the Middle East, and South Asian countries for thousands of years. Dates are rich in carbohydrates, mainly glucose and fructose, dietary fiber, vitamin B complex, minerals, carotenoids, phenolics, and antioxidants, but low in fats and proteins. Due to these essential functional compounds, dates provide a wide range of important nutrients and potential health benefits. In spite of attempts to develop functional foods containing dates and probiotics, this has not been done up until now. The aim of this study was to develop the best way to produce a novel probiotic date milk product and determine its microbiological and physicochemical properties. Lactobacillus acidophilus and mashed date fruits were encapsulated with calcium alginate using an extrusion technique. Two forms of dates were tested in the alginate beads: autoclaved and raw. In addition, the control beads, which were probiotic alginate beads without dates, were also examined to determine the effect of the dates on the product. The products were stored for 7 days at 4°C. The size of the beads was measured in millimeters and the morphology of the beads was measured using scanning electron microscopy. The texture properties of beads were examined using Texture Analyser (TA) apparatus. The survival of encapsulated Lactobacillus acidophilus was determined using a spread plate count on MRS agar. The color analysis of the milk and beads and the pH were also measured. The results showed that the microbial account and pH of the products were not affected by the date addition during a 7 days storage period at 4°C, compared to the control. Lactobacillus acidophilus was kept inside the beads without any release to the milk and the number of the bacterial cells remained in the range of the recommended dose of 10⁶-10⁷ CFU per g during the storage time. Moreover, there was no observation of pathogen growth caused by the Medjool dates in the product. Most of the beads were large in size (5-6 mm) with a teardrop shape, which affected the texture of the beads. The presence of the Medjool dates decreased the stability and the hardness of the beads. The colour of the autoclaved date beads was darker than raw date beads and the control beads, which was reflected in the colour of the milk in the same sample. The colour of autoclaved date beads was similar to the colour of the dates. From the results of this investigation, it is possible to develop date probiotic products by using the microencapsulation of probiotic bacteria with dates, and areas for future research are recommended.