Development of Lactobacillus acidophilus-fermented milk fortified with date extract

Abstract

The effect of date extract (DE) addition on the microbiological, physicochemical, rheological, and sensory characteristics of probiotic fermented milk was investigated. DE was added to milk at the level of 0–12 g/100 mL; the mixtures were then fermented with Lactobacillus acidophilus La-5. The initial probiotic concentrations ranged between 8.16 and 8.77 log10 CFU/g. Although the highest DE concentration led to a significant count reduction (from 8.16 to 6.44 log10 CFU/g), the probiotic concentration was above 6 log10 CFU/g in all samples during 14 days of storage at 4 °C. All treatments had similar ash, fat, and protein content. As the DE concentration increased, total solids (from 9.98 to 16.88 g/100 g) and ferric reducing antioxidant power (from 4.01 to 22.24 mg ascorbic acid equivalent/100 g) increased. Samples with higher DE concentration showed lower pH and syneresis, and higher acidity. DE addition could slightly increase the viscosity from 53.48 to 69.95 mPa s. According to power law model, shear-thinning behavior was observed at all concentrations. DE-added products had lower L* and higher a* color values. Fortification with DE did not adversely affect the sensory acceptability. The date extract, therefore, seems to be a suitable candidate to improve the nutritional quality of probiotic dairy foods.