Investigation of Physicochemical and Antioxidant Properties of Goat Milk Enriched with Barley Malt Extract Fermented with Some Lactic acid Bacteria

After testing and verification of resistance to gastrointestinal conditions confirming the strain selected to prepare probiotic fermented goat milk, 0.5 g of Lactobacillus plantarum (PTCC 1058( and Lactobacillus casei (PTCC 1608( were inoculated into 200 mL of goat milk sample. Then, 2, 4, and 6% of barley malt extract were added to the treatments to evaluate the effects of malt extract on the survival and activity of probiotic bacteria. Sample tests (including physicochemical, colorimetric indices, viscosity, antioxidant activity, and general acceptance) were evaluated on production days 7, 14, 21, and 28. The results showed that increasing the concentration of malt extract increased the content of soluble proteins, antioxidant activity, acidity, and decreased pH in all treatments increased (P<0.05). Also, adding malt extract and increasing its concentration increased the viscosity and brix on the day of production, but during 28 days, these parameters decreased (P<0.05). The color indices showed L* sample decreased and a* and b* increased with increasing the concentration of malt extract during storage (P<0.05). Evaluation of general acceptance of samples showed by increasing the malt extract concentration, treatment desirability declined. As well as, evaluation growth probiotic bacteria showed during the 7th day, due to the presence of sufficient nutrients, they significantly increased. Then the population of probiotic bacteria decreased (P<0.05). Generally, according to the results and sensory evaluation, probiotic goat milk containing 4% malt extract is the best sample, and recommend that consumed during the 7th day as the best time.