Browsing by Author "Kularathne, D.V.C.B."

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    Quality Characteristics of Probiotic Milk Incorporated with Stevia (Stevia rebaudiana) Leaf Extract Powder as Natural Sweetener
    (Uva Wellassa University of Sri Lanka, 2020) Kularathne, D.V.C.B.; Mudannayake, D.C.; Ranasinghe, M.K.; Jayarathne, G.G.N.
    Probiotic milk is a popular fermented dairy product. Stevia rebaudiana, leaves can be used to extract zero-calorie sweetener, which also has antioxidant and anticancer properties. The present study was done to develop value-added probiotic milk by incorporating stevia leaf extract powder and assess its quality parameters. Stevia leaf extract powder (SLEP) was prepared by hot water extraction (85°C/2 hrs) of stevia leaves filtration, rotatory evaporation, treatment with ion exchange resin followed by spray drying. Probiotic milk was prepared with 0.2% (w/v) S. thermophilus culture and different levels of SLEP and sugar at ratios of 0:5, 0.2:4, 0.4:3, 0.6:2, 0.8:1, 1:0. Stevia leaf extract powder was analyzed for moisture, fat, protein, total phenolics, total flavonoids, antioxidant activity, and soluble sugar content using gravimetric, soxhlet, kjeldhal, FolinCiocalteu (FC), AlCl3, 2,2-diphenyl-1-picryihydrazyl (DPPH) and phenol sulfuric methods, respectively. Sensory evaluation was conducted using a 9-point hedonic scale and 30 untrained panelists to select the best treatment. Probiotic milk with 0.4% (w/w) SLEP and 3% sugar was chosen as the best treatment during the sensory evaluation. The selected treatments were tested for pH, antioxidant activity, Brix value, microbial quality (E. coli, yeast, and mold), and total plate count against the control at a 7-day interval during 28 days of refrigerated storage (4°C). Further crude fat, crude protein, and soluble sugar were analyzed for the probiotic milk samples. Results revealed that probiotic milk with 0.4% (w/w) SLEP had higher (p<0.05) antioxidant activity (58.24%) and lower (P < 0.05) soluble sugar contents compared to that of the control, which contained 0.4% SLEP and 3% sugar. S. thermophilus counts were not affected by the addition of SLEP. E. coli, yeast and mold were absent in all samples. It was concluded that stevia leaf extract powder can be used to replace sugar up to 3% in probiotic milk. Keywords: Probiotic milk, Stevia leaf extract powder, Antioxidant, Microbial, Sensory