Abstract:
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
