Process Optimisation and Quality Evaluation of a Vitamin D₃-Fortified, Monk Fruit– Sweetened Fermented Milk Beverage Containing Shatavari and Ashwagandha

The combined incorporation of Ayurvedic botanicals, vitamin D₃ and alternative sweeteners into a fermented milk beverage (FMB) presents technological challenges related to fermentation, texture, phytochemical characteristics and sensory acceptance. This study developed a vitamin D₃-fortified FMB containing Shatavari ( Asparagus racemosus ) and Ashwagandha ( Withania somnifera ) and evaluated the feasibility of completely replacing sucrose with a commercial monk fruit-based bulk sweetener. A central composite rotatable design was used to optimise the concentrations of Shatavari, Ashwagandha and sucrose based on colour and appearance, body and texture, sweetness, flavour and overall acceptability. Sucrose was subsequently replaced with the monk fruit-based sweetener at concentrations ranging from 8.5 to 14.5% (w/v, based on milk volume). The optimised sucrose-sweetened herbal beverage (S-HFMB), monk fruit-sweetened herbal beverage (MF-HFMB) and non-herbal control beverage (C-FMB) were evaluated for quality parameters. Quadratic models adequately described all sensory responses (R² = 0.9559–0.9752), with maximum scores observed at intermediate ingredient concentrations. Numerical optimisation identified 0.35% Shatavari, 0.35% Ashwagandha and 12.50% sucrose as optimal, yielding a predicted overall acceptability score of 8.66 and a composite desirability of 0.96. Complete replacement of sucrose with 12.5% monk fruit-based sweetener produced the highest overall acceptability score (8.94/9). MF-HFMB contained 24.52% total solids, 3.50% protein and 4.10% fat and exhibited greater apparent viscosity than C-FMB (22.10 versus 20.40 mPa·s). Its DPPH radical-scavenging activity was 0.92 mmol Trolox equivalents (TE) L⁻¹, compared with 0.41 mmol TE L⁻¹ in C-FMB, while its measured vitamin D₃ concentration was 11.88 µg 100 mL⁻¹. MF-HFMB also exhibited greater mean in vitro antibacterial activity against the tested bacteria than C-FMB (19.63 versus 12.27 mm) while maintaining high presumptive lactobacilli and streptococci counts of 8.878 and 9.430 log₁₀ CFU mL⁻¹, respectively. A sensorially acceptable, vitamin D₃-fortified herbal fermented milk beverage can be produced with complete sucrose replacement using a commercial monk fruit-based bulk sweetener. MF-HFMB showed higher DPPH radical-scavenging activity and apparent viscosity than C-FMB, with high presumptive starter-group counts and greater in vitro antibacterial activity. These findings support further evaluation under refrigerated-storage and pilot-scale conditions.