Abstract:

Plackett-Burman design (PBD), steepest ascent design (SAD) and Box-Behnken design (BBD) were used to
optimize process parameters for the development of a composite set-type yoghurt with added Sphallerocarpus gracilis
infusion and carrot juice. Firstly, eight independent variables were evaluated by using PB design, and Sphallerocarpus
gracilis infusion, carrot juice and starter culture and sugar concentration were identified as significantly affecting
sedimentation rate. Then the center points of the four factors were determined based on steepest ascent design. Optimization
of these significant factors was carried out by using Box-Behnken design. Under the optimized conditions, namely adding
4.98% Sphallerocarpus gracilis infusion, 7.13% sugar, 9.72% carrot juice and 4.05% starter culture to raw milk, the
sedimentation rate was 45.29%, which was in good agreement with the predicted value of 44.83%. In conclusion, the
optimized process had good reliability. The resulting product was white with light pink, and moderately sweet and sour as a
nutritious food with beautiful appearance and unique taste.

Key words: Sphallerocarpus gracil, carrot juice, response surface analysis, composite yogurt, Box-Behnken design