Response surface methodology based on Box-Behnken design was employed to optimize the fermentation conditions of juice of “Milpa Alta” cactus stems (Opuntia ficus-indica Mill.) added with skimmed milk powder for producing fermented milk beverage. The optimal fermentation parameters were determined as follows: the concentrations of cactus stem juice, sucrose and starter culture (Lactobacillus bulgaricus:Streptococcus thermophilus = 1:1) were 15.3%, 9.4% and 0.16%, respectively; the fermentation was proceeded at 42 ℃ for 6.8 h. The acidity value of fermented beverage produced under these conditions was 93.2 °T, and it had a distinctive flavor and abundant nutrients.

The fermentation conditions for producing a fermented dairy beverage from skim milk added with the polysaccharide extract from Dendrobium officinale were optimized in the present study. Beverage with the best flavor was obtained when skim milk added with 50% Dendrobium officinale polysaccharide and sugar at levels of 10% and 7% (by mass), respectively was fermented at 42 ℃ for 6 h after inoculation with the starter culture (Lactobacillus bulgaricus:Streptococcus thermophilus = 1: 1) at a level of 0.10%.