The development of new food products has led the market increasingly towards probiotic and delactosed products. This work aimed to evaluate the fermentation process of six varieties of yoghurts diversifying the starting culture, the probiotic (3%) and the type of milk (0% lactose in the delactosed samples). Samples: A1: Freeze-dried culture + traditional milk; A2: Freeze-dried culture + delactosed milk; A3: work culture + L. paracasei + traditional milk; A4: work culture + L. paracasei + delactosed milk; A5: commercial yogurt + commercial L. casei + traditional milk; A6: commercial yogurt + commercial L. casei + delactosed milk. The analyzes were: pH and dornic acidity (ºD). The starting probiotic values of all the Samples was 1,40E+108-1,00E+1010. The samples were in accordance with the legislation: pH (4.55-4.86) and acidity (82-92°D). The samples A1, A2, A5 and A6 did not present statistical differences referring to milk type, similar fermentation as concerns reduction of pH. The Freeze-dried culture includes better balancing and reduced fermentation time, as well as the A5 and A6 samples with a starting concentration of 1010 CFU.ml-1. Samples A3 and A4 exhibited different results that can be justified by the type of culture and probiotic prepared and activated in the laboratory. A1 and A2 did not differ in the acidification process, which can be explained by the Freeze-dried culture. The samples A3, A4, A5 and A6 demonstrated a difference that may be related to the behavior of the culture imbalance and the of milk used with variation in the availability of sugars that favors the growth of certain bacteria contributing to acidification. The best results were in A1 and A2 and the samples A3 and A4 exhibited the slowest fermentation. The fermentation process of traditional and delactosed yoghurts might be determinant in A3, A4, A5 and A6 acidification processes.