Probiotic bacteria are among the dietary supplements with beneficial effects on human health. To produce a probiotic product from milk using auxiliary culture of Lactobacillus acidophilus, the possibility of using an initial culture step was first studied. For this purpose, the first 0.33 g of Lyophilized bacteria was added to each litre of low-fat sterilized milk of Mihan brand (in total 1 gram to 3 litres of milk) and was incubated at 42 °C until reaching the acidity of 42° Dornic and 15 grams of this product with 30 grams of low-fat yoghurt of Pegah brand was added to 3 litres of low-fat sterilized milk of Mihan brand to produce acidophilus yoghurt and was incubated at 42 °C to reach the acidity of 96° Dornic. Two other types of acidophilus yoghurt, one with a temperature of 38 °C and the other with a temperature of 42 °C and a double bacterial dose were prepared and their flavour was compared by 150 people with control yoghurt (low-fat Pegah brand). In general, the shelf life of acidophilus yoghurt with twice the bacterial dose was the lowest but the consistency was better and its flavour was sourer, the other two acidophilus yoghurts were evaluated with longer shelf life and sweeter than the control yoghurt. Also, with increasing the shelf life, the acidity indicated a significant increase.