The Bengalis are famous for their sweet preparations and Mishti Dohi sweet yoghurt is among their most well known desserts. Mishti doi is an inseparable part of all festivals in Bengal. The first to observe the presence of microorganisms in fermented milk was the Russian microbiologist Ilya Ilyich Mečnikov . He isolated the Lactobacillus bulgaricus and Streptococcus thermophilus, and recognized that these lactobacilli were responsible for the process of breaking down lactose into galactose and glucose.
These ferment act with a mechanism streptococcus works first, creating the conditions for the lactobacillus do the work of breaking down lactose. Even if the opinions are rather discordant, today, in contrast to what is touted by advertising, it is believed that these two enzymes play no active role in the human body: in fact, they die as soon as they come into contact with the gastric juices humans, not bears their acidity. In reality, it is then seen that these two microorganisms, when taken with starches or fats that reduce stomach acid and reach the intestines alive can fully become part of the probiotic intestinal flora.
Taking the result of the positive response of the use of probiotics in the medical field, today some yogurt manufacturers have begun to add to their products. The probiotic ferments , unlike the Lactobacillus bulgaricus and of Streptococcus thermophilus, are able to better withstand the acidity of gastric juices, to survive and reproduce in the gastrointestinal tract. Since, generally, bacteria already present in the human body, they fail to restore the bacterial flora to a normal condition, in case the latter has been compromised because of treatment with antibiotics , by stress or by improper nutrition.
The probiotics exert further positive action in many processes of digestion, preventing intestinal infections and attacks by fungi ; strengthen the immune system ; produce bacteriocins , the so-called natural antibiotics. The main probiotics added in the fermentation process are the following: Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus lactis, Bifidobacterium bifidum. The fermented milk obtained from their action differs slightly from the yogurt traditionally obtained only with the use of Lactobacillus bulgaricus and Streptococcus thermophilus, giving rise rather to a Kefir.