Probiotics:
Introduction:
In the last decades of 19th century, microflora was diagnosed in the gastrointestinal (GI) tracts of healthy people and was called probiotics. Microbiologists illustrated that these substances were produced by a microorganism which prompted the growth of others. Later, it was considered to be tissue extracts which helps in the stimulation of microbial growth and food additives bearing beneficial effects on animals. Probiotics are the live microbial cultures that provide health benefits along with the key nutritional value and also help maintain the intestinal flora balance. Simultaneously they sustain a subtle balance between the GI tract and immune system.
Probiotics have many applications in dairy fermentations
Probiotics are selected on the basis of strain specificity. Strains are selected from the huge repository having the best compatibility. Lactobacillus and Bifidobacterium spp. are most widely used probiotics.

Food products:
The range of probiotics food is increasing tremendously because of its health benefits. Commercially available probiotics food products are mainly dairy based containing fermented milk, yogurt, cheese, butter, ice-cream and infant formula. Non dairy products include soy based food, nutrition bars, cereals and juices. These food products are evaluated as effective when besides safety; they maintain viability during food processing, packaging and storage. Also the pH of food is an important feature for the probiotics bacteria to survive and thrive. Many bacteria are destroyed by the poor conditions in the external environment. To avoid this from happening, microencapsulation technologies have been
The pH of intestinal substances is decreased by the lactic acid production which inhibits the growth of pathogens like Salmonella spp. and E. coli. The enzymatic hydrolysis of bacteria improves the bioavailability of proteins and fats. It also results in the production of free amino acids, lactic acid, propionic acid and butyric acid. The short chain fatty acids subsidize the available energy pool of the host and provide protection against pathological changes.

Diarrhea:
Probiotics are considered to be an effective remedy for the treatment and prevention of diarrhea. Diarrhea is caused by the presence of rotavirus endotoxins and destruction of enterocytes. With the fortification of probiotics like L. rhamnosus GG and B. animalis, this infection is treated and prevented. Also they help shortening the duration of acute diarrhea. They do it by blocking the receptor sites, regulating the sensory and motility defenses, enhancing the immune response and by the production of substances which inactivate