Until recently, most studies performed with LAB have selected strains for their palatability and usability in yogurts. For this reason, most studies have been based on LAB, such as Lactobacillus acidophilus, L.casei, L. delbrueckii och Bifidobacillus adolescentis, B.bifidum, B.longum and Bifidobacterium infantis, which are common in yogurts and kefirs. It is only recently that interest has been focused on developing criteria for selecting LAB based on intraluminal biology, such as the ability to adhere to mucus or mucosal cells, the ability to ferment resistant fibers, and antioxidant capacity. For example, L.plantarum, which is often recovered from fermented fruits, vegetables, sourdoughs and silage, has been demonstrated to have a strong ability to adhere to mucosa and to break down resistant fibers. L. plantarum is the commonest LAB in human gastrointestinal tract and has shown the greatest ability of all LAB tested to survive in the gut (106 times that of L.rhamnosus for example) and activate cytokine secretion after passage through the stomach and the small intestine.