Home-made yogurt

This home-made yogurt was made with organic whole milk and a small amount of yogurt purchased in a store. By reproducing and multiplying themselves during fermentation the live active cultures in this yogurt will serve to start the bacteria cultures in the new yogurt.
There are 6 lactic acid bacterias in my yogurt: S.thermophilus, L.bulgaricus, L.acidophilus, B.bifidum, B.infantis and L,casel.
The L.bulgaricus will serve to increase acidity and the S.thermophilus will serve to develop the yogurt's taste. The rest of them contribute to taste or health effects.Additives such as gelling agents (gelatine, corn starch, pectine ...) generally used in industrial yogurts to thicken and stabilize the texture were not added. The lactic acid produced during the fermentation of lactose causes the milk protein to thicken so the fermented milk solidifies.
Preservatives like sodium citrata or malic acid were not added either because the lactic acid lowers the pH (4-5) and thus prevents the proliferation of potential pathogenics.