**2. Probiotic food products**

Probiotic microorganisms are available in three different types for direct or indirect human consumption: 1) culture concentrate to be added to a food (dried or deep-freeze form) for industrial or home uses, 2) food products (fermented or non-fermented), and 3) dietary supplements (drug products in powder, capsule or tablet forms) (Tannis, 2008). Consumption of probiotic cells via food products are the most popular and widespread way.

Worldwide, the demand for consumption of functional foods is growing rapidly due to the increased awareness of the consumers from the impact of food on health. For example, in the year 2000, the world-wide market of functional foods generated US\$ 33 billion, in 2005, this total was US\$ 73.5 billion, and was US\$ 167 billion in 2010 (Granato et al., 2010). Functional foods are those that contain chemical/microbial components that may affect beneficially one or more target functions in the body, beyond adequate nutritional effects, in a way that is relevant to either the state of well-being and health or the reduction of the risk of a disease (Diplock et al., 1999). Probiotic food products are classified in the category of functional foods and represent a significant part of this market that probiotic foods comprise between 60 and 70% of the total functional food market (Holzapfel, 2006).

During the past three decades, significant attention has been paid to dairy products containing probiotic bacteria such as fermented milks, ice cream, various types of cheese, baby-food, milk powder, frozen dairy desserts, whey-based beverages, sour cream, butter milk, normal and flavored liquid milk, and concentrated milk. Also, recently, many nondairy products such as vegetarian-based products, cereal-based products, fruit juice, soyabased products, oat-based desserts, confectionary products, breakfast cereals and baby foods) and baby foods have been developed. Causes for this ongoing trend are demands provide by vegetarianism, high prevalence of lactose intolerance in many populations around the world, and providing variety and development in probiotic food products (Granato et al., 2010; Mortazavian et al., 2011). Dairy products have the largest probiotic food market share. Today, a total of 78% of current probiotic sales in the world are delivered through yogurt (Cargill, 2009). Therefore, still, the manufacture of dairy products containing probiotic bacteria is an important issue with industrial and commercial consequences. Table 1 represents some types of probiotic products available in the world market (dairy and nondairy products). Figure 1 indicates qualitative aspects of probiotic food products.
