Functional chemical-enriched compounds
A food can be regarded as “functional” if it is satisfactorily demonstrated to beneficially affect 1 or more target functions in the body, beyond adequate nutritional effects (saxelin and others 2003). Fortified-functional dairy products are added-value products in which milk or a milk product is enriched at least with 1 chemical or microbial component with a proven health benefit.
Mineral- and vitamin-enriched milk products are the most important fortified dairy products, as mineral and vitamin deficiencies are a serious public health problem in many developing countries and often even occur in industrialized countries. Common mineral and trace element deficiencies involve iron, zinc, selenium, iodine, and calcium. The most important vitamin deficiencies today are probably those of vitamin A, vitamin D, and folic acid (Saxelin and others 2003).
Calcium enrichment of food and dairy products is gaining more and more interest with the increased awareness about the importance of higher calcium intake. Apart from prevention of osteoporosis, adequate calcium intake has been associated with reduced risk of hypertension, colon cancer, kidney stones, and lead absorption (McCarron and Heaney 2004). Therefore, dried milk and flavored milk powders are often fortified with vitamins A and D, calcium, and iron (Singh and others 2007). Although dairy products are an excellent source of dietary calcium, they can be further fortified with calcium salts to achieve higher calcium intake per serving (Vyas and Tong 2004). The recommended dietary allowance for calcium in the United States is 800 and 1200 mg/d for children and adults, respectively (RDAs and Allowances 1989). Nowadays, calcium fortification of dairy products such as cheese, ice cream, skim milk, and yogurt is a common practice.
Iron deficiency is a common nutritional deficiency worldwide, affecting mainly older infants, young children, and women of child bearing age. Dairy products are an important source of nutrients but are low in iron. Fortification of these products can increase average dietary iron intake (Zhang and Mahoney 1989). Dairy products that are often fortified with iron are cheddar cheese, brown whey cheese, mozzarella cheese, white soft cheese, baker's and cottage cheese, Harvatti cheese, yogurt (nonfat and low fat), and chocolate milk (Zhang and Mahoney 1991; Biebinger and others 2008).
Zinc is necessary for the activity of over 100 specific enzymes that are involved in major metabolic pathways, including physical growth, immune competence, reproductive function, and neurobehavioral development. Zinc-fortified cheddar cheese could be an excellent food source for replenishment of zinc levels in groups at risk of zinc deficiency (Biebinger and others 2008; Kahraman and Ustunol 2012).
Evidence demonstrates that current vitamin D intakes in adults are inadequate (Vieth 2001). Several studies suggest that higher serum vitamin D concentrations are associated with lower rates of breast, ovarian, prostate, and colorectal cancers, as well as decreased risk of developing multiple sclerosis (Vieth 2001). Therefore, fortification of fluid milk, cheese, yogurt, fermented dairy beverages, and ice cream with vitamin D3 is an important public health program (Kazmi and others 2007).
Vitamin A is a fat-soluble vitamin and represents a group of substances necessary for reproduction, cellular differentiation, the immune system, gene regulation, and eye sight. The fortification of whole milk with vitamin A is voluntary, whereas fortification of low fat milk and skim milk is strongly recommended and even mandatory in some countries because of the removal with cream of fat-soluble vitamins during centrifugations.
The protective role of folic acid in the reduction of neural tube defects, coronary heart diseases, and cancer has been recognized (Gangadharan and Nampoothiri 2011). Folic acid has also been shown to reduce the risk of colorectal and breast cancers (Prinz-Langenohl and others 2001). Milk and fermented dairy products represent a good source of natural folate and folate-binding proteins that improve the bioavailability and stability of folate (Gangadharan and Nampoothiri 2011). Folic acid can be added successfully in plain yogurt up to the recommended daily allowance of 400 μg (Boeneke and Aryana 2007).
CLA exerts a strong positive influence on human health, but its intake is typically too low, and increased consumption of CLA is recommended. A good way to increase the CLA content in the diet without a change in eating habits is enrichment of commonly consumed food products with CLA supplements (Rodríguez-Alcalá and Fontecha 2007). Many studies have demonstrated the feasibility of producing CLA-enriched dairy products with acceptable sensory characteristics and shelf life (Jones and others 2005).
Prebiotic products contain a prebiotic (nondigestible) ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of colonic probiotic bacteria (Mohammadi and others 2012). They are not digested in the upper gastrointestinal tract, because of the inability of the digestive enzymes. They are digested in the colon (Schrezenmeir and de Vrese 2001). The end products in the gut fermentation are mainly short chain fatty acids (propionic and butyric acid), lactic acid, acetic acid, hydrogen, methane, and carbon dioxide. Short chain fatty acids, especially butyric acid, are known to act as an energy source for enterocytes (Wollowski and others 2001). Heydari and others (2011) have investigated the effects of adding different prebiotic compounds to probiotic yogurt and its chemical, mirobiological, and sensory characteristics (Heydari and others 2011). Mohammadi and Mortazavian (2010) reviewed the technological aspects of prebiotics in probiotic fermented milk (Mohammadi and Mortazavian 2010).
Microalgae (cyanobacterial biomass) may be added into fermented milk in order to increase the functional characteristics of the product (Varga and others 2002). Spirulina and chlorella are blue–green microalgae that contain high antioxidant constituents, multiple amino acids, high-quality proteins, Fe, Ca, unsaturated fatty acids, and many vitamins including A, B2, B6, B9, B12, E, and K. They have antiviral, anti-inflammatory, and antitumoral effects and reduce blood lipid profile, blood sugar, body weight, and wound healing time (Gyenis and others 2005). Beheshtipour and others (2012) considered adding microalgae to probiotic yogurt based on its chemical, mirobiological, and sensory characteristics (Beheshtipour and others 2012).