1.       Introduction

The primary role of diet is to provide enough nutrients to meet metabolic requirements, while giving the consumer a feeling of satisfaction and well-being. Recent knowledge, however, supports the hypothesis that, beyond meeting nutrition needs, diet may modulate various physiological functions and may play detrimental or beneficial roles in some diseases [1]. Now concepts are expanding from the past emphasis on survival, hunger satisfaction, and preventing adverse effects to an emphasis on the use of foods to promote a well-being state, improving health, and reducing the risk of diseases. These concepts are particularly important for increasing cost of health care, the steady increase in life expectancy and the desire of older people for improved life quality [2].

Functional food is a recent concept that originated in Japan but was further developed in the United States, Europe and other parts of the world. This concept implies that foods and food components have the ability to beneficially influence body functions to help improve the state of well-being, health and reduce the risk of diseases. The market of these products is significant [3]. In total, more than 1700 functional food products have been launched in Japan between 1988 and 1998 with an estimated turnover of around 14 billion US$ in 1999. The market was estimated to be 5 billion US$ in 2003 (Side, 2006) [4] and 5.73 billion US$ in 2006, while more than 500 products were labeled as FOSHU in 2005 [4,5].

From a practical point of view, a functional food can be:

• A natural food in which one of the components has been naturally enhanced through special growing conditions.

• A food to which a component has been added to provide benefits (e.g. the addition of selected probiotic bacteria with proven health benefit characteristics to improve gut health).

• A food from which a harmful component has been removed so that the food has less adverse effects on health (e.g. the reduction of Saturated Fatty Acids [SFA]).

• A food in which the nature of one or more components has been chemically modified to improve health (e.g. the hydrolysed protein in infant formulas to reduce the likelihood of allergenicity).

• A food in which the bioavailability of one or more components has been increased to provide greater absorption of a beneficial component.

• Any combination of the preceding possibilities.

Functional foods are similar in appearance to conventional foods; the former being consumed as part of the normal diet. In contrast to conventional foods, functional foods, however, have demonstrated physiological benefits and can reduce the risk of chronic disease beyond basic nutritional functions, including maintenance of gut health [6]. When food is being cooked or prepared using "scientific intelligence" with or without knowledge of how or why it is being used, the food is called "functional food".

Functional foods may improve the general conditions of the body (e.g. pre-and probiotics), decrease the risk of some diseases (e.g. cholesterol-lowering products), and could even be used for curing some illnesses.

2.       Development of Functional Foods

Functional food development implies the incorporation of specific bioactive compounds with positive physiological effects [7]. There are different technological strategies that modify food composition to accomplish health improvement by adding those bioactive compounds [8]. Most bioactive compounds characterized as nutraceuticals are derived from plants. Numerous bioactive components isolated from legumes, cereals, grains, fruits and vegetables have been shown to be efficacious in reducing lipid and cholesterol levels, increasing bone mineral density and antioxidant status as well as possessing anticancer properties [9]. However, of the hundreds of plant-derived nutraceuticals that have been identified, few have been incorporated into common foods for habitual consumption. Table 1 shows different functional components with their source and benefits.

3.       Functional Fruits

Apart from traditional fruits, the functional fruits and vegetables like pomegranate, kiwi, Cranberry, Bottle guard, Bitter guard have meticulous health beneficial effects. Some of them are discussed here:

3.1.  Pomegranate

The health benefits of pomegranate have been attributed to its wide range of phytochemicals, which are predominantly polyphenols, including primarily hydrolyzable ellagitannins, anthocyanins, and other polyphenols (Table 2). Antioxidant activity of pomegranate has been attributed to its high polyphenolic content, specifically punicalagins, punicalins, gallagic acid, and ellagic acid. 

Pomegranate juice exert antiatherogenic, antioxidant, antihypertensive, and anti-inflammatory effects.

·                     Punicic acid, a conjugated fatty acid present in pomegranate has an in vivo anti-inflammatory effect by limiting neutrophil activation and lipid peroxidation consequences. 

·                     Pomegranate fruit and derivates endowed with a very high antioxidant activity as an antiproliferative, antiinvasive, and pro-apoptotic agent in various cancer cell lines and animal models 
·                     The protective effects of pomegranate polyphenolics against UVA- and UVB-induced cell death of human skin fibroblasts may be attributed to reduced generation of intracellular ROS and increased intracellular antioxidant capacity
·                     Pomegarnate peel possesses antibacterial properties. Several studies conducted on aril juice is reported to possess anti viral activity.

3.2.  Kiwi Fruit

Kiwi fruit is rich in vitamin C, Lutein and Xanthine and exert strong antioxidant activity. It helps to prevent cardiovascular diseases, cancer, insomnia. It improves the iron absorption and digestion.

3.3.  Cranberry

Cranberry is a rich source of bioactive phenolic compounds with antiproliferative, antioxidant, anti-inflammatory, and antimicrobial activities. Cranberries contain bioactive compounds such as anthocyanins, flavonoids and tannins. Cranberry has been traditionally used to treat and prevent urinary-tract infections.

3.4.  Tomatoes

Lycopene is the principal component of the tomato. It exhibits strong antioxidant effects to higher number of conjugative double bonds. Lycopene helps in prevention of prostate cancer and stress induced diseases.

4.5. Amla

Amla is a rich source of Vitamin C. Amla enhances food absorption, balances stomach acid, fortifies the liver, nourishes the brain and mental functioning, supports the heart, strengthens the lungs, regulates elimination of free radicals, enhances fertility, helps the urinary system, increases skin health, promotes healthier hair, acts as a body coolant, flushes out toxins, increases vitality, strengthens eyes, improves muscle tone and, acts as an antioxidant. Amla is used for hair lose, eye sight, cardiovascular disease, diarrhea, digestion disorders etc. it possesses anti-ageing components and helps in mineral absorption.

Fruits industry byproducts are rich source of dietary fibres and other bioactive compounds. Several studies have been focused on extraction of bioactive compounds from FP (Struck et al., 2016) [31].

4.       Probiotics

Probiotics are defined as ‘‘live microorganisms, consumed in adequate numbers for health benefit on the host’’. Lactic Acid Bacteria (LAB) and bifidobacteria, the most studied and widely employed bacteria within the probiotic field, are normal components of the intestinal microbiota and have a long tradition of safe application within the food industry [32]. This success of dairy probiotics can partly be explained by their general positive image among consumers [33,34]. Recently, encapsulation was found as possible technology for decreasing sensitivity of probiotics [35,36]. Fruit juice has also been suggested as a novel, appropriate medium for fortification with probiotic cultures [37]. Now a days, encapsulation of active ingredients like probiotics is used to ensures that the bioactive compounds remain stabilized and maintains their bioavailability [38].

5.       Prebiotics

Prebiotics are non-digestible food ingredients that beneficially affect the host by stimulating the growth and/or activity of one or a limited number of bacteria in the colon, thus improving host health. Fructo-Oligosaccharide (FOS), inulin, Isomalto-Oligosaccharides (IMO), polydextrose, lactulose and resistant starch are considered as the main prebiotic components. Oligosaccharides play important role in obesity control [39]. Besides being prebiotics, these compounds have shown to increase calcium absorption, thus improve both bone mineral content and Bone Mineral Density (BMD) [40]. Furthermore, they influence the formation of blood glucose, and reduce the levels of cholesterol and serum lipids [41]. Prebiotics enhance the growth and survival of the probiotic cultures by influencing the growth and metabolites of both the probiotic and the starter. Due to the potential synergy between probiotics and prebiotics, foods containing a combination of these ingredients are often referred to as synbiotics [42].

6.       Functional drinks

Another important product category within the functional food segment is non-alcoholic beverages fortified with vitamins A, C and E or other functional ingredients. Although, there is a relatively high number of a product available in this segment e.g. functional drinks are those of cholesterol-lowering drinks (with combination of omega-3 and soy), ‘‘eye health’’ drinks (with lutein) or ‘‘bone health’’ drinks (with calcium and inulin) [43].

In India, the tea is popular drink among Indian population. In some regions, the tea is incorporated with different spices and herbs which add the nutritional value to tea. Several researchers have reported the health beneficial effects of herbal tea [44,45]. Masala tea becoming quite popular all over world and excellent for preventing seasonal diseases, cough, cold, fever and influenza etc (Table 3).

6.1.              Juice Blends: A Juice blend of Pomegranate, Amla and green turmeric is consider being excellent for post cancer operated patients and coronary heart diseases. The medicinal of pomegranate and amla is already mentioned in this article. The turmeric is also known for its meticulous antiseptic, antioxidant, anti-inflammatory, neuroprotective, cardioprotective, anti depression and anti ageing effects. Curcumin (generally 3%) is the main active ingredient in turmeric. It has powerful anti-inflammatory effects and is a very strong antioxidant. Curcumin also helps to relieve arthritis pain.

6.2.              Functional soup - Moringa dried/fresh leaves powder/paste soup amalgamated with sweet corn, green pea, ginger, black pepper and cardamom is commonly used by Indian population. Moringa leaves possess good quality proteins and several medicinal effects. Moringa is also rich in vitamin A, B and C and minerals like calcium, iron and phosphorous. Moringa helps in the prevention of diabetes and high blood pressure. Other components of soup also contribute to the excellent taste and medicinal value.

7.       Functional cereals

Oat and barley, offer another alternative for the production of functional foods. Cereals can be used as fermentable substrates for the growth of probiotic microorganisms. Additionally, cereals can be applied as sources of non-digestible carbohydrates that besides promoting several beneficial physiological effects can also selectively stimulate the growth of lactobacilli and bifidobacteria present in the colon and act as prebiotics. Cereals contain water soluble fiber, such as beta-glucan and arabinoxylan, oligosaccharides, such as galacto and fructo-oligosaccharides and resistant starch, which have been suggested to fulfill the prebiotic concept. Finally, cereal constituents, such as starch, can be used as encapsulation materials for probiotics in order to improve their stability during storage and enhance their viability during their passage through the adverse conditions of the gastrointestinal tract [46].

Some functional cereal components such as beta-glucan, however, applied also in the dairy and bakery industries. Recent research has focused on the use of beta-glucans, in the manufacture of low-fat ice creams and yogurts. Incorporation of beta-glucans with other soluble dietary fiber, into low-fat dairy products can make their mouthfeel, scoopability and sensory properties resemble those of full-fat products [46].

Food industrial By-Products (BP) are rich sources of functional ingredients, such as fibre, minerals, and phytochemicals can be fortified in bakery products [47-49].

In India, the lactating women take some traditional food supplements made from Rice/Wheat Flour, dry fruits, nuts and seeds, ghee (Clarified Butter), resins, herbs, brown/black pepper, coconut shreds, gums etc. These traditional supplements are not only energy rich but also provide minerals and vitamins (Table 4).

8.       Functional meat

Meat and its derivatives may also be considered functional foods to the extent that they contain numerous compounds thought to be functional. The idea of using food for health purposes rather than for nutrition opens up a whole new field for the meat industry. In addition to traditional presentations, meat industry can explore various possibilities, including the control of the composition of raw and processed materials via reformulation of fatty acid profiles or inclusion of antioxidants, dietary fiber or probiotics, etc [50].

9.       Perspectives

The future viability and success of functional foods in the marketplace depend on several elements. The key issue is consumer acceptance of such products. For consumers to agree to pay the cost associated with functional foods, they must be convinced by its health claims through clear, truthful, and unambiguous messages.

Table 1: Examples of Functional Components.

Table 2: Functional components of different parts of pomegranate.

Table 3: Components of Masala tea.

Table 4: Functions of Components of Traditional Food Supplements for lactating women.

1. Koletzko B, Aggett PJ, Bindels JG, Bung P, Ferré P, et al. (1998) Growth, development and differentiation: a functional food science approach. Braz J Nutr 80: 35-45.
2. Roberfroid MB (2007) Concepts and strategy of functional food science: the European perspective. Am J Clin Nutr 71: 1660-1664.
3. Hilliam M (2000) Functional food: How big is the market?. The World of Food Ingredients 12: 50-52.
4. Side C (2006) Overview on marketing functional foods in Europe. Functional food network general meeting.
5. Fern E (2007) Marketing of functional foods: A point of view of the industry. International developments in science and health claims, ILSI international symposium on functional foods in Europe.
6. Food and Agriculture Organization of the United Nations (FAO) (2007) Report on Functional Foods, Food Quality and Standards Service (AGNS).
7. Hamer M, Owen G, Kloek J (2005) The role of functional foods in the psychobiology of health and disease. Nutrition Research Reviews 18: 77-88.
8. Duchateau GSMJ, Klaffke W (2008) Product composition, structure, and bioavailability. Food Bio- physics 3: 207-212.
9. Eskin NAM, Tamir S (2006) Dictionary of nutraceuticals and functional foods. Taylor and Francis Group/CRC Press, Boca Raton, FL.
10. Sarin R, Sharma M, Singh R, Kumar S (2012) Nutraceuticals: A Review. International Research Journal of Pharmacy 3: 95-99.
11. Poyrazoglu E, Gökmen V, Artιk N (2002) Organic acids and phenolic compounds in pomegranates (Punica granatum L.) grown in Turkey. J Food Comp Anal 15: 567-575.
12. Ignarro LJ, Byrns RE, Sumi D, de Nigris F, Napoli C (2006) Pomegranate juice protects nitric oxide against oxidative destruction and enhances the biological actions of nitric oxide. Nitric Oxide 15: 93-102.
13. Lansky EP, Newman RA (2007) Punica granatum (pomegranate) and its potential for prevention and treatment of inflammation and cancer. J Ethnopharmacol 109: 177-206.
14. Heber D, Seeram NP, Wyatt H, Henning SM, Zhang Y, et al. (2007) Safety and antioxidant activity of a pomegranate ellagitannin-enriched polyphenol dietary supplement in overweight individuals with increased waist size. J Agric Food Chem 55: 10050-10054.
15. Mousavinejad G, Emam-Djomeh Z, Rezaei K, Khodaparast MHH (2009) Identification and quantification of phenolic compounds and their effects on antioxidant activity in pomegranate juices of eight Iranian cultivars. Food Chem 115: 1274-1278.
16. Jaiswal V, DerMarderosian A, Porter JR (2010) Anthocyanins and polyphenol oxidase from dried arils of pomegranate (Punica granatum L.). Food Chem 118: 11-16.
17. Ozgul-Yucel S (2005) Determination of conjugated linolenic acid content of selected oil seeds grown in Turkey. J Am Oil Chem Soc 82: 893-897.
18. Fadavi A, Barzegar M, Azizi HM (2006) Determination of fatty acids and total lipid content in oilseed of 25 pomegranates varieties grown in Iran. J Food Comp Anal 19: 676-680.
19. El-Nemr SE, Ismail IA, Ragab M (2006) Chemical composition of juice and seeds of pomegranate fruit. Die Nahrung 34: 601-606.
20. Sassano G, Sanderson P, Franx J, Groot P, Van Straalen J, et al. (2009) Analysis of pomegranate seed oil for the presence of jacaric acid. J Sci Food Agric 89: 1046-1052.
21. Van Elswijk DA, Schobel UP, Lansky EP, Irth H, Van Der Greef J (2004) Rapid dereplication of estrogenic compounds in pomegranate (Punica granatum) using on-line biochemical detection coupled to mass spectrometry. Phytochem 65: 233-241.
22. Amakura Y, Okada M, Tsuji S, Tonogai Y (2000) High-performance liquid chromatographic determination with photodiode array detection of ellagic acid in fresh and processed fruits. J Chromatog A 896: 87-93.
23. Seeram NP, Aviram M, Zhang Y, Henning SM, Feng L, et al. (2008) Comparison of antioxidant potency of commonly consumed polyphenol-rich beverages in the United States. J Agric Food Chem 56: 1415-1422.
24. Ercisli S, Agar G, Orhan E, Yildirim N, Hizarci Y (2007) Interspecific variability of RAPD and fatty acid composition of some pomegranate cultivars (Punica granatum L.) growing in southern Anatolia region in Turkey. Biochem Syst Ecolo 35: 764-769.
25. Lan J, Lei F, Hua L, Wang Y, Xing D, et al. (2009) Transport behavior of ellagic acid of pomegranate leaf tannins and its correlation with total cholesterol alteration in HepG2 cells. Biomed Chromatogr 23: 531-536.
26. Kaur G, Jabbar Z, Athar M, Alam MS (2006) Punica granatum (pomegranate) flower extract possesses potent antioxidant activity and abrogates Fe-NTA-induced hepatotoxicity in mice. Food Chem Toxicol 44: 984-993.
27. Aviram M, Volkova N, Coleman R, Dreher M, Reddy MK, et al. (2008) Pomegranate phenolics from the peels, arils, and flowers are antiatherogenic: studies in vivo in atherosclerotic apolipoprotein E-deficient (E0) mice and in vitro in cultured macrophages and lipoproteins. J Agric Food Chem 56: 1148-1157.
28. Neuhofer H, Witte L, Gorunovic M, Czygan FC (1993) Alkaloids in the bark of Punica granatum L. (pomegranate) from Yugoslavia. Pharmazie 48: 389-391.
29. Gil MI, Tomas-Barberan FA, Hess-Pierce B, Holcroft DM, Kader AA (2000) Antioxidant activity of pomegranate juice and its relationship with phenolic composition and processing. J Agric Food Chem 48: 4581-4589.
30. Viuda-Martos M, Lopez J, Alvarez JA (2010) Pomegranate and its Many Functional Components as Related to Human Health: A Review. Comprehensive Reviews in food Science and Food Safety 9: 635-654.
31. Struck S, Plaza M, Turner C, Rohm H (2016) Berry pomace e a review of processing and chemical analysis of its polyphenols. International Journal of Food Science & Technology 51: 1305-1318.
32. Kociubinski G, Salminen S (2006) Probiotics: Basis, state of the art and future perspectives. Functional food network general meeting.
33. Makinen-Aakula M (2006) Trends in functional foods dairy market. In Proceedings of the third functional food net meeting.
34. Szakaly Z, Szigeti O, Mathe A, Szente V (2007) Nutrimarketing in the service of functional foods. International developments in science and health claims, ILSI international symposium on functional foods in Europe.
35. Clair AL (2007) New challenging food applications of probiotics. In Proceedings of the fourth international FFNet meeting on functional foods.
36. Mattila-Sandholm T, Myllarinen P, Crittenden R, Mogensen G, Fonden R, et al. (2002) Technological challenges for future probiotic foods. International Dairy Journal 12: 173-182.
37. Tuorila H, Cardello AV (2002) Consumer response to an off-flavour in juice in the presence of specific health claims. Food Quality and Preference 13: 561-569.
38. Martın MJ, Lara-Villoslada F, Ruiz MA, Morales ME (2015) Microencapsulation of bacteria: a review of different technologies and their impact on the probiotic effects. Innov Food Emerg Technol 27: 15-25.
39. Bosscher D (2007) Slimming foods: Latest evidence in the field of non-digestible carbohydrates. Focus on oligosaccharides. In Proceedings of the fourth international FFNet meeting on functional foods.
40. Bosscher D, Van Loo J, Franck A (2006) Inulin and oligofructose as functional ingredients to improve bone mineralization. International Dairy Journal 16: 1092-1097.
41. López-Molina D, Navarro-Martínez MD, Rojas Melgarejo F, Hiner AN, Chazarra S, et al. (2005) Molecular properties and prebiotic effect of inulin obtained from artichoke (Cynara scolymus L.). Phytochemistry 66: 1476-1484.
42. Gibson GR, Roberfroid MB (1995) Dietary modulation of the human colonic microbiota: Introducing the concept of prebiotics. Journal of Nutrition 125: 1401-1412.
43. Keller C (2006) Trends in beverages and ‘‘Measurable Health’’. In Proceedings of the third functional food net meeting.
44. Zaveri NT (2006) Green tea and its polyphenolic catechins: Medicinal uses in cancer and noncancer applications. Life Sciences 78: 2073-2080.
45. McKay DL, Blumberg JB (2006) A review of the bioactivity and potential health benefits of peppermint tea (Mentha piperita L.). Phytother Res 20: 619-633.
46. Brennan CS, Cleary L J (2005) The potential use of cereal (1-3, 1-4)-b- D -glucans as functional food ingredients. Journal of Cereal Science 42: 1-13.
47. Belghith Fendri L, Chaari F, Maaloul M, Kallel F, Abdelkafi L, et al. (2016) Wheat bread enrichment by pea and broad bean pods fibers: Effect on dough rheology and bread quality. LWT - Food Science and Technology 73: 584-591.
48. Ben Jeddou K, Bouaziz F, Zouari-Ellouzi S, Chaari F, Ellouz-Chaabouni S, et al. (2017) Improvement of texture and sensory properties of cakes by addition of potato peel powder with high level of dietary fiber and protein. Food Chemistry 217: 668-677.
49. Wani AA, Sogi DS, Singh P, Khatkar BS (2015) Influence of watermelon seed protein concentrates on dough handling, textural and sensory properties of cookies. Journal of Food Science and Technology 52: 2139-2147.
50. Scollan N (2007) Enhancing the content of beneficial fatty acids in beef and improving meat quality for the consumer. Functional Foo