Tremendous changes in lifestyle, eating habits are causing an irreversible change that is leading to multitude of health problems. Due to huge expenditure on health care each year, consumers’ desire for food products with desired health benefits continues to grow. Consumers are interested in foods that boost the immune system, reduce the risk of disease and enhance health. Nowadays, functional foods are gaining public acceptance in several countries.
A major development in functional foods pertains to foods containing probiotics and prebiotics which help in implanting health promoting microbial flora in the intestine. Fermentation has always remained the most reliable technique to develop new exotic health foods. Recently, the importance of prebiotic factors like spirulina, honey, lupin seed, oat bran, green banana flour, etc. in promoting the growth of probiotic microorganisms inside the colon is gaining acceptance.
The new approach in this area is the development of ‘synbiotic drinks’ which are known to impart the beneficial effects of both probiotics and prebiotics. When both prebiotics and probiotics are present in a food, such foods are referred to as ‘synbiotic’. A variety of traditional foods such as toddy, kanji, lugri, bushera, pozol, bushera, etc. are known to contain live probiotic microorganisms like Lactobacillus spp. thereby exhibiting synbiotic properties.
Food and Agriculture Organization (FAO) and World Health Organization (WHO) defines probiotics as ‘live microorganisms which when administered in adequate amounts confer a health benefit on the host.’ Probiotics are the microorganisms (bacteria or yeasts) that can help to reestablish and recolonise the human intestinal microbiota to exert beneficial health effects on the host. Probiotic products with health claims should have viable microorganisms at levels of 106–107cfu/mL or g or even at higher levels at the time of consumption. Probiotic strains (especially Lactobacillus and Lactococcusspecies) inhibit the growth of pathogenic microorganisms, by occupying the mucosal layer and epithelial cell surface, and also by producing antimicrobial agents such as bacteriocins or bacteriocin-like molecules, organic acids, and hydrogen.
Interest for probiotics has arisen in recent years especially in relation to the addition of Bifidobacterium, Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus casei, Lactobacillus reuteri to the fermented dairy products such as yoghurt. Lactobacillus acidophilus and Bifidobacteriumanimalis subsp. lactis are lactic acid bacteria (LAB) that are most frequently used as probiotics. One of the optimal combination of probiotic bacteria is a culture called ABT which has a combination of L. acidophilus, Bifidobacteriumlactis and S. thermophilus.Probiotics that possess antimicrobial, antidiarrhoeal and anti-inflammatory properties may offer several clinical applications. Certain probiotics have lactase activity, which is needed to properly digest lactose. Probiotics can reduce antibiotic-associated infections and diarrhoea; immune system is reported to be stimulated.
The function of a prebiotic component is selective stimulation of certain intestinal bacteria, particularly LAB such as Bifidobacteriaand Lactobacilli. Prebiotics cannot be digested by enzymes in the small intestine but are fermented by probiotic bacteria in the large intestine. Hence prebiotics show fiber-like properties, mainly stool bulking. Short-chain fatty acids (SCFA) mainly acetate, propionate and butyrate are formed and the decrease in pH enables reduction in the number of pathogenic microorganisms. The fermentation of prebiotics by the probiotic bacteria improves the host’s health by enhancing the absorption of minerals such as Ca, Mg, and Fe and producing compounds capable of preventing colon cancer.
The prebiotic compounds can be classified based on their chemical nature, chain length or degree of polymerisation (DP), mode of usage, and so on. Depending on the chemical nature, prebiotic compounds are categorised as (a) saccharide derivatives (disaccharides, oligosaccharides and polysaccharides), (b) proteins or peptides, and (c) lipids.
A number of food ingredients have been shown to be prebiotics. These include lactulose, lactitololigofructose, inulin and galacto-oligosaccharides, tagatose, iso-malto-oligosaccharides, polydextrose, and digestive resistant maltodextrin.
Most of the saccharide derivative prebiotics from plant origin include oligosaccharides (namely fructo-, gluco-, galacto-, isomalto-, xylo-, and soy-oligosaccharides), inulin, lactulose, lactosucrose, guar gum, resistant starch, pectin and chitosan. Potential plant sources for prebiotic carbohydrates include cereals and legume crops like barley, wheat, chickpea and lentils; vegetables like chicory, Jerusalem artichoke, onion, garlic, okra, and leek; and fruits like dragon fruit, jack fruit, palm fruit, nectarine and mushroom.
Prebiotic Ingredients of Plant Origin in Milk Products
High quality functional beverage mixes were produced by mixing each of yoghurt and Rayeb(traditional Egyptian natural fermented milk) with carrot juice (from red and yellow carrots). Such mixes had live LAB that served as probiotics; additionally it had natural antioxidants and used to overcome vitamin A deficiency. The role played by some valued prebiotic ingredients in fermented dairy products is depicted in Table 1.
Prebiotic Ingredients from other Source Honey
It contains oligosaccharide and is reported to exert antioxidant activity. Traditional fermented milk lassi has been used as a vehicle to carry probiotic bacteria where honey served as a natural source of prebiotic; synbioticlassi was developed using probiotic Lactobacillus helveticus MTCC 5463 and honey.
The oligosaccharides in honey stimulated the growth of good bacteria (Bifidobacteriain fermented dairy food) in the colon. The prebiotic effect of honey is greater than that of inulin. The growth of probiotic cultures such as B. longum, B. breve and B. infantis was enhanced to a greater extent when using honey rather than use of inulin or fructo-oliogosaccharide as a prebiotic ingredient.
Itis the best known genus of Cyanobacteria. Consumption of Spirulinais beneficial to health due to its essential amino acids, vitamins, natural pigments, and fatty acids, especially -6 representatives such as g-linolenic acid, a precursor of the prostaglandin hormones in the body. In addition it contains high amount of calcium, vitamin B12, Vitamin A, B2, B6, E, K and H, and many essential minerals (including iron) and enzymes. Spirulina have antiviral, anti-inflammatory and anti-tumour effects and has been implicated in reducing the blood lipid profile, blood sugar, body weight and reduced wound healing time. Spirulina could enhance the growth and increase the viability and acid production of probiotics in the milk product (yoghurt, acidophilus milk). Yoghurt has been made successfully utilisingBifidobacteriumanimalisas probiotic culture taking help of 0.3 % Spirulinaplatensispowder as a prebiotic.
Recent Developments in Synbiotic Drinks
Recently considerable research has been focused on the development of probiotic drinks utilising sources such as cereals, fruits and vegetables which serve as prebiotics. LAB with improved functionality of colonic strains has been achieved in presence of prebiotics such as non-digestible components viz., glucan, arabinoxylan, oligosachharides, resistant starch in cereals; and glucose, fructose, hemicelluloses and dietary fibersin fruits and vegetables. Cereals have also been investigated for their potential use in developing functional foods. Cereals contain water-soluble fibre (i.e. ?-glucan, arabinoxylan), oligosaccharides (i.e. galacto- and fructo-oligosaccharides) and resistant starch which fulfils prebiotic concept.
Lactobacillus acidophilus strains have been used as probiotic bacteria in various food formulations such as yoghurt, curd and ice cream. A barley-based probiotic food mixture using L. acidophilus has been developed. Freeze dried cultures of L. acidophilus NCDC 14 has proven therapeutic benefits. The optimum levels of sprouted wheat flour, oat, sprouted wheat bran and guar gum were 7.86, 5.42, 1.42 and 0.6 g respectively per 100 mL of water for the sprouted wheat-based probiotic beverage; high probiotic count could be achieved in such beverage. The wheat-based probiotic beverage (per 100 ml) had 13.19% total solids, 1.19% protein, 0.33% fat, 11.56% carbohydrates, 0.10% ash, 0.42% crude fiber, 1.45 mg iron, 15.74 mg calcium; probiotic count was 10.43 log10cfu/mL.
Examples of Probiotic Drinks
Acidophilus Milk: It is a type of fermented dairy product utilisingL. acidophilus as the culture. Bacteria populate in intestinal system and prevent the activity of harmful gas forming microorganisms. It is beneficial to people with diarrhoea and intestinal gas problems.
Acidophilus Milk and Bifidus-Acidophilus Milk: Bifidus milk is the first infant product produced with Bifidobacteria. It is produced using Bifidobacteriumbifidum and B. longum isolated from healthy humans faeces, which has ability to form L(+) lactic acid. The final product contained 108-109 cfu/ml bacteria. Acidophilus-Bifidus milk, (known as AB culture), is a fermented dairy product which is produced with L. acidophilus and Bifidobacterium species.
Yakult: It is a probiotic dairy product which is produced with L. casei strain Shirota. Such culture is resistant to gastric and duodenal acid, can populate and form antimicrobial substances in small intestine and has the ability to improve the activity and quantity of macrophages.
Other Functional Dairy Products: Sweden-based Skane Dairy’s ProViva fruit drink labelled ProViva reduces the build-up of gas in the stomach. Group Danone is marketing in the US DanActive daily dose drinks sold in 100 mL mini-bottles, labelled DanActive. Such products help strengthen the body’s immunity.
Changes in lifestyle and eating habits have led to considerable array of health problems and chronic diseases. Due to growing global concern on nutrition and personal health, functional foods are gaining public acceptance in many countries. Fermented foods are of great significance since they provide and preserve nutritious foods in a diversity of flavours, aromas and textures, while enriching the human diet. In this context, the consumer perception and demand for fermented dairy products with “health promoting” properties, such as probiotic and synbiotic products, have increased. This is a key factor driving value sales growth in global markets.
(RachanaRathwa is Assistant Professor and AtanuJana is Professor and Head, Department of Dairy Technology, SMC College of Dairy Science, Anand Agricultural University. They can be contacted at firstname.lastname@example.org)