**2. Contributions of fermented foods to human nutrition**

Human health is one of the main reasons behind food choices and this has led to a diverse range of food formulations with specific functionalities that provide better health and wellness. One of the common health disorders associated with diet patterns is gastrointestinal (GI) disorders. Such GI disorders can be prevented to some extent through routine consumption of foods with specific functionality [21]. Hence, the concept of functional foods evolved as the role of food in maintaining health and wellbeing and therefore gained greater scientific and commercial interest [22]. Lactic acid

bacteria and bifidobacteria are well known for their extensive use in the preparation of functional food products [21]. These organisms have been termed as "probiotic bacteria," which does impart certain specific health-promoting attributes through oral feeding. Simultaneously with probiotics, the other term "prebiotics" are known to be non-digestible food ingredients (higher polysaccharides) that have a beneficial effect on the host by selectively stimulating the growth and/or activity of a selected group of bacterial genera and species that are normal colon inhabitants [23].

Probiotics should have the competence to grow and sustain in the human gut in order to deliver health benefits to the host. Therefore, they must have the characteristics to survive while passing *via* the gastrointestinal tract (GIT). During this process, they get exposed to the acidic environment in the stomach, while the bile acid is in the small intestine [24]. Most of the probiotic strains are natural inhabitants of the human intestine and are generally regarded as safe (GRAS) along with acid and bile tolerance and the ability to adhere to gut epithelial cells [25, 26]. Hence, the best designed route for the entry of these probiotic bacteria is the diet, both for animals and human beings [27]. Fermented foods based on milk, cereals, and legumes are among the most accepted food carriers for the delivery of viable probiotic cultures [24]. Probiotic bacteria and their fermentation products appear to influence human health, wherein they provide colonization resistance against potentially pathogenic microorganisms [28].

Fermentation plays mainly important roles like improving the nutritional qualities of food by enhancing the flavor, aroma, and texture of food, contributing toward the preservation of food by the production of main compounds such as lactic acid, acetic acid, alcohol, and alkaline contents. The protein, vitamins, essential amino acids, and fatty acids are enriched by converting the food substrates naturally. During fermentation processes detoxify the food products. Finally, it can be claimed that the fermentation process decreases the cooking periods and requirements of fuel [2].

In several studies, researchers have demonstrated the ability of probiotic bacteria to inhibit pathogenic bacteria by the production of organic acids like lactic and acetic acids during the fermentation process, which lowers the pH of the intestine and consequently inhibits the growth of the undesirable bacteria [29]. In addition to these beneficial health effects, researchers have demonstrated that the major end products of fermentation in humans are short-chain fatty acids (SCFA) like those of acetate, propionate, and butyrate [30, 31]. Besides, a few other antimicrobial substances produced widely by lactic acid bacteria include hydrogen peroxide, carbon dioxide, diacetyl, and bacteriocins [32]. Probiotic bacteria like LAB and bifidobacteria are also known to synthesize folate, vitamin B12, and vitamin K, which are vital components of the human diet and involved in the biosynthesis of nucleotides and cofactors in many metabolic reactions [33].

There has been substantial evidence for the benefits of probiotics and prebiotics in the lowering of (i) lactose intolerance through the activity of β-galactosidase; (ii) antibiotic-associated diarrhea; (iii) colon carcinogenesis; (iv) hypocholesterolemic effect, and (v) gut mucosal dysfunction [34–38].

### **3. Traditional fermented foods**

#### **3.1 Background scenario**

Fermentation is one of the oldest methods of preserving food, which became popular at the beginning of civilization as it led to the development of a variety of *Indian Traditional Fermented Foods: The Role of Lactic Acid Bacteria DOI: http://dx.doi.org/10.5772/intechopen.110741*

tastes, flavors, textures, forms, and other sensory attributes. As a process, it involves the transformation of simple raw materials into a range of value-added products, using the phenomena of microorganism growth and their activities on different substrates. Therefore, knowledge of microorganisms' characteristics is essential to understand the fermentation process [4]. Indian-fermented foods such as *dahi*, *rai*, *gundruk*, *koozh, kanjika, sinki*, *iromba*, *handua,* and *iniziangsang* have been considered as important nutritious diets with significant medicinal properties. Among these fermented food products *koozh*, *dahi,* and *kanjika* are habitually consumed by the local population because of their health benefits [39]. Currently, various fermented foods and beverages have evolved over the years.

#### **3.2 Nutritional status of Indian traditional foods**

In the background of a diverse range of traditional Indian foods, the most popular and widely consumed are those based on either milk alone or cereals and legumes with milk. The scientific knowledge on nutritional benefits derived from milk and dairy products is well documented. On the other hand, the same is not true with those of cereals and legumes-based foods, as the raw materials available are specific to the region and store house of complex nutrients. This complexity is linked to the type of fermentation process, product preparation parameters, and final profile that offers ample opportunities to highlight the importance of nutritional constituents in cereals and legumes-based Indian traditional foods.

Cereals and legumes are considered one of the most important sources of dietary proteins, carbohydrates, vitamins, minerals, and fiber for human nutrition. Often, the nutritional quality of cereals and legumes is not on par with that of milk and dairy products. This is further attributed to the complex nature of macronutrients, as well as the prevalence of antinutritional factors, which makes their bioavailability more difficult [40]. In addition, processing methods like soaking, sprouting, milling, fermentation, and cooking/heating have enabled the improvement of nutritional attributes of cereals and legumes [41].

In general, the natural fermentation of cereals and legumes leads to a decrease in the level of complex carbohydrates such as non-digestible poly- and oligosaccharides. In addition, certain amino acids and vitamins, especially B-group vitamins, can be synthesized and become available. Increased amounts of riboflavin, thiamine, niacin, and lysine due to the action of LAB in fermented cereal mixtures were reported in some of the studies [42, 43]. Fermentation also provides ideal pH conditions for the enzymatic degradation of phytate, which is present in cereals in the form of complexes with iron, zinc, calcium, magnesium, and proteins. This reduction in phytate can increase the bioavailability of iron, zinc, and calcium in several folds [40, 44–48]. Thus, fermentation is known to prolong shelf life and impart improved and acceptable texture, taste, and aroma to the final product. During the cereal fermentation process, several volatile compounds are formed, which contribute to a complex mixture of flavors in the products [40]. The presence of aromas representative, that is, diacetyl, acetic acid, and butyric acid make fermented products based on cereals and legumes more appetizing. In many parts of the world, traditional fermented foods are prepared from the most common types of cereals and pulses, such as rice, wheat, soy bean, sorghum. Some of them are utilized as breakfast or light meals, beverages, and colorants, while some are used as main food meals in the regular diet.

Most of these food products are naturally fermented, which mainly encompasses mixed cultures of LAB, yeasts, and fungi. Often, the predominant microflora can be functionally similar, while few others can become functional in a sequential manner with an altered environment due to the fermentation process. Common fermenting bacteria are species of *Lactobacillus, Leuconostoc, Streptococcus, Pediococcus, Micrococcus,* and *Bacillus*. The fungal genera known to be commonly present are *Aspergillus, Cladosporium, Fusarium, Penicillium,* and *Trichothecium*. Common fermenting yeasts are species of *Saccharomyces*, which generally predominate in an alcoholic fermentation [49]. The type of bacterial flora developed in each fermented food depends on the water activity, pH, salt concentration, temperature, and the composition of the food matrix.

The lactic fermentation process enhances the nutritional value, shelf life, safety, and acceptability of a varied range of cereal-based foods [50]. In this process, cereal grains are commonly cleaned, followed by immersion in water for a few days. During this period, there will be the progression of naturally occurring microorganisms which will result in an increase in the LAB population. Moreover, in this course, the endogenous amylases of the grains become active and produce fermentable sugars that aid as an energy source for the LAB. Considering that other practices including grinding, salting, or heating can also change the properties of the final product [47].

A variety of indigenous fermented foods that are prepared in India are basically using cereals with a combination of legumes, which improves the overall protein quality of the food products. Because, cereals contain the highest amount of cysteine and methionine, but lack lysine content, whereas legumes are rich in lysine but lack sulfur-containing amino acids. Therefore, the overall quality of the protein in food products can be improved by mixing both cereals and legumes [51].

In fermented foods like *idli*, *dosa,* and *dhokla*, the fermenting desirable microflora is considered essential for the leavening of the batter and for acid production in *idli* [52, 53]. Fermentation of *idli* batter appears to significantly increase the essential amino acids and simultaneously reduce the antinutrients (phytic acid), enzyme inhibitors, and flatus-causing sugars [54].

#### **3.3 Milk-based fermented foods**

Fermentation of milk, either knowingly or unknowingly, has occurred since the earliest times, resulting in various fermented milk products. Fermented dairy products are known for their taste, nutritive value, and therapeutic properties. The nature of these products differs from region to region depending on the indigenous microflora, which in turn depends upon the surrounding environmental factors [55]. The most popular traditional fermented milk products from the Indian subcontinent are *Dahi*, *Cheese* (*Chhurpi*), *Chhur churpen, Philu, mohi*, *Mishti doi*, *Shyow, Somar, Lassi*, *Shrikhand,* and others. The use of desired microorganisms as in the case of controlled fermentation would greatly increase the chances of obtaining products with uniform and consistent quality of acceptable attributes [56].

Lactic acid bacteria convert the lactose from the milk into lactic acid and selective strains produce an antibacterial substance, that is, bacteriocin to destroy milk curdling by unwanted bacteria. For example, in milk, when *Lactococcus lactis* is inoculated, it converts lactose into energy (Adenosine triphosphate ATP) by enzyme synthesis. Here, lactic acid is the byproduct of ATP that coagulates milk, which can be utilized for the preparation of whey and cheese. Therefore, the bacterium is not just curdling the milk, but it preserves the products by inhibiting the growth of unwanted microorganisms that is by lowering the pH of the product by lactic acid production.

#### *Indian Traditional Fermented Foods: The Role of Lactic Acid Bacteria DOI: http://dx.doi.org/10.5772/intechopen.110741*

Some "food grade" starter strains, that is, *L. lactis* ssp. *lactis* produce nisin, are an antibiotic-like substance called a bacteriocin. It has natural antimicrobial activity against a wide variety of Gram-positive bacteria, including food-borne pathogens such as *Listeria monocytogenes, Staphylococcus aureus*, *Bacillus cereus,* and *Clostridium* sp. It is believed that the nisin's primary target is the cell membrane, which does not need a receptor to interact with the cell membrane of the microbe. It is a natural preservative prevalent in cheeses prepared with *L. lactis* ssp. *lactis* and is currently recognized as a safe food preservative. Hence, it is used as a preservative in thermally processed and low pH foods, also in various pasteurized dairy products and canned vegetables, baked, beverages, high-moisture flour products, and pasteurized liquid eggs. As nisin cannot be chemically synthesized, the nisinproducing *L. lactis* strains are used for their industrial synthesis. A highly purified nisin preparation has led to an interest in the use of nisin for human ulcer therapy and mastitis control in cattle, while different enzymes and other metabolic products produced by *Lactococcus lactis* contribute to the more subtle aromas and flavors that distinguish different cheeses.

Most foods mentioned below in this category are prepared by simply adding LAB to the milk of cow, buffalo, or yak and allowed to ferment.

#### *3.3.1 Dahi*

*Dahi* is one of the most popular fermented dairy products on the Indian subcontinent highly accepted for its mild acidic taste and pleasant flavor. The main properties of good quality *dahi* are steady with uniform consistency, sweet aroma, and light sour taste. The surface of the *dahi* will be smooth, shiny, and free of cracks as well as gas bubbles. It is believed that *dahi* possesses nutritional and therapeutic values at a higher level when compared to the milk utilized for its preparation. *Dahi* is easy to digest and has been found to possess several health benefits [57]. One of the primary compositions of *dahi* made with whole milk is as follows: water 85–88%, fat 5–8%, protein 3.2–3.4%, lactose 4.6–5.2%, lactic acid 0.5–1.1%, ash 0.7–0.75%, calcium 0.12–0.14%, and phosphorus 0.09–0.11% as reported by Laxminarayana et al. [58].

The lactic acid bacterial cultures commonly associated with the inoculum are strains of *Lactococcus lactis* ssp. *lactis*, *Lactococcus lactis* ssp. *cremoris*, *Lc*. *lactis* ssp. *diacetylactis*, *Leuconostoc cremoris*, *Lactobacillus delbrueckii* ssp. *bulgaricus*, *Lactobacillus acidophilus*, and *Lactobacillus helveticus*. Choosing a good starter culture is important to attain a good flavor with desirable characteristics. Both mesophilic and thermophilic starters have been reported to be used in a number of different combinations [59, 60]. The addition of probiotic cultures such as *Lactobacillus* acidophilus and Bifidobacterium bifidum combined with the regular lactic cultures for *dahi* preparation helps to increase the therapeutic and nutritional value [61]. *Dahi* has been recognized as a potential source of lactic acid bacteria, chiefly species of *Lactobacillus* that are active against foodborne pathogenic and spoilage bacteria such as *Staphylococcus aureus*, *Bacillus cereus*, Bacillus licheniformis, Bacillus subtilis, Escherichia coli and *Klebsiella* sp., and *Pseudomonas* sp. [62]. In addition, a strain of *Lactobacillus* delbrueckii ssp. *bulgaricus* produces heat-resistant bacteriocin with broad-spectrum antibacterial activity and the potential for use as a food biopreservative isolated from *dahi* [63]. As such, *dahi* differs from yogurt in the use of mixed starters of mesophilic lactococci. Diacetyl is one of the main metabolites that induce flavor in *dahi* products, which is accepted more by South Asian origin people than acetaldehyde flavor in yogurt (**Figure 1**) [64].

**Figure 1.** *Dahi (courtesy: Zee news).*

#### *3.3.2 Cheese*

*Cheese* (*Chhurpi*) made from yak and cattle milk is mainly consumed in the Himalayan plateau and industrial production of this product has not yet become the norm. *Chhurpi* is in white color, soft in texture with a mild to strong flavored taste, and is eaten as a curry blend with edible wild ferns (*Diplazium* spp.), pickles, and condiments along with cooked rice in meals [65]. Yak cheese contains the following chemical composition, 68.2% of total solid, 49.4% of butterfat on a dry matter basis, and 1.37% of salt [66, 67]. In mature *Chhurpi*, LAB count 7.5 log CFU/g was recorded. All LAB strains except *Leuconostoc mesenteroides* BFE1637 showed a high level of hydrophobicity. This is an important property of LAB that helps to colonize epithelial cells. LAB strains produce enzymes such as peptidases and esterase-lipases that play an important role in the improvement of *cheese* quality.

Similarly, *Chhu*, *Shyow*, *Mohi*, *Somar*, and *Philu* are traditional fermented milk products in the Himalayan plateau, predominantly fermented by LAB. *Chhu* (*Sheden*) is a strong-flavored cheese-like product, LAB were mainly present at 8.1–8.8 log CFU/g. *Shyow* is a thick curd-like product, prepared with yak milk. *Mohi* is buttermilk, prepared with churning *dahi*, consumed as a refreshing beverage. *Somar* is a soft paste, strong flavored with a bitter taste, eaten as a soup along with cooked rice or finger-millets, whereas *Philu* is a typical indigenous cream-like milk product obtained from cow milk or yak milk and is consumed as a cooked paste delicacy with boiled rice [68, 69]. These products are rich in LAB that produces various enzymes such as esterase, phosphatase, leucine-arylamidase, β-galactosidase, and peptidase. These bacterial strains inhibited the growth of pathogens such as Enterobacter agglomerans, Enterobacter cloacae*,* and Klebsiella pneumoniae. Fermented milk products have been reported to contain more common LAB such as Streptococcus cremoris, Streptococcus lactis, Streptococcus thermophilus*, Lactobacillus* bulgaricus*, Lactobacillus* acidophilus*, Lactobacillus* helveticus*, Lactobacillus cremoris, Lactobacillus* plantarum*, Lactobacillus* curvatus*, Lactobacillus* fermentum, *Lactobacillus* paracasei *subsp. pseudoplantarum, Lactobacillus* alimentarius*, Lactobacillus kefir, Lactobacillus* hilgardii*,* Enterococcus faecium*, L. mesenteroides, Lactobacillus* farciminis*, Lactobacillus* brevis*,* Lactococcus lactis *subsp. cremoris, Lactobacillus* casei *subsp. Casei*, and *Lactobacillus* bifermentans (**Figure 2**) [39].

*Indian Traditional Fermented Foods: The Role of Lactic Acid Bacteria DOI: http://dx.doi.org/10.5772/intechopen.110741*

**Figure 2.** *Cheese (courtesy: Healthy nibbles).*
