**1. Introduction**

The production of fermented foods is one of the oldest food processing technologies well known to mankind. Since the beginning of civilization, methods of fermenting milk, cereals, legumes, vegetables, and meats have been described [1]. The preparation of these kinds of fermented foods will be with us in the far future, as they are a source of alcoholic foods/beverages, vinegar, pickled vegetables, sausages, cheeses, yogurts, vegetable protein amino acid/peptide sauces, and pastes with meat-like flavors, and leavened and sourdough breads, and so on. Fermented foods are of great importance because they provide

and preserve an enormous amount of nutritious foods with a wide variety of flavors, aromas, and textures that enrich the human diet. As used herein, the term "nutrition" or "nutrient" will include providing the consumer with calories/energy, protein, essential amino acids/peptides, essential fatty acids, vitamins, and mineral requirements that contribute to the solution of nutritional problems and diseases in the human population [2].

In most cases, the procedures and knowledge associated with the manufacture of these food products were passed on from generation to generation within local communities, monasteries, and medieval farms. In the mid-nineteenth century, two events occurred that had a significant impact on our understanding of the method and process of food fermentation. First, a huge number of residents from the villages started moving toward the towns and cities due to the more opportunities in industrial sectors. Hence, the practicing of conventional methods to prepare food for more population was no longer operative. This led to inventing new processes for the manufacturing of vast quantities of food products, which demanded the industrialization of the food sector. Second, the progress in the field of microbiology in the 1850s led to an understanding of the basic science of the fermentation process for the first time. Consequently, the important function of lactic acid bacteria, yeasts, and molds in the production of fermented foods was understood, which eventually led to a more controlled and efficient fermentation process [3].

For many fermented foods particularly dairy products, the characterization of microorganisms that are responsible for fermentation is very important for their usage in the dairy industry. Therefore, in the late nineteenth-century isolation of starter cultures and manufacturing on a large scale was initiated to supply to the factories involved in the manufacture of dairy products [3]. Generally, starter culture strains are often used to improve the nutritive value and sensory characteristics of fermented foods, maintain safety and quality, and promote nutrition [4]. In recent years, it has been a great strategy in food microbiology to study microorganisms with various functions, to use as a starter culture [5]. Several studies have reported the preparation of food products using multifunctional microorganisms, wherein lactic acid bacteria (LAB) are particularly recommended as starter cultures for the fermentation process due to their benefits in terms of probiotic properties, antimicrobial production, beneficial enzyme production, and enhancement of other functionality [6–11]. They are normally considered safe and widely used as a starter culture in the production of fermented foods [12]. Due to the unique metabolic characteristics, they are involved in many fermentation processes of milk, cereals, vegetables, and meats. They are effective as probiotics and exhibit beneficial properties such as the production of antimicrobial compounds, enzymes, involvement in immune regulation, and antioxidant activity [13]. The microbiota in the human gut displays significant influence on host immunity, nutrition supply to the body as well as a contribution toward physiological function, whereas the enhanced therapeutic role of beneficial microbes in the gut is mainly due to the improvement of their population in intestinal microbial communities and their subsequent correlation with human physiology and disease pathogenesis [14]. In 2006, FAO/ WHO defined probiotics as "live microorganisms, which upon ingestion in adequate amounts confer a health benefit to the host [15]." Hence, probiotics are considered as safe products for the host when consumed. The key criteria for the selection of probiotics which are mainly based on the FAO/WHO guidelines include safety (nonpathogenic strains without toxicity), resistance to gastric and bile acids, adhesion to epithelial cells, and antimicrobial activity (antagonism against pathogens). These guidelines recommend performing *in vivo* experiments on strains that have demonstrated potential health benefits based on *in vitro* experiments. In addition, probiotic properties are strain-specific, and hence, each strain characteristic needs to be verified [16].

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

The lactic acid bacteria (LAB) are considered as probiotics and play important role in the preservation and production of healthy fermented food products. The genera of LAB consist of *Lactobacillus*, *Leuconostoc*, *Lactococcus*, *Enterococcus*, *Pediococcus*, *Streptococcus*, *Weisiella*, etc. The genus *Lactobacillus* includes 261 species that differ greatly in their phenotypic, genotypic, and ecological properties. Recently, [17] proposed reclassification of lactic acid bacteria into 25 genera. The phylogeny is based on whole-genome sequences, which includes the revised genera *Lactobacillus* and *Paralactobacillus*. The remaining 23 genera are novel: *Holzapfelia*, *Amylolactobacillus*, *Bombilactobacillus*, *Companilactobacillus*, *Lapidilactobacillus*, *Agrilactobacillus*, *Schleiferilactobacillus*, *Loigolactobacilus*, *Lacticaseibacillus*, *Latilactobacillus*, *Dellaglioa*, *Liquorilactobacillus*, *Ligilactobacillus*, *Lactiplantibacillus*, *Furfurilactobacillus*, *Paucilactobacillus*, *Limosilactobacillus*, *Fructilactobacillus*, *Acetilactobacillus*, *Apilactobacillus*, *Levilactobacillus*, *Secundilactobacillus*, and *Lentilactobacillus*. Those LAB belong to the homo- and hetero-fermentative groups and generally require enriched artificial media. They grow naturally on most food substrates which led to the lowering of pH to a point where other competing microorganisms are unable to grow. For example, *Lactococcus* and *Leuconostoc* normally lower the pH to 4.0–4.5, whereas *Lactobacilli* and *Pediococci* lower the pH to 3.5 as reported by [18]. Several research studies have shown that the use of LAB as fermentation agent for the preparation of food products is considered as safe for consumption [7, 10, 11].

It is well-known fact that India is recognized for its rich traditional fermented food products. Generally, in the Indian subcontinent, fermented foods are prepared using indigenous food crops and other biological resources. Hence, the nature of food products and their base materials varies in each province. Presently, there are a number of fermented food products with different base materials and preparation methodologies have been reported. Each fermented food is allied with a unique group of microbiota, which has the potential to increase the level of proteins, vitamins, essential amino acids, and fatty acids. In local communities, the preparation of traditional fermented foods is still done by spontaneous fermentation method and their microbiota profile get varies each time. Hence, limited knowledge is available about the microbiota of these kinds of food products [19, 20].

This chapter outlines the role of lactic acid bacteria in food fermentation, their probiotic properties (gastrointestinal tract acidic tolerance, adhesion, hydrophobicity, and auto-aggregation), multifunctional characteristics (antimicrobial, antioxidant, phytase, and *β*-galactosidase activities), and the mechanisms of antagonistic nature of LAB as well as a brief explanation of some significant traditional fermented foods from India. It is expected that more research needs to be carried out toward strain improvement with beneficial properties in order to use in the fermentation of food products, which would benefit both the producer and consumer.
