Use of Novel Lactic Acid Bacterial Strains with Antagonistic Activity for the Preparation of Safe Indigenous Fermented Dairy Foods (Dahi and Raita)

Abstract

Attempts were made to isolate natural antagonistic lactic acid bacteria (LAB) and use them in production of dahi and raita for increased safety. Seventy isolates of LAB were isolated from dahi obtained from different sources. These isolates were tested for their antagonistic activity against selected pathogenic strains of Staphylococcus aureus subsp. aureus and Escherichia coli AB 1157 by adopting agar well assay method. Out of the 70 lactic acid bacterial isolates, 8 were found to have antagonistic activity against both pathogenic organisms. These isolates achieved the desired fermentation rate. Dahi produced by these isolates was found acceptable according to sensory evaluation. The LAB isolates with antagonistic activity were identified by molecular characterization. It is concluded that the identified antagonistic cultures were effective in inhibiting the growth of E. coli and Sta. aureus in dahi and raita. Practical Applications Milk products like dahi and raita are widely consumed, and market for them has existed in many parts of the world for many generations. There is an increased demand by the consumer for high‐quality natural food, free from artificial preservatives and contaminating microorganisms. The presence of Escherichia coli in milk products indicates the presence of enteropathogenic microorganisms, which constitute a public health hazard. Staphylococcus aureus causes minor skin infection to life‐threatening diseases such as pneumonia, meningitis, endocarditis and septicemia. Because the fermented products are very popular in Indian diet, the use of a starter culture that can ferment as well as check the growth of pathogenic organism would be very ideal. Hence, novel antagonistic strains of lactic acid bacteria was identified from natural sources and used successfully as starter culture for production of indigenous fermented milk products, namely dahi and raita, with increased safety.

Effect of organic acids or probiotics alone or in combination on growth performance, nutrient digestibility, enzyme activities, intestinal morphology and gut microflora in broiler chickens

“…For probiotics, the possible mechanisms for the reduction in pathogens are competition for nutrients and sites of adhesion in the mucosa of the small intestine (LutfulKabir, 2009), stimulation of adaptive immunity and alteration of the caecal microbiome (Neal-McKinney et al, 2012). Furthermore, the inhibitory effects on the growth of several enteropathogenic bacteria are likely associated with the antimicrobial compounds produced by LAB, such as bacteriocin and lactic, acetic and other short-chain organic acids, which are responsible for a reduction in the intestinal pH (Cheng, Yu, & Chou, 2003;LutfulKabir, 2009;Servin & Coconier, 2003;Varalakshmi, Balasubramanyam, Surendranath, Bagath, & Rajendran, 2013). These indicate the synergistic effects of organic acids and probiotics in improving the intestinal health of poultry.…”

Effect of Lactobacillus sp. isolates supernatant on Escherichia coli O157:H7 enhances the role of organic acids production as a factor for pathogen control

“…Cheng et al (2003) studied the influence of organic acids, including acetic acid, propionic acid and lactic acid on the growth and survival of E. coli O157:H7. The authors reported that lactic acid exerts greater inhibitory effects on the growth of the pathogenic bacteria than acetic acid and propionic acid; however, the combination of the organic acids exhibited an important synergic effect in the inhibition of this pathogen (Cheng et al 2003, Varalakshmi et al 2013). According to Diez-Gonzalez & Russell (1997) small amounts of sodium acetate (1.6g.…”

“…Furthermore, the inhibitory effect on the growth of several enteropathogenic bacteria is likely associated with the antimicrobial compounds produced by lactic acid bacteria, such as bacteriocin and lactic, acetic and other short-chain organic acids, which are responsible for a reduction in the intestinal pH (Servin & Coconnier 2003, Cheng et al 2003, Varalakshmi et al 2013. Lactic acid represents the main antimicrobial compound present in cultures of lactic acid bacteria (Earnshaw 1992, Navarro et al 2000, Todorov & Dicks 2005, Rossland et al 2005, Moraes et al 2013.…”

Identification and partial characterization of lactic acid bacteria isolated from traditional dairy products produced by herders in the western Tianshan Mountains of China

“…; Varalakshmi et al . ). Although central China has only a poor tradition of dairy consumption, nomadic groups living in Inner Mongolia, the Tibetan Plateau and Xinjiang Tianshan and Altai Mountain regions have developed a variety of distinctive traditional local fermented dairy products, such as koumiss, cheese, irimshik, kefir and sour cream from fermented sheep, mare, camel and yak milk (Irigoyen et al .…”

“…The lactic acid bacteria (LAB) microflora in traditional fermented dairy foods plays an important role in conferring the dairy products' specific characteristics and indigenous flavour (Leroy and Vuyst 2004;Yu et al 2011;Varalakshmi et al 2014). Although central China has only a poor tradition of dairy consumption, nomadic groups living in Inner Mongolia, the Tibetan Plateau and Xinjiang Tianshan and Altai Mountain regions have developed a variety of distinctive traditional local fermented dairy products, such as koumiss, cheese, irimshik, kefir and sour cream from fermented sheep, mare, camel and yak milk (Irigoyen et al 2005;Yi et al 2011;Ao et al 2012;Zuo et al 2013).…”