Tracing Streptococcus thermophilus strains in three-component yogurt starters

Abstract

Three-component starters for yogurt were obtained on the base of starter LBB.BY 5-12 for traditional Bulgarian yogurt, containing strains Lactobacillus delbrueckii ssp. bulgaricus B5 and Streptococcus thermophilus A with the addition of either an exopolysaccharide-producing S. thermophilus strain 6V or the fast acidifying S. thermophilus strain N1. To differentiate between the three strains in the starter cultures, randomly amplified polymorphic DNA (RAPD) technique was applied to develop strainspecific probes. Southern hybridization against dot-blots of chromosomal DNA from the three S. thermophilus strains confirmed that two probes, derived from a 770 bp RAPD product obtained with primer RAPD-4 and a 290 bp sequence obtained with primer OPP-7 were specific for S. thermophilus 6V and S. thermophilus A, respectively, while no hybridization to S. thermophilus N1 DNA was observed. The selected probes were used to differentiate between S. thermophilus colonies on a solid agar medium by colony hybridization. The evaluation of the viable cell counts revealed that the populations of S. thermophilus A and the added S. thermophilus strains 6V or N1 in the three-component starters and in yogurt had nearly equal proportion allowing each strain to contribute to the enriched properties of starter and product.

Selection and characterization of naturally occurring high acidification rateStreptococcus thermophilusstrains

“…The effectiveness of three-component yoghurt starters, the third component being an additional S. thermophilus strain, conferring an additional property to the starter, such as improved texture or activity, was discussed in a previous work. [ 16 ] Here, the technological potential of the fast-acidifying strains was demonstrated when strains TN1 or M23 were applied as adjunct culture to industrial yoghurt starter LBB.BY5-12, to obtain a three-component starter. The fast-acidifying S. thermophilus strains contributed to a shortening of the fermentation time with more than 30 min when three-component starters were compared to LBB.BY5-12 ( Figure 6 ).…”

Lactic acid bacteria: an essential probiotic and starter culture for the production of yoghurt

“…LAB thus have been credited with immense superior benefits and characteristic properties that could serve multiple applications and efficiently enhance the quality of dairy products. Different strains of LAB are important starter cultures that are distinctively endowed with superior fermentation performance, thus making them a go‐to bacteria for many food applications (Urshev et al ., 2006). The quest to achieve desired product qualities using LAB has always been the hallmark for many players in the food and dairy sector.…”

“…In the food and dairy industry, various probiotic bacteria are being explored with the aim of manufacturing products with excellent health benefits but with limited cost of fermentation processes. As such, the development of starter cultures for fermented dairy products relies on the combination of different LAB that have superior fermentation performance (Urshev et al ., 2006). Generally, some of the characteristics of dairy starter cultures include flavour and aroma production, resistance to bacteriophages and antibiotics (Mohammadi et al ., 2012).…”

Influence of Different Acidifying Strains of <i>Lactobacillus delbrueckii</i> subsp. <i>bulgaricus</i> on the Quality of Yoghurt

“…The increasing consumer demand for yoghurt with favorable flavour and stable texture during shelf life led to considerable interest in researching and exploiting yoghurt starters (Skriver et al, 2003). The development of starter cultures for fermented milk relies on the combination of different lactic acid bacteria (LAB) having superior fermentation performance (Urshev et al, 2006).…”

“…The increasing consumer demand for yoghurt with favorable flavour and stable texture during shelf life led to considerable interest in researching and exploiting yoghurt starters (Skriver et al, 2003). The development of starter cultures for fermented milk relies on the combination of different lactic acid bacteria (LAB) having superior fermentation performance (Urshev et al, 2006).The most important fermentation performances of yoghurt starter culture are rapid acidification, texturing capacities, specific flavour compounds, weak post-acidification and health benefits (Ongol et al, 2007;Ruas-Madiedo et al, 2002 give considerable rheological effects, mouthfeel, and creaminess to commercial yoghurt (Guzel-Seydim et al, 2005;Purwandari et al, 2007;Robitaille et al, 2009;Wu et al, 2014). L. bulgaricus is also important in producing acid, forming flavour and granting healthy functions (Settachaimongkon et al, 2014;Soomro and Masud, 2012).…”