Contribution of the novel sulfur-producing adjunct Lactobacillus nodensis to flavor development in Gouda cheese.

We assessed the efficacy of Lactobacillus nodensis CSK964 as an adjunct culture in Gouda cheese under various industrial conditions. We set up 4 different systems: a direct vat inoculum with and without adjunct using the calf rennet Kalase, and an undefined bulk starter culture with and without adjunct using the microbial rennet Milase (both rennets from CSK Food Enrichment, Ede, the Netherlands). During ripening, we subjected the cheeses to the following analyses: viability of starter and adjunct cells, composition, proteolysis, and flavor development by detection of sulfur compounds and descriptive sensory analysis. In general, the presence of Lb. nodensis increased secondary proteolysis and influenced cheese flavor, particularly in relation to volatile sulfur compounds; hydrogen sulfide and methanethiol were present in higher abundances in cheeses containing Lb. nodensis. The primary starter also influenced the range of volatile sulfur compounds produced. Methanethiol and dimethyl disulfide were more abundant in the nisin-producing direct vat inoculum cheese with adjunct; hydrogen sulfide was more prevalent when bulk starter culture was used with Lb. nodensis. Sensory analysis revealed that the direct vat inoculum cheese with adjunct scored significantly better in terms of smell and taste than the direct vat inoculum cheese without adjunct and lacked the dominant sulfur flavors of the bulk starter cheese with adjunct. Subsequent analysis using lead acetate paper and modified motility broth as indicators of hydrogen sulfide production confirmed that Lb. nodensis produced hydrogen sulfide in broth and in the cheese matrix. This study suggests that the inclusion of Lb. nodensis as an adjunct culture can significantly alter the flavor profile of the final cheese. However, the selection of a suitable primary starter is imperative to ensure a desirable product.

A novel consortium of Lactobacillus rhamnosus and Streptococcus thermophilus for increased access to functional fermented foods.

BACKGROUND: The lactic acid bacterium Lactobacillus rhamnosus GG is the most studied probiotic bacterium with proven health benefits upon oral intake, including the alleviation of diarrhea. The mission of the Yoba for Life foundation is to provide impoverished communities in Africa increased access to Lactobacillus rhamnosus GG under the name Lactobacillus rhamnosus yoba 2012, world's first generic probiotic strain. We have been able to overcome the strain's limitations to grow in food matrices like milk, by formulating a dried starter consortium with Streptococcus thermophilus that enables the propagation of both strains in milk and other food matrices. The affordable seed culture is used by people in resource-poor communities. RESULTS: We used S. thermophilus C106 as an adjuvant culture for the propagation of L. rhamnosus yoba 2012 in a variety of fermented foods up to concentrations, because of its endogenous proteolytic activity, ability to degrade lactose and other synergistic effects. Subsequently, L. rhamnosus could reach final titers of 1E+09 CFU ml(-1), which is sufficient to comply with the recommended daily dose for probiotics. The specific metabolic interactions between the two strains were derived from the full genome sequences of L. rhamnosus GG and S. thermophilus C106. The piliation of the L. rhamnosus yoba 2012, required for epithelial adhesion and inflammatory signaling in the human host, was stable during growth in milk for two rounds of fermentation. Sachets prepared with the two strains, yoba 2012 and C106, retained viability for at least 2 years. CONCLUSIONS: A stable dried seed culture has been developed which facilitates local and low-cost production of a wide range of fermented foods that subsequently act as delivery vehicles for beneficial bacteria to communities in east Africa.

Draft Genome Sequence of Streptococcus thermophilus C106, a Dairy Isolate from an Artisanal Cheese Produced in the Countryside of Ireland.

The lactic acid bacterium Streptococcus thermophilus is widely used for the fermentation of dairy products. Here, we present the draft genome sequence of S. thermophilus C106 isolated from an artisanal cheese produced in the countryside of Ireland.

Inhibitory activity of Lactobacillus plantarum LMG P-26358 against Listeria innocua when used as an adjunct starter in the manufacture of cheese.

Lactobacillus plantarum LMG P-26358 isolated from a soft French artisanal cheese produces a potent class IIa bacteriocin with 100% homology to plantaricin 423 and bacteriocidal activity against Listeria innocua and Listeria monocytogenes. The bacteriocin was found to be highly stable at temperatures as high as 100°C and pH ranges from 1-10. While this relatively narrow spectrum bacteriocin also exhibited antimicrobial activity against species of enterococci, it did not inhibit dairy starters including lactococci and lactobacilli when tested by well diffusion assay (WDA). In order to test the suitability of Lb. plantarum LMG P-26358 as an anti-listerial adjunct with nisin-producing lactococci, laboratory-scale cheeses were manufactured. Results indicated that combining Lb. plantarum LMG P-26358 (at 108 colony forming units (cfu)/ml) with a nisin producer is an effective strategy to eliminate the biological indicator strain, L. innocua. Moreover, industrial-scale cheeses also demonstrated that Lb. plantarum LMG P-26358 was much more effective than the nisin producer alone for protection against the indicator. MALDI-TOF mass spectrometry confirmed the presence of plantaricin 423 and nisin in the appropriate cheeses over an 18 week ripening period. A spray-dried fermentate of Lb. plantarum LMG P-26358 also demonstrated potent anti-listerial activity in vitro using L. innocua. Overall, the results suggest that Lb. plantarum LMG P-26358 is a suitable adjunct for use with nisin-producing cultures to improve the safety and quality of dairy products.