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.