Development of lactic acid bacteria starters for cheesemaking isolated from different dairy matrices in Gran Canaria (Canary Islands)

Introduction: Isolating autochthonous lactic acid bacteria (LAB) from dairy matrices for cheesemaking offers technological and sensory advantages, as these strains are metabolically adapted to the food matrix. Methodology: Raw milk (cow, sheep, goat), curd, whey, and cheeses at different ripening stages (fresh, semi-ripened, ripened) were sampled from 15 artisan dairies in Gran Canaria (Spain). Samples were homogenized in sterile peptone water, serially diluted, and duplicate-plated on LAB-selective media at 30°C under aerobiosis or anaerobiosis as appropriate. Isolates were identified by 16S rDNA sequencing and typed at the intraspecific level by RAPD. LAB were characterized in milk for growth/viability, acidification kinetics, and sensory profile (4-member panel). Selected strains were tested for compatibility in mixed cultures prior to scale-up in a 20 L bioreactor and freeze-drying. Results and Discussion: Ten LAB strains were identified: five Lactococcus lactis subsp. lactis, three Lc. lactis subsp. cremoris and two Leuconostoc mesenteroides. Most reached high viable counts in milk (>10⁹ CFU/mL). Five were discarded for limited acidification capacity (>20 h to reach pH 5.0): Lc. lactis subsp. lactis 9, 10 and 42, and Lc. lactis subsp. cremoris 22 and 24, the latter also showing limited growth (<10⁵ CFU/mL). The remaining five, combining fast acidification and a pleasant sensory profile, were selected: Lc. lactis subsp. lactis 14 and 25, Lc. lactis subsp. cremoris 15, and Leuconostoc mesenteroides 38 and 43. These strains were combined into five starter consortia (1A, 1B, 2A, 2B, and 3A). Mixed cultures showed no antagonism, confirming compatibility. The five freeze-dried consortia were stable for 18 months at <6°C and met microbiological safety specifications. Conclusion: This work represents the first development of autochthonous LAB starter cultures from dairy matrices in Gran Canaria. Their application in cheesemaking will be evaluated to determine their effects on the sensory, nutritional, and bioactive properties of the final products.