Ampicillin resistant texturizing lactic acid bacteria strains

A method for obtaining a mutant texturizing lactic acid bacteria strain, comprising:

• (a) selecting and isolating, from a pool of lactic acid bacteria strains obtained from a mother strain without genetic engineering, a pool of mutant lactic acid bacteria strains which are resistant to the antibiotic ampicillin as determined by the amount of ampicillin that reduces the OD600 measured growth of the lactic acid bacteria strain, after 20 hours growth at 37° C. in a medium suitable for growth of the lactic acid bacteria strain, by 20% as compared to the OD600 measured growth in the medium without ampicillin being higher than 400 ng/ml;
• and
• (b) selecting and isolating from the pool of mutant lactic acid bacteria strains which are resistant to ampicillin a mutant lactic acid bacteria strain that exhibits a texturing property such that the efflux time of 28 ml of full fat cow milk containing 2% (w/v) skimmed milk powder, inoculated with at least 104 CFU/ml of the lactic acid bacteria strain and acidified at 37° C. for 20 hours, from a polystyrene 25-ml pipette is at least 50 seconds.