ACCELERATED RIPENING OF LOW-FAT RAS CHEESE BY ATTENUATED LACTOBACILLICELLS

Thirteen Pas cheese were made from 4% fat raw milk; 3% raw and heat tr eated; 2% raw and heat treated milks in order to study the effect of f reeze-shocked or heat-shocked L. casei NIH 334 or L. helveticus CNRZ 5 3 on the quality of the resultant cheeses. The soluble nitrogen, solub le tyrosine, soluble tryptophan, total volatile fatty acids, titratabl e acidity and organoleptic evaluation scores increased as ripening per iod progressed, while moisture decreased. Neither strain nor the heate d lactobacilli had significant effects on moisture content of cheeses, while increasing their acidity. Cheeses with freeze-shocked L. casei or L. helveticus had higher titratable acidity than cheeses in which h eat-shocked cells were added. However, cheeses added L. helveticus had higher acidity than those with L. casei. Ripening indices (soluble ni trogen, soluble tyrosine, soluble tryptophan and total volatile fatty acids) and organoleptic evaluation scores had similar trends. Cheeses with attenuated lactobacilli had higher ripening indices and cheese sc ores than cheeses without lactobacilli. Addition of either freeze-shoc ked L. casei or L. helveticus yielded cheeses having higher ripening i ndices and organoleptic scores than cheeses made with heat-shocked lac tobacilli. The best cheeses were made from 3% fat milk heated to 70 de grees C, and containing freeze-shocked L. helveticus followed by chees es made from 2% fat milk heated to 75 degrees C and containing freeze- shocked L. helveticus. (C) 1997 Published by Elsevier Science Ltd on b ehalf of the Canadian Institute of Food Science and Technology.