Lysis of Lactobacillus casei 5Mn 373 accelerates Grana cheese ripening

The influence of the adjunct of a peptidolytic Lactobacillus casei strain on Grana cheese ripening was studied. Strain erythromycin resistance enabled the monitoring of its growth and death kinetics during cheese maturation. Cell lysis was estimated by the dosage of intracellular X-prolyl-dipeptidyl aminopetidase in cheese extracts. L. casei growth reached a maximum level after the second month of cheese ripening when the initial added cell level was 5×10⁵ cfu/g cheese, while L. casei counts decreased from the beginning of the ripening period when the initial added cell level was 4.5×10⁷ cfu/g cheese. The maximum death rate occurred two months after the maximal cell growth, and bacterial lysis was observed approximately two months later. The characteristic amino acid pattern of control Grana cheese was obtained for all of the mature experimental cheeses independently of the inoculum size, and more rapidly when higher amounts of inocula were used due to L. casei cell lysis. The adjunct of the L. casei strain to cheese-milk substantially shortened the ripening time with no negative effects on cheese-making, chemical gross composition or flavour in the mature experimental cheeses compared to the control.