Influence of a bacteriocin-producing lactic culture on proteolysis and texture of Hispanico cheese

Hispanico cheese was manufactured in duplicate experiments, each consisting of two 50-L vats, and ripened for 75 days. Lactic cultures for experimental cheese were 0.5% Lactococcus lactis subsp. lactis INIA 415 (Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria, Madrid, Spain), a bacteriocin-producing (Bac(+)) strain harbouring the structural genes of nisin Z and lacticin 481, 0.5% L. lactis subsp. lactis INIA 415-2, a Bac(-) mutant and 2% TA052, a commercial Streptococcus thermophilus culture. Lactic cultures for control cheese were 0.5% L. lactis subsp. lactis INIA 415-2, and 2% TA052. S. thermophilus counts were lower, and levels of cell-free intracellular aminopeptidases higher, from day 1 in cheese made with the bacteriocin producer, indicating early lysis of the thermophilic culture. Experimental cheese showed reduced proteolysis of alpha(s)-casein and lower levels of hydrophilic and hydrophobic peptides than control cheese. However, proteolysis as estimated by the o-phthaidialdehyde method and total level of free amino acids were in experimental cheese 1.38- and 2.47-fold, respectively, those in control cheese on day 25, and 1.49- and 2.34-fold, respectively, on day 75. Higher values of fracturability, elasticity and hardness were recorded from day 50 for cheese made with the bacteriocin producer, which were related to its higher residual alpha(s)-casein content. The use of a bacteriocin-producing culture, though retarding alpha(s)-casein proteolysis and softening of texture, enhanced considerably secondary proteolysis during cheese ripening. (C) 2004 Elsevier Ltd. All rights reserved.