HYNES Erica Rut
congresos y reuniones científicas
Influence of probiotic bacteria on the proteolysis profile of a semi-hard cheese
BERGAMINI CARINA,; ERICA HYNES; CARLOS ANTONIO, ZALAZAR
Congreso; 4th NIZO Dairy Conference; 2005
Two probiotic strains, Lactobacillus acidophilus and Lactobacillus paracasei subsp. paracasei, were used as adjunct cultures in semi-hard cheese-making experiences, in order to study their influence on proteolysis during ripening. In each trial, a control cheese (without probiotic bacteria) and experimental cheeses, with the addition of probiotics, were manufactured. Cheeses were analysed to assess gross composition, and primary starter and probiotic bacteria populations were enumerated. Proteolysis was studied by nitrogen fractions and electrophoresis; peptide and amino acid profiles were also obtained by liquid chromatography. Gross composition of experimental and control cheeses was similar. Population of probiotic bacteria remained above 107 UFC mL-1 during all ripening, demonstrating that the product maintained its probiotic status at least for 60 days. The added probiotic bacteria did not influence primary proteolysis, as significant differences between control and experimental cheeses were not detected in electrophoretic patterns and soluble nitrogen at pH 4.6. On the contrary, Lactobacillus acidophilus produced a significant increase in the level of soluble nitrogen in phosphotungstic acid 2.5%, which suggested that the adjunct culture influenced on the production of short peptides and free amino acids. Similarly, cheeses with Lactobacillus acidophilus showed an increased amount of individual free amino acids compared to control cheeses, and the amino acid profile was also different. Multivariate analysis of peptide profiles showed that samples were grouped mainly by ripening time, although the impact of probiotics was also detected. Lactobacillus acidophilus showed an early influence, since cheeses with this adjunct culture were grouped in a different cluster than control cheeses both at 30 and 60 days of ripening. The influence of Lactobacillus paracasei was evidenced later, because only 60-day-old experimental cheeses were grouped separately. These results showed that the two tested strains influenced distinctly on the proteolysis pattern of cheeses during ripening, probably as a consequence of their different proteolytic systems and their activity in the alimentary matrix.