INLAIN   20354
INSTITUTO DE LACTOLOGIA INDUSTRIAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Influence of an exopolysaccharide (EPS) extract obtained from Lactobacillus fermentum Lf2 on the texture parameters, starter viability and primary proteolysis of Cheddar cheese
Autor/es:
CIOCIA, F.; MCSWEENEY, P.; REINHEIMER, J. A.; ALE, E.; BINETTI, A. G.
Lugar:
Rosario
Reunión:
Congreso; CAAM ALAM 2016; 2016
Institución organizadora:
AAM
Resumen:
Some lactic acid bacteria are known to produce exopolysaccharides (EPS), which are excreted into the medium, changing its characteristics because of their thickening and emulsifying properties. Apart from the techno-functional relevance, there is increasing evidence that suggests a positive impact on human health. Many studies were done about the effect of EPS on dairy products when it is produced in situ, but the addition of EPS as an extract in cheese has not been reported yet. The aim of the present work was to study the influence of the addition of an EPS extract produced by Lactobacillus fermentum Lf2, an autochthonous strain isolated as a non-starter culture in cheese manufacture, on the texture, primary proteolysis and microbiologic characteristics of Cheddar cheese. This extract was obtained from the culture after 72 h of fermentation in SDM broth at pH 6 and 30°C, with continuous stirring, in a 2 L fermenter (conditions selected according to previous experiments). Briefly, the medium was centrifuged and 2 volumes of chilled absolute ethanol were added to precipitate the EPS. Then, the EPS fraction was obtained after centrifugation, resuspended in bidistilled water, dyalized for 3 days and freeze-dried. This powder was added to the pasteurized milk in a concentration of 1g/L and gently mixed some minutes before adding the starter culture. Cheddar cheeses were made in triplicate, 3 with EPS and 3 controls, and composition was determined at 10 days of ripening. For the texture profile analysis (TPA) a Texture Analyzer TA-XT2i was used. Cheese samples were cut into cylinders and compressed to 30 % of their original height in two consecutive cycles at a rate of 1 mm/s. Hardness, springiness, cohesiveness, adhesiveness, fracturability, chewiness, resilience and gumminess were determined in quadruplicate at 1, 2, 3 and 4 months of ripening. The microbiologic analysis was done for those 4 time points too, using LM17 agar for starter bacteria and Rogosa agar for non-starter bacteria. The primary proteolysis was evaluated at 3 days and 4 months of ripening for each sample with urea polyacrylamide gel electrophoresis. For the texture parameters between control an treated cheeses, a clear tendency could be described. Cheddar cheeses with 1 g/L of EPS extract presented higher values of hardness, springiness, cohesiveness, gumminess, chewiness and resilience for all the times of ripening evaluated. On the other hand, adhesiveness was similar between both groups and fracturability was not detected in cheeses with EPS at 2, 3 and 4 months of ripening, while the controls presented values between 5000 and 6000 g. Cell counts were similar during ripening for both groups and no differences were detected for the primary proteolysis neither, as expected. These results indicate that this EPS extract could have interesting effects on the texture of Cheddar cheese, and future assays using a higher concentration could improve the influence observed.