Physicochemical, microbiological and sensory profiles of fermented milk containing probiotic strains isolated from kefir.

A two-strain starter culture containing Lactobacillus plantarum CIDCA 83114, a potential probiotic strain isolated from kefir grains, and Streptococcus thermophilus CIDCA 321 was tested for the preparation of a fermented milk product. Kluyveromyces marxianus CIDCA 8154, a yeast with immunomodulatory properties was included to formulate a three-strain starter culture. Supernatants of enterohaemorragic Escherichia coli, shiga-toxin-producing strain, along with a two-strain or a three-strain starter culture were included in the medium of Vero-cell surface cultures. The results demonstrated that these combinations of microorganisms antagonize the cytopathic action of shiga toxins. The cell concentration of Lb. plantarum did not decrease during fermentation, indicating that the viability of this strain was not affected by low pH, nor did the number of viable bacteria change during 21 days of storage in either fermented products. The number of viable yeasts increases during fermentation and storage. Trained assessors analyzed the general acceptability of fresh fermented milks and considered both acceptable. The milk fermented with the two-strain starter culture was considered acceptable after two week of storage, while the product fermented with the three-strain starter culture remained acceptable for less than one week. The main changes in sensory attributes detected by the trained panel were in sour taste, milky taste and also in fermented attributes. The correlation between different sensory attributes and acceptability indicated that the panel was positively influenced by milky attributes (taste, odour, and flavour) as well as the intensity of flavour. In conclusion, the two-strain starter culture would be the more promising alternative for inclusion of that potential probiotic lactobacillus in a fermented milk product.

PCR and RAPD identification of L. plantarum strains isolated from ovine milk and cheese. Geographical distribution of strains.

Lactobacilli, and specifically Lactobacillus plantarum, are an important group of microorganisms in ovine cheeses, even though they are not ordinarily included in the starter cultures added. The present study effected counts of lactobacilli in Roncal Protected Designation of Origin (PDO) milk and cheese samples and isolated a total of 1026 strains. The strains were identified to species level by polymerase chain reaction (PCR) using L. plantarum-specific oligonucleotide primers, and the strains belonging to this species were then characterized by randomly amplified polymorphic DNA (RAPD). The percentage of L. plantarum present in the cheeses depended on the plant where the cheese was manufactured. Cluster analysis of the RAPD profiles obtained revealed seven main clusters. On comparing the strains, most of the strains present in the cheese were found not to have come from the raw milk.