Investigation on ropiness development by isolates of the genera Lactobacillus, Alcaligenes and Feta cheese starter cultures Original Research Article

Lactobacillus pseudoplantarum and Alcaligenes spp. were isolated from ropy brine and milk, respectively, and their ability to develop ropiness was investigated. Vigorous ropiness was developed by L. pseudoplantarum in whey with 7% NaCl, after 21 days of incubation at 15°C. Alcaligenes spp. developed ropy colonies on PCA, containing up to 2% NaCl at incubation temperature of 4°C and 15°C. Also reconstituted skim milk inoculated with Alcaligenes spp. became ropy after 5–13 days of incubation only at 4°C. Ropiness was not noticed when NaCl was added to the skim milk. In order to investigate the ropiness development in Feta cheese brine, a commercial yoghurt culture was used to make Feta cheese in combination with the two bacteria isolates and a ropy yoghurt culture. The results revealed that only the ropy yoghurt culture and not the normal one, developed very high ropiness in brine during ripening at 15°C. The results also showed that Alcaligenes spp. and L. pseudoplantarum intensified ropiness of brine. To avoid ropiness, it is recommended that yoghurt starter cultures used for Feta should be selected and bacterial contaminants that could cause ropiness in brine should be eliminated.