Major technological differences between an industrial-type and five artisan-type Greek PDO Galotyri market cheeses as revealed by great variations in their lactic acid microbiota

Galotyri is a Greek PDO acid-curd, traditionally ripened, soft spread cheese produced from boiled (>80-90 degrees C), naturally acidified ewes' or ewes'/goats' milk in the regions of Epirus and Thessaly. In this survey study, the microbiology of an industrial Galotyri cheese variety (11 batches) was compared with five artisan-type Galotyri cheese varieties (1-2 batches each), with emphasis on the species of lactic acid bacteria (LAB) prevailing in the final product. All market cheese samples distributed either in packaged or bulk form, were purchased from retail outlets at Ioannina, Epirus during two sampling periods, 2003-2006 and 2014-2019. A total of 366 (189 industrial and 177 artisan) cheese LAB isolates were identified by key biochemical criteria. Strains of Streptococcus thermophilus and/or Lactobacillus delbrueckii subsp. bulgaricus were isolated nearly as a pure symbiotic starter culture (97.4%) from all industrial batches, labeled as a fresh cheese combining the nutritional properties of yogurt. Conversely, the artisan-type cheeses were ripened and more diversified in terms of LAB ecology. They contained strains of Lactococcus lactis (19.8%), Lb. plantarum (16.9%), S. thermophilus (14.7%), Leuconostoc mesenteroides group (11.3%), Pediococcus inopinatus (7.3%), Enterococcus faecalis (8.5%), E. faecium (6.2%), E. durans (5.1%), Lb. rhamnosus (3.4%), Lb. gasseri (3.4%), Lb. bulgaricus (2.8%) and Lb. acidipiscis (0.6%); the prevalence of each species was cheese product batch-dependent. In conclusion: (i) the industrial Galotyri cheese technology results in a fresh yogurt-like cheese of limited (thermophilic) LAB diversity; (ii) the artisan-type Galotyri cheese technologies may vary significantly, but share a decisive ripening step that favors the predominance of mesophilic LAB species in the final market products; (iii) a regulatory distinction between fresh and ripened varieties of commercial PDO-certified Galotyri cheeses is required.