Abstract
Despite the continuous academic interest in blue cheese, there has not been a lot of research covering discoloration, like pinking. Across other cheeses, pink discoloration has been determined to be caused by Lactobacillus helveticus, Glutamicibacter arilaitensis, Thermus thermophilus, and Yarrowia lipolytica. Resolving pink discoloration in blue cheese is important because discolored cheese can reduce the amount of sellable product and thus profit. For this research, we were approached by a blue cheese producer to investigate potential causes of pinking in their blue cheese. For this, culture-independent and culture-dependent methods were used to identify the potential microorganism(s) that cause pink discoloration in blue cheese. Two groups of samples, one exhibiting internal pinking within the blue cheese wheel and the other exhibiting external pinking along the rind surface, were studied using the 16S rRNA gene and the ITS gene sequencing as well as culture dependent methods. The internally pink cheese samples had a higher abundance of Lactobacillus. The externally pink cheese samples had a higher abundance of Arthrobacter/Glutamicibacter, Staphylococcus, and Debaryomyces. The high abundance in the pink samples suggests these genera may be potential contributors to pink discoloration. However, the high abundance of unidentified species suggests that further research is needed to narrow down which species in these genera are responsible and if other microorganisms may be interacting with them to cause the pinking defect. Additionally, for the externally pink blue cheese samples, Bacillus amyloliquefaciens was isolated from the samples exhibiting pink pigmentation, but not from samples not exhibiting pinking. Some Bacillus species are known to exhibit pigmentation, however more work is needed to be done to determine if Bacillus amyloliquefaciens can develop pigmentation in a blue cheese environment.