Arthrobacter arilaitensis strains isolated from ripened cheeses: Characterization of their pigmentation using spectrocolorimetry

- Arthrobacter arilaitensis is an emerging bacterium in the dairy industry.
- Color of surface-ripened cheeses is important for consumer.
- Contribution of A. arilaitensis to this color is not known up to now.
- Our results on milk ingredient-based agar will be useful for the cheese industry.

Pigmentation of a total 14 strains of Arthrobacter arilaitensis isolated from smear-ripened cheeses was evaluated using quantitative spectrocolorimetry. After 14 days of cultivation on milk ingredient-based solid medium on Petri dish, the bacterial biofilms were measured and expressed in the CIE L*a*b colorimetric system. Alignments of hue value from each experimental (a*b) pair ranged from 72.39 to 240.83° that could be statistically divided into 9 groups (P < .05). Eight strains, out of 14, presented yellow to greenish-yellow pigmented cultures. The effect of light exposure against storage in the dark was also investigated using this approach. Three groups depending on a coloration behavior affected by light were illustrated for these 14 A. arilaitensis strains e.g. positively sensitive, negatively sensitive and not sensitive to light. This study is the first one describing the color contribution of A. arilaitensis, an emerging industrial dairy bacterium, to cheese ripening.