Cheese Spoilage by Yeast: Smears on Cheese Surface

Surface spoilage deteriorates the quality of cheese and may lead to product rejection. Red, yellow, and orange smears are associated with pigment-forming yeasts that produce carotenoids. Yeast enters cheese either with milk and brine, or from contaminated production environment. Production conditions, e.g., ripening or storage temperature, do not prevent yeast development and pigment formation. This research featured ripe soft and semi-hard cheeses produced in Mordovia, Krasnodar, Altai Region, and Moscow Region. All samples had surface defects, i.e., red and reddish-brown smears. The authors used standard methods of microbiological analysis to study the microflora from the colored areas in order to determine the microbiological defect risks and identify the pigment-forming microorganisms. Yeast proved to be the predominating microflora. Its development during ripening caused the formation of red and reddish-brown smears on soft and semi-hard cheeses. The coloration was usually light-induced and occurred during low-temperature ripening and storage.