Pink discolouration defect in commercial cheese: A review

Abstract

Development of a pink color defect is an intermittent but persistent defect in a wide range of ripened cheese varieties (Swiss, Cheddar, Grana, and Italian types) which may or may not contain an added colorant, e.g., annatto. Pink discoloration results in downgrading or rejection of a product with consequential economic loss to producers. Pink discolorations can manifest in a number of ways, e.g., patches at the surface or within the cheese block, or as a uniform pink border occurring below the surface of cheese blocks. Little consensus exists as to what the discolorations and their underlying causes are. This review seeks to provide an overview and interpretation of the underlying factors associated with the defect for both research and commercial audiences. In cheeses without added colorant, pink discoloration has been associated with: certain strains of thermophilic lactobacilli and propionic acid bacteria, Maillard reactions, and microbial pigments (e.g., carotenoids and phenolic compounds), which may be responsible for development of pink-brown or dark brown discoloration. In cheeses with added colorant (usually annatto), the development of pink discoloration has been associated with: alteration of annatto colorant due to factors such as varying pH levels within the cheese matrix (particularly < pH 5.4), oxidation of bixin in storage under high intensity fluorescent lights in display cabinets, presence of oxygen, variations in redox potential, interactions between nitrates and annatto present in plastic surface coating and also due to interactions between colorants, and the use of high heat treatment during processed cheese manufacture. © INRA and Springer-Verlag, France 2012.