Tyrosine metabolism in pigment-forming Yarrowia lipolytica strains isolated from English and European speciality mould-ripened cheese exhibiting a brown discolouration defect

Yarrowia lipolytica s4fd was isolated from a UK-manufactured speciality mould-ripened cheese as the causative micro-organism of a brown surface discolouration spoilage defect. Comparative studies utilizing Y. lipolytica isolates indicated that inter-strain variations in pigment accumulation were attributable to differences in tyrosine uptake and metabolism to homogentisic acid. The range and activity profiles of proteolytic enzymes involved in tyrosine release and turnover in isolates that differed in pigment formation were, however, similar. Homogentisic acid formation was affected by physiological parameters, and approaches that may be developed by the cheesemaker to prevent spoilage losses associated with the development of the brown discolouration defect are discussed.