Chapter 12 - Blue Cheese: Microbiota and Fungal Metabolites

Abstract

Blue cheeses undergo complex fermentation and maturation processes mainly mediated by lactic acid bacteria and fungi. Penicillium roqueforti is a common secondary starter culture for blue-veined cheese manufacture and largely contributes to the characteristic blue cheese flavor and color of the final product, although fungi other than P. roqueforti may occur in artisanal style blue-veined cheeses. Penicillium roqueforti is particularly well adapted to the conditions encountered during blue cheese manufacture including low oxygen levels and temperatures. This species is also actively involved in lipolysis and proteolysis and produces many volatile and nonvolatile aroma compounds among which methylketones are the most abundant. Penicillium roqueforti produces about a dozen secondary metabolites some of which, like PR-toxin, are toxic and may represent a problem for human health. Others, like roquefortines C and D, are well known, but they do not pose health problems. Andrastins are antitumor molecules and are present in significant concentrations in blue-veined cheeses and mycophenolic acid is an antifungal agents, clinically used as an immunosuppressant. Advances in molecular genetics and metabolite biosynthesis allow us to understand how they are synthesized and secreted by P. roqueforti. The possibility of using high-quality P. roqueforti strains unable to produce toxic secondary metabolites in cheese is of great interest.