Bleu cheese flavor production by submerged fermentation with on-line monitoring by gas chromatography

Abstract

Eight cultures ofPenicillium roqueforti and related species were compared in shake-flask cultures on the basis of aroma.P. decumbens IFO 7091 was chosen as having the aroma closest to real Bleu cheese, and was used for fermentation studies. Gas chromatography was employed to obtain a continuous record of 2-pentanone concentration in the fermentor. Methyl ketones are characteristic of Bleu cheese flavor, and a subjective correlation was observed between the aroma of the fermentor off-gas and the 2-pentanone concentration measured. Cell growth and milk fat utilization increased consistently with increasing agitation and aeration, but 2-pentanone production did not correlate with growth and was maximum at intermediate values of agitation and aeration. The maximum 2-pentanone concentration, 100 ppm, was approximately ten times the concentration in Bleu cheese on a dry solids basis. Production of Bleu cheese flavor by submerged fermentation offers the opportunity for a new commercial value-added product from butterfat.