FORMATION OF 2-ACETYL-1-PYRROLINE BY SEVERAL BACILLUS-CEREUS STRAINS ISOLATED FROM COCOA FERMENTATION BOXES

2-Acetyl-1-pyrroline was identified as the principal component responsible for a ''popcorn, corn chip'' aroma produced by several Bacillus cereus strains isolated from cocoa fermentation boxes in Bahia, Brazil. The analysis of direct solvent extracts and headspace volatiles consistently demonstrated the presence of 2-acetyl-1-pyrroline at temperatures well below those reported for its thermal formation. An examination of volatile compounds isolated by simultaneous distillation-solvent extraction showed five B. cereus strains to produce 30-75 mu g/kg after a 2 day incubation on standard plate count agar. 2-Acetyl-1-pyrroline was produced by several ATCC B. cereus strains but not from ATCC Bacillus mycoides and Bacillus thuringensis strains nor from Bacillus circulans, Bacillus Licheniformis, Bacillus megaterium, and Bacillus subtilis previously isolated from cocoa fermentation heaps. A series of C-13- and N-15-labeling experiments showed B. cereus to utilize glucose, glutamic acid, and proline for the formation of 2-acetyl-1-pyrroline. Since B. cereus occurs naturally in many unprocessed cereal grains, these results suggest the possibility that specific strains might be an unrecognized factor involved with 2-acetyl-1-pyrroline formation.