VOLATILE ORGANIC AROMA COMPOUNDS PRODUCED BY THERMOPHILIC AND MESOPHILIC MIXED STRAIN DAIRY STARTER CULTURES

The potential of different commercial dairy starter cultures to form v olatile organic compounds was assessed. Special interest was taken in the so-called minor constituents that are present in the low mug/kg ra nge in the aroma of the end products of the investigated starter cultu res. Volatile organic compounds produced by the starter bacteria are f ormed during production or within the first 24 h of storage. Quantitat ive changes that occurred after 2 and 4 wk proved to be less significa nt. Many of the aldehydes (pentanal and homologues up to undecanal) as well as some alcohols (1-propanol, 1-butanol, 1-pentanol) present in fermented dairy products were not produced by starter bacteria but ori ginated from the milk. Only five of the compounds (dimethyl sulfide, 2 ,3-butanedione, 2,2-pentanedione, limonene and undecanal) together wit h ethanal are considered to have an impact on the resulting aroma, pro viding odour unit values >1.5. Using multiple stepwise regression anal ysis it was possible to differentiate between the five different cultu re types, and to discern the age of an unknown sample independent of i ts culture type.