R. Imhof et al., VOLATILE ORGANIC-COMPOUNDS PRODUCED BY THERMOPHILIC AND MESOPHILIC SINGLE STRAIN DAIRY STARTER CULTURES, Lebensmittel-Wissenschaft + Technologie, 28(1), 1995, pp. 78-86
The potential of different commercially used starter cultures to form
volatile organic compounds were determined. Special interest was laid
on the so-called minor constituents compounds that al-e present in the
low mu g/kg-range in the end-product aroma of the investigated starte
r cultures. The variability of the tested single sti-ain cultures was
very wide within the investigated species. It was not possible to grou
p the strains according to the species by applying statistical procedu
res such as principal component analysis or cluster analysis on the GC
-MS-data of the samples. Applying the concept of odour unit values to
all cultures tested, it was possible to estimate the impact of each vo
latile organic compound investigated on the resulting aroma of the end
product. Of 32 quantified compounds only 2,3-butanedione (odour unit
values between 6 and 362), 2,3-pentanedione (between 0 and 363), and t
o a lesser extent demethyl sulfide (between 6 and 12), and benzaldehyd
e (between 0 and 3) are supposed to have such an impact. Mixed culture
s were formed, using three strains of Lb. delbruckii sap. bulgaricus a
nd S. salivarius ssp. thermophilus, respectively, to produce yogurt. T
he most interesting finding was that 2,3-pentanedione is produced by a
ll mixed strain cultures in three to five times the amount of the sum
produced by the respective single strains.