368 Chapter 14
by distillation at minimum temperatures
necessary for volatilizing the essential fl avor
compounds and trapped in a suitable sol-
vent. Starter distillates contain not only
diacetyl but also other balancing and com-
plementing fl avor compounds to impart a
full fl avor.
Seitz (1990) has provided an extensive
review of starter distillates. The concept of
starter distillates was introduced by Ruehe
(1938). He proposed the idea of using starter
distillates to eliminate variations in the inten-
sity of fl avor commonly encountered from
batch to batch in creamery butter. The vari-
ability could be traced to inherent differences
in the performance of starter cultures, the
differences in citrate concentrations in cream
seasonally and through the course of the lac-
tation period, and day to day variations in
production conditions in the creamery.
Furthermore, with the introduction of sweet
cream for butter making, a reliable method
for ensuring uniform, high fl avored butter
was needed to avoid keeping quality issues
linked to ripened cream. Starter distillates
that were standardized to deliver the needed
fl avor fulfi lled the demand.
In 1938, Ruehe published his procedure
for producing starter distillate. It called for
careful selection of a mixed - strain dairy
starter containing mesophilic fl avor bacteria,
and meticulous culture maintenance. The
starter was propagated in a milk - based
medium fortifi ed with 0.15$ to 0.3% citric
acid. At the appropriate stage ferric chloride
was added to the culture to oxidize the acetoin
in the culture to diacetyl, and the volatiles
were steam distilled. The distillate was then
standardized to a diacetyl concentration of
1,000 mg/L. Ruehe (1938) pre - empted the
fi ling of patents on starter distillates by
placing this technology in the public realm.
Seitz (1990) has summarized several varia-
tions of the process that have been published
on starter distillates.
Starter distillates in liquid and powdered
forms have long been marketed by the leadingapplications include “ sweetish, creamy/
buttery ” notes and “ sulphury ” notes. While
these bases make up the major portion of the
fl avor desired, the intense and specifi c fl avor
attributes may only be achieved by formulat-
ing a WONF (with other natural fl avors).
This involves the careful selection and pro-
portioning of fermentation - derived products
to give the top notes needed in a fi nished
fl avor.
The addition of key intermediates such as
succinic acid is necessary in the development
of intense dairy fl avors. Several important
fl avor compounds are derived from this key
tricarboxylic acid cycle molecule. Certain
Lactobacillus reuteri strains have been found
to convert citric acid or its salts effi ciently to
succinic acid. Such biological conversions
aid in the development of intense dairy fl avor
blocks (Seitz, 1991 ). Other important fl avor
compounds needed in dairy fl avors consist of
different esters, which impart the fruity notes
needed in dairy and food fl avors. Such mol-
ecules may be derived by fermentating
branched chain amino acids by dairy - derived
yeasts. Farbood et al. (1986) patented a suc-
cessful process for such conversions for
industrial scale applications.
The various microorganisms and enzyme
systems involved in the development of such
fl avorings are discussed in reviews by Seitz
(1990) and Vedamuthu (1979, 1988).
Purifi ed Bio - fl avorings
Starter distillates, derived from culturing
dairy substrates with selected fl avor bacterial
combinations, are used to fl avor or boost
fl avor in butter, margarine, and dairy des-
serts, puddings, and confectionaries. Starter
distillates contain the volatile fl avor com-
pounds generated in suitable dairy substrates
using selected high fl avor - generating lactic
cultures. Optimum pH and temperature are
maintained in these fermentations with con-
tinuous replenishment of citrate. At appro-
priate stages the volatiles are stripped off