Various chemical compounds contribute
to the naturally pleasant flavor of milk.
Over time, however, and with unwanted
chemical reactions, loss of flavor is inevitable.
This study was conducted to identify
and quantify volatile flavor compounds
associated with off-flavored and
commercial reduced-fat milk products.
Fresh milk was used for the preparation of
altered milk samples having off-flavors
such as “light-oxidized” and “high-acid.”
Milk lacking freshness (i.e., milk produced
two weeks before sampling and maintained
at 40oF in the dark) also was compared
with fresh unaltered milk and two
commercial milk samples. For headspace
analysis, milk samples were subjected to
SPME-GC for volatile compound identification.
In addition, the composition and
aerobic and coliform microbial counts for
all milk samples were analyzed. The milk
samples did not differ in the concentrations
of volatile flavor constituents. When
comparing “light-oxidized” milk samples
(200 lx exposure for 1 or 3 hr), 2-butanone
and pentanal concentrations tended to increase
as light exposure time increased.
All milk samples had similar fat and total
solids contents. “High-acid” milk had a
greater total aerobic microbe count than
the other milk samples. Fresh milk had a
greater octanal concentration than the offflavored
reduced-fat milk samples did.
This might indicate that octanal is an important
contributor to fresh milk flavor and
deserves further study.
