While it is relatively easy to measure "stability" in quantitative
terms, the same is not true for "quality," which is notoriously
vague and elusive. Initially, sensory panels of people trained in utilizing
sight, smell, and taste were used to provide some measure of "quality."
But a new instrumentation technique was just becoming available to researchers
in the early 1950s. As a method of analyzing even the trace amounts of
individual chemical components in a mixture, gas chromatography (GC) quickly
became the method of choice in studying aroma and flavor because it could
detect which compounds were responsible for the sensory effects, and how
much of each component was present. Now that the compounds responsible
for off-flavor and rancidity could be measured, the WRRC staff developed
many new uses for GC in flavor and food chemistry. They were particularly
successful in sampling the space above a frozen food and injecting this
directly into the GC, a technique now known as "static headspace
sampling" that is still a standard in the food industry.
For example, rancidity in meats derives from the breakdown of fats in
an oxidation process that immediately leads through a series of complicated
chemical reactions to aldehydes and hydroxy compounds that are responsible
for the rancid flavor and odor. These reactions can also occur in frozen
meat and fish when rancidity accelerators are present. One method of quality
measurement is to use GC analysis to look for these known components of
rancidity and determine their amounts. In the early 1960s, WRRC scientists
were among the first to combine GC with another analytical technique,
mass spectrometry. The sensitive and rapid combined gas chromatography-mass
spectrometry procedure simplified the study of food flavor and aroma compounds
and improved the objective determination of food quality. Among the key
aroma components first identified at WRRC are those of orange, apple,
rice, tortilla chips, carrots, cabbage, broccoli, popcorn, plums, and
Even though these new techniques helped quantify "quality,"
sensory panels were always an important part of the T-TT work. They were
often used to verify the conclusions reached through chemical tests such
as chlorophyll degradation or loss of ascorbic acid, especially in determining
that point in storage where there was a "just notable difference"
and correlating that to the appropriate chemical measurement.