Defining "Quality"

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 pineapple.

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.

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Early methods of food preservation | A chance discovery | Frozen food chemistry | U.S. Agriculture turns to science | Frozen food research begins at WRRC | Defining "Quality"Chemical reactions at low temperaturesChlorophyll as a benchmark | Major scientific results from the T-TT programSocietal impact of the T-TT program | Landmark designation | Further reading and acknowledgments

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