Relate cheddar cheese flavor to chemical components.

Research on the chemical and sensory analysis of cheddar cheese flavor has been conducted for more than 30 years. However, there hasn't been an extensive amount of research undertaken that directly links chemical components of the product with descriptive sensory attributes.

Literally thousands of volatile compounds have been found in foods. However, only a small proportion of these actually make an impact on a food's perceived aroma. Whether or not a volatile compound is aroma-active depends on the concentration at which it is present in the food and upon its odor detection threshold in the food matrix.

Generally, if an odorant is present at a level that exceeds its threshold, it should contribute to aroma. In some cases, odorants with very low thresholds (parts-per-trillion) contribute substantially to aroma but cannot be detected by modern instrumental methods, such as GC-MS. Therefore, GC-MS profiles of a product often do not account for the presence or potential contribution of these potent odorants.

Coupling instrumental methods, such as GC, with sensory analysis (sniffing or olfaction) in a technique called GC-olfactometry (GCO) allows us to detect these very low threshold odorants as they exit the GC column. That is, individual aroma-active peaks are detected by GCO even when no instrumental detection registers. By combining GC-MS and GCO data, we can gain a more complete picture of the overall aroma. Then, if desired, a more sensitive or targeted analysis can be used to quantify the trace aroma constituents.

Scientists at the University of Illinois have developed and validated a cheddar cheese flavor lexicon that has standard descriptive language, definitions and standard rating scales. Their current research has focused on the identification and confirmation of specific cheddar cheese flavor (aroma) components (chemical anchors) that are responsible for each sensory descriptor identified in the lexicon.

The investigators faced a number of challenges related to the development and application of instrumental sensory-based flavor analysis techniques for the identification of key odorants responsible for characteristic sensory flavor notes identified by descriptive sensory analysis. Such challenges included being able to properly identify compounds responsible for characteristic cowy-barny (p-cresol) and earthy (2-methoxy-3-isopropylpyrazine) aroma notes in farmhouse cheddar cheese and the nutty (3-methylbutanal) note that's predominant in some cheddar cheeses.

The unambiguous linking of flavor descriptors with causative chemical components will permit cheese researchers to precisely relate sensory flavor quality with the chemistry and technology of cheddar cheese production.

Further information. Keith Cadwallader, Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 202 Agricultural Bioprocess Laboratory, 1302 West Pennsylvania Ave., Urbana, IL 61801; phone: [phone]; fax: [phone]; email: [e-mail].