Citral is a mixture of two terpenoids and commonly used as a citrus aroma. The two compounds, geranial and neral, are different isomers of 3,7-dimethyl-2,6-octadienal. They are unstable under acidic or oxidizing conditions, which is problematic since lemon-flavored products usually also contain acids. Decomposition of the compounds leads to a loss of citrus aroma and can create undesirable flavors or scents.

Robert J. Cannon and colleagues, International Flavors & Fragrances Inc., Union Beach, NJ, USA, have found thiophenes with a citral-like aroma in fried chicken. The chicken was marinated, battered, and fried using a traditional recipe. Afterwards, the meat was separated from the breading, chopped, and extracted with dichloromethane (DCM). The team then used gas chromatography−mass spectrometry (GC-MS) and NMR spectroscopy, as well as taste and smell tests, to identify potential flavor compounds in the extract.

The researchers found several alkyl thiophenecarbaldehydes with aromas similar to citral. Based on this discovery, they synthesized 35 different thiophenecarbaldehyde derivatives, e.g., 3-butyl-2-thiophenecarbaldehyde and 3-(3-methylbut-2-en-1-yl)-2-thiophenecarbaldehyde, and investigated their aroma. Several of the compounds have strong citrus notes, and proved to be more stable under acidic conditions than citral itself.

• The Discovery of Citral-Like Thiophenes in Fried Chicken,
  Robert J. Cannon, Nicole L. Curto, Cynthia M. Esposito, Richard K. Payne, Adam J. Janczuk, David O. Agyemang, Tingwei Cai, Xiao-Qing Tang, Michael Z. Chen,
  J. Agric. Food Chem. 2017.
  DOI: 10.1021/acs.jafc.7b01371