Sweet aroma of sautèed onions

<p>[Purpose] Onions are a widely consumed foodstuff in all types of cooking, and are known to be prepared in a variety of ways, including boiling, frying, and sautéing, as well as eating raw. In particular, ‘’caramelized onion,’’ which is prepared by carefully sautéed onions, has a characteristic sweet flavor, and is used in a variety of dishes, including stews and curries. The authors started their research with the aim of elucidating the components of the unique sweet and rich flavor of caramelized onions.</p><p>[Methods] The AEDA (Aroma extract dilution analysis) method was used to analyze the aroma of sautéed onions. The sample onions were late season yellow onions produced in Hokkaido, Japan. Sautéed onions with different cooking times were prepared, and the one with most favorable flavor and color was determined by sensory evaluation and used as the sample for AEDA analysis. The components of sautéed onions with different cooking times were analyzed by the HPLC.</p><p>[Results and Discussion] The results of the AEDA analysis showed that sulfide compounds with a pungent odor characteristic of onions, as well as furan compounds with a sweet aroma, were detected with a higher FD factor (Flavor Dilution Factor). Among furan compounds in particular, HDMF (hydroxy-2,5-dimethyl-3(2H)-furanone) was found to have the highest FD factor and contributed the most to the overall sweet flavor. The HDMF concentrations of sautéed onions at different cooking times were determined and compared by HPLC, respectively, and showed a tendency to increase over time. HDMF is a compound reported to be formed by the Maillard reaction and a sweet, heavy flavor. This study suggests that HDMF formed by the Maillard reaction during the onion heating process is important for the formation of the sweet, rich flavor characteristic of caramelized onions.</p>