Foods can sometimes flavors and scents that we do not normally experience. Experts call these sensations “off-flavors.” They do not necessarily signal that the food is harmful to health, but these deviations from an expected flavor reflect quite poorly on manufactured foods in the eyes of customers. Off-flavors are known to have various causes. Sources can be internal (originating from compounds within the food) or external (invading or permeating from the outside). Our intention is to explore techniques to avoid and eliminate off-flavors in food products, present ways to control them, and delve into how they develop.

In this report, we show the difference off-flavor analysis of food and the general analysis of flavor with some cases of food.

Flavor and off-flavor compounds in fish and shellfish are summarized. Lipid oxidative derivatives, such as alcohols and aldehydes, contribute to fresh fish flavor. The smell of fish and shellfish susceptible to deterioration of freshness becomes strong according to the increase of lipid oxidatives, amines, sulfur compounds and acids. Fish and shellfish off-flavors are caused by specific native flavor, degradation of freshness, environmental pollutions or contrived treatments. In most cases strict thermal management is important to avoid off-flavors in fish and shellfish. Environmental pollutions often cause off-flavors even in these days.

We investigated the structure-odor relationships of khusimol, which is the main odor component of vetiver, and its derivatives. Khusimol has a woody, earthy odor. To examine the importance of the characteristic khusimol structure, various compounds were synthesized to explore multiple structural features that were expected to affect the odor. For retaining the woody, earthy odor, the khusimol structure was more important than the substituents.

The sense of smell arises from the binding of odor compounds to olfactory receptors, and the structure of odor compounds is a critical factor. However, the relationship between compound structures and receptors is highly complex and systematic knowledge of this relationship remains inadequate. This study focused on γ-lactones, which are components in the aroma of peaches. γ-Lactones consist of a 4-carbon lactone ring and often bear a hydrocarbon side chain, the length of which affects the aroma. The effects of the γ-lactone ring on aroma were investigated by synthesizing several chain esters with different cleavable bond sites and comparing the odors of the resultant compounds with those of their cyclized lactone counterparts. The results showed that the ester bond and partial structure adjacent to the ester bond played an important role in aroma of γ-lactone, while the hydrocarbon side chain length played a smaller role.

Odor is complex because it arises from many components. Differences in odor result from receptors recognizing differences among the structures of odor molecules. However, the same receptors recognize odor molecules with similar structures. The relationship between odor molecules and receptors is complex and there is a lack of systematic knowledge about structure-odor relationships. We examined the structure-odor relationships of vanillin derivatives. Vanillin is a natural odor molecule with a trisubstituted structure. We found that the presence, type, and position of substituents affect the odor of vanillin derivatives.