Olfaction structure-activity relations

The most extensive studies on structure-activity relations In olfaction - apart from those on humans - have been on fish. 

There are three problems in particular that complicate interpretation of much of the data on structure-activity relations in olfaction. First, the different techniques used often yield data that are not strictly comparable. Recordings from a single or a few receptors, for example, are more reliable indicators of the odorant-receptor interaction than are recordings of the massed action of many neural elements in the olfactory bulb. 

Human perception of flavor occurs from the combined sensory responses elicited by the proteins, lipids, carbohydrates, and Maillard reaction products in the food. Proteins Chapters 6, 10, 11, 12) and their constituents and sugars Chapter 12) are the primary effects of taste, whereas the lipids Chapters 5, 9) and Maillard products Chapter 4) effect primarily the sense of smell (olfaction). Therefore, when studying a particular food or when designing a new food, it is important to understand the structure-activity relationship of all the variables in the food. To this end, several powerful multivariate statistical techniques have been developed such as factor analysis Chapter 6) and partial least squares regression analysis Chapter 7), to relate a set of independent or "causative" variables to a set of dependent or "effect" variables. Statistical results obtained via these methods are valuable, since they will permit the food... 

Of particular importance is to keep in mind the in vivo nature of food-related studies, where it is expected the simultaneous activation of several biochemical pathways. For that reason, the selection and applicability of the different methods need to be understood. In addition, the source of the data may play a major role, in most cases the information is collected from different laboratories and the variability of the data might be due not only to the chemical structure but also to the different conditions under which the experiments were performed. As an example, problems arising from the collection of data in olfaction studies have been reviewed by Chastrette (1998). 

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