Carvone

Or How about "Carpedium" -- Seize the new element!

Food flavour is generally made up of taste (chemical effect), aroma (chemical effect), texture while chewing (physical effect), and appearance (psychological effect as it contributes to your expectations of how the food will taste). I believe most people above have already hit the nail on the head saying that we crave high caloric content and in general things with high sugar (universal sweetness), fat (high calories per gram, a flavour/aroma carrier and adds creamy texture), and salt (a flavour enhancer promoting volatility of flavour compounds and potentiating taste receptors to have greater sensitivity although there are no calories from salt being a mineral!). All flavour comes from small molecules (aromas, sugars, fats, salts, peptides) as large molecules (proteins, starches, gums and other polysaccharides) will be bland due to being non-volatile and too large to attach to taste receptors, but do contribute to food texture in pastiness (water-binding by starch) or gelation (water-trapping by gums). The threory with fruit is that they do not want to be eaten when not ripe so are sour and bland in flavour. When ripe, enzymes have broken down polysaccharides and glycosides into sugars and flavour compunds making them sweeter, more flavourful and moist (due to hydrolysis) and hence softer in texture. Ripeness is when the fruit has matured to where it is most reproductive, and it now it wants to be eaten by animals so the seeds can be carried to different areas before being passed through into feces. Bitterness on the other hand is almost universally disliked and in fact it has the lowest sensory threshold of all five taste groups. This is because most poisons and toxins are usually bitter (eg. alkaloids), and generally bitterness is detected at the back of the tongue to cause gag reflex to bring up any toxins, while sweetness is detected at first at tip of tongue (more sweet taste receptors there) Some bitter compounds such as caffeine in coffee/tea, and hops extracts in beer can have an acquired taste with some people but are in dilute amounts and are generally masked by other ingredients. In most cases, it is said that nutrition will be promoted by a balanced diet meaning consumption of a variety of foods (fruits and vegetables with healthful phytochemicals and antioxdants), high in vitamins and certain minerals, with moderation to calorie-dense foods with little else. Cola is not unhealthy for you in the sense that it does not have anything harmful to your body (OK high sugar and phosphoric acid can help rot teeth), but really it supplants the consumption of healthier drinks such as natural juice and milk.

As a flavour chemist, I can verify that noses can become fatigued to smelling the same aroma repetitively, and when we lose our sensitivity to an odour we are trained to stick our nose into our arm at the elbow joint and smell ourselves to cleanse the olfactory receptors. So with a fart, it could be a case of loss of sensitivity to our own brand, but I also think, as mentioned above, it has a bit to do with being proud of our own brand, at least we are expecting our fart and prepared mentally for it, and can then admire it, while someone elses always hits you off guard. Also, although someone above quoted the composition of a fart, and this may be correct for the major gas constituents (although I am not sure), there are definitely many more odour compounds present in trace amounts. And like flavour compounds, our noses are very sensitive to these trace amounts (parts per million to par per trillion) with much lower sensory thresholds than say methane. Hydrogen sulfide (rotten egg) has a very low sensory threshold. Also different people have differences in sensitivity to different compounds, thus why some farts are detected by others and not you and vice versa. I have often been curious to analyze a fart on the GC-MS, but never gotten around to it. (Kinda gross I guess). Also I figured there would be great variability in the trace aroma compounds in a fart based on many variables such as the foods eaten previously, the microflora in the intestine, enzymes, how much water or ethanol are present to act as solvents, etc. After all, aroma compounds are the small molecular weight fragments broken off of or are the microbial waste byproducts of large molecules such as carbohydrates, proteins and fats.

I am not aware of a single marker for determining age, but it may be possible to run a multivariate statistical analysis of different components within blood to determine age, similar to identifying the strain of bacteria based on a multivariate analysis of the ratio of all fatty acids in a GC fatty acid methyl ester analysis. It is probable that as an organism ages, some things in blood increase (eg. cholesterol build up) and some decrease but this will vary widely across populations, so only with some sort of multiple regression of a large data set could this be determined, though I am not aware if any study like this has been attempted.