Our actual sense of "taste" is limited to four flavors: sweet, sour, bitter, salt. Everything else that we "taste" in food is actually sensed by smell. The odors waft up into our nose while we're biting it, or the back way behind our mouth through the sinuses as we're chewing. That's why things don't "taste" quite right when we have a really bad cold or other blockage, the odor receptors are out of service.
Knowing that, examine how the smell of food cooking or just sitting nearby is very similar to the sensation of "tasting" it in your mouth. The only parts of the flavor that you can't smell are sweet, sour, bitter, and salt.
Notice that the categories of food that aren't really all that alluring by smell are the ones for which a primary component of the taste is one of those four. Pastry: sweet. Pretzels: salt.
I have never seen a list of all the different types of odor receptors we have, I don't think anyone has ever identified them and catalogued them, either by finding the nerve endings in a lab or by isolating individual molecules and asking test subjects how they smell. For all I know there may be a thousand different individual smells.
And don't forget the things that we smell unconsciously: pheromones, especially the ones secreted by our own species. The chemicals we generate when we're afraid or horny. Those are picked up by specialized receptors in our nasal passage just like things we smell consciously like perfume and chicken soup.
The entire vertebrate higher brain evolved from the olfactory lobe in the most primitive fishes. All of our ability to reason and create civilization is an extension of the survival behaviors of fish based on "reasonable" reactions to things they smell in the water. Food, predators, good or bad weather, sex partners. Swim toward the good stuff and away from the bad stuff.
We still have that behavior. You can see it more clearly in mammals with more highly developed senses of smell like dogs. (They have about 25,000 smell receptors in their noses, we have only 5,000.) A male dog knows that there's a female dog in estrus two miles away. If he gets out of the yard he can find her by following the breeze. They can smell aggression in a tougher dog and fear in a weaker one.
It's been hypothesized, although not proven as far as I know, that we still have a few non-smellable pheromone receptors like that. We sometimes react inexplicably to things. The adrenaline or the testosterone or some other hormone starts pumping or we just feel dread, panic, or harmony, even though there's absolutely no smell in the air. It's pheromones, chemicals that our noses sense and send the signals to our brain, without any conscious odor.
Our olfactory lobe is still the most basic, primitive part of our brain. Have you ever noticed that it seems to store some of our deepest, oldest memories? I was born in Chicago but we moved away when I was so young I barely remember it. Forty years later I found myself in Chicago on a consulting engagement. I walked past a White Castle hamburger stand and suddenly I was overwhelmed. The smell, that beautiful, wonderful smell! I suddenly remembered my mother taking me downtown with her to turn in her address labels at the advertising company Reuben Donelly. (They didn't have computers in those days, there were a lot of jobs for typists. They let people work at home and they paid them for what they produced instead of for the number of hours they could tolerate sitting in a cubicle. Where did life go wrong?) And on the way back to catch the elevated train we'd stop and have White Castle hamburgers. It was so exciting, the highlight of my week.
I probably can't tell you three other things I remember about Chicago in 1949. But I remembered the smell of a White Castle hamburger like I'd just had one the previous day.
Smells have a lot of power over us. Beware the day when the electronics industry finally develops a way to reproduce and broadcast smells. They will have a thousand times more control over our feelings and our behavior than they already have.