Imagine a world where the inhabitants bodies have a simpler metabolism:
They need to get reactant A and reactant B, and combine them internally into AB, which they use as their energy source.
These creatures don't have other mineral needs (they can get minerals through breathing), and don't have anything like "essential amino acids" - they can manufacture all that stuff. Everything's just run by this AB molecule.
The precise ratios of A and B they need are set chemically. They wouldn't have much interest in variety - every bite they take would need to have the proper ratio in order to taste "good".
If too much extra A or B in the system had negative effects, the way these guys ate would really be interesting - they'd be obsessed with reducing "variety" in food and making it as consistent as possible.
They'd really like to eat things in the proper ratio. Their mouths would have sensors for the presence of A or B, and if they were eating too much of one or the other, it'd be a waste, or even taste bad. Preparing food would mean mixing it so that it had the right consistency. The more proper the ratios were, the better the food would taste. Similar to humans, they would probably be obsessed with the last tiny percentage.
Historically, traditional food blending methods would be good, and most people would eat "good" things most of the time - soups, or strips of two sources in the right balance.
Once they discovered blenders, they'd be super happy, cause they'd be able to almost exactly match A and B levels. So by the time they got to ~1900 or so level technology, everyone would be eating really well. Once they got to the modern era, everyone would be eating nearly the best possible food.
It's likely that the genetic setup they have to create sensors for this are not calibrated perfectly, either, so they tend to desire a bit too much of one or the other - which just like in humans would lead to various syndromes (over-A or over-B).
Possibly their internal systems would use secondary signals for the presence of A/B, without actually measuring it. So snacks would develop which trigger that, regardless of the actual presence of the nutrient.
The same thing has happened to humans. Most of our food desire is captured by our attraction to texture or crunchiness - which are not innately related to food value.
On long space missions, preserved food would be about as good as regular food - unless A or B decayed at different rates. They might detect purity as well - so if A decays into Ax, they would probably think that it tastes worse - there's only 90% A purity. But this distaste wouldn't be nearly as bad as an imbalance.
Lack of A or B (B or A overdose) would produce different symptoms - and there would be famines of lack of just one of the two. They would probably have two words for famine - one for "lack of A" and the other for "lack of B"