I chose oranges today because I am soon bidding farewell to the warmer climes of the southeastern US until Christmas when I will be back in Florida (hopefully!) and once again able to enjoy my parents’ satsumas right off the tree. And, confirming my many years of experience drinking my orange juice off the tree, a study for 2008 revealed that the scent degrades rapidly. This must be why the taste of orange juice is best right after squeezing and not as good even 10 minutes later!
Apparently of the 300 or so volatiles in freshly squeezed OJ, only 25 are significant (although there is variation based on extraction method, how ripe the fruit is, cultivation style etc). The authors state:
‘Although there are generally accepted character impact compounds for grapefruit and lemon juices such as 1-p-methene-8-thiol and citral (neral/geranial)respectively, no single volatile in orange juice can be considered a character impact compound. Therefore, it is generally accepted that orange odor and aroma are the result of a collection of aroma active volatiles present in low concentrations (Shaw, 1991; Marin et al., 1992; Hinterholzer and Schieberle, 1998; Bazemore et al., 1999). It is the number and composition of aroma active compounds required to reproduce orange odor which still has not been generally accepted.’
As with most fruits and flowers, esters are a key volatile. Naturally, there are many kinds of esters but different cultivars of oranges share ethyl butanoate as a the most important ester and also a key odorant. But esters are only one class of odorants that create that invigorating morning aroma: in the orange 14 aldehydes are key odorants. Indeed the authors note that beyond the cultivar used for the glass of OJ (my favorite is the blood orange), other factors play a huge role. If the orange was fresh picked and juiced, it will be extremely different from the (typically) waxed (and often dyed) store varieties: the wax helps seal moisture but creates anaerobic condition that increase ethanols and an off-flavour. And, if the juice is reconstituted, the odor is even more removed from the original due to the thermal treatment it undergoes. The authors conclude that any synthetically produced fresh-squeezed orange juice odor will have to use between 15-25 odorants to achieve the desired result–a complex odor to simulate!
The message today is, if you have the chance, pick a fruit from the tree and squeeze it right away. See how it compares to the synthesized version of store-bought oranges, orange juice, and orange juice from concentrate.
The Smell of Evolution 