There is a difference between the different brands of orange liqueres. Grand
Marnier is by far the best choice but for a fruitcake i think triple sec would
be fine. Curacao is more bitter than the other two and might ruin the flavour
of the cake. As for shelf life, sunlight or exposure to air can both break
down citrus compounds. I'm not sure about a sealed bottle though. The
armagnac would not have changed, however, if it was not exposed to light and
the bottle sealed. High proof liquors last for as long as you can keep them
with little deterioration of flavour.
> I am wondering how long an opened bottle of liqueur is still good for
> using in recipes.
> I have a bottle of Triple Sec that is about 10yrs old. I would like
> to use it in a fruitcake recipe that calls for Grand Marnier or other
> orange-flavored liqueur. I tasted the Triple Sec and found the orange
> flavor to be pretty weak. However, I don't recall how it tasted the
> first time I used it. (I'm not a Margarita drinker). I probably
> should spring for a new bottle. Would Orange Curacao have more
> orange flavor than Triple Sec?
> In general, how long can an opened bottle of liqueur be kept before
> the flavor deteriorates? I also have a bottle of Armangnac that was
> opened 2yrs ago and hasn't been touched since. It's stored in a
> brown paper bag in a kitchen cabinet.