The female hop flower is used in beer for flavour and preservation. For flavour, it imparts both bitterness and aromatics. Depending on a what time a hop is added to the boiling process during beer production will determine if and how much either bitterness or flavour it gives the final beer. In craft, particularly in pale ales such as IPAs, the aromatics of hops are prized and a great deal of effort goes into capturing in the brew as much aromatics as possible.

Source: Four Peaks Brewing Co. - Beer Fact Friday: Terpenes.

In craft beer there are a lot of pale ales that you’d describe as “fruity beers”. These fruity flavours aren’t because we’ve added pineapple, orange, guava,… etc, it’s because these flavours are coming from the hops themselves. Us brewers are a revolting lot and if we find a rule we are likely to break it just for fun. So yes, we do ALSO add fruit to our beer, but it’s more occasionally, and when we do we skite about it and tell you so on the packaging. Therefore, unless we’ve been bragging about it, any “fruity” flavour in the beer assume it’s from the terpenes of the hops.

Terpenes are the name given to the aromatic compounds in plants, particularly produced in conifers. Hops, a conifer, contains many of the flavours and aromas we find pleasing in fruit, herbs, spices, and other flowers. This is why the hop flavour can taste “fruity” or “floral” or “spicey” or “herbal”. Here are eight of the most common terpenes in hop essential oil that you’d associate with other plants you know:

Farnesene: sweet, woody, herbal (found in turmeric, chamomile, quince)
Caryophyllene: peppery, clove, woody (found in pepper)
Humulene: floral, earthy, spicy (found in sage)
Myrcene: herbal, grassy, herbaceous (found in cannabis)
Limonene: citrus, orange, lemon (found in lemons)
Pinene: piney, woody (found in conifer trees)
Linalool: floral, lavender, bergamot (found in lavender)
Geraniol: floral, roselike (found in rose oil)

Cornerstone of Beer Flavour: Hop