Hops used in beer are the flowers from the hop vine. They are the ingredient that give the beer 

its bitter flavour. Bigger breweries tend to use hops grown in larger quantities in North America, 

whereas craft breweries can purchase hops grown in New Zealand, with those from Canterbury 

being very popular. Different varieties of hops produce a different flavour in the finished product, 

so a lot of different flavours can be accessed with the locally grown hops (Schohn, 1999).

Yeast is produced during fermentation of beer, and while this has to be separated from the 

product before it is bottled, it is often not reused as it is contaminated with the beer already 

brewed within that batch.