old hops ok for bittering?

I have about 2oz of 1 year old opened perle, and 4 oz fresh centennial to make a nice american ipa with. I was wondering if i can save the centennial for more of the flavour and aroma and use the old perle for bittering?

The perle hops (about 2oz @ 7%AA) were opened one year ago, sealed back up and kept in a cold fridge since. Are they no good for bittering hops any more?

aiming for around 1.060 OG and 60IBU

The thought process is that hops lose a lot of the classic bittering properties when they've aged a bit. But as they lose certain things, they gain others. Ray Daniels talks about it in Designing Great Beers.

I'd say go ahead and use them. They probably won't give you the classic exact bittering charge that you may expect, but they may give you a different favor that you may really enjoy. Some brewers age their hops especially for this purpose. Maybe try and do another brew with fresh ones so you can do a nice side by side comparison.

Bitterness drops off faster than flavor and aroma. As kmlavoy said some brewers actually age their late hops, I say use the fresh ones for bittering if you want your IBUs to be accurate.

ok yeh you guys are probably right. heres an idea for the recipe then trying my best to roughly convert to US units.

American Centennial IPA (20 litres, 5.25 US gallons)

12lbs Pale Malt
1/2lb 60L crystal malt

1oz centennial 10%AA 60min
1oz centennial 10%AA 30min
1/2oz centennial 10%AA 15min
1/2oz centennial 10%AA 5min
1oz centennial 10%AA dry hop