We've all heard the stories "I meant to use it sooner, but X, Y, and Z happened". I've have a few Oz. of hops in mylar bags in the fridge for either 3 or 4 weeks. I don't have it in front of me, but I believe it was cascade, centennial, and horizon. I will be near a brew store tomorrow, should I replace them, or am I OK?
I've got .75 oz magnum that are about 7 months old. I plan on adding them to my bittering charge in an IPA soon (along with some fresher magnum hops). The alpha acids will degrade over time, so adjust accordingly, but in your case 3-4 weeks is really not that much. They will still be fine to use.
FWIW, here's a calculator that someone spent a lot of time on to help solve this type problem: http://brewerslog.appspot.com/HopAlphaCalc IMO, your bigger problem is these hops are at least a year old (could be more) and you have no idea how they were stored before you accepted custody.
If they are moldy,wet or bad smelling dump them, otherwise, figure you have lose much of the hop qualities Brewers want and adjust your additions up.
Consider that hops are harvested annually. That means if you brew year round, the average age of your hops is six months. I wouldn't worry.
That thought crossed my mind. I know I've read posts about the "fragility" of hops if they are not sealed up and frozen. But we have no way of knowing how old the hops is when we get it, and what it's been through.
The work around is to buy your hops from a reputable dealer at the end of harvest (now) and protect them like your beer depends upon it. Sometime in Nov I'll put in my order for American hops, the Euro H. lupulus usually is available Jan/Feb . . . then keep them stored under my control.
I've kept whole hops for over 18 months, frozen. I wouldn't think twice about using your 3-4 week old refrigerated hops in a brew. go for it. Now if you were brewing commercially and this was a flagship beer, I would toss them and use a more reliable source.
