HSI

Does the HSI value in the hops have much to do with the amount of hops you use, as well as the alpha acid delivered? I'm confused some are 15% some 40% etc. Who sets the HSI and I guess more to the point do we need to pay any attention to it. Thanks in advance fellow brewers.
Simie

The short answer is "Yes and Yes."

The storage index was designed to help you determine exactly those two traits, plus a few other qualities. More recent data is suggesting that not all Alpha acids degrade at the same rate, so the texture and flavor of the hop changes. Plus, contrary to long standing wisdom, it appears that Beta Acids do play a modest role in bitterness, which becomes more important as the hopa age.

Hops are harvested one time per year. They are not static, even under the best of circumstances.

My own experience has led me to ignore hsi.  Every time I adjust my additions for age I end up with an overly bitter beer.  I store my hops in the freezer in o2 barrier bags, with as much air removed asppossible.  I generally buy a yearswworth in the fall in small vacuum sealed packages 1-4 oz. 

As a result I no longer adjust for age.

However, if I bought a 1 lb bag, and kept it in the fridge or pantry, I probably would adjust for hsi. I know I would do some taste experiments to see how well the model fit my storage method.

All good info. I played around with it in BeerSmith and even though I change the HSI on my hops it doesn't alter anything on the recipe. We always vacuum seal and store in freezer. So I guess not to worry to much about it. Generally we go through everything in 2 years max. Thanks you guys....Simie