Whey protein is sold in many different concentrations and states. We have always focused on buying whey protein that was concentrated to a least and 80% level. This protein has been given the moniker "Concentrate". We have always felt that Whey Protein Concentrate (AKA WPC 80) has always been the best deal for your dollar.
In addition to buying WPC 80 for our products we have always tried to get a WPC 80 that is agglomerated (AKA instant or instantized). The reason we preferred the more expensive Instant WPC 80 was it's mix-ability. Instant WPC 80 mixes easily enough you can usually do it with a spoon, whereas regular WPC 80 will require more stirring to completely dissolve into your liquid.
Now you won't be albe to notice the enhanced mix-ability of Instant WPC 80 over regular WPC 80 if you are mixing with a blender or a shaker cup, but if you mix you whey with a spoon, it will take more stirring to completely dissolve the regular WPC 80.
The quality, protein content, assays, etc. of the two protein powders are the same, only the mix-ability is different.
Now if you really want in-depth agglomeration info here are some URLs that maybe helpful
Journal of Dairy Sciencehttp://jds.fass.org/cgi/content/full/90/2/570Food Product Designhttp://www.foodproductdesign.com/articles/2004/07/food-product-design-applications--july-2004--us.aspx?nck=1US patent from Googlehttp://www.google.com/patents?id=pAcyAAAAEBAJ&pg=PA1&lpg=PA1&dq=United+States+Patent+3852506&source=bl&ots=iVud_nlvPH&sig=7UIjjJJ79Q_idWsObJxSqMHB_P0&hl=en&ei=c6gGTN6FD8GAlAeBupT1Cg&sa=X&oi=book_result&ct=result&resnum=8&ved=0CDMQ6AEwBw#v=onepage&q=United%20States%20Patent%203852506&f=false
