I chew a kernel or two of every grain, taste the pumpkin or whatever else I add to the mash, taste the mash, taste the part I boil for decoction, taste the runnings off the sparge, taste a spoon or two during the boil, taste the sample I take for O.G., taste the sample I take for F.G., I'll even taste a fingertip of a yeast if I've never used it.. I taste it all.
For you to be surprised at not tasting the pumpkin leads me to think I take way more taste tests than you.
As for the sour part, hold an unopened bottle or two up to the light and look for rings in the necks. If you don't see then they the sour flavor is probably caused by something other than an infection that, as most do, leaves rings in the necks of bottles.