Sifting through back issues of Cooks Illustrated looking for a particular article this morning, I chanced upon something I missed the first time around about jalapeno peppers. Something that really got my attention because I had, like them apparently, come to the conclusion that the larger the jalapeno the milder the flavor and I tended to pick the smaller or larger ones every time I buy (almost weekly) depending on the heat desired for the end use. If I have no dish planned but am buying a couple just to have on hand, I typically select two large and two small.
Also, the larger and milder peppers have seemed more a recent thing to me, so I was kind of presuming that modern agribusiness had been meddling with nature's recipe in order to produce jalapenos more appealing to the masses.
About all of the above? Per Cook's, apparently not. "But when we arranged a tasting of jalapenos of various sizzes, there seemed to be no correlation between size and heat. To investigate the matter further, we sent five similarly sized jalapenos to the lab, requesting levels of capsaicin and dihydrocapsaicin. Sure enough some chiles were nearly 10 times hotter than others--even though they all looked alike."
So, back to the drawing board on that one.