Riedel invested a lot of money and research and have decided that the Junmai glass requires a special vessel, in essence to draw out the flavors of umami. Beau Timken of True Sake was in Yamagata prefecture during the International Wine Challenge and met with the head of Riedel to discuss the glass (initially he dissed it first until he tried it for himself to understand what was being done). Unless you have the extra sensory to pick up the subtle bits, it may or may not be worth it. However I am curious, so if I find one in Japan and if I can bring it over with breaking it…I’ll see how it goes. Some say the choice of vessel is not quite as important after you get to a certain stage, but that really depends on your preference at the end and what you can pick up and interpret from tasting through it. Some might even argue drinking sake from wine glass is a placebo effect.
Not qualified to properly explain pasteurization from a professional or brewing standpoint, but I can tell you that all regular sake is twice pasteurized; once after pressing and before storage, and a second time before bottling. You will find some single pasteurized sake as well on the market (e.g. Born: Gold Junmai Daiginjo). Non pasteurized sake are original “nama” sake (some people refer to it as nama nama), and single pasteurized sake could either be nama zume, or nama chozo. Nama zume only goes through the first pasteurization, and nama chozo skips the first pasteurization and goes straight to the 2nd. Nama chozo sake could be matured in bottle for unspecified or targeted periods of time before release to give it more character. Most nama zume (at least the ones we can get here or through True Sake) are also Hiyaroshi sake, or seasonal fall/autumn “draft” release (and thus are limited). These are worth trying (actually any seasonal release) just once so you get a better understanding of the different profiles from one brewery or more throughout the year.
My guess is pasteurization via higher temperatures (~60 degrees C or so) neutralizes the enymes and yeast, to prevent further fermentation and/or ensure they don’t interfere with the flavor, profile, and characteristics of the brew as desired by the master brewer and end result.