For absolute purists, the bottle of gin, the mixing glass, and the vermouth are all at room temperature prior to mixing. This is so a small quantity of cold water is diluted into the drink when the ingredients are stirred with ice. This infusion of water particularly brings out the floral notes of juniper, gin's primary flavoring ingredient. The dilution of the cocktail also brightens the flavors, opens the nose, and allows more delicate notes to blossom on the palate. Unfortunately, many bartenders now store their gin and mixing glass in a freezer, which results in a blunter, more one-dimensional drink with an oily, soft texture. As far as frozen implements go, it is acceptable to cocktail purists[who?] to pour a martini into a frozen cocktail glass, as, by this point in the drink-making process, the dilution has already taken place.
W. Somerset Maugham declared that "martinis should always be stirred, not shaken, so that the molecules lie sensuously one on top of the other," James Bond from the Albert R. Broccoli films ordered his "shaken, not stirred", a departure from the default and properly called a Bradford.(Embury 1948, p. 101) The concept of "bruising the gin" as a result of shaking a martini is an oft-debated topic. The term comes from an older argument over whether or not to bruise the mint in preparing a mint julep, and with gin refers to a certain bitterness developed by shaking. A shaken martini is different from stirred for a few reasons. The shaking action breaks up the ice and adds more water, slightly weakening the drink but also altering the taste. Some would say the shaken martini has a "more rounded" taste. Others, usually citing obscure scientific studies, say that shaking causes more of a certain class of molecules (aldehydes) to bond with oxygen, resulting in a "sharper" taste. Shaking also adds tiny air bubbles and ice particles, which can lead to a cloudy drink instead of a clear one. If the drink is used as an aperitif, to cleanse the mouth before eating, the tiny air bubbles restrict the gin (or vodka) from reaching all tastebuds. This is why purists would claim that a martini should always be stirred. Some martini devotees believe the vermouth is more evenly distributed by shaking, which can alter the flavor and texture of the beverage as well. Recent medical research has shown that shaken martinis have a slightly higher antioxidant level than those stirred, though the exact mechanism for this was not derived. In some places, a shaken martini is referred to as a "martini James Bond" or a "007"—Fleming actually named Bond's drink the "Vesper", after the heroine of the first novel Casino Royale, though it is a specific recipe using gin, vodka, and Lillet.
Shaken and stirred Martinis were taste-tested side-by-side on a 2008 episode of Mythbusters. All of the testers noticed a difference in taste between the two methods. Although they were not blindfolded, the drinks were allowed to sit so that there would be no visual difference between them.
Some references also cite a classic difference in the fundamental recipe of the drink. While the modern martini uses very little Vermouth in relation to Gin or Vodka - it is documented that pre-prohibition martinis were equal parts Gin and Vermouth. The abundance of "dry" Vermouth, and not the absence of vermouth, is said to be the origin of the drink's name.