When does the pour matter?

Question

Especially when it comes to serving beer, such as Guinness, it is debatable that the pour is the most important aspect. This is something I understand due to the layering and carbonation...

When is it important to pay attention to the pour for other alcoholic beverages?

For example, I dated a waitress that was adamant about the proper way to pour wine - thumb in the bottom, on the forearm with a napkin, presenting the label during the pour, finally properly spinning the bottle at the end of the pour... Is this all due to presentation or does it have anything to do with consumption, as well?

Considering cocktails, I do not mean shaken vs stirred...

Answer 1

This is very broad so I will stick to wine in my answer. There are many considerations for pouring, you have the aesthetic aspects and presentation, and you have the mechanical aspects which can change the properties of the served drink.

For wine, the waitress was right from a presentation point of view when served in a fine dining setting. Holding the bottle by the base gives the server the maximum reach with good control, twisting at the end helps reduce drips, the napkin can be used for any cleanup quickly, and showing the label assures the customer they are being served the wine of their choice. This technique does not effect the consumption, if you are entertaining at home there's no right or wrong way really, although I find the hold and twist give me the same advantages when I'm serving wine at my table.

From a mechanical aspect, with wine the major considerations are sediment with red wines and bubbles with sparkling wine. If you have a red wine with sediment you need to be careful to not shake up the bottle and to leave the dregs in the bottom as you pour (or decant it through a strainer). With sparkling wine you need to be sure not to overfill. With most wines how you pour it makes no detectable difference on the flavor.

Answer 2

Guinness' perfect-pour is actually a marketing scheme that gives them an exclusivity factor. They have training courses and will invite patrons that visit Guinness to become masters of The Perfect Pour. However, it has no real impact on the beer.

The actual answer to pouring is much less mystic and much more scientific. The pour does matter for several different reasons.

First - Why does foaming occur? Carbon Dioxide is actually in solution inside of the beer. Several things play a factor; but, the biggest two are temperature and pressure. CO2 goes into solution easily around 36ºF (Here is a link to a slide that lists the temperature and PSI of beer). Therefore - the warmer the beer when poured, the more head you tend to get (because the CO2 is leaving solution). The other big reason is pressure differentials - inside the keg/can/bottle the pressure is keeping the CO2 in solution. When the pressure outside is less than in the keg (like when you open a beer bottle or pour the beer) the CO2 starts escaping.

The reason pour matters is really the following mixture of craftsmanship and business.

1. Head retention (or the froth that stays at the top of your beer) is really important! It gives off a lot of aromatics that you get to experience before even tasting the beer. When you make beer - the hops added at the beginning of the process give the bittering falvors that balance the malty-sweetness while hops added toward the end (or even during fermentation) impart less bittering and more aromatics. Therefore, a lot of the beer's personality shines through the foamy-head. Let's be honest... what beer lover doesn't think that the way a freshly poured Left-Hand Nitro Stout (or other beers that have that tan-cascade of CO2 falling away from the head) is beautiful?
2. For businesses foamy-pours are money wasters. This link from TurboTapsUSA describes why their tap is a money saver. It comes down to lost beer. We know that a beer with foam 3 inches from the top turns into a beer with only about 1.5 inches of space from the top. So, when you see bartenders or others pouring until there is just beer to the top while foam pours out in the drain are just wasting money.
3. Glass shape plays a big part in foaming. Nucleation sites help create carbonation (discussed at length in this forum). When you want a lot of head retention, this is a good thing. There is also a reason that glassware is shaped the way it is. It allows smells from the foam to be directed towards the imbiber's nose, allows the drink to breathe like wine, or keeps your hands from warming up the beer too much.