An ice-cold Pacifico and a Mazatlan sunset. There truly is nothing finer in this world. There is something magical about our local brew, and no where else on Earth does it taste as good. We used to drink Pacifico in Fort Worth, where it arrived world weary from it's travels across the border. It was a very fine beer even there, but here, at home, it is excellent. On a hot day when the sweat is trickling between your shoulder blades and into your bra, add a pinch of salt and a squeeze of lime, and its sublime.

What's funny is back in Fort Worth, we never added the lime or the salt. Just drank it straight. And really, Pacifico is a great beer in no need of help from condiments. So why when we are in Mexico do we all add lime to our beer? Probably because it's served with lime.

The longer I live here, the more I understand there is a reason for everything I see, no matter how quirky it seems at first glance. It's easy to assume that you get lime with your beer simply because everything in Mazatlan is served with lime – soup, tacos, steak, salad, Coke, whatever. It's the #1 condiment. I happen to adore a squeeze of lime, but taste is not the reason for the prevalence of the lime. Lime is a great germ killer.

Even though I figured out the lime-germ thing awhile back, I hadn't quite connected it to beer. The beer comes in a sealed bottle. What kind of disinfecting does it need? But then I noticed a distinct difference in the way foreigners and locals use the lime.

Most of the foreigners squeeze the lime the same way: Sprinkle a little salt on the lime, then delicately pinch the lime while holding the lime above the mouth of the bottle, being careful not to drip any juice on the outside of the bottle, but usually getting a squirt in the eye in the process. Most locals crush the lime on the mouth of the bottle, spilling juice down the inside and outside of the neck. Most places will thoughtfully serve your beer wrapped in a napkin that will catch the cascading juice before if reaches your hand and makes a sticky mess.

So what's up with that?

It's the ice. Almost no bar or restaurant in Mazatlan has an electric beer cooler. Beer is iced.

If you are out around Olas Altas around 2 pm, you will see the afternoon ice delivery to all the bars and restaurants along that stretch of road. A truck filled with giant blocks of ice trundles down the street and drops off a block or two at most locations. The same thing happens throughout the city. The ice is brought inside, chunked up with an ice pick, and used to make all the beer deliciously cold.

Here's the thing: the blocks of ice are not made with purified water. So, even though your wonderful beer is sealed, the bottle is floating in unpurified ice. The lime is used to chase away any clinging germs. If you are ever served a drink with chunked rather than cubed ice, don't drink it.

So I sort of solved the mystery of the Pacifico and lime. There are some holes in my theory – like if you order a Modelo or an import like Michelob, you don't get the lime. But I like my theory anyway. I'm really left with only one burning question. 90% of Pacifico drinkers, foreigners and locals alike, jam the lime into the bottle after they squeeze it. There is a deposit on Pacifico bottles, and they all go back to Pacifico to be sanitized and reused. Does Pacifico have a special lime extracting machine?