At its most basic, beer is simply the malt, water, yeast, and hops. Everything else is just extra added on to the base. And while hops get much of the credit for flavor, they’re not necessarily the most important ingredient.

I asked 15 brewers what the most underrated ingredient in beer is. Here are their responses.

“Water.” — Pete Anderson, co-owner of Pareidolia Brewing Company.

“Water is the most important ingredient to beer quality that is routinely ignored by beer drinkers at large. Breweries either require a high-quality water source nearby, or invest heavily in water purification and treatment systems. This should make sense — beer is usually 90 to 95 percent water, so it has a large impact on the final product. Additionally, the salts and ions that are in the water bring out various flavors in the other ingredients. For example, darker beers were developed in Dublin and Munich because the local water was high in chalk, which made hops taste soapy but let roasted flavors shine through. Inversely, the water near Burton-on-Trent was high in gypsum, which made hops bright and crisp, giving rise to the pale ale. By roughly matching the dissolved ion contents of those famous towns, craft brewers have been able to mimic styles that were originally region-specific due to their water. So, next time you’re drinking a fantastic pilsner in Colorado, thank your local brewer’s obsession with water quality.” — Alan Windhausen, head brewer at Pikes Peak Brewing Company.

“Water. I think people underestimate the quality of the water and how it affects the taste of the beer. We are fortunate in Lafayette, Colo., to have some amazing water. But even with that, we still filter and chemically treat our water for each beer style. Grain, yeast, and hops will never make beer made with poor quality water or incorrect water chemistry taste perfect.” — Davin Helden, CEO of Liquid Mechanics.

“Water. We take it pretty darn seriously.” — Chris Riphenburg, co-owner and head brewer of Ale Asylum.

“Water. Outside of the server beer training I do, I never hear anyone talk about it. Yet it can be one of the most complicated ingredients that certainly affects the final flavor of beer.” — Larry Chase, brewer at Standing Stone Brewing Company.

“Water. It’s the offensive lineman of the beer — you only notice it when it screws up. If you’re not thinking about it, it’s doing everything it needs to. And just like the lineman, it’s pretty boring to talk about with 95 percent of people, but that 5 percent gets what it means to have something that reliable and important.” — Jon Mansfield, brewery operations manager at Warhorse Brewing Company.

“Process. I think there is too much emphasis on the ingredients of beer. I often hear a beer is brewed with ‘these hops’ or ‘this yeast,’ so it must be good, but that isn’t always true. There are only four ingredients in beer; the difference is how we use them.” — Patrick Byrnes, head brewer at Islamorada Beer Company.

“Malt.” — Eric Meyer, brewmaster at Cahaba Brewing.

“Malt! I give a lot of brewery tours at Throwback Brewery. When I ask people to tell me what’s in a beer, only about 20 percent of the time does someone say ‘malt’! Malt is the heart of a beer. It drives color, alcohol, flavor, body, and more! If that’s not sexy, I don’t know what is?!” — Nicole Carrier, co-founder and president of Throwback Brewery.

“Malt. It really is the backbone of the beer, but people nowadays seem to care so little about it” — Kevin Blodger, co-founder and director of brewing operations at Union Craft Brewing.

“Malt. The right variety, origin, maltster, etc. are extremely important, and are still not fully appreciated by many brewers in my opinion.” — Chris Davison, head brewer at Wolf’s Ridge Brewing.

“At this point consumers are pretty savvy, so I don’t think any ingredient is woefully underrated, but we are huge malt fans here and love the layers of flavor complexity and the impact on body and balance grains bring to the table.” — Damian Brown, brewmaster at Bronx Brewery.

“Yeast. Yeast is a huge factor in the flavor of the beer. We brew 6-7 different styles of beer and carry 3 different types of yeast. You can change up the malts and hops all you want, but you want to find the right yeast and fermentation temperature that really brings all of the other ingredients together.” — Ian Smith, co-owner of Three Rings Brewery.

“No doubt in my mind: yeast. It’s the only ingredient that can kill a good beer recipe, and the only ingredient that can save a bad one.” — John Falco, head brewer at Lincoln’s Beard Brewing Company.

“Yeast is just now starting to be truly appreciated as a driver in flavor.” — Don Oliver, head brewer at Dust Bowl Brewing.