A Nightmare on LOX Street

DUN DUN DUN.

It stalks your beers and murders its taste and texture, reducing luscious hazies to flat oat milk and crispy pilsners to limp lagers. Lipoxygenase (LOX for short, and not the delicious smoky kind on your bagel) stalks your beer freshness like a horror-movie monster. Just like Freddy Krueger favored chasing co-eds with his claw, LOX is using trans-2 nonenal (T2N) and trihydroxyoctadecenoic acid (THOD) to do its dirty work. Dread it, run from it, oxidation arrives all the same. So how to stop LOX from oxidizing your beer? Or at least slow it down?

The answer is LOXless malt. And here’s how we learned to stop ignoring and start addressing LOX-derived oxidation in beer.

LOX. Never heard of it before? Lipoxygenase is a bit obscure as a beer concern. But make no mistake, LOX is killing your beer right now. Most brewers have rightfully latched on to oxidation as a leading cause of beer-flavor instability but have only ever looked at mechanical means with which to address its influence. From reducing dissolved oxygen (DO) during packaging to maintaining a vigorous cold chain to the liquor store, brewers go to terrific lengths to make sure their beer shows up to the consumer fresh and ready. But what happens when it leaves those caring hands?

LOX, T2N, and THOD

Flavor stability is arguably the greatest challenge in brewing. Even under ideal packaging conditions, beer develops stale flavors (cardboard, sherry, soy sauce, etc.) as oxidation products accumulate. T2N is a by-product of LOX (as is THOD, which kills beer foam) and arguably the greatest cause of stale-beer flavor. When IPAs start to taste like old ale, T2N is to blame. T2N has an extremely low flavor threshold (0.15 parts per billion), and for the past several decades researchers, maltsters, and brewers have focused vast amounts of attention on how T2N forms. The answer lies in the very barley that is used to make your beer—and the lipids that fuel barley growth.

Lipids

Barley contains numerous lipid compounds, and these compounds are essential for yeast nutrition and cellular metabolism during fermentation. The downside is that these lipids are highly susceptible to oxidation. Unsaturated fatty acids are especially reactive in the presence of oxygen and can be transformed into aldehydes and ketones that generate stale aromas. Most of this lipid content is destroyed during various parts of malting and brewing, but not all, and it takes only a little to affect beer flavor.

Between 2.5 and 4.7 percent of barley’s kernel composition is lipids, Meanwhile, an oat kernel’s composition includes a whopping 4.5 to 10.3 percent lipids. So, if you’ve ever wondered why hazy IPA tends to lose its intention of flavor so quickly, LOX-derived T2N is a chief cause. Rice kernels, on the other hand, contain only 0.9 to 3.1 percent lipids. So, if you’ve ever wondered how lagers made with rice have such reliable flavor stability, that might be your answer.

To get technical: T2N is primarily formed through the oxidation of unsaturated fatty acids, and LOX enzymes in barley catalyze the oxygenation of those fatty acids, creating hydroperoxides that later degrade into aldehydes such as T2N, with THOD as a co-product. To be nontechnical, fat makes your beer taste flat.

Importantly, beer-flavor staling via LOX doesn’t “wait”; it begins attacking beer immediately. T2N formation pathways develop during mashing and continue through boiling, fermentation, packaging, and storage. On average, the intensity of a papery note in beer doubles during the first month, then doubles again by month three or four. And flavor instability doesn’t come from any one single source. Rather, oxidation products hide in precursor-bound forms until aging releases them. This is the basic idea behind why beer starts out tasting fresh and then degrades over time.

Maltsters do terrific work in reducing LOX during kilning of the malt. Brewers also traditionally reduce LOX through good brewing practices, such as limiting oxygen pickup during the mash, optimizing the boil, improved packaging control, and cold storage. But researchers have increasingly realized that barley genetics themselves might be a better long-term solution. Studies have identified LOX-1 (there are three main types) as a key source of T2N production. What if you could just get rid of the LOX in the barley?

“At Dawn, Look to the East”

Okayama University in Japan was one of the first research centers to begin aggressively searching through their barley germplasm, finding a handful of barley strains that lacked the lipoxygenase gene. With LOX-1 as the prime producer of T2N precursors, the identification of barley strains lacking LOX-1 activity was a major development toward greater beer-flavor stability. Greater still was the introduction of CDC PolarStar in 2010, the first crossbred LOXless variety on North American soil. PolarStar was entirely developed through existing breeding programs (i.e. no GMOs), and in sensory evaluation, flavor was rated superior to its parent breeding varieties.

More importantly, beers made with LOXless malt had significantly improved flavor stability during storage. T2N levels were dramatically reduced, with sensory panels consistently finding the beers fresher after aging. LOXless malt overperformed in every way, with reduced T2N precursors, fewer staling aldehydes, and improved flavor and freshness as the beer aged. Studies revealed that LOXless malt didn’t completely eliminate oxidation pathways, but it did greatly reduce LOX activity.

Got Foam?

Foam was another component of beer that was dramatically improved through use LOXless malts. Lipids are known to be foam-negative; the fatty acids disrupt protein structure and compromise bubble density. Because LOXless malts disrupt this disruption, brewers consistently noticed improved foam. Ever wonder why dark beers typically have such fantastic foam? A greater proportion of the malt is roasted, and roasting destroys LOX and—by extension—foam-killing THOD.

Flavor Freshness Doesn’t Happen in a Vacuum

The findings with LOXless malt are highly promising but are not a silver bullet to prevent all beer problems. LOXless malt isn’t a catchall to compensate for bad brewing practices, and brewers shouldn’t look at it as such. Good raw material selection, minimizing oxygenation, a tight packaging game, and a quality cold chain are all important components of ensuring maximum beer-flavor stability. But the benefits of LOXless malt for flavor stability are undeniable.

Likewise, brewers shouldn’t view lipids as only good or only bad. Lipids play an essential role in the brewing process, but their oxidation can cause staling in beer. The lipids that LOX turns into T2N are less the problem than controlling the oxidative reaction to them. LOXless malt takes great strides toward eliminating this problem by short-circuiting the pathways that LOX uses to do so.

Research covered in the Polish Journal of Microbiology even hinted that T2N could exhibit cytotoxic and genotoxic properties under experimental conditions, giving a further impetus to reduce the compound. Perhaps there is something to the adage that stale beer not only tastes bad, but also makes you feel bad.

LOXless malt translates directly to increased shelf life. Malt-derived staling of beer is directly correlated to loss of perceived hop flavor. When packaged beer has to spend wildly varying amounts of time on the shelf, in hot trucks, and in non-temperature-controlled distributor warehouses, flavor fades fast. LOXless malt buys a brewer precious weeks of flavor stability, ensuring beer tastes as intended. LOXless malt preserves delicate hop-flavor aromatics when all other preventative steps fail.

Again and again, LOXless malts have demonstrated superior flavor stability and fuller foam in finished beer. As breeding programs develop, expect LOXless malts to progress from being an obscure curiosity to an unmistakable standard. The future is now in the world of malt, and that future is LOXless barley.

Digging In

If you want to dive deeper, sources include the collected research of Dr. Xiang Yin as presented during his AMBA presentation on LOXless barley, as well as the following articles, videos, and papers.