beer

Scientists unlock secret to thick, stable beer foams

For many beer lovers, a nice thick head of foam is one of life’s pure pleasures, and the longer that foam lasts, the better the beer-drinking experience. A team of Swiss researchers spent seven years studying why some beer foams last longer than others and found that the degree of fermentation—i.e., whether a given beer has been singly, doubly, or triply fermented—is crucial, according to a new paper published in the journal Physics of Fluids.

As previously reported, foams are ubiquitous in everyday life, found in foods (whipped cream), beverages (beer, cappuccino), shaving cream and hair-styling mousse, packing peanuts, building insulation, flame-retardant materials, and so forth. All foams are the result of air being beaten into a liquid formula that contains some kind of surfactant (active surface agent), usually fats or proteins in edible foams, or chemical additives in non-edible products. That surfactant strengthens the liquid film walls of the bubbles to keep them from collapsing.

Individual bubbles typically form a sphere because that’s the shape with the minimum surface area for any volume and hence is the most energy-efficient. One reason for the minimizing principle when it comes to a bubble’s shape is that many bubbles can then tightly pack together to form a foam. But bubbles “coarsen” over time, the result of gravity pulling down on the liquid and thinning out the walls. Eventually, they start to look more like soccer balls (polyhedrons). In a coarsening foam, smaller bubbles are gradually absorbed by larger ones. There is less and less liquid to separate the individual bubbles, so they press together to fill the space.

This “jamming” is why foams are typically far more rigid than their gas (95 percent) and liquid (5 percent) components. The more tightly the bubbles jam together, the less they can move around and the greater the pressure inside them becomes, giving them properties of a solid.

Various factors can affect foam stability. For instance, in 2019, Japanese researchers investigated a phenomenon known as “collective bubble collapse,” or CBC, in which breaking one bubble at the edge of a foam results in a cascading effect as the breakage spreads to other bubbles in the foam. They identified two distinct mechanisms for the resulting CBCs: a so-called “propagating mode,” in which a broken bubble is absorbed into the liquid film, and a “penetrating mode,” in which the breakage of a bubble causes droplets to shoot off and hit other bubbles, causing them to break in turn.

Rice could be key to brewing better non-alcoholic beer

beer, chemistry, fermentation, Science / Beth Washington / July 3, 2025

small glass of light colored beer with a nice foam head — Rice enhances flavor profiles for nonalcoholic beer, reduces fermentation time, and may contribute to flavor stability. Credit: Paden Johnson/CC BY-NC-SA

He and his team—including Christian Schubert, a visiting postdoc from the Research Institute for Raw Materials and Beverage Analysis in Berlin—brewed their own non-alcoholic beers, ranging from those made with 100 percent barley malt to ones made with 100 percent rice. They conducted a volatile chemical analysis to identify specific compounds present in the beers and assembled two sensory panels of tasters (one in the US, one in Europe) to assess aromas, flavors, and mouthfeel.

The panelists determined the rice-brewed beers had less worty flavors, and the chemical analysis revealed why: lower levels of aldehyde compounds. Instead, other sensory attributes emerged, most notably vanilla or buttery notes. “If a brewer wanted a more neutral character, they could use nonaromatic rice,” the authors wrote. Along with brewing beers with 50 percent barley/50 percent rice, this would produce non-alcoholic beers likely to appeal more broadly to consumers.

The panelists also noted that higher rice content resulted in beers with a fatty/creamy mouthfeel—likely because higher rice content was correlated with increased levels of larger alcohol molecules, which are known to contribute to a pleasant mouthfeel. But it didn’t raise the alcohol content above the legal threshold for a nonalcoholic beer.

There were cultural preferences, however. The US panelists didn’t mind worty flavors as much as the European tasters did, which might explain why the former chose beers brewed with 70 percent barley/30 percent rice as the optimal mix. Their European counterparts preferred the opposite ratio (30 percent barley/70 percent rice). The explanation “may lie in the sensory expectations shaped by each region’s brewing traditions,” the authors wrote. Fermentation also occurred more quickly as the rice content increased because of higher levels of glucose and fructose.

The second study focused on testing 74 different rice cultivars to determine their extract yields, an important variable when it comes to an efficient brewing process, since higher yields mean brewers can use less grain, thereby cutting costs. This revealed that cultivars with lower amylose content cracked more easily to release sugars during the mashing process, producing the highest yields. And certain varieties also had lower gelatinization temperatures for greater ease of processing.

International Journal of Food Science, 2025. DOI: 10.1080/10942912.2025.2520907 (About DOIs)

Journal of the American Society of Brewing Chemists, 2025. DOI: 10.1080/03610470.2025.2499768

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