Nuclear Magnetic Resonance Reveals Why Some Burgers Taste Juicier Than Others

Juiciness is the quality that can make or break a burger, whether it comes from a cattle feedlot or a plant-protein extruder. Yet for all the billions invested in plant-based meat alternatives, replicating the moist, lubricated mouthfeel of real beef remains stubbornly elusive. A new study from Ben-Gurion University of the Negev, published in Current Research in Food Science, offers a strikingly physical explanation for why: the secret may lie not in how much water a burger holds, but in how freely its water molecules can move through the matrix before the first bite is ever taken.

Moshe H. Azachi and Zeev Wiesman compared two commercially available products that could hardly be more different in structure: an Angus beef burger and a soy-based vegan burger. Both were cooked in an air fryer to an internal temperature of 72 degrees Celsius, then probed with an arsenal of techniques including low-field time-domain nuclear magnetic resonance (TD-NMR), cryogenic scanning electron microscopy, texture profile analysis, and a trained sensory panel. The question was deceptively simple: could measurements of the water inside the burger, taken before anyone chewed it, explain which one would taste juicier?

The answer hinged on a subtle but crucial distinction in physics. When a burger is chewed, the teeth compress and fracture a hydrated soft material, generating pressure gradients that squeeze fluid through interconnected pathways. This mechanically driven serum release is what food scientists increasingly regard as the true proximal driver of perceived juiciness. Molecular self-diffusion, by contrast, is the spontaneous, thermally driven jiggling and translational motion of individual water molecules, measured by pulsed-field-gradient NMR in a completely undeformed sample. The two processes are physically distinct, but the researchers hypothesized they might share common structural determinants: the size of water-filled domains, the connectivity of the aqueous network, tortuosity, interfaces, and the strength of water-protein interactions.

The first surprise came from the moisture numbers. The beef burgers started with 68.05 percent water and the soy burgers with 62.61 percent, a difference that did not reach statistical significance. During cooking, the beef patties lost far more mass, shedding 35.73 percent of their weight compared with 21.21 percent for the soy burgers, and shrank nearly twice as much in diameter. By conventional food-science logic, the soy burger should have been the juicier product: it held onto its water more tenaciously. Instead, the opposite happened. A panel of thirteen trained assessors, scoring five juiciness-related attributes on a ten-point scale, rated the beef burger dramatically higher on every single one, from first-bite juiciness to sustained juiciness, rate of juice release, and mouthcoating. The composite Sensory Juiciness Index came to 7.46 for beef versus 5.00 for the soy burger, a difference the authors report as highly significant.

The decisive instrumental signal came from the NMR diffusion measurements. Using a 20 MHz Bruker Minispec mq20 and the classic Stejskal-Tanner pulsed-field-gradient sequence, the team measured an apparent water self-diffusion coefficient in both the interior and the cooked outer layer of each burger. The beef interior showed the highest value, 1.03 by ten to the minus nine square meters per second, while the soy burger’s outer region showed the lowest, just 0.36 by ten to the minus nine. At the whole-burger level, beef averaged 1.030 and soy 0.704 by ten to the minus nine square meters per second, a difference with a p-value below 0.001. In both products, diffusion decreased from the moist interior toward the dehydrated surface, but the formulation gap dwarfed the regional one.

What makes this result conceptually important is what did not differentiate the burgers. Transverse relaxation times, the T2 values that reflect local molecular environments and confinement, told a murkier story. The longest relaxation components exceeded roughly 300 milliseconds in both matrices and did not differ significantly, and the mean long-T2 values at the parent-burger level were statistically indistinguishable. The soy burger’s outer layer was especially instructive: it combined a comparatively long mono-exponential T2 with a very low diffusion coefficient, demonstrating that water molecules can be locally mobile yet still encounter severe barriers to longer-range displacement. Relaxation and diffusion, in other words, probe different aspects of the water state and cannot be used interchangeably.

Cryogenic scanning electron microscopy provided visual context. The researchers flash-froze small sections from the interior and outer regions of each cooked burger, fractured them under cryogenic conditions, etched them, and imaged them with an in-lens detector at around minus 120 degrees Celsius. The beef samples revealed a heterogeneous architecture of irregular pore-like and hydrated domains with apparently greater continuity, while the soy matrix appeared denser and more homogeneous, with thicker solid regions and lower apparent connectivity, especially in the cooked outer layer. This qualitative morphology paralleled the spatial ordering of the diffusion coefficients, though the authors are careful to note that pore size, mesh dimensions, tortuosity, and three-dimensional connectivity were not quantified, so the structural explanation remains a hypothesis rather than a demonstrated mechanism.

Texture told a similarly incomplete story. The beef burgers were numerically harder and chewier than the soy burgers, though these differences did not reach significance with only three independent parent burgers per formulation, and only cohesiveness differed significantly. The juiciness gap therefore cannot be reduced to a simple soft-versus-hard distinction. What the study does support is a multiscale framework: food architecture shapes the pre-deformation molecular state of water, which TD-NMR can measure non-destructively; during mastication, deformation generates pressure gradients that drive macroscopic serum displacement through whatever pathways the architecture permits; and that released serum lubricates the mouth, producing the sensation of juiciness. The intermediate links in this chain, the actual serum flux and oral lubrication, were not measured here and remain testable propositions for future work.

The authors are equally candid about the limits of their evidence. Because the sensory ratings and the NMR measurements were obtained from separate experimental units rather than matched observations from the same parent burgers, no within-sample correlation between diffusion and juiciness could be calculated. The findings represent concordant formulation-level contrasts, not proof of causation. The study also compared only one commercial beef product and one commercial soy product, so it establishes a contrast between two matrices rather than a universal law of animal versus plant. An exploratory Water Accessibility Index, defined as the ratio of diffusion to relaxation, showed a significant difference between formulations but remains an empirical, unit-dependent descriptor pending external validation.

Even so, the implications for food designers are concrete. Strategies aimed solely at maximizing water-holding capacity or minimizing cooking loss may be fundamentally insufficient: a highly hydrated matrix can still taste dry if its architecture strongly restricts the redistribution of fluid during chewing. The design objective, the authors argue, is not simply to trap water but to retain it through manufacture and cooking while making an appropriate fraction available at the moment of mechanical deformation. Variables such as protein-network organization, domain connectivity, structural anisotropy, lipid distribution, and protein-polysaccharide interactions all become levers worth pulling. And because TD-NMR diffusion is rapid and non-destructive, it could serve as a screening tool that predicts, before a single taste test, whether a reformulated plant-based patty has the architectural prerequisites for a genuinely juicy bite.

Subject of Research: Water self-diffusion measured by TD-NMR in cooked beef and soy-based burger matrices and its relationship to sensory juiciness

Article Title: Water self-diffusion differentiates two protein-based burger matrices with contrasting sensory juiciness

Article References: Azachi, M. H., & Wiesman, Z. (2026). Water self-diffusion differentiates two protein-based burger matrices with contrasting sensory juiciness. Current Research in Food Science, 13, Article 101562. https://doi.org/10.1016/j.crfs.2026.101562

Image Credits: AI Generated

DOI: 10.1016/j.crfs.2026.101562

Keywords: water self-diffusion, TD-NMR, plant-based meat analogues, juiciness, food microstructure, soy protein, beef burgers, sensory evaluation, serum release, Cryo-SEM, food oral processing, water-holding capacity