The problem the researchers set out to tackle is familiar to food scientists everywhere. Commercial vegetable butter owes its baking performance to a continuous network of fat crystals formed by saturated lipids. That network traps air during creaming, holds dough together, controls spreading in the oven and delivers the tender, coherent structure consumers expect. Replacing it with liquid vegetable oil would improve the nutritional profile, since excessive saturated and trans fat intake is linked to cardiovascular and metabolic disease, but liquid oil alone cannot build the crystal scaffold that dough development requires. The result is typically cookies that spread too much, lose their shape and develop unpleasant textures.

Oleogels have emerged as a promising middle path. They convert liquid oils into semi-solid materials without substantially raising saturated fat content. Among the most elegant oleogelators are phytosterols and gamma-oryzanol, plant-derived molecules that self-assemble into fibrillar tubular structures capable of immobilizing oil while preserving a high proportion of unsaturated fatty acids. Yet oleogels alone have a weakness in baking: they bind oil well but hold water poorly, and cookie production demands careful management of both lipid structure and moisture. Bigels solve this by combining an oleogel phase with a hydrogel phase, pairing oil-binding with water-holding capacity in a single material.

In the new study, the team prepared a bigel by dissolving phytosterols and gamma-oryzanol in a 2:3 ratio at a total concentration of 8 percent in canola oil, then mixing the resulting oleogel with a dilute sodium alginate hydrogel at an 80:20 mass ratio. This bigel was blended into melted commercial vegetable butter at substitution levels of 25, 50 and 75 percent, plus a full replacement formulation, and every blend was characterized at the crystal level before any dough was mixed. Polarized light microscopy revealed the first transformation. The original vegetable butter displayed densely packed spherulitic crystal clusters forming a continuous network, while the bigel showed a sparse arrangement of elongated birefringent structures produced by the self-assembled phytosterol-oryzanol tubules. As bigel content rose, the spherulitic aggregates of the butter became progressively less prominent and the elongated structures spread through the blend.

X-ray diffraction added a molecular dimension to the picture. The vegetable butter carried diffraction signatures of both beta and beta-prime crystal polymorphs, the latter being the fine-crystal form prized in plastic fats for its processing performance. The bigel on its own showed predominantly beta-type structures, and the blends retained detectable features of both forms, though diffraction intensity fell steadily as bigel content increased. Pulsed nuclear magnetic resonance measurements confirmed a matching decline in solid fat content across the temperature range from 0 to 50 degrees Celsius, and differential scanning calorimetry showed that the melting behavior of the blends shifted, with the butter’s characteristic melting feature near 44 to 45 degrees drifting lower as bigel proportion grew. Together, these measurements document what the authors call a reconstruction of fat crystal organization, meaning changes in crystal morphology, polymorphism, solid fraction and thermal behavior, rather than a molecular dismantling of individual crystals.

Those crystal-level changes propagated directly into the dough. Cryogenic scanning electron microscopy showed that dough made with pure vegetable butter had a compact, continuous matrix with fine, uniform surface morphology, while doughs containing bigel became increasingly heterogeneous, with larger discrete structural features and more open regions. Rheological testing confirmed that all doughs behaved as predominantly elastic materials, but both the storage modulus and the loss modulus fell progressively as bigel content rose, tracking the decline in solid fat content. Dough hardness followed the same pattern, dropping from 0.576 newtons for the butter dough to 0.272 newtons for the all-bigel dough.

Water behavior added a surprising twist. Low-field nuclear magnetic resonance revealed three water populations in every dough, corresponding to bound, immobilized and free water. As bigel content increased, the immobilized and free water peaks shifted toward shorter relaxation times, indicating reduced water mobility, an effect attributed to the sodium alginate hydrogel network retaining water within its three-dimensional structure. Because the hydrogel phase carried its own water, total dough water rose from 3.6 grams in the butter formulation to 9.6 grams in the all-bigel version. Intriguingly, this lower water mobility did not translate into stronger dough; the bigel-rich doughs were softer despite holding their water more tightly, showing that the weakened crystalline fat contribution outweighed any firming effect of water immobilization.

The baked cookies told the final chapter of the structural story. Scanning electron microscopy showed that butter cookies contained relatively large, irregular pores with several collapsed cavities, while the 50:50 blend produced cookies with more numerous, smaller and more evenly distributed pores. All cookies kept their shape in the oven, but diameter and spread ratio fell as bigel content rose, from 4.31 for the butter control to between 3.65 and 3.90 for bigel-containing versions. The researchers attribute the reduced spreading to the joint effects of lower solid fat content, altered fat-phase organization, the hydrogel phase and the higher total water content, which likely modified the hydration and thermal behavior of gluten proteins and starch. Cookie color also shifted noticeably, with lightness rising from 50.63 to 60.27 as bigel replaced butter, mainly because the bigel formulations lacked the beta-carotene present in the commercial product, while higher water content delayed surface heating and moderated Maillard browning.

Mechanical testing showed that breaking force climbed from 25.63 newtons for butter cookies to 30.97 newtons for the all-bigel version, a firming effect the authors link to the altered dough structure and water distribution during baking. Oil migration, a key shelf-life concern, remained low in the extremes, at 0.47 percent for butter and 0.89 percent for full bigel replacement, though the intermediate blends migrated more oil, peaking at 3.48 percent for the 50:50 blend, possibly because their less aggregated crystal structure altered lipid-phase continuity. Baking loss showed no significant differences across formulations, ranging only from 8.58 to 9.04 percent.

Perhaps most striking for the industry, consumer perception favored the healthier cookies. Sixty untrained assessors scored all samples on a five-point hedonic scale, and while the butter cookies won on flavor, at 4.13, thanks partly to added flavoring in the commercial product, the bigel cookies scored higher on appearance and color. Overall acceptability rose from 2.88 for the butter control to 4.38 for the fully replaced version, driven largely by the lighter color and more regular shape of the bigel cookies. The authors caution that the specific contribution of each crystal polymorph to cookie quality remains to be clarified, and that storage stability and flavor evolution during long-term storage still need investigation. But the central message is clear: controlling the crystalline structure and solid fat functionality of structured fats can guide the design of alternative fat systems for bakery applications, and a phytosterol-oryzanol bigel can carry that control from the crystal scale all the way to the cookie on the plate.

Subject of Research: Bigel-based reconstruction of fat crystal organization in blended fat systems and its impact on dough architecture and cookie quality

Article Title: Reconstruction of fat crystal organization by a phytosterol/γ-oryzanol bigel: Linking structural evolution in blended fat systems to dough architecture and cookie quality

Article References: Peng, Y., Zhou, K., Han, L., Yang, Y., He, J., Chen, C., Liu, P., & Feng, J. (2026). Reconstruction of fat crystal organization by a phytosterol/γ-oryzanol bigel: Linking structural evolution in blended fat systems to dough architecture and cookie quality. Current Research in Food Science, 13, Article 101564. https://doi.org/10.1016/j.crfs.2026.101564

Image Credits: AI Generated

DOI: 10.1016/j.crfs.2026.101564

Keywords: bigel, oleogel, phytosterol, gamma-oryzanol, fat crystal network, solid fat content, cookie quality, dough architecture, saturated fat replacement, polymorphism, water distribution, bakery products