INFORM February 2025 Volume 36 (2)

inform February 2025, Vol. 36 (2) • 21

PLANT PROTEIN BASED BIGELS Plant-based proteins, found naturally in sources like soy beans, pulses (such as peas, chickpeas, and lentils), and cereals (like wheat, barley, and zein) serve as a rich reser voir of amino acids. These proteins consist of amino acid chains linked by peptide bonds, forming diverse structures that vary based on amino acid type, number, and sequence. With their unique blend of polar and non-polar amino acids, many plant proteins are amphiphilic, making them ideal for food applications requiring emulsification, gelation, and foaming. Most plant proteins are considered globular, and their gelling process typically involves partial unfolding to allow the formation of stabilizing bonds. This partial denaturation enables these proteins to form gels that stabilize the bigel structure, enhancing texture and nutritional value while supporting clean-label standards, which can add significant appeal to food products. Although researchers have explored bigels that rely on animal-based proteins, such as collagen, gelatin, and whey protein the demand for plant-based alternatives presents new opportunities—and challenges—in bigel formulation. To meet these challenges, researchers blended plant proteins with polysaccharides to improve the hydrogel phase. For instance, bigels created with a blend of soy protein iso late and konjac glucomannan demonstrated that adjust ing protein concentration within hydrogels can control the bigel phase inversion by modulating the oil-water inter face and hydrogel stability ( https://doi.org/10.1016/j.food hyd.2024.110176). Another study showcased the emulsifying properties of pea protein in bigel beads formulation, where a calcium alginate hydrogel and glycerol monostearate oleogel were used to encapsulate nutraceuticals effectively ( https://doi.org/10.1016/j.foodhyd.2024.110101 ). But what if, instead of combining plant proteins with hydrocolloids, we use plant protein by itself or different plant protein blends to create a bigel? This approach could yield a fully plant protein-based bigel system, offering a nutritionally balanced alternative for innovative food products. Recently we explored the combination of plant pro teins to create a stable bigel system. The bigel was prepared by combining chickpea and potato protein hydrogels with a glycerol monostearate (GMS)-based oleogel, using a two step, hot emulsification process (https://doi.org/10.1016/j. foostr.2024.100378 ). In the first step, we prepared bigels made from chickpea protein-based hydrogel and GMS oleo gel with a range of protein concentrations, hydrogel-to-oleo gel ratios, and oleogelator concentrations. The results showed that bigels with higher protein and oil concentrations achieved a firmer, more stable texture— similar to cream cheese—while lower concentrations led to softer textures. The bigels demonstrated strong stability with no separation of the oil or water phases even after two months of storage at 4 °C. From the various formulations, bigel based on a 70 to 30 hydrogel-to-oleogel ratio, 15 per cent chickpea protein (out of the water phase), and 30 per

cent GMS (out of the oil phase) showed the best balance of firmness, smoothness, and stability. In a second homogenization step, our team added six percent potato protein and transglutaminase (TG) to improve the formulation. The potato protein boosted the overall pro tein content and amino acid diversity, while the TG strength ened the protein network through enzymatic crosslinking by introducing covalent bonds—20 times stronger than hydrogen bonds. The addition of the enzyme made the bigel three times harder, more elastic, and resilient without changing its melting point, which remained around 53–55 °C. Temperature dependent mechanical tests showed that while the bigel softened slightly at lower temperatures, it became firmer at higher temperatures. The TG-crosslinked bigel retained less water, resulting in a less sticky texture. When cooked, both bigels developed a crispy, brown-orange surface with a pleasant aroma. However, the crosslinked bigel retained its shape and integrity better after cooking, while the non-crosslinked version became harder with a thick crust. The plant-based bigel had a heterogeneous structure made up of canola oil/GMS oleogel droplets embedded within a fine, dense protein network as seen by high-resolution scan ning electron microscopy (see page 20). These oil droplets had smooth surfaces and layered GMS crystal structures, while the dense protein matrix surrounding the droplets contributed to the bigel’s solid-like behavior. Confocal imaging confirmed the formation of an oleogel-in-hydrogel organizational structure, showcasing well-distributed oil droplets in a protein matrix with no significant difference between the sample with and without TG. We then used a single protein-based formula to obtain a firm, stable bigel using canola and pea protein. We observed that the protein type and the addition of TG have an obvi ous effect on the bigel microstructure and integrity. The visual micrographs show the important role of TG in stabilizing these bigels while the color difference observed can be related to Visual appearance and confocal images of bigels prepared using a six weight percent candelilla wax in oil oleogel a 15 weight percent canola and pea protein in water hydrogel, at a 40:60 hydrogel:oleogel ratio with and without the addition of transglu taminase. The oil phase is in red (Nile red) and the water phase is in blue (Nile Blue A)( Scale bar 50 µm). Source: Davidovich-Pinhas lab