Improving the quality of gluten-free plant-based meat analogs based on soy protein isolate with insoluble soy fibers and low acyl gellan gum

This study describes the effects of incorporating insoluble soy fiber and low acyl gellan gum as an alternative for wheat gluten in plant-based meat analogs made from soy protein isolate (SPI). The formulations containing insoluble soy fiber (ranging from 0 to 3%) and low acyl gellan gum (0–2%) were processed in a high-temperature shear cell (HTSC) and then analyzed in terms of macrostructure, microstructure, rheological properties, tensile strength, and water absorption capacity (WAC). Macrostructural analysis revealed that the control product containing SPI without insoluble soy fiber and low acyl gellan gum exhibited a dense and gel-like structure, devoid of visible fibers. The addition of 1, 2, and 3 wt.% of insoluble soy fiber increased the formation of visually elongated fibers in both macro- and microscopic levels in the shear direction, resulting in anisotropic plant-based meat analogs with improved tensile strength and elasticity. The use of 1 and 2 wt.% low acyl gellan gum led to the formation of short and thin filaments that were less oriented in the shear direction, resulting in decreased tensile strength. When combined with low acyl gellan gum, insoluble soy fiber failed to produce lengthy and elongated fibers, resulting in short and thin fibrils. These findings suggest that the interaction between insoluble soy fiber and low acyl gellan gum under the processing conditions may hinder fiber formation and mechanical anisotropy. Microscopic examination reveals smoother regions in products enriched with insoluble soy fiber and rougher surfaces in those containing low acyl gellan gum. Moreover, X-ray microtomography confirms that insoluble soy fiber enhanced air retention, contributing to enhanced structural integrity. In contrast, low acyl gellan gum introduces irregularly shaped air bubbles, compromising structural improvement. In summary, this study underscores the potential of insoluble soy fiber to enhance the structural and the textural properties of plant-based meat analogs. However, it also highlights the challenges posed by low acyl gellan gum, which, despite improving water retention, may hinder fiber formation and mechanical anisotropy. These findings offer insights for advancing the quality of plant-based meat products.