ABSTRACT: Meat analogs produced by high-moisture extrusion of soy proteins are good alternatives to animal meat and have many health benefits. In addition to textural properties, an abundant fibrous structure in such extrudates is a key factor for consumer acceptance. Although several techniques have been developed for quantifying fiber formation in extrudates, their applications for real-time quality control in manufacturing process have been challenging. In this study, we developed a nondestructive imaging technique to quantify fibrous structures in soy protein extrudates. The spatial distribution of light reflectance on sample surface was imaged and a fiber formation index was derived based on the random-walk theory of light transport in anisotropic media. This method has a potential to be used as a nondestructive, real-time quality control tool for products with fibrous structures.