Biological materials are characterized by a complex structure and composition, leading to a viscoelastic behaviour. Their viscoelastic characterization is important for process evaluation, design and optimization in order to ensure high quality products. The proposal of analysis methodologies and modelling are critical steps for studying the rheological properties of these materials. In this context, a new model was recently proposed to describe the stress-relaxation behaviour of biological material: the Guo-Campanella model, which is based on fractional calculus. The present work conducted an independent evaluation of this new model, considering 10 different samples, comprising in natura and processed foods, from both vegetable and animal base: Mozarella cheese, in natura potato, radiative dried and rehydrated potato, in natura pumpkin, convective dried and rehydrated pumpkin, restructured melon, acidified restructured melon, sausage, in natura yellow melon and acidified yellow melon. For comparison, a Generalized Maxwell model with two bodies and a residual spring element and the Peleg model were also evaluated. The three models adequately explained the stress-relaxation data. However, although the Generalized Maxwell model and Peleg model fitted better the data, the Guo-Campanella model has less parameters than the Generalized Maxwell model and with more interesting explanation parameters than Peleg model. In the Guo-Campanella model, the fractional order parameter described the sample “degree of viscoelasticity”, varying from zero (pure elastic/solid behaviour) to one (pure viscous/fluid behaviour). It was demonstrated as a useful index for food evaluation. The Guo-Campanella model could describe the viscoelastic behaviour of biological material with different structures, sources and processing. Consequently, it was considered as validated, demonstrating that it can be successfully used for future viscoelastic studies.