## 2 Rheology of Starch--Its Measurement, Instrumentation, and Limitations  
As stated in the previous section, starch can be defined as a complex biopolymer material due to its ability to undergo physical changes, such as swelling, gelatinization, and retrogradation [13; 14]. The study of how materials like starch flow and deform under various physical forces, such as shear or compression, is known as rheology [13; 14]. The measurement of the rheological characteristics or properties of a sample implies that a controlled deformation or strain is applied to a material over a given time [14]. The resulting force response from this process is measured. This response provides an indication of different parameters and characteristics of the material or sample such as the stiffness, modulus, viscosity, hardness, strength, or toughness of the material [14]. Consequently, rheology is utilized in different ways to quantify and describe the mechanical properties of a given material, to collect information associated with the molecular structure and composition of such material, to characterize and simulate the performance of a given material during processing, or to predict the final product quality of the sample [8,15, 16, 17, 18]. Techniques that are used to measure rheological properties in cereals have been classified into descriptive empirical techniques or those based on fundamental measurements [8,15, 16, 17, 18]. Techniques classified as fundamental rheological tests are based on the grounds that the sample geometry is constant and well defined, with both the stress and strain states of the samples being controlled and uniform [15, 16, 17, 18]. These measurements require sophisticated and expensive instrumentation that is time-consuming, difficult to maintain in an industrial environment, and requires high levels of technical skills [15, 16, 17, 18]. In starch rheology, the measurement of a starch's pasting properties (e.g., cereals, starch foods, and other polysaccharides) is the result of cooking starch in an excess of water [19]. This principle is utilized by most commercial viscometers, including the RVA. This instrument operates by applying a controlled shear force to the sample while simultaneously subjecting it to precise thermal cycling [19]. The RVA is not the only instrument available, where other practical rheological methods (e.g., Brabender viscomarylograph and Brookfield Viscometer) have been extensively utilized in both cereal and starch research to evaluate both the gelatinization and the pasting properties of the samples associated with the functional properties of the starch [19, 20, 21]. The RVA is preferred over the Brabender visco-amyloid graph for its faster heating and cooling rates, smaller sample size, and higher sensitivity to viscosity changes, ensuring more precise and reproducible results for starch pasting and gelation analysis. Unlike the Brookfield Viscometer, which measures viscosity at a constant shear rate and is suited for steady-state assessments, the RVA captures dynamic pasting properties such as gelatinization, peak viscosity, breakdown, and setback. This comprehensive analysis makes the RVA particularly valuable for food formulation, quality control, and ingredient performance testing. However, the application of these empirical methods is often associated with some drawbacks that can be considered limiting factors in some food applications [19, 20, 21].