EFFECT OF EXTRACTION METHOD ON STRUCTURAL AND PASTE PROPERTIES OF ANDEAN FAVA BEAN STARCHES

Fava beans are legumes used in traditional cuisine as a nutrient-rich ingredient. These sources have a high starch content; however, little is known about their structure and properties. Therefore, this study evaluated the effect of two different extraction methods: aqueous (H₂O) and with a reducing agent (sodium metabisulfite at 0.2% active SO₂ w/v), from the fava bean (Vicia faba L.) var. Quelcao, native from Cusco (13°31′06″S, 71°58′41″W), Peru. The paste properties were subsequently analyzed using a Rapid Visco Analyzer, gel strength (N) using a texturometer, and optical microscopy under plane-polarized light. The data were evaluated using the t-test (p<0.001). The pasting properties of fava bean starches showed differences in all evaluated parameters, where the reducing method presented higher values ​​of peak viscosity (1996 cP), final viscosity (2765 cP) and pasting temperature (75.05 °C), indicating greater efficiency in the removal of non-starch components and favoring greater water absorption and granule expansion. Aqueous extraction showed higher setback (1234 cP) and breakdown (349 cP) values, indicating greater paste stability and resistance to shear and heating. Moreover, the starch gel strength was higher in the aqueous method (41.35 N) compared with extraction using a reducing agent (21.51 N). This difference may reflect a stronger molecular reorganization during storage in the starch obtained from the aqueous method, associated with increased retrogradation in the gel state. These results suggest that while the aqueous method provides more stable pastes during processing, it may also favor retrogradation phenomena in the final gel structure. Optical microscopy showed irregular granules of varying sizes, with heterogeneous distribution. Starch granules under polarized light showed a clear Maltese cross in small granules and a diffuse cross in larger granules. Neither microscopy indicated any visible changes in the microstructure of the faba bean starch granules, suggesting that neither method significantly affected their microstructure. Therefore, the results showed that the extraction method significantly influenced the properties of faba bean starch, with the reducing agent being more efficient in obtaining starches with higher viscosity, while the aqueous method favored the formation of firmer gels. These differences highlight the technological potential of the Andean fava bean and the importance of choosing the extraction process according to the desired application.