Effect of drying temperatures on chemical and morphological properties of acorn flours

Drying curves at different temperatures were established for Quercus suber and Quercus rotundifolia fruits. Flours produced by milling fruits dried at different conditions were evaluated for colour, starch granules morphology, amylose and sugars content. The drying temperature was positively related to the reducing sugar content and negatively to starch content. The amilose content generally increased with drying temperature and the effect was more evident for the Q. rotundifolia. Results showed that flour colour parameters generally decreased with increased drying temperature. However, the drying temperature does not seem to affect starch morphology. It can also be stated that Q. suber produced darker flours, higher amylose and reducing sugar content, and bigger starch granules. Q. rotundifolia showed a lower level of damaged starch and higher fat and disaccharides content. According to the results, it was possible to conclude that drying temperature exerted marked effects on the properties of acorn flours in both studied species.