The study was aimed to clarify the changes in moisture content, fiber microstructure, and metabolites during the hot air drying process of areca nut, and to precisely regulate the drying time. This study focuses on areca nut and five models were used to fit the hot air drying curves of areca nut at different temperatures, and a betel nut drying kinetics model was established. At the same time, scanning electron microscopy, LC-MS were used to explore the changes in the microstructure and metabolites of areca nut during the drying process. The results showed that the drying curve of betel nut showed an exponential decrease, and the drying rate curve was divided into two stages: acceleration and deceleration. Temperature had a significant impact on the drying rate. The Page model fit the hot air drying curve of areca nut well, with a coefficient of determination R2 above 0.98 and a RMSE in the range of 0.02-0.06. The difference between the predicted and true values of the model was not significant, and it could better reflect the water changes during the areca nut drying process. Microstructure analysis shows that the fiber layer of areca nut became dense and compact with increasing drying time, and the whitening treatment caused the fiber structure of areca nut to become loose. The texture results indicated that with the increase of drying time, the hardness and chewiness of areca nut increased, while the elasticity decreased. The differential metabolite results showed that the drying process affected organic acids, lipids, and lipid molecules by affecting the metabolism of amino acid, linoleic acid, central carbon, flavonoid biosynthesis, and phenylpropanoid biosynthesis. This study would enrich the basic research on areca nut processing and provide a theoretical basis for the selection of hot air drying time for areca nut.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |