Paper Title (use style: paper title)
Figure 4. Combined convection-IR drying temperature as a function of the effective moisture diffusion coefficient
Yüklə 240,33 Kb.
|
- Bu səhifədəki naviqasiya:
- Table 3 Drying models for mulberry under different combined convection-IR drying conditions χ 2 , R 2 and RMS
- Model name b Drying conditions R 2
- Table 4 Influence of convection drying temperature on the quality of dried mulberry products
- Table 5 Effect of infrared radiation power on the quality of dried mulberry products
|
Figure 4. Combined convection-IR drying temperature as a function of the effective moisture diffusion coefficient.
Fitting of the drying kinetics model. The results of the drying process fitting of mulberry fruit in this study are shown in Table 3. The Page model had the highest mean R value2 (0.99882) and the lowest mean values χ2 and SEE (2.89×10-4, 9.86×10-4), indicating the best fit of the Page model, which is consistent with the results obtained by Chottamom and Adabi et al. In addition, the two-terminal model also corresponded well with the experimental drying data. Table 3 Drying models for mulberry under different combined convection-IR drying conditions χ2 , R2 and RMS
Effect of combined convection-IR drying on the quality of dried mulberry products. Influence of temperature and convection on the quality of dried mulberry products in combined convection-IR drying. Under conditions of constant IR power (280 W) and varying convection temperature, the results given in Table 2.4 show that retention of anthocyanins in mulberry decreases with increasing convection drying temperature, while the value of ΔE increases with increasing drying temperature. Table 4 Influence of convection drying temperature on the quality of dried mulberry products
Note: Different letters in the same data column represent significant differences under the same drying conditions (p<0.05), below. This could be due to the degradation of the heat-sensitive anthocyanin with increasing temperature, resulting in a yellow-brown colour on the surface of the dried mulberry products. The results shown in Table 4 show that the rehydration factor of the dried product increased with increasing temperature and vice versa for hardness. This is explained by the fact that with increasing drying temperature the effective water diffusion coefficient in mulberry increased, the drying rate also increased and the pore size of dried product increased [9]. The hardness of the material decreases when the rehydration factor increases. However, when the drying temperature is 65 ℃, the drying time is too long and the product hardness is too high; at 75 ℃, the material will be subject to local burn; when the drying temperature is 70 ℃, the material is quite hard. The drying time is shorter and the quality is better. Therefore, a combined convection-infrared drying temperature of 70 ℃ is preferable for mulberry fruit. Influence of IR radiation power of combined convection-IR drying on the quality of dried mulberry products. A comparison of the quality of dried products at a constant temperature of 70 °C and at different IR radiation powers is shown in Table 5. As can be seen from the table, the retention of mulberry anthocyanin decreased with increasing IR power and the ΔE value increased with increasing IR power. Table 5 Effect of infrared radiation power on the quality of dried mulberry products
This may be due to the fact that with increasing IR power the heat flux density during drying increases, and if the power is too high, even scorching occurs and the anthocyanin of mulberry is destroyed. The colour of the dried product deteriorates and the ΔE value increases. The experimental results shown in Table 5 also show that the rehydration coefficient of the dried product increased with increasing IR power, while the hardness did not change significantly. In contrast to the effect of increasing temperature, with increasing IR power. The drying rate of mulberry fruit does not change regularly. When the IR power is 230 and 260 W, the effective water diffusion coefficient increases, the pore space of the dried product increases, the water retention coefficient increases slightly, but the surface layer of the material is easily scorched. When the infrared power is 230 W, the dried product has a good colour and a high degree of nutrient retention, so the drying power should be 230 W. Comparison of the quality of dried mulberry products using different drying methods. Here, the moisture content of the product in all three drying methods is the moisture content of the dry base. The optimum conditions were chosen for drying at 70 °C with an air speed of 0.2 m/s and an infrared power of 230 W. The optimum microwave drying mode was selected as 3 min at 500 W. A room temperature of 26-28 °C was also selected as the optimum conditions for drying in the shade. The experimental results shown in Table 6 show that mulberry products dried in a vacuum have the best nutritional quality and the highest anthocyanin content. Yüklə 240,33 Kb. Dostları ilə paylaş:
|