Table 4. Phenolic contents (gallic acid, chlorogenic acid, vanillic acid, caffeic acid, syringic acid, vanillin, p-coumaric and 2-hydroxycinnamic acid) and flavonoid contents (rutin and quercetin) as affected by different drying temperatures and times.
| Drying time (mins) | mg/g dry weightψ | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Gallic acid | Chlorogenic acid | Vanillic acid | Caffeic acid | Syringic acid | Vanillin | p-coumaric | 2-hydroxycinnamic acid | Rutin | Quercetin | |
| Fresh | – | 8.24hi± 0.08 | – | – | 0.36ab± 0.06 | – | – | – | 4.24b± 0.04 | 0.03bc± 0.01 |
| 60 °C | – | – | – | |||||||
| 30 | – | 0.75j± 0.07 | – | – | 0.35b± 0.07 | – | – | – | 3.13e± 0.07 | – |
| 60 | – | 8.73h± 0.05 | – | 1.14d± 0.05 | – | – | – | – | 3.41d± 0.12 | – |
| 120 | – | 7.41i± 0.05 | – | 1.36c± 0.06 | – | – | – | – | 2.54gh± 0.08 | – |
| 1440* | – | 1.53j± 0.03 | 0.45f± 0.11 | – | – | – | – | – | 1.62k± 0.02 | 0.02bc± 0.01 |
| 80 °C | – | |||||||||
| 30 | – | 14.33c± 0.68 | 0.65e± 0.06 | 1.54a± 0.04 | – | – | – | – | 3.25de± 0.13 | – |
| 60 | – | 12.05d± 0.22 | 0.63e± 0.04 | 1.37c± 0.05 | – | – | – | – | 2.64fg± 0.07 | – |
| 120 | – | 17.25b± 0.14 | 1.06c± 0.06 | 1.46b± 0.03 | 0.43a± 0.04 | – | – | – | 3.85c± 0.06 | – |
| 600* | 0.48d± 0.05 | 16.69b± 0.39 | 1.87a± 0.05 | 0.85e± 0.03 | 0.18c± 0.03 | – | – | – | 2.83f± 0.05 | 0.02bc± 0.01 |
| 100 °C | ||||||||||
| 30 | – | 11.82de± 0.25 | – | – | – | – | – | – | 2.73fg± 0.07 | – |
| 60 | – | 8.66h± 0.38 | – | – | – | – | – | – | 1.76k± 0.06 | – |
| 120 | – | 14.31c± 0.23 | 0.78d± 0.05 | – | – | – | – | – | 3.48d± 0.04 | 0.03ab± 0.00 |
| 270* | 0.41e± 0.05 | 12.57d± 0.54 | 1.22b± 0.05 | – | – | – | – | 0.05b± 0.00 | 2.58gh± 0.16 | 0.03ab± 0.00 |
| 120 °C | ||||||||||
| 30 | – | 14.75c± 0.26 | 0.06g± 0.01 | – | – | – | – | – | 4.29b± 0.06 | 0.04a± 0.01 |
| 60 | – | 20.61a± 0.32 | 0.96c± 0.05 | – | – | – | – | 0.07a± 0.01 | 5.15a± 0.07 | 0.03ab± 0.00 |
| 120 | – | 11.31def± 0.55 | 0.62e± 0.01 | – | – | – | – | – | 2.56gh± 0.05 | 0.02bc± 0.00 |
| 210* | 0.47de± 0.05 | 12.37d± 0.49 | 1.15b± 0.06 | – | – | – | – | 0.04c± 0.01 | 2.37hi± 0.07 | 0.02bc± 0.00 |
| 140 °C | ||||||||||
| 30 | – | 12.24d± 0.48 | – | – | – | – | – | – | 3.29de± 0.04 | – |
| 60 | – | 10.60efg± 0.49 | – | – | – | – | – | – | 2.75fg ± 0.12 | – |
| 120 | 1.29c± 0.04 | 11.41def± 0.49 | – | – | – | – | – | 0.04c± 0.01 | 2.78fg± 0.07 | 0.02bc± 0.00 |
| 180* | 5.94b± 0.05 | 15.42c± 0.50 | – | – | – | – | – | 0.05b± 0.00 | 2.77fg± 0.03 | 0.02bc± 0.00 |
| 160 °C | – | – | – | – | – | |||||
| 30 | – | 8.58hi± 0.47 | – | – | – | – | – | – | 2.55gh± 0.05 | – |
| 60 | 0.21f± 0.02 | 9.46gh± 0.61 | – | – | – | – | – | – | 2.26ij± 0.07 | – |
| 120* | 6.83a± 0.06 | 10.47fg± 0.51 | – | 0.44f± 0.04 | 0.37ab± 0.06 | – | – | – | 2.11j± 0.07 | 0.01d± 0.00 |
| 180 | ND | ND | ND | ND | ND | ND | ND | ND | ND | NA |
Notes.
Data represents the means ± standard error (n = 69) for each sample; mean values with different superscript letters within the same column differ significantly at p < 0.05.
*
Drying time when moisture content reached 12–13% w.b.
ψ at moisture content of each sampling time.
- ND
- not determined
- –
- not detected