Fig. 1:
Fig. 2:
Fig. 3:
![Formation of acetyl pyridine at various pH / SO2 [mg/L] / ascorbic acid [mg/L] / temperature [°C] levels in model solutions over time](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/695387527c29e05adc52765a/j_mittklbg-2025-0009_fig_003.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKGAMUWEUU%2F20251230%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251230T122332Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEOz%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJHMEUCIBusXaendWAPK%2FnG4pqPJEc87DH68XQSQIkZvpDHtTGoAiEA3PbV1rnsbxZ1T4g8HAXozlM2FZooVav9RELWHSH01qAqxgUItf%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FARACGgw5NjMxMzQyODk5NDAiDIbmUgvBa5eATq9KuiqaBVRLYuarRaFZd31t7Nlzqu%2BTSzncrRVdkoVlqyZ3i4COEqDEWTBXIDlg7xpumX%2Bpw4v1%2Beswl%2BgqyMd2XMu3IfMLllJkKr8JmmOwAPSGnPFNpYffaIUJCnGLuKjcON7Q51nA%2Bq%2Bp0IdXqVN1PqSEXBhokJaFGj%2FkF2vOFwTszPNhncFy1bS6J48R9RG9Acg35F6aaJiq3eZqoBqZICCcZwJulSkQeTS9Xny9APa9XUAK3pQqHK8oNGMo7L73yLF%2BBH8TFSF2onflT9UOMOcFPk4FUPZnEZaclQknUuMq795rG5fmN4GzWHMEnF%2FhCWIBvLA8215wRn8dGxNcdRJPa6kxwP6HWoYaUl7hgaWCULH4wNywyUs%2BTDh4Icj%2F8%2BdZaxEPVo7UILxUfYs88u5WeNmkwWX%2FmNtkFhAc6WDRCMJJgD9avuU6dGuCbuFs7z%2FPpWnlAIMATaTtdutroM7bdegRzR3UnHCcdUiRCfOqEEIAAISwqNOkBwYzb5ZlyBB5FZEBmD3mfRgWHvcGGBoiYz6a1QSL1e2d5CtRW2ugem%2BfHRbUH6FRa7Ljm0CffnTB2bX9BwEIplv8vwdTic68C8gEgF%2BxlzCy%2BoJ7s%2Bdc4d926Pvlx3jx2%2FNI9%2F%2FFyFbGtl3WlO4htF%2Br%2Ft%2B4nZH0Ps%2Btixw7y3VLEMMpA%2B2GZnpF117i%2BEVtPyOMcJH9u4q205nYWa2W9RWu60O5ZWOppAoAsPUBMbkO%2BhyK2kK9TjDpIaM6qpTeQJqBLmRPqlx8FhQtDmL%2FjYSd0TycYCw0JNQUIp6pMZs6usdIOc16TFJE1F4rxLcyWFDOESmA7DubLKJgf8Y8wBr4rMCfP%2BCgdAGbod1BsLU3sM5tvUeJsSjZLG5V4WudOPPuCjC1%2Bc7KBjqxAdI%2BNWkI8xQZJyoGTjhCGCFdtnJ7c6FYbrWL%2FEkp3qgXPs6yu9ouLHz84QshxTH1llxwIIJZJuAXC5AdhRJL30y0ufKoisFn6luiIODpThDmtVseNbqUL8j%2F8dmZ%2FP1LBuwmoLrNIP8wYOmwEbffNbwpOuzm06cyPt1%2F%2B0RoA2vyTm2TCJoPo2QYvpcfics6wofNcWgjRGHF9EQsIp6tgES06vylOUxtIA3U6fT%2F66z%2FMA%3D%3D&X-Amz-Signature=b56ebc58454324741190904b400069835bf27c144511c42b3306bf12f7c84ad7&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Fig. 4:
![Dependency of the formation of acetyl pyridine [area units] on pH and temperature [°C] in model solutions after 106 days](https://sciendo-parsed.s3.eu-central-1.amazonaws.com/695387527c29e05adc52765a/j_mittklbg-2025-0009_fig_004.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Credential=ASIA6AP2G7AKGAMUWEUU%2F20251230%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20251230T122332Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEOz%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJHMEUCIBusXaendWAPK%2FnG4pqPJEc87DH68XQSQIkZvpDHtTGoAiEA3PbV1rnsbxZ1T4g8HAXozlM2FZooVav9RELWHSH01qAqxgUItf%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FARACGgw5NjMxMzQyODk5NDAiDIbmUgvBa5eATq9KuiqaBVRLYuarRaFZd31t7Nlzqu%2BTSzncrRVdkoVlqyZ3i4COEqDEWTBXIDlg7xpumX%2Bpw4v1%2Beswl%2BgqyMd2XMu3IfMLllJkKr8JmmOwAPSGnPFNpYffaIUJCnGLuKjcON7Q51nA%2Bq%2Bp0IdXqVN1PqSEXBhokJaFGj%2FkF2vOFwTszPNhncFy1bS6J48R9RG9Acg35F6aaJiq3eZqoBqZICCcZwJulSkQeTS9Xny9APa9XUAK3pQqHK8oNGMo7L73yLF%2BBH8TFSF2onflT9UOMOcFPk4FUPZnEZaclQknUuMq795rG5fmN4GzWHMEnF%2FhCWIBvLA8215wRn8dGxNcdRJPa6kxwP6HWoYaUl7hgaWCULH4wNywyUs%2BTDh4Icj%2F8%2BdZaxEPVo7UILxUfYs88u5WeNmkwWX%2FmNtkFhAc6WDRCMJJgD9avuU6dGuCbuFs7z%2FPpWnlAIMATaTtdutroM7bdegRzR3UnHCcdUiRCfOqEEIAAISwqNOkBwYzb5ZlyBB5FZEBmD3mfRgWHvcGGBoiYz6a1QSL1e2d5CtRW2ugem%2BfHRbUH6FRa7Ljm0CffnTB2bX9BwEIplv8vwdTic68C8gEgF%2BxlzCy%2BoJ7s%2Bdc4d926Pvlx3jx2%2FNI9%2F%2FFyFbGtl3WlO4htF%2Br%2Ft%2B4nZH0Ps%2Btixw7y3VLEMMpA%2B2GZnpF117i%2BEVtPyOMcJH9u4q205nYWa2W9RWu60O5ZWOppAoAsPUBMbkO%2BhyK2kK9TjDpIaM6qpTeQJqBLmRPqlx8FhQtDmL%2FjYSd0TycYCw0JNQUIp6pMZs6usdIOc16TFJE1F4rxLcyWFDOESmA7DubLKJgf8Y8wBr4rMCfP%2BCgdAGbod1BsLU3sM5tvUeJsSjZLG5V4WudOPPuCjC1%2Bc7KBjqxAdI%2BNWkI8xQZJyoGTjhCGCFdtnJ7c6FYbrWL%2FEkp3qgXPs6yu9ouLHz84QshxTH1llxwIIJZJuAXC5AdhRJL30y0ufKoisFn6luiIODpThDmtVseNbqUL8j%2F8dmZ%2FP1LBuwmoLrNIP8wYOmwEbffNbwpOuzm06cyPt1%2F%2B0RoA2vyTm2TCJoPo2QYvpcfics6wofNcWgjRGHF9EQsIp6tgES06vylOUxtIA3U6fT%2F66z%2FMA%3D%3D&X-Amz-Signature=d2e8bde73e6b0cee3037f75343f67865394b67f1a33509025a090ef250ea61b9&X-Amz-SignedHeaders=host&x-amz-checksum-mode=ENABLED&x-id=GetObject)
Experimental design (central composite design) calculated by XLSTAT based on Tab_ 1
| Observations | pH | SO2 [mg/L] | Ascorbic acid [mg/L] | Temperature [°C] |
|---|---|---|---|---|
| Obs1 | 3.0 | 25.0 | 125.0 | 14.0 |
| Obs2 | 4.0 | 25.0 | 125.0 | 14.0 |
| Obs3 | 3.0 | 50.0 | 125.0 | 14.0 |
| Obs4 | 4.0 | 50.0 | 125.0 | 14.0 |
| Obs5 | 3.0 | 25.0 | 250.0 | 14.0 |
| Obs6 | 4.0 | 25.0 | 250.0 | 14.0 |
| Obs7 | 3.0 | 50.0 | 250.0 | 14.0 |
| Obs8 | 4.0 | 50.0 | 250.0 | 14.0 |
| Obs9 | 3.0 | 25.0 | 125.0 | 25.0 |
| Obs10 | 4.0 | 25.0 | 125.0 | 25.0 |
| Obs11 | 3.0 | 50.0 | 125.0 | 25.0 |
| Obs12 | 4.0 | 50.0 | 125.0 | 25.0 |
| Obs13 | 3.0 | 25.0 | 250.0 | 25.0 |
| Obs14 | 4.0 | 25.0 | 250.0 | 25.0 |
| Obs15 | 3.0 | 50.0 | 250.0 | 25.0 |
| Obs16 | 4.0 | 50.0 | 250.0 | 25.0 |
| Obs17 | 2.5 | 37.5 | 187.5 | 19.5 |
| Obs18 | 4.5 | 37.5 | 187.5 | 19.5 |
| Obs19 | 3.5 | 12.5 | 187.5 | 19.5 |
| Obs20 | 3.5 | 62.5 | 187.5 | 19.5 |
| Obs21 | 3.5 | 37.5 | 62.5 | 19.5 |
| Obs22 | 3.5 | 37.5 | 312.5 | 19.5 |
| Obs23 | 3.5 | 37.5 | 187.5 | 8.5 |
| Obs24 | 3.5 | 37.5 | 187.5 | 30.5 |
| Obs25 | 3.5 | 37.5 | 187.5 | 19.5 |
SPME-HS-GC-MS parameters
| SPME | |
|---|---|
| Fiber | Carbon WR/PDMS - 95/10 |
| Conditioning Temperature | 250 °C |
| Pre-Injection Conditioning Time | 10.00 min |
| Post-Injection Conditioning Time | 1.00 min |
| Needle Purge flow | 0.8 bar |
| Sample Incubation | 5.00 min, 50 °C |
| Headspace Sampling | 45.00 min, 50 °C |
| Agitator on | 5 s |
| Agitator off | 2 s |
| Sample Vial Depth | 35 mm |
| Sample Desorption | 10.00 min, 280 °C |
| GC | |
| Column flow | 1 mL/min |
| Carrier gas | Helium |
| Injector | 280 °C |
| Liner | Quartz Liner for splitless Operation ID 1 mm |
| Split | 50 ml/min @1.00 min |
| Gas Saver | 20 ml/min @14.00 min |
| Oven Temperature Program | 40 °C/0.00 min – 3 °C/min/80 °C/0.00 min – 6 °C/min/150 °C/0.00 min – 10 °C/min/240 °C/5.00 min |
| MS | |
| Electron energy | 70 eV |
| Transferline | 280 °C |
| Ion source | 220 °C |
| Solvent Delay | 1.00 min |
| Scan Mode | 1.10 – 39.00 min |
| Scan m/z | 38–250 amu |
| Scan Time | 0.2 s |
| Inter-Scan Delay | 0.025 s |
| SIR Mode (2-AP) | 12.00–15.00 min |
| m/z | 52, 78, 79, 93, 121 |
| Inter-Channel Delay | 0.01 s |
| Data evaluation | sum 79+93+121 |
Parameters analyzed within the scope of the study
| pH | SO2 [mg/L] | Ascorbic acid [mg/L] | Temperature [°C] |
|---|---|---|---|
| 3,0 | 25 | 125 | 14 |
| 4,0 | 50 | 250 | 25 |
Results of the GC/MS measurements on AP in model solutions after 106 days (AP: acetyl pyridine)
| Observations | pH | SO2 [mg/L] | Ascorbic acid [mg/L] | Temperature[°C] | AP [area units] |
|---|---|---|---|---|---|
| Obs1 | 3.0 | 25.0 | 125.0 | 14.0 | 291 |
| Obs2 | 4.0 | 25.0 | 125.0 | 14.0 | 279 |
| Obs3 | 3.0 | 50.0 | 125.0 | 14.0 | 0 |
| Obs4 | 4.0 | 50.0 | 125.0 | 14.0 | 238 |
| Obs5 | 3.0 | 25.0 | 250.0 | 14.0 | 185 |
| Obs6 | 4.0 | 25.0 | 250.0 | 14.0 | 209 |
| Obs7 | 3.0 | 50.0 | 250.0 | 14.0 | 298 |
| Obs8 | 4.0 | 50.0 | 250.0 | 14.0 | 318 |
| Obs9 | 3.0 | 25.0 | 125.0 | 25.0 | 1536 |
| Obs10 | 4.0 | 25.0 | 125.0 | 25.0 | 1485 |
| Obs11 | 3.0 | 50.0 | 125.0 | 25.0 | 964 |
| Obs12 | 4.0 | 50.0 | 125.0 | 25.0 | 1195 |
| Obs13 | 3.0 | 25.0 | 250.0 | 25.0 | 1304 |
| Obs14 | 4.0 | 25.0 | 250.0 | 25.0 | 657 |
| Obs15 | 3.0 | 50.0 | 250.0 | 25.0 | 1148 |
| Obs16 | 4.0 | 50.0 | 250.0 | 25.0 | 1170 |
| Obs17 | 2.5 | 37.5 | 187.5 | 19.5 | 343 |
| Obs18 | 4.5 | 37.5 | 187.5 | 19.5 | 137 |
| Obs19 | 3.5 | 12.5 | 187.5 | 19.5 | 267 |
| Obs20 | 3.5 | 62.5 | 187.5 | 19.5 | 65 |
| Obs21 | 3.5 | 37.5 | 62.5 | 19.5 | 34 |
| Obs22 | 3.5 | 37.5 | 312.5 | 19.5 | 301 |
| Obs23 | 3.5 | 37.5 | 187.5 | 8.5 | 31 |
| Obs24 | 3.5 | 37.5 | 187.5 | 30.5 | 3519 |
| Obs25 | 3.5 | 37.5 | 187.5 | 19.5 | 367 |