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=ASIA6AP2G7AKHK5S3VML%2F20260222%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20260222T075256Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEPX%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJIMEYCIQCxKFb%2FLk1byg8FI2SBkHVT1VFCI1qQo46ii2C3N1QyNgIhAMWrQzeQ%2FDMe5Y%2BZyhZMo6tQW%2B7YNGyKG%2FCi8ldK1WboKsUFCL7%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQAhoMOTYzMTM0Mjg5OTQwIgzgg6POvEloLXedNi0qmQWK%2BFo7cZ0GYJ%2BE4qjIwefUQZ6L3RlsEn6DmZwHsZCx5KpGXY1qOZ47RSbnmX60NymiIPfYrs%2BV7JWVL%2FW3VKDLtU%2BLBSmvgU4g6kvngTlvz0Hl5RoGgh2BYuZJtFj6v3rGlIyg0ySD96YZYHAhwQI3PkIITFUVEL9QBmoDi2q4JeXzSDktMWjlxC7yX6YNhLoriv7aQkO%2BsKFNB9o1ipWDhGJerHuh9P5ZW2%2F3b%2Bclyzy549G%2BUw3N%2BXFJvorCyEZs5xlZ%2Fdez4clnnWLbNKCbnFv2luhR%2BajwNcBC2ydqqT%2ByS57L29iDClnTP8FHSl63EIAZgT9vCPTCSGTwfUWewCJ9udWf3umDR19fBlAaBzQTRBTk%2BwPYfwW6fdhkjADHQalfgHP4XAL9SBp%2Bcz%2BkkAmyU5iAnu%2Fv2eWXpqSKyABNt993PO9m2IyXbVCedNeuaP%2BOmX7vEAz7v%2FTKBJLpvzoPvbYNWzAUPcx6HHxCUZEhIKvYtp7LlIMUDTdb3Y5EqhC1NqMOYCw3cht6hdL48s1xRPbqTbC2LyaqgpeddKoVWoqX0WZsdYzpmiNk7EBStmmX3VeQWDnBy%2BoAwVkOG1IcmMvD9vJucJEBYeXjzbM65R4ETy87ILIPEhZKjytrsCZHPrC4dqj1Yz%2F0ryIMe579PReYUL4LvctCC46VKrrIp65UY%2BCYqphiXG7VHmgdxZDU3%2F5VBPCDmFMSvoZNFUtt3e5vlsMrY68wj9lQNXXLfUmPKYMOqDIQAA4wR1%2BVusq28Cf0e77xMCjaHstTMQaHxx3qfpU4hn8aaVeBIFX%2BhWh6IV8bQ9rqimoBWFlAU9FlWVBuW2nLm%2BrBAUJcq919yaoxF0Lh66P%2FY4jCWJoYZQ7Eu8iAijDklurMBjqwAX18QV1gLrnnyRqFGrPKrWCckfi8pyQ%2FQFGiArsJKDc2ao8syWC6mLRFK%2FGwXRI%2FWHDMcV3BRPLrcILIXDrdQCTNNkko3mGSMVgzVqIBADPypVX00AaKZSipDLtiS4OMLqnM6CMttavrzmg6HCf1sFL9HimU8aeyVRYGi49zfGJC8AHYwAWiaYQg1zth6mnVJ3NYKXim81yDB1LH9xnsGHQErt2Gu3hUzo6f%2BzGy0GvL&X-Amz-Signature=be9b83b0d152dbe256de62371780047ed4865c2b677892339ca45ff9f98e5e61&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=ASIA6AP2G7AKHK5S3VML%2F20260222%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Date=20260222T075256Z&X-Amz-Expires=3600&X-Amz-Security-Token=IQoJb3JpZ2luX2VjEPX%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGV1LWNlbnRyYWwtMSJIMEYCIQCxKFb%2FLk1byg8FI2SBkHVT1VFCI1qQo46ii2C3N1QyNgIhAMWrQzeQ%2FDMe5Y%2BZyhZMo6tQW%2B7YNGyKG%2FCi8ldK1WboKsUFCL7%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQAhoMOTYzMTM0Mjg5OTQwIgzgg6POvEloLXedNi0qmQWK%2BFo7cZ0GYJ%2BE4qjIwefUQZ6L3RlsEn6DmZwHsZCx5KpGXY1qOZ47RSbnmX60NymiIPfYrs%2BV7JWVL%2FW3VKDLtU%2BLBSmvgU4g6kvngTlvz0Hl5RoGgh2BYuZJtFj6v3rGlIyg0ySD96YZYHAhwQI3PkIITFUVEL9QBmoDi2q4JeXzSDktMWjlxC7yX6YNhLoriv7aQkO%2BsKFNB9o1ipWDhGJerHuh9P5ZW2%2F3b%2Bclyzy549G%2BUw3N%2BXFJvorCyEZs5xlZ%2Fdez4clnnWLbNKCbnFv2luhR%2BajwNcBC2ydqqT%2ByS57L29iDClnTP8FHSl63EIAZgT9vCPTCSGTwfUWewCJ9udWf3umDR19fBlAaBzQTRBTk%2BwPYfwW6fdhkjADHQalfgHP4XAL9SBp%2Bcz%2BkkAmyU5iAnu%2Fv2eWXpqSKyABNt993PO9m2IyXbVCedNeuaP%2BOmX7vEAz7v%2FTKBJLpvzoPvbYNWzAUPcx6HHxCUZEhIKvYtp7LlIMUDTdb3Y5EqhC1NqMOYCw3cht6hdL48s1xRPbqTbC2LyaqgpeddKoVWoqX0WZsdYzpmiNk7EBStmmX3VeQWDnBy%2BoAwVkOG1IcmMvD9vJucJEBYeXjzbM65R4ETy87ILIPEhZKjytrsCZHPrC4dqj1Yz%2F0ryIMe579PReYUL4LvctCC46VKrrIp65UY%2BCYqphiXG7VHmgdxZDU3%2F5VBPCDmFMSvoZNFUtt3e5vlsMrY68wj9lQNXXLfUmPKYMOqDIQAA4wR1%2BVusq28Cf0e77xMCjaHstTMQaHxx3qfpU4hn8aaVeBIFX%2BhWh6IV8bQ9rqimoBWFlAU9FlWVBuW2nLm%2BrBAUJcq919yaoxF0Lh66P%2FY4jCWJoYZQ7Eu8iAijDklurMBjqwAX18QV1gLrnnyRqFGrPKrWCckfi8pyQ%2FQFGiArsJKDc2ao8syWC6mLRFK%2FGwXRI%2FWHDMcV3BRPLrcILIXDrdQCTNNkko3mGSMVgzVqIBADPypVX00AaKZSipDLtiS4OMLqnM6CMttavrzmg6HCf1sFL9HimU8aeyVRYGi49zfGJC8AHYwAWiaYQg1zth6mnVJ3NYKXim81yDB1LH9xnsGHQErt2Gu3hUzo6f%2BzGy0GvL&X-Amz-Signature=1e035d6c963fde9ba6cffb8d1c4301bbdad5d636236a98c71ce40a0e53b248a1&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 |