Determination of 2-acetyl-1-pyrroline in alginate encapsulated pandanus flavorings by static headspace (SHS) and gas chromatography with nitrogen–phosphorus detection (GC-NPD)

Abstract

A new form of Pandanus flavoring has been developed using the ionic gelation method. Among the four Pandanus species investigated by solid-phase microextraction (SPME)–gas chromatography–mass spectrometry (GC–MS), the leaves of P. amaryllifolius Roxb. contained the highest content of the impact aroma compound, 2-acetyl-1-pyrroline. Some terpene volatiles were identified for the first time in these Pandanus species. Acidic extraction with aqueous tartaric acid at pH 5 was the most suitable solvent for obtaining 2-acetyl-1-pyrroline from Pandanus leaves. Moreover, the extract was directly subjected to ionic gelation with the optimized sodium alginate and calcium chloride concentrations of 1.5 and 3% w/v, respectively. Automated static headspace–gas chromatography with a selective nitrogen–phosphorus detection was developed and validated to determine 2-acetyl-1-pyrroline in the dried green alginate beads. The response surface optimization of headspace sample parameters resulted in an optimal equilibration time of 20 min and oven temperature at 123 °C. The 2-acetyl-1-pyrroline standard calibration curve was linear from 1.0 to 640 μg g⁻¹ with a correlation coefficient of 0.9998. The limits of detection and quantification were 0.10 and 0.80 μg g⁻¹, respectively. On average, a 2-acetyl-1-pyrroline content of 18.49 μg g⁻¹ (16.89 to 26.91 μg g⁻¹) was encapsulated in the green dried alginate flavoring products, which was two to three times higher than contained in fresh Pandanus leaves. After 90 days of storage, the 2-acetyl-1-pyrroline content remaining in the green dried alginate beads was 79% of the initial content.

Keywords:

• 2-Acetyl-1-pyrroline
• food flavorings
• gas chromatography–mass spectrometry (GC–MS
• gas chromatography–nitrogen phosphorus detection (GC-NPD)
• static headspace (SHS)

Acknowledgments

The Research Center on Chemistry for the Development of Health-Promoting Products from Northern Resources, Chiang Mai University (CMU) is gratefully acknowledged.

Additional information

Funding

This work was supported by the Science Achievement Scholarship of Thailand (SAST), and the Centre of Excellence for Innovation in Chemistry (PERCH-CIC), Ministry of Higher Education, Science, Research and Innovation, Thailand.