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.