Development and assessment of GC/MS and HPAEC/PAD methodologies for the quantification of α -galacto-oligosaccharides (GOS) in dry beans ( Phaseolus vulgaris )

The quantification of alpha-Galacto-oligosaccharides (GOS) in beans has been increasingly approached through different methodologies. However, reported GOS contents revealed up to 8-times disparity, which cannot be only attributed to the bean cultivar and underlines the need of using validated analytical methodologies. This study aimed to optimize and validate the extraction of the most abundant GOS found in beans, namely raffinose, stachyose and verbascose, and comparatively assess their determination by High-Performance Anion Exchange Chromatography/Pulsed Amperometric Detector (HPAEC/PAD) and Gas Chromatography/Mass Spectrometry (GC/MS). Hot sonication followed by shaking with 70% ethanol resulted in excellent GOS extraction efficiencies (92.54-107.94%). GC/MS determination was more reliable than HPAEC/PAD, with limits of quantification of 4.48-224.31 mg/kg and intra/inter-day repeatabilities <10%. The analysis of six bean varieties proved the feasibility of the GC/MS methodology, displaying total GOS contents from 1453.07 +/- 169.31 to 2814.34 +/- 95.28 mg/100 g. Stachyose was significantly (p < 0.05) the main GOS in all samples.

Automated summary

The quantification of alpha-Galacto-oligosaccharides in beans has been approached through different methodologies, but with reported contents showing up to 8-times disparity. This study aimed to optimize and validate the extraction of the most abundant GOS found in beans and comparatively assess their determination by HPAEC/PAD and GC/MS. GC/MS determination was found to be more reliable than HPAEC/PAD, and stachyose was identified as the main GOS component in all samples.