Assessment of Purslane (Portulaca oleracea L.) Total Oxalate Content, Ascorbic Acid, and Total Organic Acids Using Near-Infrared Spectroscopy

Abstract

Purslane (Portulaca oleracea L.) has been regaining its reputation as a valuable food and source of nutrients and biologically active compounds, but a high content of oxalates reduces mineral bioavailability and poses nutritional limitations. This study evaluated the influence of culinary processing on oxalate content in purslane and the potential of near-infrared (NIR) spectroscopy for non-destructive assessment of total oxalates, ascorbic acid, and total organic acid. The ascorbic acid and total organic acid in fresh samples, and the total oxalate content of fresh, blanched, and pickled samples were determined. Culinary treatments (blanching and pickling) reduced oxalate content. The highest oxalate content was observed in fresh samples (33.38–61.84 g/100 g), lower in blanched samples (19.07–34.36 g/100 g), and the lowest content in pickling samples (10.48–18.31 g/100 g). NIR spectra (900–1700 nm) of the analyzed samples were measured, and PLS regression was used for the determination of tested components. The NIR spectroscopy achieved high predictive accuracy for ascorbic acid, total organic acid, and oxalate content. Rcval > 0.98 and SECV values between 0.02 and 0.38 g/100 g for oxalate content. NIR spectroscopy provides a rapid, accurate, and non-destructive alternative to conventional methods for oxalate determination in fresh, blanched, and pickled plant tissues, ascorbic acid and organic acid in fresh samples.