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Description
Salep powder, derived from dried tubers of wild terrestrial orchids, is a high-value ingredient used to prepare a thick, hot winter beverage valued for its many reported health benefits. However, products marketed as salep are often diluted, adulterated or falsified, unless specifically declared as pure, with low-cost ingredients such as sugars and starches. The lack of rapid and robust methods for verifying product authenticity poses a significant challenge to the protection of legal and consumer rights, emphasizing the need for the development of fast and reliable authentication techniques.
In this work, VIS–NIR spectra (350-2500 nm) recorded from commercial salep products available on the domestic market, including products spiked with pure authentic salep, were analyzed by principal component analysis (PCA) after standard normal variate (SNV) correction. Unsupervised PCA loading profiles showed the visible range (400–700 nm) as an appropriate marker region for the authentication, reflecting the contrasting color of off-white salep relative to the whiter diluents, and a near-infrared band near 1850–1900 nm, corresponding to the O–H stretch-plus-bend combination band of the hydroxyl-rich, high-bound-water glucomannan matrix. In addition to his, a Hotelling’s T² analysis flagged three commercial products as containing little or no genuine salep. These results show that a single, rapid, non-destructive and low-cost VIS–NIR measurement can both quantify salep content and thus expose its near-absence in cheap commercial preparations.