A rapid and high-throughput fraud detection method of Philippine coconut wine (lambanog) using ¹H qNMR spectroscopy

Methanol contamination of the Philippine coconut spirit lambanog (often called coconut wine) is the major cause of lambanog-related deaths in the country. Hence, a strict quality control and detection method must be established for methanol in tandem with ethanol analysis. In this study, a quantitative Nuclear Magnetic Resonance spectroscopy (qNMR) method using ¹H analysis was developed to quantify the methanol and ethanol in 26 lambanog samples collected from four different provinces in Luzon, Philippines. A certified qNMR standard was used as an internal standard for the ¹H NMR analyses to increase the accuracy of the measurements. The calculated limit of detection and limit of quantification of methanol with values of 0.076%(v/v) and 0.25%(v/v), respectively, were sufficiently low and allow the monitoring of methanol within the acceptable safety level. Moreover, the results of methanol and ethanol analysis using the proposed method were in good agreement with those obtained from GC-FID analysis which is the conventional method for alcohol analysis. In contrast to GC-FID, the qNMR method for simultaneous alcohol analysis can provide results in a shorter period. The results of this study show the potential of the qNMR method to be used as an alternative analytical method which widens the range of analytical possibilities to detect methanol in lambanog samples for the safety of the consumers.