WW ASB 18-01
Small and smart: Cost-effective high throughput spectrophotometric method for the determination of YAN
Department of Viticulture and Oenology, Stellenbosch University
Aleixandre-Tudo, J A
Practically speaking, scanning a sample takes less time (higher throughput) and is more efficient than classical YAN measurements. From one scan, if the instrument is calibrated, various measurements can be done – glucose, fructose, malic acid, TA, pH, VA, etc. We propose to add YAN to this extremely relevant list (ammonia and FAN separately, and even individual or groups of amino acids) to decrease the time and the cost for these measurements in the future.
YAN, FAN, and ammonia were measured with a reference method. Amino acids were determined by derivatization with AccQ-Tag followed by HPLC separation and UV-Vis detection. All the samples were also scanned with FOSS, Alpha, and MPA.
PLS models were built based on calibration/prediction sets of 66/34 and 50/50. Additional tasks were given to be able to test the robustness of the models. FOSS generally outperformed the other two instruments, but all three gave acceptable results in terms of statistical parameters tested. This means that all three instruments can be used to
measure YAN, FAN, and ammonia.
Discussion and Conclusion:
The results obtained in this study show that it is indeed possible to calibrate IR spectroscopic instruments for the accurate measurement of YAN, FAN, and ammonia concentrations. Transmission FT-IR (FOSS and MPA) spectroscopy was, however, observed to show the most promising results; however, FT-NIR spectroscopy (FOSS) also produced models capable of good to excellent quantification, primarily for YAN and FAN. Furthermore, both of these instruments showed sufficient robustness against samples originating from different varieties, growing conditions, and vintages, addressing the concerns of applying this technology to the agricultural industry. Therefore, applying this rapid, cost-effective, and environmentally friendly method in an industrial setup is a plausible option, despite the inherent variability and complexity of the grape juice matrix. Moreover, the possibility of measuring the YAN status of samples from a new vintage are one of the most important findings in this study as it demonstrates the feasibility of this technology in an industrial set-up. This is because calibrations will most likely be based on samples originating from previous vintages and used for analysis of subsequent vintages.