Impact of Freeze-Drying on the Determination of the Geographical Origin of Almonds (Prunus dulcis Mill.) by Near-Infrared (NIR) Spectroscopy

Abstract Near-infrared (NIR) spectroscopy is a proven tool for the determination of food authenticity, mainly because good classification results and possibility industrial use due to its easy fast application. Since water shows broad absorption bands, content sample should be as low possible. Freeze-drying commonly used preparatory step this reduce in sample. However, freeze-drying, also known lyophilization, very time-consuming impeding widespread usage NIR analysis rapid method incoming goods inspections. We set 72 almond samples from six economically relevant almond-producing countries investigate question how important lyophilization obtain well-performing model. For approach, were ground lyophilized 3 h, 24 48 h compared non-freeze-dried samples. Karl-Fischer titration non-lyophilized showed that contents ranged 3.0 10.5% remained constant at 0.36 ± 0.13% after freeze-drying period h. The accuracy 93.9 6.4%, which was same range freeze-dried (94.2 7.8%), (92.5 8.7%), (95.0 9.0%). Feature selection performed using Boruta algorithm, signals lipids proteins are origin determination. presented study with content, especially nuts, can analyzed without preparation robust results, required inspection.