Microwave drying and NIR spectroscopy for the rapid moisture measurement of yerba mate (Ilex paraguariensis) leaves during storage

Abstract

Microwave technology was assessed and compared with traditional kiln drying to analyze the moisture content of yerba mate leaves/sticks. The moisture content was also measured by near-infrared spectroscopy (NIR). The samples were stored under different conditions of temperature, relative humidity (RH), and time, until 180 days. The microwave method was similar to the official kiln drying method when 900 W/4.3 min was applied. The use of microwave drying showed similar results to the kiln method in the moisture range of 0–10 g/100 g raw material. The partial least square (PLS) models obtained from NIR spectroscopy showed low predictive power, due to the natural heterogeneity of the samples.