Determination of Moisture by Mid Infrared Transmission Spectroscopy
Abstract An investigation was undertaken to determine whether commercially available mid infrared filter instrumentation (i.e., Multispec MK1) could be used to determine moisture in a manner similar to the AOAC near infrared method. Using a specially designed IR scanning spectrophotometer capable of working with aqueous systems, functional sample (6.02 jtm) and reference (5.56 iim) wavelengths were determined for quantitating water-methanol mixtures, and a standard curve was derived. Skim milk powder, bread crumbs, and flour were mixed with dry methanol to extract moisture into the solvent; moisture was quantitated relative to 3 AOAC methods. The results indicated that the wavelength pair selected worked well and had the potential to determine moisture content of low moisture food products, given that appropriate moisture extraction protocols were derived. This work indicates that the capabilities of commercial filter-based mid infrared instruments could be expanded to include moisture analyses if such instruments were equipped with the appropriate interference filters to carry out this determination.