Influence of temperature on the measurement of NaCl content of aqueous solution by short-wavelength near infrared spectroscopy (SW-NIR)

Abstract

Short-wavelength near infrared (SW-NIR) spectroscopy can provide a rapid and nondestructive determination of salt content in food products, and potentially monitor salt concentration of brines during processing. This is of significant importance for ensuring the safety and quality of cured and smoked foods. One of the constraints is having reliable models to predict salt concentration as temperature varies. The effect of temperature (4.0-42.9°C) on SW-NIR spectra (594-1,105 nm) of aqueous salt solution (0-10.03% w/v) was tested in this study. A partial least squares (PLS) model based upon spectra from the entire tested temperature range, had similar predictability for salt content as PLS models developed using spectra over shorter temperature ranges (root mean square error of prediction was 0.35% versus 0.37-0.38%). The result indicated that temperature compensation with mathematical approaches for NIR spectral measurements is feasible. This could limit the cost and time necessary to collect samples over a wide range of temperature for developing and validating calibration models for salt measurement in food processing and similar applications.

Detection of Water pH Using Visible Near-Infrared Spectroscopy and One-Dimensional Convolutional Neural Network

“…As shown in Figure 6 , half the number of filters (#1, #2, #5, #6, #7, #14, #15, and #16) have high activations on variables between 960~980 nm, and the theoretical peak around 970 nm is related to the third overtones of O-H bonds in water [ 19 ]. Seven filters (#1, #2, #6, #7, #10, #15, #16) have high responses on variables between 840~860 nm, which around the O-H weak absorption bands [ 20 ]. The uninformative variables are reduced to zero.…”

“…As shown in Figure 1 , the key chemical features appear near the ~970 nm, which is related to the third overtones of O-H bonds in water [ 19 ]. The small mounds near ~840 nm and ~750 nm, which can be correlated to 2 v 1 + v 2 + v 3 and 3 v 1 + v 3 combination transition, respectively, where v 1 is the symmetric O-H stretch, v 2 is the O-H bending mode, and v 3 is the antisymmetric O-H stretch [ 20 ].…”

Influence and correction of temperature on optical measurement for fat and protein contents in a complex food model system

“…Many investigations have reported the influence of temperature on spectral measurements of food systems, chemical materials, and some complex mixtures [6][7][8][9]. These investigations indicated that spectral measurements of the samples are affected by temperature.…”