Measurement of effective penetration depth of line laser into wheat flour in Raman hyperspectral imaging system

Abstract

The penetration depth of the same light source to different samples is determined by the physical properties of the samples, and the determination of the penetration depth is the basis for the effective detection of the samples using spectral technology. This paper aimed to determine the effective penetration depth of line laser into wheat flour with different gluten in Raman hyperspectral imaging system. Double-layer samples were prepared using L-ascorbic acid (LAA) and wheat flour with different gluten, and Raman hyperspectral images of LAA, wheat flour with different gluten, and double-layer samples were collected, respectively. The single-band image corresponding to the Raman characteristic peak of LAA was selected from the doublelayer sample image, and the threshold segmentation method was used to create a detection image to identify LAA pixels. The penetration rate of the line laser into different thickness of wheat flour layer was calculated according to the identification results. The results showed that the Raman characteristic peak of LAA was located at 1658 cm−1, which had the highest intensity and did not coincide with the Raman peak of wheat flour with different gluten. The maximum penetration depth of the line laser into the wheat flour layer was 4 mm in the average Raman spectrum of the double-layer sample. The penetration rate of the line laser into the 2 mm wheat flour layer in the detection image of the double-layer sample was more than 99%, and this thickness was regarded as the effective penetration depth. The accuracy and reliability of 2 mm effective penetration depth were verified by tests on wheat flour of the same gluten and different brands. The results laid a foundation for the subsequent effective identification of additives in wheat flour.