Spectroscopy and RGB-Colorimetry for Quantification of Plant Pigment and Fruit Content in Fruit Drinks
Abstract: Collimated Transmission Spectroscopy (CTS) is a technique that is commonly used to study the optical absorption of different media. In this work CTS was used to measure the absorbance of pure raspberry juice in order to investigate how well the fruit content may be determined in a commercially available raspberry fruit drink. Another method, RGB colorimetry, which is a much more available technique that can be performed using a standard camera in e.g. a smartphone was also tested for the same purpose. The aim was to evaluate the viability and accuracy of CTS in quality monitoring of fruit drinks as compared to two differently sophisticated approaches to RGB colorimetry. CTS was indeed found to be the most accurate of the techniques, but the more sophisticated of the colorimetry methods, which used partial least squares regression to evaluate unknown concentrations was found to have some merit. The simpler of the colorimetry methods was found to be the most inaccurate, but it could potentially be used to make rough estimates of concentrations, and it has the advantage of being simple and available for e.g. educational or consumer purposes.
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