Evaluation of Total Solids of Curry Soup Containing Coconut Milk by near Infrared Spectroscopy

Abstract

The aim of this research was to perform a feasibility study of the potential of near infrared (NIR) spectroscopy to evaluate the total solids content of instant curry soups containing coconut milk; these included green curry, red curry, massaman curry and panang curry. The soup samples were collected from mixing tanks, water adjusting tanks, ultra-high temperature process line and laminated cartons. Adjusted samples were made from the same recipe as in the processing line but with the total solids increased by 30%, 60% and 90%, and reduced by 30%, 60% and 90% total solids from normal levels. Each sample was scanned with a Fourier transform NIR spectrometer. A prediction model for total solids was established using NIR spectral data in conjunction with reference data using partial least squares regression, which was validated using leave-one-out validation and test set validation. The test set validation showed better prediction performance as proved by using an unknown sample set. The test set validation model was developed using multiplicative scatter correction of spectra for the 6102–5446.3 cm−1 and 4605.4–4242.9 cm−1 regions, and provided a coefficient of determination for prediction ( r2), root mean square error of prediction ( RMSEP), bias and ratio of standard error of prediction to the standard deviation ( RPD) of 0.92, 0.95%, −0.20% and 3.71, respectively. It was shown that NIR spectroscopy could be applied in an instant curry soup production line for process control and quality assurance.