Spectroscopic and chemometric exploration of food quality: Early prediction of meat quality

Dorthe Kjær Pedersen

Publikation: Ph.d. afhandling/ kandidat/ diplomPh.d. afhandlingForskningpeer review

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The desire to develop non-invasive rapid measurements of essential quality parameters in foods is the motivation of this thesis. Due to the speed and noninvasive properties of spectroscopic techniques, they have potential as on-line or atline methods and can be employed in the food industry in order to control the quality of the end product and to continuously monitor the production. In this thesis, the possibilities and limitations of the application of spectroscopy and chemometrics in rapid control of food quality are discussed and demonstrated by the examples in the eight included publications. Different aspects of food quality are covered, but the focus is mainly on the development of multivariate calibrations for predictions of rather complex attributes such as the water-holding capacity of meat, ethical quality of the slaughtering procedure, protein content of single wheat kernels and contamination of fish oil by toxic environmental substances. Fourier transform infrared (FT-IR) and Raman spectroscopy proved to be of potential utility for process line measurements of meat quality (water-holding capacity). Preliminary studies revealed a high correlation (r = 0.89) between waterholding capacity and FT-IR spectra with prediction errors of 0.85-1.4 % drip loss using Partial Least Squares Regressions. A further development of vibrational spectroscopic methods can be of valuable use in the slaughtering industry, aiming at a better utilization of the raw material through early classification of the meat. Visual and near infrared (VIS/NIR) spectroscopy was evaluated for the ability to assess the depth of CO2 stunning of slaughter pigs. Near infrared transmittance (NIT) was applied for the assessment of the quality of single wheat kernels. The combination of fluorescence measurements of fish oil and multi-way chemometrics demonstrated the potential for screening of environmental contamination in complex food samples. Significant prediction models were established with correlation coefficients in the range from r = 0.69 to r = 0.97 for dioxin. Further development of the fluorescence measurements of dioxin in fish oil will, for the fish industry, be a valuable tool for monitoring the quality of their oil products, especially when the EU introduces a limit of 6 ng/kg dioxin later this year. In order to improve calibrations and model interpretation, methods of spectral pretransformations, including the recently developed Extended Invented Signal Correction, and variable region selection were used during the data analysis throughout this study. The uncertainty of reference analyses and their influence on the subsequent multivariate spectroscopic calibration are discussed throughout the thesis. A general challenge during the development of multivariate calibrations in this study was the accuracy of the reference parameters of interest. It is emphasized that it is of utmost importance to incorporate knowledge of the chemical and biological nature of the samples and of the qualifications of the applied spectroscopic and reference methods during the validation of multivariate calibrations.
StatusUdgivet - 14 jun. 2002