Mixture analysis by NMR as applied to fruit juice quality control.

Nuclear magnetic resonance (NMR) spectroscopy is rapidly gaining importance in mixture analysis, originally driven by the pharmaceutical and nowadays also by clinical applications within metabonomics. Quality control of food-related material has very similar requirements, as it also deals with mixtures, and many of the compounds found in body fluids are analyzed as well. NMR allows analysis in two ways within one experiment: namely, targeted and untargeted. Targeted stands for the safe identification and consequent quantification of individual compounds, whereas untargeted means the detection of all deviations visible by NMR using statistical analysis based on normality models. Very important is the stability and reproducibility of the NMR instrumentation used, and this means inherent minimized system internal variance. NMR is especially suited for such requirements, as it allows detection of the smallest concentration changes of many metabolites simultaneously. High-throughput flow-injection NMR as the basis for fruit juice screening allows low cost per sample and delivers substantially more relevant information than any other method and is probably the only method to produce such results.