The origin of foods plays an important role in their metabolome (the set of compounds present as products of metabolic events). The compositions of food plants are inevitably determined by a number of inherent and external factors – most importantly by the genotype (species, subspecies, cultivar, variety) and the prevailing conditions and weather parameters at each growth environment. The declaration of food origin can be defined and protected by law. The constantly increasing consumer awareness towards food origin, authenticity and quality has set the need for efficient tools for their verification. Metabolomics based on nuclear magnetic resonance (NMR) spectroscopy is increasingly being applied in analysing food composition and quality and in detecting food frauds and adulterations. 

The aim of the current work was to determine the influence of origin-related variables in food composition and quality by using 1H NMR metabolomics. The model foods – sea buckthorn (Hippophaë rhamnoides) berries, oilseeds of Brassica spp. and varietal honey – represent different foods with special sensory, nutritional, bioactive, commercial and national significance. The sea buckthorn berry metabolites were investigated in respect to the genotype (subspecies, cultivar) and geographical origin, with special emphasis on the influence of northern latitudes and related conditions. In the oilseeds, the inter-species variation and the influence of environmental and developmental stage on the seed composition was investigated. NMR profiling was applied in characterising the marker compounds for different honey types for botanical authentication. Multivariate analysis methods such as principal component (PCA) and discriminant analyses (PLS-DA, OPLS-DA) were applied in every sub-study to determine the key metabolites and origin-related factors characterising the food samples. 

The sea buckthorn subspecies were mainly distinguished by the relatively high content of ethyl-β-D-glucopyranoside (ssp. rhamnoides) and malic acid and vitamin C (ssp. sinensis). The northern latitude and respective conditions (the length of growth season, temperature, radiation and precipitation) was shown to alter the chemical composition of berries of the same genetic origin. In subarctic latitudes, the berries formed more ascorbic acid while the levels of ethyl glucose remained relatively low. The berries of cultivar 'Tytti' contained more ethyl glucoside while the berries of 'Terhi' contained more quinic acid in comparison. Calculated from the start of the growing season until harvest, the effective temperature sum (degree days) and the radiation sum correlated positively with ethyl glucoside that accumulated up to six-fold in overripe berries in southern Finland. The sea buckthorn berries (ssp. sinensis) grown at over 2000 m altitude contained typically more ascorbic and malic acids. 

The seeds of turnip rape was characterised by a relatively higher sucrose and polyunsaturated fatty acid content over oilseed rape that had a higher content of sinapine and oil in general. Growth conditions with reduced temperature added to the level of unsaturation in the oilseed lipids and delayed the seed development. The varietal honeys were classified with the aid of NMR profiling, as the typical sugar composition and other botanical markers were characterised. Also, previously unreported markers were designated for dandelion honeys. 
The correlations between complex food metabolomes and the origin-related variables were easily accomplished with NMR metabolomics. Especially, the effect of northern conditions on the growth place-dependent compositional flexibility (phenotypic plasticity) of the plant foods was deemed considerable. The results of this thesis can be further used to determine food quality, origin and authenticity and as an aid in plant breeding operations.